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ترجمه مقاله و پروژه های دانشجویی - مطالب اردیبهشت 1394

دانلود ترجمه مقاله انگلیسی Economics of the arts and literature اقتصاد هنر و ادبیات


دانلود ترجمه مقاله انگلیسی Economics of the arts and literature اقتصاد هنر و ادبیات تعداد صفحات انگلیسی: 7 صفحه (pdf) تعداد صفحات ترجمه فارسی: 9

 صفحه (pdf) دانلود متن انگلیسی Abstract Economics of the arts and literature or cultural economics (used below for convenience) is a branch of economics that studies the economics of creation, distribution, and the consumption of works of art and literature. For a long time the arts were confined to visual and performing arts in the Anglo-Saxon tradition. Usage has widened since the beginning of the 1980s with the study of cultural industry (cinema and music publishing), and the economy of cultural institutions (museums, libraries, historic



برچسب ها: دانلود ترجمه مقاله انگلیسی Economics of the arts and literature اقتصاد هنر و ادبیات تعداد صفحات انگلیسی: 7 صفحه (pdf) تعداد صفحات ترجمه فارسی: 9 صفحه (pdf) دانلود متن انگلیسی Abstract Economics of the arts and literature or cultural economics (used below for convenience) is a branch of economics that studies the economics of creation، distribution، and the consumption of works of art and literature. For a long time the arts were confined to visual and performing arts in the Anglo-Saxon tradition. Usage has widened since the beginning of the 1980s with the study of cultural industry (cinema and music publishing)، and the economy of cultural institutions (museums، libraries، historic،  

تاریخ : پنجشنبه 31 اردیبهشت 1394 | 08:39 ب.ظ | نویسنده : sinister | نظرات

دانلود ترجمه مقاله انگلیسی New discoveries in Afraz کشفیات جدید در افراز (ارگ بم)

دانلود ترجمه مقاله انگلیسی New discoveries in Afraz کشفیات جدید در افراز (ارگ بم)

تعداد صفحات انگلیسی: 4 صفحه تعداد صفحات ترجمه فارسی: 4 صفحه دانلود متن انگلیسی برآورد عمر هسته دیوار دفاعی بم عدل در این‌باره توضیح داد: باروی ارگ بم به ظاهر یک دیوار یکدست است، ولی در حقیقت از لایه های مختلفی تشکیل شده که در دوره‌های مختلف و در طول این سال ها به دیواره اصلی آن اضافه شده‌ است. و به این نحو دیوار کنونی شکل گرفته است. در پژوهش‌های جدید در بخش مرکزی، پیشرفت‌های زیادی حاصل شده و از آنجا که علوم جدید اجازه‌ استفاده از فنون پیچیده را برای تعیین عمر دقیق ستون های رسی می دهد، هیأت باستان‌شناسی ارگ بم نمونه‌ برداری‌های لازم را انجام داده است تا تاریخ دقیقی برای شکل‌گیری دیوار ارگ یا حتی بخش حاکم‌نشین و قلعه های کهن منطقه گسل ارائه شود. البته چنین تحلیل هایی فقط در چند آزمایشگاه در دنیا انجام می‌شود.





برچسب ها: دانلود ترجمه مقاله انگلیسی New discoveries in Afraz کشفیات جدید در افراز (ارگ بم) تعداد صفحات انگلیسی: 4 صفحه تعداد صفحات ترجمه فارسی: 4 صفحه دانلود متن انگلیسی برآورد عمر هسته دیوار دفاعی بم عدل در این‌باره توضیح داد: باروی ارگ بم به ظاهر یک دیوار یکدست است، ولی در حقیقت از لایه های مختلفی تشکیل شده که در دوره‌های مختلف و در طول این سال ها به دیواره اصلی آن اضافه شده‌ است. و به این نحو دیوار کنونی شکل گرفته است. در پژوهش‌های جدید در بخش مرکزی، پیشرفت‌های زیادی حاصل شده و از آنجا که علوم جدید اجازه‌ استفاده از فنون پیچیده را برای تعیین عمر دقیق ستون های رسی می دهد، هیأت باستان‌شناسی ارگ بم نمونه‌ برداری‌های لازم را انجام داده است تا تاریخ دقیقی برای شکل‌گیری دیوار ارگ یا حتی بخش حاکم‌نشین و قلعه های کهن منطقه گسل ارائه شود. البته چنین تحلیل هایی فقط در چند آزمایشگاه در دنیا انجام می‌شود.،  

تاریخ : پنجشنبه 31 اردیبهشت 1394 | 08:37 ب.ظ | نویسنده : sinister | نظرات

دانلود ترجمه مقاله انگلیسی: دانلود ترجمه مقاله انگلیسی Archeologist or Photographer باستان شناس یا عکا س


دانلود ترجمه مقاله انگلیسی Archeologist or Photographer باستان شناس یا عکا س تعداد صفحات انگلیسی: 8 صفحه تعداد صفحات ترجمه فارسی: 7 صفحه دانلود متن انگلیسی ژاك ژان ماری دومورگان در سوم ژوئن سال١٨٥٧ میلادی در یك خانواده ی اشرافی در شهرك اویسو سوركوسون به دنیا آمد. تحصیلات ابتدایی و دوره ی متوسطه را در همان شهرك به اتمام رساند. شوق جوانی او را به سوی جمع آوری عتیقه سوق داد. برای ادامه ی تحصیل به پاریس رفت و پس از پایان تحصیلات در « مدرسه ی معدن شناسی» در سال ١٨٨٢ به كسب دیپلم این آموزشگاه نایل آمد.


برچسب ها: دانلود ترجمه مقاله انگلیسی: دانلود ترجمه مقاله انگلیسی Archeologist or Photographer باستان شناس یا عکا س،  

تاریخ : پنجشنبه 31 اردیبهشت 1394 | 08:36 ب.ظ | نویسنده : sinister | نظرات

دانلود مقاله ترجمه شده: دانلود ترجمه مقاله انگلیسی کارائی مرور وب با پردازش thin client بی سیم Web Browsing Performance of Wireless Thinclient Computing

دانلود ترجمه مقاله انگلیسی کارائی مرور وب با پردازش thin client بی سیم Web Browsing Performance of Wireless Thinclient Computing


تعداد صفحات انگلیسی: 7 صفحه تعداد صفحات ترجمه فارسی: 7 صفحه دانلود متن انگلیسی . مقدمه : محبوبیت برنامه های کاربردی وب و افزایش شبکه های بی سیم موجود ، رشد دستگاه های پردازش همراه و بی سیم را می افزاید. به موازات این رشد ، سیستم های پردازش تین کلاینت بی سیم نیز در حال پدیدار شدن هستند . INTRODUCTION The popularity of web applications and the increasing availability of wireless networks are fueling a growing proliferation of wireless and mobile computing devices.

برچسب ها: دانلود مقاله ترجمه شده: دانلود ترجمه مقاله انگلیسی کارائی مرور وب با پردازش thin client بی سیم Web Browsing Performance of Wireless Thinclient Computing،  

تاریخ : پنجشنبه 31 اردیبهشت 1394 | 08:33 ب.ظ | نویسنده : sinister | نظرات

آموزش ایمپلنت با سیستم ITI

surrounding the abutment. 6. Restoration Prosthetic procedure 5 4 143 Step 4 – Placing the denture caps Place the denture caps w pp ith the black processing males onto the LOCATOR® abutments. Step 5 – Hollowing out the denture base ppHollow out the existing denture base in the areas of the LOCATOR® denture caps. Note Ensure that the denture caps fixed on the abutments do not touch the prosthesis. 6. Restoration Step 6 – Filling the connecting holes ppFill the connecting holes with prosthetic resin from lingual and anchor the caps in the denture (lightcure or selfcuring resin). ppRemove any excess resin after curing and polish the denture. Note If the white LOCATOR® block-out spacer does not completely fill the space between the gingiva and the denture caps, any remaining undercuts must be blocked out to prevent resin flowing under the caps. This can be accomplished by stacking two or more LOCATOR® block-out spacers. Once the resin has cured, remove the denture from the mouth and discard the white LOCATOR® block-out spacers. Prosthetic procedure 7 v v v v v 144 Step 7 – Selecting the replacement males Implant divergence u pp p to 10° for a single implant: 6. Restoration Color Retention blue 0.23 kg pink 1.36 kg clear 2.27 kg ppImplant divergence between 10° and 20° for a single implant: Color Retention red 0.23 kg green 1.36–1.82 kg Note Always start with the lowest retention replacement males. Prosthetic procedure 8 9 10 145 Step 8 – Removing the processing males To place the replacement ma pp les in the denture housing, remove the black processing males from the housing (p. 148). Step 9 – Inserting the replacement male ppInsert the replacement male with the core tool (p. 146). 6. Restoration Step 10 – Inserting the finished denture ppInsert the finished denture and check the occlusion. Prosthetic procedure 146 6. Restoration 6.9.4 LOCATOR® Abutment – Further references 1. Using the LOCATOR® core tool The LOCATOR® core tool is a three-piece multifunction instrument. Gap The tip is used for removing replacement males from the denture caps. To do this, the tip must be unscrewed by two full turns. A gap is visible between the tip and the middle section. The tip is passed in a straight line into the denture cap with a replacement male. The sharp edges of the tip hold the replacement male while it is being removed. The instrument is drawn out of the denture cap in a straight line. To remove the replacement male from the instrument, the tip must be screwed clockwise completely onto the middle section. This activates the loosening pin inside the tip, which releases the replacement male. 147 The middle section of the LOCATOR® core tool is used for inserting replacement males into the denture caps. To do this, the tip is unscrewed. The exposed end of the replacement male is pressed into the denture cap. The replacement male is fixed firmly in the cap when a click is heard. The end (gold-colored) of the LOCATOR® core tool is used by the dental technician for screwing and unscrewing the LOCATOR® abutments to and from the analogs. 2. Determining the implant divergences Snap the LOCATOR® parallel posts onto the LOCATOR® abutments. Use the LOCATOR ® angle measurement guide to determine the angulation of the LOCATOR ® abutments in relation to each other. Hold the angle measurement guide behind the placed parallel posts and read off the angle for each abutment. Note Choose the appropriate LOCATOR® replacement males according to the angulation measured for each abutment. Tie dental floss through the lateral holes of the angle measurement guide to prevent aspiration. 6. Restoration 148 6. Restoration 3. Using the black processing male Both the LOCATOR® female analog and the LOCATOR® denture cap are supplied with a preassembled black processing male. The black processing male functions as a space keeper for the various LOCATOR® replacement males. For the relining of a LOCATOR-anchored overdenture, the LOCATOR® replacement males must be removed from the denture caps and exchanged with black processing males. The black processing males keep the denture in a stable vertical position during the relining procedure. When the relining of the denture is finished, the black processing males are exchanged with the corresponding new LOCATOR® replacement males. 4. Important cleaning instructions The proper cleaning of the LOCATOR®-borne denture and the LOCATOR® abutments is a prerequisite to ensure the long-term performance of both the abutments and the nylon processing inserts. An accumulation of plaque on the abutment that imbeds into the nylon processing insert can abrade, over time, the titanium abutment to a smaller diameter and thus cause it to lose retention. According to the specific situation, the patient might be put on shorter recall appointments to monitor the proper cleaning of the denture and the abutments. 149 7.1 SCS Scre wdri ver The SCS* screwdriver is used for the fixation of the prosthetic parts and healingcomponents. The star shape of the screwdriver tip connects to the top of the healing components and abutment screw heads for safe pick-up and handling. *SCS = Screw Carrying System SCS screwdriver for manual use Article: extra short, short, long Lengths: 15 mm, 21 mm, 27 mm Art. Nos.: 046.400, 046.401, 046.402 Material: Stainless steel 7. Aids and instr uments 7. Aids and instruments 150 7. Aids and instruments 7.2 Polis hing Aid The polishing aid is used during polishing and other lab procedures to protect the abutment’s prosthetic connection and to establish a convenient fixation extension. Art. Nos.: 025.2920, 025.4920 Material: Stainless steel 151 7.3 Ratc het and Torque Contr ol Device The ratchet (Art. No. 046.119) is a two-part lever arm instrument with a rotary knob for changing the direction of force. It is supplied with a service instrument (Art. No. 046.108), which is used to loosen the headed screw. After loosening, the ratchet bolt can be removed from the body of the ratchet. The ratchet gap must be disassembled for cleaning and sterilization. To apply a certain torque when tightening an abutment screw, use the ratchet together with the torque control device (Art. No. 046.049) and the holding key (Art. No. 046.064). Ratchet The ratchet is used in combination with the torque control device to torque in all Straumann abutments and screws (it is the same ratchet used for placing Straumann implants manually). Note The ratchet and service instrument are packaged together. looped end flared part nut directional arrow ratchet disassembled 7. Aids and instruments 152 7. Aids and instruments pin forked end Torque control device Connected to the ratchet, the torque control device is used to measure the value of Ncm (Newton centimeter) applied when inserting Straumann abutments and screws. Service Instrument The Service Instrument is used to assemble and disassemble the ratchet. Holding key The forked end of the holding key can be used to assembleand disassemble the ratchet. The pin can be used to stabilize drivers when abutments and screws are placed (also used for implant placement). fluted end torque scale tear drop 1a 2a 1b 2b 153 Step 1 – Loosening Loosen the ratchet n pp ut with the service instrument or the holding key. 7.4 asse mbling the Ratc het and the Torque Contr ol Device Step 2 – Removing ppUnscrew and remove the internal bolt from the ratchet body. 7. Aids and instruments 3a 3b 4a 4b 154 7. Aids and instruments Step 3a – Insertion Insert the ratchet body i pp nto the torque control device (flared part of the ratchet must be flush with fluted end of torque control device). Step 3b – Insertion ppInsert the internal bolt into the opposite end of the torque control device. Tighten it firmly by hand. Step 4 – Tightening ppTighten the nut of the ratchet with the service instrument or the holding key. Do not overtighten. ppThe ratchet and torque control device are now assembled and ready for use. 1 2 3 155 Step 1 – Insertion and tightening Insert th pp e abutment into the implant. ppTighten the abutment screw by hand using the SCS screwdriver. 7.5 tig htening an ab utment to 35 Ncm Step 2 – Placing the ratchet ppPlace the looped end of the assembled ratchet with the torque control device over the driver handle. The directional arrow must be pointing clockwise (towards the torque bar with tear drop). If not, pull the arrow out, flip it over, and let it snap in. Step 3 – Stabilizing the ratchet ppFor stabilization, put the pin end of the holding key into the coronal hole on the driver handle. 7. Aids and instruments 4 156 Step 4 – Positioning of appropriate Ncm mark Use one h pp and to hold the holding key and use the other hand to hold the torque bar. Grasp only the tear drop and move the torque bar to 35 Ncm mark. Step 5 – Removing the ratchet ppAfter reaching the 35 Ncm mark, return the torque bar to its starting position. ppLift and remove the holding key, the ratchet with torque control device and the driver. Note Proper care and maintenance are important to ensure correct function of the ratchet and torque control device. Always clean and sterilize disassembled. For detailed instructions on how to care for these instruments, please refer to their package inserts. Recommended tightening torques Hand-tight 15 Ncm 15–35 Ncm 35 Ncm Closure screws Healing abutments Temporary copings Copings Temporary abutments Final abutments 7. Aids and instruments 157 Straumann abutments and components are not sterile when delivered. Use the following procedure for sterilization prior to use. Note Parts that have been modified or altered from their original state may require different sterilization procedures. To prevent tension cracks in PMMA products do not use the following: alcohol; UV radiation; sterilization; immersion in liquid for more than one hour; temperatures over 60 °C (140 °F). 8. About Sterilization 8. abo ut sterilization Material Method Conditions Ti, Ti alloy Autoclave, moist heat 134 °C (273 °F) for 18 min PEEK, PEEK with Ti inlay POM Metal alloy Ceramicor® Composition in weight %: Au 60%, Pd 20%, Pt 19%, Ir 1% ZrO2 Dry heat 160 °C (320 °F) for 4 h 158 Disclaimer of liability The Straumann dental implant and other Straumann products are part of an overall concept and may be used only in conjunction with the corresponding original components and instruments according to Institut Straumann AG’s instructions and recommendations. Use of products made by third parties, which are not distributed through Institut Straumann AG, in conjunction with the Straumann® Dental Implant System will void any warranty or other obligation, expressed or implied, of Institut Straumann AG. Instructions as to the application of our products take place verbally, in writing, by electronic media or in hands-on trainings corresponding to the state of the art at the time of introduction of the product. The user of Straumann products is responsible for determining whether or not any product is suitable for a particular patient and circumstances. Straumann disclaims any liability, expressed or implied, and bears no responsibility for any direct, indirect, punitive or other damages, arising out of or in connection with any errors in professional judgment or practice in the use or installation of Straumann products. The user is also obliged to study the latest developments of the Straumann® Dental Implant System and their applications regularly. Please note The descriptions contained in this document are not sufficient for immediate use of the Straumann® Dental Implant System. Knowledge of dental implantology and instruction in the handling of the Straumann® Dental Implant System provided by an operator with the relevant experience are always necessary. Availability Some of the products listed in this brochure are not available in all countries. Validity Upon publication of this brochure, all previous versions are superseded. Caution In addition to the caution notes in this basic information, our products must be secured against aspiration when used intraorally. Do not use damaged or blunt instruments. Units per package Unless stated otherwise, there is one unit in each package. Documentation For detailed instructions on the Straumann® Dental Implant System contact your Straumann representative. Copyright and trademarks Straumann documents may not be reprinted or published, in whole or part, without the written authorization of Institut Straumann AG. Straumann® and/or other products and logos from Straumann® that are mentioned here are trademarks or registered trademarks of Straumann Holding AG and/or its affiliates. Definition SLActive® Sand-blasted, Large grit, Acid-etched, chemically active and hydrophilic Definition SLA® Sand-blasted, Large grit, Acid-etched Explanation of the symbols on labels and instruction leaflets Batch code Catalogue number Sterilized using irradiation …min. Lower limit of temperature …max. Upper limit of temperature …max. …min. Temperature limitation Caution: U.S. Federal law restricts this device to sale by or on the order of a licensed dentist. Do not re-use Non-sterile STERILE NON Caution, consult accompanying documents Use by Keep away from sunlight Straumann Products with the CE mark fulfi ll the requirements of the Medical Devices Directive 93/42 EEC 0123 Consult operating instructions Colored warning labels YELLOW = CAUTION Indicates hazards or unsafe handling which might cause minor injury or damage to property ORANGE = WARNING Indicates hazards which might cause serious or fatal injury RED = DANGER Indicates hazards which might cause immediate serious or fatal injury IMPORTANT GUIDELINES 9. Important Guidelines 9. Important GUIDELINES 159 10. Index Abutment Anatomic 48 Cementable 90 for bars 123 CARES 77 Gold, for bridge 67 Gold, for crown 55 LOCATOR® 133 Meso 48 Multi-Base 105 PLAN 45 Temporary 27 Anchorage Cement-retained 6 Screw-retained 6 Auxiliary Modelling aid 55, 67 Polishing aid 150 Scanbody 80 Stabilization pin 119 Connection 4 Healing Abutment Bottle shape 18 Conical 16 Customizable 25 Instrument Holding Key 152 Ratchet 151 SCS Screwdriver 149 Service Instrument for Ratchet 152 Torque Control Device for Ratchet 152 Planning PLAN Set/Abutment 45 Pre-operative 12 Polymer Impression cap 94 Healing Abutment 25 Modelling aid 55, 67 Protective Cap 95 Temporary Abutment 27 Temporary Coping 95 Prosthetics Abutment Overview 8 Prosthetic options 6 Removable overdenture 6, 123, 133 Restoration Final 45, 48, 55, 67, 77, 90, 105, 123, 133 Temporary 27 Soft tissue management 15 Template Drill 13 Thermoplastic drill 14 X-ray 12 Tightening torque 156 10. Index International Headquarters Institut Straumann AG Peter Merian-Weg 12 CH-4002 Basel, Switzerland Phone +41 (0)61 965 11 11 Fsurrounding the abutment. 6. Restoration Prosthetic procedure 5 4 143 Step 4 – Placing the denture caps Place the denture caps w pp ith the black processing males onto the LOCATOR® abutments. Step 5 – Hollowing out the denture base ppHollow out the existing denture base in the areas of the LOCATOR® denture caps. Note Ensure that the denture caps fixed on the abutments do not touch the prosthesis. 6. Restoration Step 6 – Filling the connecting holes ppFill the connecting holes with prosthetic resin from lingual and anchor the caps in the denture (lightcure or selfcuring resin). ppRemove any excess resin after curing and polish the denture. Note If the white LOCATOR® block-out spacer does not completely fill the space between the gingiva and the denture caps, any remaining undercuts must be blocked out to prevent resin flowing under the caps. This can be accomplished by stacking two or more LOCATOR® block-out spacers. Once the resin has cured, remove the denture from the mouth and discard the white LOCATOR® block-out spacers. Prosthetic procedure 7 v v v v v 144 Step 7 – Selecting the replacement males Implant divergence u pp p to 10° for a single implant: 6. Restoration Color Retention blue 0.23 kg pink 1.36 kg clear 2.27 kg ppImplant divergence between 10° and 20° for a single implant: Color Retention red 0.23 kg green 1.36–1.82 kg Note Always start with the lowest retention replacement males. Prosthetic procedure 8 9 10 145 Step 8 – Removing the processing males To place the replacement ma pp les in the denture housing, remove the black processing males from the housing (p. 148). Step 9 – Inserting the replacement male ppInsert the replacement male with the core tool (p. 146). 6. Restoration Step 10 – Inserting the finished denture ppInsert the finished denture and check the occlusion. Prosthetic procedure 146 6. Restoration 6.9.4 LOCATOR® Abutment – Further references 1. Using the LOCATOR® core tool The LOCATOR® core tool is a three-piece multifunction instrument. Gap The tip is used for removing replacement males from the denture caps. To do this, the tip must be unscrewed by two full turns. A gap is visible between the tip and the middle section. The tip is passed in a straight line into the denture cap with a replacement male. The sharp edges of the tip hold the replacement male while it is being removed. The instrument is drawn out of the denture cap in a straight line. To remove the replacement male from the instrument, the tip must be screwed clockwise completely onto the middle section. This activates the loosening pin inside the tip, which releases the replacement male. 147 The middle section of the LOCATOR® core tool is used for inserting replacement males into the denture caps. To do this, the tip is unscrewed. The exposed end of the replacement male is pressed into the denture cap. The replacement male is fixed firmly in the cap when a click is heard. The end (gold-colored) of the LOCATOR® core tool is used by the dental technician for screwing and unscrewing the LOCATOR® abutments to and from the analogs. 2. Determining the implant divergences Snap the LOCATOR® parallel posts onto the LOCATOR® abutments. Use the LOCATOR ® angle measurement guide to determine the angulation of the LOCATOR ® abutments in relation to each other. Hold the angle measurement guide behind the placed parallel posts and read off the angle for each abutment. Note Choose the appropriate LOCATOR® replacement males according to the angulation measured for each abutment. Tie dental floss through the lateral holes of the angle measurement guide to prevent aspiration. 6. Restoration 148 6. Restoration 3. Using the black processing male Both the LOCATOR® female analog and the LOCATOR® denture cap are supplied with a preassembled black processing male. The black processing male functions as a space keeper for the various LOCATOR® replacement males. For the relining of a LOCATOR-anchored overdenture, the LOCATOR® replacement males must be removed from the denture caps and exchanged with black processing males. The black processing males keep the denture in a stable vertical position during the relining procedure. When the relining of the denture is finished, the black processing males are exchanged with the corresponding new LOCATOR® replacement males. 4. Important cleaning instructions The proper cleaning of the LOCATOR®-borne denture and the LOCATOR® abutments is a prerequisite to ensure the long-term performance of both the abutments and the nylon processing inserts. An accumulation of plaque on the abutment that imbeds into the nylon processing insert can abrade, over time, the titanium abutment to a smaller diameter and thus cause it to lose retention. According to the specific situation, the patient might be put on shorter recall appointments to monitor the proper cleaning of the denture and the abutments. 149 7.1 SCS Scre wdri ver The SCS* screwdriver is used for the fixation of the prosthetic parts and healingcomponents. The star shape of the screwdriver tip connects to the top of the healing components and abutment screw heads for safe pick-up and handling. *SCS = Screw Carrying System SCS screwdriver for manual use Article: extra short, short, long Lengths: 15 mm, 21 mm, 27 mm Art. Nos.: 046.400, 046.401, 046.402 Material: Stainless steel 7. Aids and instr uments 7. Aids and instruments 150 7. Aids and instruments 7.2 Polis hing Aid The polishing aid is used during polishing and other lab procedures to protect the abutment’s prosthetic connection and to establish a convenient fixation extension. Art. Nos.: 025.2920, 025.4920 Material: Stainless steel 151 7.3 Ratc het and Torque Contr ol Device The ratchet (Art. No. 046.119) is a two-part lever arm instrument with a rotary knob for changing the direction of force. It is supplied with a service instrument (Art. No. 046.108), which is used to loosen the headed screw. After loosening, the ratchet bolt can be removed from the body of the ratchet. The ratchet gap must be disassembled for cleaning and sterilization. To apply a certain torque when tightening an abutment screw, use the ratchet together with the torque control device (Art. No. 046.049) and the holding key (Art. No. 046.064). Ratchet The ratchet is used in combination with the torque control device to torque in all Straumann abutments and screws (it is the same ratchet used for placing Straumann implants manually). Note The ratchet and service instrument are packaged together. looped end flared part nut directional arrow ratchet disassembled 7. Aids and instruments 152 7. Aids and instruments pin forked end Torque control device Connected to the ratchet, the torque control device is used to measure the value of Ncm (Newton centimeter) applied when inserting Straumann abutments and screws. Service Instrument The Service Instrument is used to assemble and disassemble the ratchet. Holding key The forked end of the holding key can be used to assembleand disassemble the ratchet. The pin can be used to stabilize drivers when abutments and screws are placed (also used for implant placement). fluted end torque scale tear drop 1a 2a 1b 2b 153 Step 1 – Loosening Loosen the ratchet n pp ut with the service instrument or the holding key. 7.4 asse mbling the Ratc het and the Torque Contr ol Device Step 2 – Removing ppUnscrew and remove the internal bolt from the ratchet body. 7. Aids and instruments 3a 3b 4a 4b 154 7. Aids and instruments Step 3a – Insertion Insert the ratchet body i pp nto the torque control device (flared part of the ratchet must be flush with fluted end of torque control device). Step 3b – Insertion ppInsert the internal bolt into the opposite end of the torque control device. Tighten it firmly by hand. Step 4 – Tightening ppTighten the nut of the ratchet with the service instrument or the holding key. Do not overtighten. ppThe ratchet and torque control device are now assembled and ready for use. 1 2 3 155 Step 1 – Insertion and tightening Insert th pp e abutment into the implant. ppTighten the abutment screw by hand using the SCS screwdriver. 7.5 tig htening an ab utment to 35 Ncm Step 2 – Placing the ratchet ppPlace the looped end of the assembled ratchet with the torque control device over the driver handle. The directional arrow must be pointing clockwise (towards the torque bar with tear drop). If not, pull the arrow out, flip it over, and let it snap in. Step 3 – Stabilizing the ratchet ppFor stabilization, put the pin end of the holding key into the coronal hole on the driver handle. 7. Aids and instruments 4 156 Step 4 – Positioning of appropriate Ncm mark Use one h pp and to hold the holding key and use the other hand to hold the torque bar. Grasp only the tear drop and move the torque bar to 35 Ncm mark. Step 5 – Removing the ratchet ppAfter reaching the 35 Ncm mark, return the torque bar to its starting position. ppLift and remove the holding key, the ratchet with torque control device and the driver. Note Proper care and maintenance are important to ensure correct function of the ratchet and torque control device. Always clean and sterilize disassembled. For detailed instructions on how to care for these instruments, please refer to their package inserts. Recommended tightening torques Hand-tight 15 Ncm 15–35 Ncm 35 Ncm Closure screws Healing abutments Temporary copings Copings Temporary abutments Final abutments 7. Aids and instruments 157 Straumann abutments and components are not sterile when delivered. Use the following procedure for sterilization prior to use. Note Parts that have been modified or altered from their original state may require different sterilization procedures. To prevent tension cracks in PMMA products do not use the following: alcohol; UV radiation; sterilization; immersion in liquid for more than one hour; temperatures over 60 °C (140 °F). 8. About Sterilization 8. abo ut sterilization Material Method Conditions Ti, Ti alloy Autoclave, moist heat 134 °C (273 °F) for 18 min PEEK, PEEK with Ti inlay POM Metal alloy Ceramicor® Composition in weight %: Au 60%, Pd 20%, Pt 19%, Ir 1% ZrO2 Dry heat 160 °C (320 °F) for 4 h 158 Disclaimer of liability The Straumann dental implant and other Straumann products are part of an overall concept and may be used only in conjunction with the corresponding original components and instruments according to Institut Straumann AG’s instructions and recommendations. Use of products made by third parties, which are not distributed through Institut Straumann AG, in conjunction with the Straumann® Dental Implant System will void any warranty or other obligation, expressed or implied, of Institut Straumann AG. Instructions as to the application of our products take place verbally, in writing, by electronic media or in hands-on trainings corresponding to the state of the art at the time of introduction of the product. The user of Straumann products is responsible for determining whether or not any product is suitable for a particular patient and circumstances. Straumann disclaims any liability, expressed or implied, and bears no responsibility for any direct, indirect, punitive or other damages, arising out of or in connection with any errors in professional judgment or practice in the use or installation of Straumann products. The user is also obliged to study the latest developments of the Straumann® Dental Implant System and their applications regularly. Please note The descriptions contained in this document are not sufficient for immediate use of the Straumann® Dental Implant System. Knowledge of dental implantology and instruction in the handling of the Straumann® Dental Implant System provided by an operator with the relevant experience are always necessary. Availability Some of the products listed in this brochure are not available in all countries. Validity Upon publication of this brochure, all previous versions are superseded. Caution In addition to the caution notes in this basic information, our products must be secured against aspiration when used intraorally. Do not use damaged or blunt instruments. Units per package Unless stated otherwise, there is one unit in each package. Documentation For detailed instructions on the Straumann® Dental Implant System contact your Straumann representative. Copyright and trademarks Straumann documents may not be reprinted or published, in whole or part, without the written authorization of Institut Straumann AG. Straumann® and/or other products and logos from Straumann® that are mentioned here are trademarks or registered trademarks of Straumann Holding AG and/or its affiliates. Definition SLActive® Sand-blasted, Large grit, Acid-etched, chemically active and hydrophilic Definition SLA® Sand-blasted, Large grit, Acid-etched Explanation of the symbols on labels and instruction leaflets Batch code Catalogue number Sterilized using irradiation …min. Lower limit of temperature …max. Upper limit of temperature …max. …min. Temperature limitation Caution: U.S. Federal law restricts this device to sale by or on the order of a licensed dentist. Do not re-use Non-sterile STERILE NON Caution, consult accompanying documents Use by Keep away from sunlight Straumann Products with the CE mark fulfi ll the requirements of the Medical Devices Directive 93/42 EEC 0123 Consult operating instructions Colored warning labels YELLOW = CAUTION Indicates hazards or unsafe handling which might cause minor injury or damage to property ORANGE = WARNING Indicates hazards which might cause serious or fatal injury RED = DANGER Indicates hazards which might cause immediate serious or fatal injury IMPORTANT GUIDELINES 9. Important Guidelines 9. Important GUIDELINES 159 10. Index Abutment Anatomic 48 Cementable 90 for bars 123 CARES 77 Gold, for bridge 67 Gold, for crown 55 LOCATOR® 133 Meso 48 Multi-Base 105 PLAN 45 Temporary 27 Anchorage Cement-retained 6 Screw-retained 6 Auxiliary Modelling aid 55, 67 Polishing aid 150 Scanbody 80 Stabilization pin 119 Connection 4 Healing Abutment Bottle shape 18 Conical 16 Customizable 25 Instrument Holding Key 152 Ratchet 151 SCS Screwdriver 149 Service Instrument for Ratchet 152 Torque Control Device for Ratchet 152 Planning PLAN Set/Abutment 45 Pre-operative 12 Polymer Impression cap 94 Healing Abutment 25 Modelling aid 55, 67 Protective Cap 95 Temporary Abutment 27 Temporary Coping 95 Prosthetics Abutment Overview 8 Prosthetic options 6 Removable overdenture 6, 123, 133 Restoration Final 45, 48, 55, 67, 77, 90, 105, 123, 133 Temporary 27 Soft tissue management 15 Template Drill 13 Thermoplastic drill 14 X-ray 12 Tightening torque 156 10. Index International Headquarters Institut Straumann AG Peter Merian-Weg 12 CH-4002 Basel, Switzerland Phone +41 (0)61 965 11 11 F


برچسب ها: surrounding the abutment. 6. Restoration Prosthetic procedure 5 4 143 Step 4 – Placing the denture caps Place the denture caps w pp ith the black processing males onto the LOCATOR® abutments. Step 5 – Hollowing out the denture base ppHollow out the existing denture base in the areas of the LOCATOR® denture caps. Note Ensure that the denture caps fixed on the abutments do not touch the prosthesis. 6. Restoration Step 6 – Filling the connecting holes ppFill the connecting holes with prosthetic resin from lingual and anchor the caps in the denture (lightcure or selfcuring resin). ppRemove any excess resin after curing and polish the denture. Note If the white LOCATOR® block-out spacer does not completely fill the space between the gingiva and the denture caps، any remaining undercuts must be blocked out to prevent resin flowing under the caps. This can be accomplished by stacking two or more LOCATOR® block-out spacers. Once the resin has cured، remove the denture from the mouth and discard the white LOCATOR® block-out spacers. Prosthetic procedure 7 v v v v v 144 Step 7 – Selecting the replacement males Implant divergence u pp p to 10° for a single implant: 6. Restoration Color Retention blue 0.23 kg pink 1.36 kg clear 2.27 kg ppImplant divergence between 10° and 20° for a single implant: Color Retention red 0.23 kg green 1.36–1.82 kg Note Always start with the lowest retention replacement males. Prosthetic procedure 8 9 10 145 Step 8 – Removing the processing males To place the replacement ma pp les in the denture housing، remove the black processing males from the housing (p. 148). Step 9 – Inserting the replacement male ppInsert the replacement male with the core tool (p. 146). 6. Restoration Step 10 – Inserting the finished denture ppInsert the finished denture and check the occlusion. Prosthetic procedure 146 6. Restoration 6.9.4 LOCATOR® Abutment – Further references 1. Using the LOCATOR® core tool The LOCATOR® core tool is a three-piece multifunction instrument. Gap The tip is used for removing replacement males from the denture caps. To do this، the tip must be unscrewed by two full turns. A gap is visible between the tip and the middle section. The tip is passed in a straight line into the denture cap with a replacement male. The sharp edges of the tip hold the replacement male while it is being removed. The instrument is drawn out of the denture cap in a straight line. To remove the replacement male from the instrument، the tip must be screwed clockwise completely onto the middle section. This activates the loosening pin inside the tip، which releases the replacement male. 147 The middle section of the LOCATOR® core tool is used for inserting replacement males into the denture caps. To do this،  

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to the inner part of the protective cap and cement it onto the abutment. Note Use temporary cement in order to remove the temporary restoration in due time. Protective caps must not be kept longer than 28 days in the mouth. 1a 2 1b 98 Lab procedure 6. Restoration Step 2 – Preparation Fabricate the master c pp ast in a conventional manner (see instructions in chapter 5, p. 34). ppModel a full anatomical wax-up for optimal esthetic planning. Use the corresponding burn-out coping as a basis for this wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the restoration. Step 1 – Fabricating the master cast ppClick the corresponding analog in the impression. Note Ensure that the color code of the analog corresponds to the color code of the impression cap. The white ring on the abutment indicates the abutment height (AH). It corresponds to the white arrowon top of the impression cap and the white clicking mechanism inside of the impression cap. Lab procedure 3 6. Restoration 99 Step 3 – Customizing ppDepending on the individual situation, height adaptations can be made without harming the anti-rotational grooves. ppIndividualize the abutment portion of the analog according to the individual situation. ppFabricate a grinding template for the practitioner. This will enable the precise transfer of the individualization into the mouth of the patient. Note To ensure proper stability and retention of the restoration, a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. Lab procedure 4c 4d 4a 4b 100 6. Restoration Step 4 – Fabricating the crown Select the burn-out c pp oping and place it on the analog. ppFabricate the superstructure on the (modified) abutment using standard modeling methods. ppCheck the wax-up with the silicone key. ppShorten it, if necessary. Lab procedure 5a 5b 5c 6. Restoration 101 Step 5 – Casting and veneering ppCast the framework using the standard casting methods. ppAdjust the framework so that it can be attached to the analog. Remove the clamping ring using a circular motion. Do not harm the rotational faces nor the exact margin fit. ppCheck the spatial conditions with the silicone key. ppVeneer the superstructure. Lab procedure 1 102 6. Restoration Step 1 – Final insertion Remove the temporary restoration i pp n a conventional manner. ppIf necessary, do the required customization of the abutment by using the reduction coping from the dental technician. ppClean the abutment thoroughly and remove all remaining temporary cement. ppCement the crown to the abutment. ppRemove superfluous cement. Prosthetic procedure Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. 2b 1 2a 103 Option B: Impression taking on implant level Take the impression according to the instructions in chapter 5, p. 34. Lab procedure 6. Restoration Step 1 – Abutment insertion Select the correct s pp ize of the cementable abutment by using the PLAN set (see instructions in chapter 6.1, p. 45). ppHand-tighten the abutment on the analog in the master cast. Step 2 – Customizing ppMake height adaptations according to the individual situation without harming the anti-rotational grooves. Note The ensure proper stability and retention of the restoration, a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. Follow the corresponding steps as described for the impression on abutment level (p. 98). ppApply the transfer aid and attach it to the adjacent teeth. ppDeliver the customized abutment with the attached transfer aid and the final restoration to the doctor’s office for insertion. Lab procedure 1 104 6. Restoration Step 1 – Final insertion Position the cleaned abutment i pp n the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppInsert the abutment together with the transfer aid for a better orientation. ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This later allows removal of the abutment. ppCement the crown to the abutment. ppRemove superfluous cement. Prosthetic procedure Prosthetic procedure The final restoration is delivered to the doctor‘s office on the master cast. 88 88 105 6.7 Multi -Base Abutment Intended use ppScrew-retained bridges ppBar-retained implant-borne dentures in the mandible and maxilla Characteristics Simple ppFlexible impression taking on implant or abutment level ppEasy choice of components thanks to color-coding ppHighly flexible due to 30° cone and low occlusal height Reliable ppCrossFit™ Connection ppPerfect fit due to prefabricated components ppProper fit of abutment level impression cap verified by clear-cut response Note Do not use the multi-base abutment for single-tooth restorations. Use new occlusal screws for the final insertion of the bar. Prosthetic procedure: p. 107–111, 120, 122 Lab procedure: p. 112–119, 121 6. Restoration GH D 1 mm 2,5 mm 4 mm 106 D = Diameter GH = Gingiva Height Multi-Base Abutment, angled 25° 6.7.1 Multi-Base abutment coding Multi-Base Abutment, straight Narrow CrossFit™ Regular CrossFit™ Diameter (D) 3.5 mm (blue coding) 4.5 mm (yellow coding) 4.5 mm (grey coding) 6.5 mm (brown coding) Narrow CrossFit™ Regular CrossFit™ 6. Restoration 1 mm 2.5 mm 4 mm 1a 1b 107 Step 1 – Abutment insertion Select the appropriate s pp ize of the multi-base abutments using the PLAN set (see instructions in chapter 6.1, p. 45). Option A: Impression taking on abutment level – Prosthetic procedure ppClean and dry the interior of the implants thoroughly. ppPosition the abutments in the implants. Tighten them to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). Note Do not modify the abutments. Prosthetic procedure 6. Restoration 2a 2b 108 Prosthetic procedure Step 2 – Impression taking on abutment level Click the impression caps o pp r screw the impression posts onto the abutments. Check the proper fit of the impression cap by rotating it on the abutment. ppTo ensure accuracy of the impression procedure, do not damage the inner aspect of the impression cap. ppTake the impression using an elastomeric impression material (polyvinyl siloxane or polyether rubber). Note Due to its low tensile strength, hydrocolloid materials are not suitable for this application. 6. Restoration 3c 3a 3b 109 Prosthetic procedure Using the temporary coping Step 3 – Preparation Mount the temporary c pp opings on analogs. ppMark the appropriate heights according to the individual situation and shorten the copings as necessary. ppSandblast the copings and coat them with opaquer to avoid the titanium showing through. ppScrew the copings onto the abutments in the patient’s mouth and seal the screw channels (e.g. with cotton). Temporary coping Protective cap Chairside temporization of the abutments 6. Restoration 4a 4b 4c 110 Prosthetic procedure Step 4 – Creating the provisional Use a standard technique to f pp abricate the provisional (e.g. prefabricated crown form or vacuum-formed sheet technique as shown here). The retention elements ensure proper mechanical bonding of the veneering material to the coping. ppRemove excess acrylic, reopen the screw channel and finish the temporary restoration. 6. Restoration 5 3 111 Prosthetic procedure 6. Restoration Step 5 – Inserting the provisional Clean the polished temporary r pp estoration, place it on the abutments and tighten the screw to 15 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppCover the screw head with absorbent cotton or gutta- percha and seal the screw channel with temporary veneering material (e.g. composite). Note Keep the temporary restoration out of occlusion. Using the protective cap Step 3 – Mounting the protective caps ppHand-tighten the screws of the protective caps with the SCS screwdriver on the abutments. Note Do not keep protective caps in the patient’s mouth longer than 28 days. 1a 1b 2 112 Lab procedure Note Ensure that the color code of the analogs corresponds to the color code of the impression caps or posts. Impression material can get under the cap. In this case, remove the remains prior to repositioning the analogs. Step 1 – Fabricating the master cast Click the corresponding analogs i pp nto the impression or reposition and fix the analog in the impression using the guide screw. Step 2 – Preparation ppFabricate the master cast in a conventional manner (see instructions in chapter 5, p. 34). ppModel a full anatomical wax-up for optimal esthetic planning. Use the corresponding gold or burn-out copings as a basis for the wax-up (here the procedure using a gold coping is shown). ppYou can define the optimal shape of the restoration by making a silicone key over the full wax-up. 6. Restoration Lab procedure for bridge restoration 3a 3b 3c 113 Lab procedure 6. Restoration Step 3 – Fabricating the bridge Place the gold copings on th pp e analogs and hand-tighten the occlusal screws using the SCS screwdriver. Note When using burn-out copings, do not over-tighten the copings. This precaution prevents the wax framework from undergoing excessive stress while loosening the occlusal screw after the wax modellation. ppShorten the modelling aids to the height of the occlusal plane according to the individual situation. Working with the modelling aid ensures a clean and sharp-edged finish of the screw channel. ppFabricate the superstructure on the abutments using standard modelling methods. ppMake sure that the wax layer on the abutment is sufficiently thick (at least 0.7 mm). Do not cover the delicate margin of the copings with wax. 3d 4a 114 Lab procedure 6. Restoration Check the spatial conditions b pp efore casting the bridge framework with the silicone key of the wax-up. ppCheck the wax-up with the silicone key. Step 4 – Investment ppCheck that the wax framework of the bridge is absolutely tension-free before investing the framework. This is accomplished according to commonly known bridge techniques. ppInvest the bridge framework according to standard methods without using wetting agents. 4b 4c 4d 115 Lab procedure 6. Restoration Note In order to avoid overflow of the cast-on alloy, clean the copings thoroughly prior to investment (removal of wax particles, insulating agents with a cotton pellet or brush moistened with alcohol). Ensure that there is no wax on the delicate margin. The use of investment materials for rapid heating methods (speed investment materials) is not recommended. When processing the investment material, follow the manufacturer’s instructions. Observe the recommended mixing ratio and preheating time exactly. Make sure the screw channel and the internal configuration of the copings are filled with investment material from the bottom to the top in order to avoid air bubbles (see graphic). 5b 5a 116 Lab procedure Step 5 – Casting and veneering Cast and devest the framework u pp sing standard methods (see also instructions in chapter 6.4.1, p. 72–73). Note The long term success of the prosthetic work depends on the accurate fit of the restoration. The entire procedure will have to be repeated, if casting errors occur, similar to the examples on p. 64. ppCheck the spatial conditions with the silicone key. 6. Restoration ppControl for tension-free fitting on the master cast by applying the Sheffield test. If the bridge is not tension-free and wiggles, cut the bridge and resplint it tension-free. Note In order to take the bridge off the master cast, all occlusal screws need to be removed first. 5c 5d 117 Lab procedure 6. Restoration Do an additional try-pp on of the tension-free fit of the framework in the patient’s mouth. ppVeneer the superstructure. 1a 1b 118 6. Restoration Lab procedure Step 1 – Fabricating the master cast Click the corresponding analogs i pp nto the impression or reposition and fix the analog in the impression using the guide screw. Lab procedure for bar restoration Note Ensure that the color code of the analogs corresponds to the color code of the impression caps or posts. Impression material can get under the cap. In this case, remove the remains prior to repositioning the analogs. 2 3 6. Restoration 119 Step 2 – Preparation ppBefore placing the copings we recommend mounting the occlusal screws onto the SCS screwdriver. After this step place the occlusal screws into the copings for bars. ppMount the copings onto the abutment and hand-tighten the occlusal screws using the SCS screwdriver. Step 3 and following steps – Fabrication of the bar ppFollow the steps described on p. 125–130 for the fabrication of the soldered gold bar or laser-welded titanium bar. Note Always use stabilization pins for the soldering of a gold bar. Lab procedure 1 120 6. Restoration Prosthetic procedure Step 1 – Final insertion Remove the t pp emporary restoration. ppClean the abutments thoroughly. ppCheck the tension free fit of the bridgework or bar before tightening it in the patient’s mouth. Do not insert the bridge or bar in case of movements due to tensions in the bridgework or bar. ppTighten the occlusal screws to 15 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppFor bridgework, close the SCS configuration of the screws with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the bridge work if needed. Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. 1a 1b 6. Restoration 121 Step 1 – Abutment insertion ppSelect the correct size of the multi-base abutments by using the PLAN set (see instructions in chapter 6.1, p. 45). ppHand-tighten the abutments on the analogs in the master cast. Step 2 and following steps – Fabrication of the bridge/bar ppFollow the corresponding steps described on p. 112 for the fabrication of the bridge. ppFollow the corresponding steps described on p. 125–130 for the fabrication of the soldered gold bar or laser- welded titanium bar. Note Always use stabilization pins for the soldering of a gold bar. Option B: Impression taking on implant level Take the impression according to the instructions in chapter 5, p. 34. Lab procedure for bridge and bar restoration Lab procedure 1 122 6. Restoration Prosthetic procedure Step 1 – Final insertion Position the cleaned abutments i pp n the implants. Tighten them to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppCheck the tension-free fit of the bridgework/bar before tightening it in the patient’s mouth. Do not insert the bridge/bar in case of movement due to tensions in the bridgework/bar. ppTighten the occlusal screws to 15 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppFor bridgework, close the SCS configuration of the screws with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the bridge work if needed. Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. 88 88 123 6.8 Abutment for bars Intended use ppBar-retained implant-borne dentures in the mandible and maxilla ppStabilisation and primary splinting of the implants Characteristics Simple ppEffective one piece solution provides uncomplicated bar restorations for standard situations. ppA 15° cone allows implant divergence flexibility up to 30°. ppAbutment can be easily shortened due to 7 mm distance from soft tissue level. Reliable ppFlexible design for soldered and laser-welded bar constructions with prefabricated components Note Use a new basal screw for the final insertion of the abutment. 6. Restoration Lab procedure: p. 120–131 Prosthetic procedure: p. 132 1 2a 2b 124 Step 1 – Fabricating the master cast Fabricate the master cast u pp sing standard methods and type 4 dental stone (DIN 6873). 6. Restoration 6.8.1 Abutment for bars – Lab procedure Step 2 – Preparation ppPlace the abutment for bars on the analogs and hand- tighten the screw using the SCS screwdriver. Lab procedure 3 4a 4b 125 Step 3 – Placing the bar segments Place the individual b pp ar segments between the abutment units. Note The space between the bar and the gingiva must be at least 2 mm. To achieve a good joint, the gap between the abutment and the bar should be as small as possible. 6. Restoration Soldered gold bar (For the lab procedure of a laser-welded titanium bar continue at step 3 on p. 129.) Step 4 – Fixation of the bar segments ppUse a residue-free burn-out plastic to fix the bar segments to the abutments. Note Do not cover the basal screws. Lab procedure 5 126 6. Restoration Step 5 – Removing the bar framework Carefully remove the bar f pp ramework after loosening the screws. ppPlace the framework on the polishing aids and handtighten the screws. The polishing aids ensure that the abutments are anchored accurately in the soldering investment during soldering. Lab procedure 6a 6b 6c 127 Step 6 – Soldering the bar Note To prevent possible distortion of the bar through unevenpreheating with the flame, preheat the soldering investment to 500–600 ºC (932–1112 ºF) in a preheating furnace. After preheating, solder th pp e invested bar according to standard procedure. ppOnce soldering is complete, cool down the investment to room temperature. ppDevest and clean the bar in an ultrasonic bath. ppRemove the oxides and soldering flux residues in an acid bath. Note Do not sandblast the framework. 6. Restoration ppCheck the fit. Note Stress-free repositioning of the bar on the implant analogs should be possible without securing it with the screws. Lab procedure 6d 6e 128 Shorten the bar in height i pp f necessary and polish it. ppSend the finished bar with 4 new basal screws to the doctor’s office. Note At this point the screws used for soldering are extremely oxidized. Therefore, do not use them to secure the bar in the mouth. See p. 132 for the prosthetic procedure. 6. Restoration Lab procedure 3a 3b 129 Step 3 – Placing the bar segments Fit the bar segments t pp o the master cast, allowing for a certain gap that will be offset by the addition of titanium (see graphic 3b). Note The space between the bar and the gingiva must be at least 2 mm. 6. Restoration Laser-welded titanium bar Lab procedure 4a 4b 4c 130 ppCheck the fit. Step 4 – Welding of the segments ppWeld the segments together with adequate argon gas rinsing. 6. Restoration ppIf necessary, shorten the height of the bar and polish it. Note Stress-free repositioning of the bar on the implant analogs should be possible without securing it with the screws. Lab procedure 4d 131 Send the finished b pp ar with 4 new basal screws to the doctor’s office. Note At this point the screws used for soldering are extremely oxidized. Therefore, do not use them to secure the bar in the mouth. 6. Restoration Lab procedure 1 132 Step 1 – Final insertion Position the cleaned bar in th pp e implants. Ensure the stressfree repositioning of the bar on the implants. ppTighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). 6. Restoration 6.8.2 Abutment for bars – Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. Prosthetic procedure 88 88 133 6.9 LOCATOR® Abutment Intended use ppDentures retained by implants in the mandible and maxilla Characteristics Simple ppDivergence compensation up to 40° between two implants ppMinimum component height for limited occlusal space Reliable ppDual retention for optimal abutment-denture connection ppExcellent long-term performance due to high wear resistance of components The LOCATOR® components are a registered trademark of Zest Anchors, Inc. Manufacturer: Zest Anchors, Inc. Escondido, CA 92029 USA 0473 6. Restoration Lab procedure: p. 134–137 Prosthetic procedure: p. 138–145 1 2 134 6.9.1 LOCATOR® Abutment – Lab procedure Option A: Master cast from implant level impression Take the impression according to the instructions in chapter 5, p. 34. Step 1 – Selecting the abutment height ppSelect the height of the LOCATOR® abutment by determining the height of the replica gingiva at its highest point on the master cast. The top margin of the abutment should be 1 mm above the mucosa. Note Inserting the prosthesis is easier for the patient when the LOCATOR ® abutments are on the same horizontal level. Step 2 – Abutment insertion ppScrew the abutment hand-tight into the implant analog using the LOCATOR® driver. 6. Restoration Lab procedure 1 2 135 Step 1 – Female analog insertion ppInsert the LOCATOR® female analogs into the LOCATOR® impression copings. Step 2 – Fabricating of the master cast ppFabricate the master cast using standard methods and type 4 dental stone (DIN 6873). Option B: Master cast from abutment level impression For abutment level impression-taking, special LOCATOR® analogs are used. The selection of the LOCATOR® abutments has already been made by the prosthodontist. 6. Restoration Lab procedure 1 2 136 Construction of an overdenture with LOCATOR® denture housings You can construct a new overdenture or upgrade an already existing and well-functioning overdenture with LOCATOR® components. Option A: Construction of a new overdenture Step 1 – Placing the white block out spacers and denture caps Place one white block-pp out spacer over each abutment. ppPlace the denture caps with the black processing males onto the LOCATOR® abutments, or the LOCATOR® analogs in the master cast. Step 2 – Overdenture construction ppConstruct the overdenture according to the standard procedure, adding the LOCATOR® denture housing. ppReturn the completed overdenture to the doctor’s office with the black processing males still in place. 6. Restoration Lab procedure 1 2 3 137 Option B: Upgrading an existing overdenture Step 1 – Placing the white block out spacers and denture caps Place one white block-pp out spacer over each abutment. ppPlace the denture caps with the black processing males onto the LOCATOR® abutments, or the LOCATOR® analogs in the master cast. Step 2 – Hollowing out the denture base ppHollow out the existing denture base in the areas of the LOCATOR® denture caps. Step 3 – Overdenture rebase pp Rebase the overdenture according to the standard procedure, adding the LOCATOR® denture housing. ppReturn to the dentist the completed overdenture with the black processing males still in place. 6. Restoration Lab procedure 1 138 6.9.2 LOCATOR® Abutment – Prosthetic procedure (standard) Impression taking 6. Restoration Step 1 – Selecting the abutment height Make sure the top of th pp e implant is not covered by hard or soft tissue. Note It is imperative that all hard and soft tissue is removed from the implant shoulder to ensure correct seating of the LOCATOR ® abutment. ppSelect the height of the LOCATOR® abutment by determining the height of the gingiva at its highest point in the patient‘s mouth. Choose the corresponding abutment tissue cuff height or the next closest higher size available. Note Prosthesis insertion is easier for the patient if the LOCATOR® abutments are on the same horizontal level. Option B: Abutment level impression taking For abutment level impression taking, special LOCATOR® impression components are used. As a consequence, abutment heights are selected by the doctor on the patient. Prosthetic procedure 2 3 4 6. Restoration 139 Step 2 – Abutment insertion ppScrew the abutment into the implant hand-tight, using the LOCATOR® driver. ppTighten the abutment to 35 Ncm using the ratchet along with the torque control device (see instructions in chapter 7.5, p. 155) and the LOCATOR ® driver (p. 146). Step 3 – Placing spacer and impression coping ppPlace a white block-out spacer ring on each abutment. The spacer ring is used to block out the area surrounding the abutment. ppPlace the LOCATOR® impression copings on the LOCATOR ® abutments. Step 4 – Impression taking ppTake the impression utilizing the mucodynamic technique (vinyl polysiloxane or polyether rubber). ppSend the impression to the dental laboratory. Prosthetic procedure 1 v v v v v 140 The dental technician returns the completed LOCATOR® overdenture to the doctor’s office for final placement. The finished denture is delivered with the black processing males still in place. Step 1 – Selecting the replacement males Implant divergence u pp p to 10° for a single implant: 6. Restoration Final restoration Color Retention blue 0.23 kg pink 1.36 kg clear 2.27 kg ppImplant divergence between 10° and 20° for a single implant: Color Retention red 0.23 kg green 1.36–1.82 kg Note Always start with the lowest retention replacement males ( p. 146). Prosthetic procedure 2 3 4 6. Restoration 141 Step 2 – Removing the processing males ppRemove the black processing males from the housing ( p. 146). Step 3 – Inserting the replacement male ppInsert the replacement male with the core tool (p. 146). Step 4 – Inserting the finished denture ppInsert the finished denture and check the occlusion. Prosthetic procedure 2 3 1 142 Step 1 – Selecting the abutment height Make sure the top o pp f the implant is not covered by the gingiva. ppSelect the height of the LOCATOR® abutment by determining the height of the gingiva at its highest point. The upper cylindric border should be 1 mm or more (next higher size available) above the mucosa. Note Prosthesis insertion is easier for the patient if the LOCATOR® abutments are on the same horizontal level. Step 2 – Inserting the abutment ppScrew the abutment into the implant by hand using the LOCATOR® driver. ppTighten the abutment to 35 Ncm using the ratchet along with the torque control device (see instructions in chapter 7.5, p. 155) and the LOCATOR ® driver attached (p. 146). 6.9.3 LOCATOR® Abutment – Prosthetic procedure (chairside) For an already existing and well-functioning overdenture, the LOCATOR® system can be used in a chair-side procedure. Step 3 – Placing the block-out spacer ppPlace a white block-out spacer ring on the abutments. The spacer is used to block out the area 
برچسب ها: to the inner part of the protective cap and cement it onto the abutment. Note Use temporary cement in order to remove the temporary restoration in due time. Protective caps must not be kept longer than 28 days in the mouth. 1a 2 1b 98 Lab procedure 6. Restoration Step 2 – Preparation Fabricate the master c pp ast in a conventional manner (see instructions in chapter 5، p. 34). ppModel a full anatomical wax-up for optimal esthetic planning. Use the corresponding burn-out coping as a basis for this wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the restoration. Step 1 – Fabricating the master cast ppClick the corresponding analog in the impression. Note Ensure that the color code of the analog corresponds to the color code of the impression cap. The white ring on the abutment indicates the abutment height (AH). It corresponds to the white arrowon top of the impression cap and the white clicking mechanism inside of the impression cap. Lab procedure 3 6. Restoration 99 Step 3 – Customizing ppDepending on the individual situation، height adaptations can be made without harming the anti-rotational grooves. ppIndividualize the abutment portion of the analog according to the individual situation. ppFabricate a grinding template for the practitioner. This will enable the precise transfer of the individualization into the mouth of the patient. Note To ensure proper stability and retention of the restoration، a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. Lab procedure 4c 4d 4a 4b 100 6. Restoration Step 4 – Fabricating the crown Select the burn-out c pp oping and place it on the analog. ppFabricate the superstructure on the (modified) abutment using standard modeling methods. ppCheck the wax-up with the silicone key. ppShorten it، if necessary. Lab procedure 5a 5b 5c 6. Restoration 101 Step 5 – Casting and veneering ppCast the framework using the standard casting methods. ppAdjust the framework so that it can be attached to the analog. Remove the clamping ring using a circular motion. Do not harm the rotational faces nor the exact margin fit. ppCheck the spatial conditions with the silicone key. ppVeneer the superstructure. Lab procedure 1 102 6. Restoration Step 1 – Final insertion Remove the temporary restoration i pp n a conventional manner. ppIf necessary، do the required customization of the abutment by using the reduction coping from the dental technician. ppClean the abutment thoroughly and remove all remaining temporary cement. ppCement the crown to the abutment. ppRemove superfluous cement. Prosthetic procedure Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. 2b 1 2a 103 Option B: Impression taking on implant level Take the impression according to the instructions in chapter 5، p. 34. Lab procedure 6. Restoration Step 1 – Abutment insertion Select the correct s pp ize of the cementable abutment by using the PLAN set (see instructions in chapter 6.1،  

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abutments indicate gingiva height), axial alignment and screw axis of the potential restoration. Lab procedure Prosthetic procedure 47 6.1.3 Cleaning and sterilizing PLAN abutments Clean the PLAN abutments thoroughly with water o pp r ethanol after intra-oral use. ppAfter cleaning, moist-heat-sterilize (autoclave) PLAN abutments 18 minutes at 134 °C (273 °F). ppRefer to the manufacturer’s specifications for the heat-sterilization device. Note Do not sterilize PLAN abutments more than 20 times. Do not g-sterilize PLAN abutments. Do not sterilize the cassette or its components. 6. Restoration Prosthetic procedure 88 88 48 6.2 Anat omic (and mes o) Abutment Intended use ppCement-retained restorations Characteristics Simple ppLess grinding necessary due to prepared mucosa margins ppAdaptation to natural soft tissue contour due to prepared mucosa margins in different heights ppOval shape resembles emergence profile of a natural tooth Reliable ppCrossFit™ Connection Note Not suitable for direct ceramic veneering. A minimum height of 3 mm above the mucosa margin of the abutment must be maintained in order to maintain proper stability of the abutment. The cement margin must not be more than 2 mm below the mucosa. Use a new basal screw for the final insertion of the abutment. 6. Restoration Lab procedure: p. 49–53 Prosthetic procedure: p. 54 1a 1b 1c 49 6.2.1 Anatomic (and Meso) Abutment – Lab procedure The following case describes the fabrication of a cement-retained single crown by using the anatomic abutment. 6. Restoration Lab procedure Step 1 – Fabricating the master cast and wax-up Fabricate the master cast i pp ncluding a gingiva mask with the corresponding implant analog (see instructions in chapter 5, p. 34). ppFor optimal esthetic planning, model a full anatomical wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the customized abutment. 2a 2b 50 Step 2 – Preparing the Anatomic or Meso Abutment The anatomic a pp butment and the meso abutment (p. 51) consist of titanium and can be modified as required. Note To maintain proper stability of the abutment, a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. 6. Restoration Lab procedure ppThe anatomic abutment after modification. 2c 2d 2e 51 If the anatomic abutment does not fit your individual demands or if you prefer grinding the mucosa margins yourself, you can use the meso abutment. The processing of the meso abutment corresponds to the one of the anatomic abutment. 6. Restoration Lab procedure 3 52 Step 3 – Fabricating the superstructure Fabricate the superstructure on the modified abutment using the standard modelling, casting and veneering methods. Place the modified abutment o pp n the polishing aid/analog and hand-tighten the screw using the SCS screwdriver. ppWax an individual resin cap onto the abutment. ppContour a wax model according to the anatomical circumstances of the individual cast. ppCheck the wax-up with the silicone key. 6. Restoration Lab procedure 4a 4b 53 Step 4 – Casting and veneering Cast the framework using th pp e standard casting methods. ppVeneer the superstructure. 6. Restoration Lab procedure ppCheck the framework with the silicone key before veneering. 54 6. Restoration 6.2.2 Anatomic Abutment – Prosthetic procedure Step 2 – Final insertion Position the cleaned abutment i pp n the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. ppCement the superstructure to the abutment. ppRemove superfluous cement. The final restoration is delivered to the doctor’s office on the master cast. Step 1 – Preparation ppRemove the healing cap or temporary restoration. ppRemove the superstructure from the master cast and unscrew the abutment from the analog. ppClean and dry the interior of the implant and the abutment thoroughly. Prosthetic procedure 88 88 55 6.3 Gold Abutment for cr own Intended use ppScrew-retained or cement-retained crowns ppCement-retained bridges via mesostructure (custom abutment technique) ppTelescopic crowns and telescopic bridges Characteristics Simple ppEasy wax-up and protection of the screw channel due to modelling aid (burn-out polymer) ppEasy-to-achieve esthetics due to individual contouring of the emergence profile and adaptation to the margin of the gingival contour Reliable ppSuperfluous cement easily removable by raising the cement margin using an individually designed mesostructure ppCrossFit™ Connection Note Not suitable for direct splinting with other gold abutments. For screw-retained bridges the gold abutment for bridge must be used (see instructions in chapter 6.4, p. 67). Use a new basal screw for the final insertion of the abutment. Do not shorten the gold abutment for crown by more than 1.5 mm. 6. Restoration Lab procedure: p. 56–65 Prosthetic procedure: p. 66 1a 1b 1c 56 6.3.1 Gold Abutment for crown – Lab procedure The following case describes the fabrication of a cement-retained single crown by utilizing the custom abutment technique. Step 1 – Fabricating the master cast and wax-up Fabricate the master cast i pp ncluding a gingiva mask with the corresponding implant analog (see instructions in chapter 5, p. 34). 6. Restoration ppFor optimal esthetic planning, model a full anatomical wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the customized abutment. Lab procedure 2c 2a 2b 2d 57 Step 2 – Preparing the Gold Abutment Place the gold abutment o pp n the analog and hand-tighten the screw using the SCS screwdriver. 6. Restoration ppShorten the modelling aid to the height of the occlusal plane according to the individual circumstances. Working with the modelling aid ensures a clean and sharp-edged finish of the screw channel. ppAttach the gold abutment to the polishing aid for easier handling during manipulation outside of the model. Lab procedure 3d 3a 3b 3c 58 Step 3 – Wax modelling Contour a wax-up shape a pp ccording to the individual anatomical situation. The silicone key shows the exact space for the cement-retained crown, which will be made over the customized abutment. Note The picture displays the optimal configuration of a customized abutment, showing an ideal emergence profile. This configuration ideally adapts the crown contours to the margin of the gingival contour. For reasons of hygiene, the cement margin must not be more than 2 mm below the gingival level. 6. Restoration ppMake sure that the wax layer on the abutment is sufficiently thick (at least 0,7 mm). Do not cover the delicate margin of the abutment with wax. Lab procedure ppCheck the wax-up with the silicone key. 4 59 Step 4 – Investment Invest the customized abutment a pp ccording to standard methods without using wetting agents. Note In order to avoid overflow of the cast-on alloy, thoroughly clean the abutment prior to investment (removal of wax particles, insulating agents with a cotton pellet or brush moistened with alcohol). Always do the cast with the modelling aid. Otherwise, the dental casting alloy will not or only too thinly flow out at the upper coping rim. Ensure that there is no wax on the delicate margin. The use of investment materials for rapid heating methods (speed investment materials) is not recommended. When processing the investment material, follow the manufacturers’ instructions. Observe the recommended mixing ratio and preheating time exactly. 6. Restoration Lab procedure 5b 5a 5c 60 Step 5 – Casting and devestment ppCast the customized abutment. ppGently devest the customized abutment with ultrasound, water jet, pickling acid or a glass fiber brush. Note For the devestment of the gold abutment with sandblasting (maximum pressure: 2 bars; maximum alumina particle size: 50 μm), the inner configuration has to be protected from infiltration with sand with the polishing aid. ppThe wax-fixed polishing aid allows better fixation and protects the pre-polished part of the gold abutment. 6. Restoration Lab procedure 5e 5d 61 The gold a pp butment after sandblasting. Note Do not sandblast the inner configuration of the gold abutment. 6. Restoration Lab procedure 6a 6b 7a 62 Step 6 – Polishing After trimming, polish the finished c pp ustomized abutment. ppThe customized abutment is now ready for the fabrication of the cement-retained single crown. 6. Restoration Lab procedure Step 7 – Fabricating the cement-retained single crown ppBlock out the screw channel and wax the framework directly over the customized abutment. ppThe silicone key shows the spatial relations for the restoration. 7b 7c 63 Cast the framework in the conventional ma pp nner. After trimming the cast, the metal crown fits precisely on the customized abutment. 6. Restoration Lab procedure ppThe silicone key shows the spatial relations for veneering. ppVeneer the superstructure. 64 6. Restoration Lab procedure Note The long-term success of the prosthetic work depends on the accurate fit of the restoration. The entire procedure has to be repeated if… p … trimming through the cast-on alloy prohibits the Ceramicor®surface from being covered with ceramic veneering material (Ceramicor® is a non-oxidizing alloy and does not allow ceramic bonding). Ground down to abutment level Failed casting Casting beads and overflow of alloy … the cast-pp on gold did not flow out entirely. pp…intruded casting metals and casting pearls cannot be removed from the connection part of the gold abutment. Casting errors and incorrect handling 6. Restoration 65 Lab procedure Using alloys with castable Ceramicor® components Ceramicor® is only suitable for cast-on procedures Ceramics can not be bonded directly to cast-on Cermicor® components as this alloy does not form bonding oxides. When selecting the casting alloy, ensure that it is compatible with the high-fusing alloy of the Ceramicor® components. The melting range of the casting alloy must not exceed a liquidus temperature of 1350 °C/2462 °F. Ceramicor® must not be cast on with base metal casting alloys because gold in combination with nickel or cobalt destroys the components. Suitable dental casting alloys ppHigh noble alloys ppPrecious metal alloys with a minimum content of gold and platinum group metals of 25% ppPalladium-based alloys with a minimum content of palladium of 50% ISO standard alloy types Alloy types according to the following ISO standards are suitable for cast-on procedures to the prefabricated Cermicor® component: ppISO standard 9693 ppISO standard 1562 ppISO standard 8891 Note The alloy manufacturer’s recommendation must be followed. Due to diffusion at the alloy and the cast-on coping interface, components made from an unsuitable alloy may form phases with low-strength, reduced corrosion resistance or a lower melting range. Ceramicor® is a registered trademark of Cendres & Métaux SA (Biel-Bienne, Switzerland). 66 6. Restoration 6.3.2 Gold Abutment for crown – Prosthetic procedure Step 1 – Preparation Remove the healing cap or t pp emporary restoration. ppRemove the superstructure from the master cast and unscrew the abutment from the analog. ppClean and dry the interior of the implant and the abutment thoroughly. Option B: Cement-retained crown ppPosition the cleaned abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the customized abutment in case a crown replacement is required. ppCement the crown to the mesostructure. ppRemove superfluous cement. Step 2 – Final insertion Option A: Screw-retained crown ppPosition the cleaned abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the customized abutment in case a crown replacement is required. The final restoration is delivered to the doctor’s office on the master cast. Note The figure displays the optimal configuration of a customized abutment, showing an ideal emergence profile. This configuration ideally adapts the crown contours to the margin of the gingival contour. For reasons of hygiene, the cement margin must not be more than 2 mm below the gingival level. Prosthetic procedure 88 88 67 6.4 Gold ab utment for bridge Intended use ppScrew-retained bridges ppScrew-retained customized bars Characteristics Simple ppEasy wax-up and protection of the screw channel due to modelling aid (burn-out polymer) ppEasy-to-achieve esthetics due to individual contouring of the emergence profile and adaptation to the margin of the gingival contour Reliable ppNo cement gap ppOne-screw solution Note Not suitable for single crowns. For single crowns the gold abutment for crown must be used (see instructions in chapter 6.3, p. 55). Use a new basal screw for the final insertion of the abutment. Do not shorten the gold abutment for bridge by more than 2.5 mm. 6. Restoration Lab procedure: p. 68–75 Prosthetic procedure: p. 76 1b 1a 1c 68 Step 1 – Fabricating the master cast and wax-up Fabricate a master cast i pp ncluding a gingiva mask with the corresponding analogs (see instructions in chapter 5, p. 34). 6. Restoration 6.4.1 Gold abutment for bridge – Lab procedure The following case describes the planning of a screw-retained bridge. ppFor optimal esthetic planning, model a full anatomical wax-up. ppMake a silicone key over the full anatomical wax-up in order to define the optimal shape of the customized bridge. Lab procedure 2b 2a 2c 69 Step 2 – Preparing the gold abutments Place the gold abutments f pp or bridge on the analogs and hand-tighten the screws using the SCS screwdriver. 6. Restoration Lab procedure ppTo avoid a deformation of the conical design of the connection it is highly recommended to always attach the gold abutment to the polishing aid while working outside of the model. ppShorten the modelling aids to the height of the occlusal plane according to individual circumstances. Working with the modelling aid ensures a clean and sharp-edged finish of the screw channel. 3a 3b 70 Step 3 – Wax modelling Contour a wax-up shape a pp ccording to the individual anatomical situation. ppMake sure that the wax layer on the abutment is sufficiently thick (at least 0,7 mm). Do not cover the delicate margin of the abutments with wax. ppCheck the spatial conditions before casting the bridge framework with the silicone key of the wax-up. 6. Restoration Lab procedure 4 71 Step 4 – Investment Check that the wax framework o pp f the bridge is absolutely tension-free before investing the framework. This is accomplished according to commonly known bridge techniques. ppInvest the bridge framework according to standard methods without using wetting agents. Note In order to avoid overflow of the cast-on alloy, thoroughly clean the abutments prior to investment (removal of wax particles, insulating agents with a cotton pellet or brush moistened with alcohol). Ensure that there is no wax on the delicate margin. The use of investment materials for rapid heating methods ( speed investment materials) is not recommended. When processing the investment material, follow the manufactures’ instructions. Observe the recommended mixing ratio and preheating time exactly. 6. Restoration Lab procedure 5b 5a 5c 72 Step 5 – Casting and devestment ppCast the bridge framework. Note The long term success of the prosthetic work depends on the accurate fit of the restoration. The entire procedure will have to be repeated, if casting errors occur, similar to the examples on p. 64. 6. Restoration Lab procedure ppAllow for enough cooling time of the casted bridge before the devestment. ppGently devest the bridge framework with ultrasound, water jet, pickling acid or a glass fiber brush. For the devestment of the gold abutments with sandblasting (maximum pressure: 2 bars; maximum alumina particle size: 50 μm), the inner configuration has to be protected from infiltration from sand with the polishing aid. ppThe wax-fixed polishing aid allows better fixation and protects the pre-polished part of the gold abutments. 5e 5d 5f 6. Restoration 73 Note To help ensure success of the restoration, a perfect prosthetic fit in the internal connection of the implant is mandatory. Take particular care not to let the bridge reconstruction fall down onto any surface. Due to the weight of the bridge construction, this might have a negative impact on the high precision connection of the gold abutment. If the construction falls down at anytime, repeat the entire procedure. Lab procedure ppDo not sandblast the inner configuration of the gold abutment. 6b 6a 6c 74 Step 6 – Preparation before veneering Remove the sprues a pp nd smooth the removal areas. ppCheck the spatial conditions with the silicone key. 6. Restoration ppControl tension-free fitting on the master cast ( Sheffield test). If the bridge is not tension-free and therefore wiggles, cut the bridge and resplint it in a tension-free manner. Note In order to take the bridge off the master cast, all basal screws need to be removed first. Lab procedure 7 6d 6. Restoration 75 Step 7 – Veneering ppVeneer the superstructure. Lab procedure ppDo an additional try-on of the tension-free fit of the framework in the mouth of the patient. 76 Step 1 – Preparation Remove the healing abutment or t pp emporary restoration. ppRemove the superstructure from the master cast and unscrew the bridge from the analogs. ppClean and dry the interior of the implants and the bridgework thoroughly. ppCheck the tension free fit of the bridgework before tightening it in the mouth of the patient. Note Do not insert the bridge in case of movements due to tensions in the bridgework. Step 2 – Final insertion ppPosition the cleaned bridgework in the implants. ppTighten the screws to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screws with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the bridge work if needed. 6. Restoration 6.4.2 Gold abutment for bridge – Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. Prosthetic procedure 88 88 77 6.5 CARES ab utment Intended use ppCement-retained crowns ppCement-retained bridges via mesostructure ppScrew-retained crowns (ceramic abutments only) Characteristics Simple ppAnatomic emergence profile ppGingival situation visible on the screen ppFast scan and design process ppCost and time savings in the dental lab Reliable ppCrossFit™ Connection ppHigh performance materials ppStraumann® warranty for CARES components1 6. Restoration Lab procedure: p. 79–86 Prosthetic procedure: p. 82, 87–89 1 Terms of the CARES warranty are located at the following link: /CARES 78 6.5.1 Technical Requirements For the use of Straumann® CARES, the dental lab and/or the doctor needs the following components: Scanners inLab1 The multifunctional inLab CAD/CAM system includes a compact grinding unit with integrated laser scanner2, controlled by a standard PC with sufficient computing power. inEos1 The scanner records the data from single-tooth models, dye models, complete jaw models as well as the opposing jaw for the occlusion. The scan of the dental model serves as the basis for designing the abutment with the inLab 3D software. 3D Camera of the Cerec1 3 Unit The Cerec 3 system is well suited to record the implant position directly in the patient’s mouth. Scanbody To record the implant position during the scan process a scanbody is required. The scanbody consists of a scan post, which is directly screwed into the implant/ implant analog, and a scan cap. A scanbody (scan post and scan cap) is included in each CARES set. InLab 3D Software The abutment 3D software for designing the abutment shape is part of the inLab 3D software, available from authorized dental equipment distributors. Internet connection A broadband connection is recommended. 1 inLab, inEos and Cerec are registered trademarks of Sirona Dental Systems GmbH, D-64625 Bensheim, Germany. 2 With the inLab system, only the scanner can be used. The abutments can be produced only in the Straumann production center. 6. Restoration 1c 1a 1b 79 Step 1 – Fabricating the scan model Fabricate a master cast with th pp e corresponding analog (see instructions in chapter 5, p. 34). Option A: Fabricate a duplicate model made from scan plaster1. Option B: Cast the master cast directly by using scan pl aster. ppFor optimal esthetic planning, model a full anatomical wax-up and scan it too. ppTo determine the spacing available for further processing, the silicone key can be viewed on-screen. For more details, see chapter 6.5.2.3. 6. Restoration 6.5.2 CARES abutment – Lab procedure 6.5.2.1 Fabricating the model 1 Information on suitable plasters can be obtained from Sirona Dental Systems GmbH, D-64625 Bensheim, Germany (http://) or authorized dental equipment distributors. Lab procedure 1 2 80 Step 1 – Preparing the scan – duplicate model Position th pp e scan post in the implant analog. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. ppDuplicate the master cast including scanbody to produce a scan model made from scan plaster. ppAdjust the sector to be scanned to the available space on the model holder of the inLab. Note For an accurate scan, the scanbody must point upward vertically, i.e. it must be visible without undercuts. The model must be mounted onto the model holder in such a way, that it points towards clamping shank in the mesial direction. With a correctly positioned scanbody, there is no gap and no rotation between the scan post, implant analog, scan cap and scan post. Scanbodies are intended for single use only, to ensure optimal fit and precision. 6. Restoration 6.5.2.2 Scanning of the model situation Option A: Scanning with the inLab unit Step 2 – Scanning ppPut the scan model in the inLab and scan it with the laser scanner. distal mesial Lab procedure 1 6. Restoration 81 Step 1a – Preparing the scan – duplicate model ppPosition the scan post in the implant analog. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. ppDuplicate the master cast including scanbody to produce a scan model made from scan plaster. Step 1b – Preparing the scan – scan spray ppSpray the model. ppPosition the scan post in the implant analog of the master cast. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. Note Avoid direct spraying of the implant analog. Insert the scanbody into the master cast after spraying the model. With a correctly positioned scanbody, there is no gap and no rotation between the scan post, implant analog, scan cap and scan post. Scanbodies are intended for single use only, to ensure optimal fit and precision. Step 2 – Scanning ppAdjust the model to be scanned on the model holder. ppPut the scan model under the camera of the inEos. Option B: Scanning with the inEos scanner Lab procedure 1a 1b 2 82 Step 1a – Preparing the scan – without scan spray Remove the healing cap or t pp emporary restoration. ppPosition the scan post in the implant. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. 6. Restoration Option C: Scanning with the Cerec 3 Unit 3D Camera Step 2 – Scanning ppScan with the 3D Camera. Step 1b – Preparing the scan – with scan spray To improve the contrast of the virtual impression, a scanspray may be used. ppRemove the healing cap or temporary restoration. ppSpray the situation. ppPosition the scan post in the implant. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. Prosthetic procedure Note Avoid direct spraying of the implant. Insert the scan post and the scan cap into the mouth after spraying the site. With a correctly positioned scan post and scan cap, there is no gap and no rotation between the scan post, implant, scan cap and scan post. Scanbodies are intended for single use only, to ensure optimal fit and precision. 6. Restoration 83 ppShape the CARES abutment on screen, using the abutment 3D software. This software is part of the inLab 3D design software. Design guidelines ppYou can choose between 0 and max. 2 mm when setting the cement line of the abutment. Menu: Settings – Parameter – Gingival depth ppYou can view the virtual silicone key via the scanned full wax-up. Menu: View – Antagonist ppFurther information and a step-by-step manual for designing CARES abutments can be found at the following Straumann link: http:// /CARES 6.5.2.3 Designing the abutment shape Lab procedure 84 6. Restoration After you have finished th pp e design, send your data over the internet to the Straumann production center at the following link: http://cares.straumann.com ppAfter the data transmission is completed, an email confirmation is sent. ppAs soon as the data is tested and validated, you will receive an order confirmation. Note Before the CARES abutment is fabricated at the Straumann production center, the data is subjected to an incoming inspection. If the data record is found to contain errors or is incomplete, a message is sent to you for corrections to be made. A definitive order confirmation will be sent by Straumann only after completing this step. 6.5.2.4 Online ordering Lab procedure 6. Restoration 85 6.5.2.5 Manufacturing and delivery Fabricating the abutment at Straumann ppBased on the design data, the customized CARES abutment is manufactured at the Straumann production center. Delivery to the dental laboratory ppThe CARES abutment is immediately delivered after production. ppIn just a few working days, the dental laboratory receives the order. Delivery of the CARES abutment is available through the following service providers: ppInternational: DHL () ppSwitzerland: Swiss Post () After the order has left the Straumann production center, you will receive an order tracking number together with the delivery notification. With this number you can check the status of your order on the “track & trace” website of the corresponding service provider. Lab procedure 86 6. Restoration 6.5.2.6 Product completion at the dental laboratory CARES ceramic abutment Fabricate a screw-retained c pp rown with a ceramic synchronized to the thermal expansion coefficient of zirconia. ppCARES ceramic abutments made of zirconia have a thermal expansion coefficient of 10,5 2 10-6/K (25 °C – 500 °C, 77 °F – 932 °F). Note Particular attention must be given to an even layer thickness of the porcelain veneered on the abutment. ppMount the CARES ceramic abutment on the implant anal og. ppUse a standard procedure to fabricate the cement- retained single crown. ppVeneer the structure. CARES titanium abutment The procedure for the CARES titanium abutment is the same as the procedure for the cement-retained CARES ceramic abutment, ZrO2, option B. Lab procedure Option A: Screw-retained crown Option B: Cement-retained crown 1 6. Restoration 87 Step 1 – Preparation ppRemove the healing cap or temporary restoration. ppRemove the superstructure from the master cast and unscrew the abutment from the analog. ppClean and dry the interior of the implant and the abutment thoroughly. Note Use transfer aids if the model contains more than one abutment. Never use cement when the abutment is inserted into the implant. CARES abutments made from zirconia are not autoclavable and must not be cleaned by steam blasting. Prosthetic procedure 6.5.3 CARES abutment – Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. 88 6. Restoration Step 2 – Final insertion CARES ceramic abutment Option A: Screw-retained crown Position the cleaned CARES c pp eramic abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. Option B: Cement-retained crown ppPosition the cleaned CARES ceramic abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. ppCement the superstructure to the abutment. ppRemove superfluous cement. Note Use only the special basal screws provided for the CARES ceramic abutment. Prosthetic procedure 6. Restoration 89 Step 2 – Final insertion CARES titanium abutment Option B: Cement-retained crown ppPosition the cleaned CARES titanium abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. ppCement the superstructure to the abutment. ppRemove superfluous cement. Note Direct ceramic veneering is not possible. Use only the basal screws provided for the CARES titanium abutment. Prosthetic procedure 88 88 90 6. Restoration 6.6 Cementable ab utment Intended use ppCement-retained crowns and bridges Characteristics Simple ppFlexible impression taking on implant or abutment level ppEasy handling of prefabricated copings ppReduce adjustment work (e.g. height adjustment) ppEasy choice of components thanks to color-coding Reliable ppCrossFit™ Connection ppPerfect fit due to prefabricated components ppProper fit of abutment level impression cap verified by clear-cut response Note Cement margin must be no more that 2 mm below the gingiva. A minimum height of 3 mm above the mucosa margin of the abutment must be maintained to ensure proper stability and retention of the restoration. Lab procedure: p. 98–102 Prosthetic procedure: p. 92–97, 103–104 GH 4 mm AH 5,5 mm 1 mm 2 mm 3 mm D 6. Restoration 91 6.6.1 Cementable abutment coding Narrow CrossFit™ Regular CrossFit™ Diameter (D) 3,5 mm (blue coding) 5 mm (yellow coding) 5 mm (grey coding) 6,5 mm (brown coding) AH 4 mm (black marking) AH 5,5 mm (white marking) D = Diameter AH = Abutment Height GH = Gingiva Height 1a 1b 92 Prosthetic procedure Option A: Impression taking on abutment level – Prosthetic procedure Step 1 – Abutment insertion Select the appropriate s pp ize of the cementable abutment using the PLAN set (see instructions, in chapter 6.1, p. 45). 6. Restoration ppThoroughly clean and dry the interior of the implant. ppPosition the abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). 2 93 Prosthetic procedure Step 2 – Customizing the abutment Make height adjustments a pp ccording to the individual situation. This can be done down to the bottom of the black/white ring. Note The abutment level impression does not carry any information of potential customizations. In this case, the abutment level impression has to be taken without any auxiliaries. We recommend taking the impression on implant level, and then ask the technician to customize the abutment according to the individual situation. We recommend customizing the abutment right before the final crown is integrated, if the spatial surroundings allow it (no chewing forces against the abutment). Ask your dental lab to supply you with a grinding template. 6. Restoration 3a 3b 94 Step 3 – Impression taking on abutment level Click the impression c pp ap onto the abutment. ppThe white ring on the abutment indicates the abutment height (AH). It corresponds to the white arrowon top of the impression cap and the white clicking mechanism inside of the impression cap. ppTake the impression using an elastomeric impression material (polyvinyl siloxane or polyether rubber). Prosthetic procedure 6. Restoration Note Due to its low tensile strength, hydrocolloid materials are not suitable for this application. 4a 4b 95 Prosthetic procedure 6. Restoration Chairside temporization of the abutment Using the temporary coping* Step 4 – Preparation Snap the temporary c pp oping onto the abutment in the mouth of the patient. ppMark the appropriate height according to the individual situation and shorten the coping as necessary. ppIf you intend to provisionalize a bridge, remove the rotational feature of the temporary coping. Note Do not use Vaseline (aliphatic isolation agent) for insulation of the abutment. Temporary coping Protective cap * Using the protective cap look at step 4, p. 97 5a 5b 5c 96 Prosthetic procedure 6. Restoration Step 5 – Creating the provisional Use a standard procedure to f pp abricate the provisional (e.g. prefabricated crown form or vacuum-formed sheet technique). The retention rings ensure proper mechanical bonding of the veneering material to the coping. The plateau of the coping helps to prevent the veneering material from flowing under the abutment. ppAfter the polymerization is completed, take the provisional out of the mouth and place it on the analog. ppGrind down and polish the emergence profile of the coping and the restoration to achieve an even profile. To avoid tissue irritation, the interface needs to be smooth and flush with the restoration. 4 6 97 Prosthetic procedure 6. Restoration Step 6 – Inserting the provisional Close the SCS configuration o pp f the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the provisional. ppApply temporary cement to the inner part of the coping and cement it onto the abutment. Note Keep the temporary restoration out of occlusion. Use temporary cement in order to remove the temporary restoration in due time. Temporary copings must not be kept longer than 28 days in the mouth. Using the protective cap Step 4 – Cementing the protective cap ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the provisional. ppApply temporary cement 
برچسب ها: abutments indicate gingiva height)، axial alignment and screw axis of the potential restoration. Lab procedure Prosthetic procedure 47 6.1.3 Cleaning and sterilizing PLAN abutments Clean the PLAN abutments thoroughly with water o pp r ethanol after intra-oral use. ppAfter cleaning، moist-heat-sterilize (autoclave) PLAN abutments 18 minutes at 134 °C (273 °F). ppRefer to the manufacturer’s specifications for the heat-sterilization device. Note Do not sterilize PLAN abutments more than 20 times. Do not g-sterilize PLAN abutments. Do not sterilize the cassette or its components. 6. Restoration Prosthetic procedure 88 88 48 6.2 Anat omic (and mes o) Abutment Intended use ppCement-retained restorations Characteristics Simple ppLess grinding necessary due to prepared mucosa margins ppAdaptation to natural soft tissue contour due to prepared mucosa margins in different heights ppOval shape resembles emergence profile of a natural tooth Reliable ppCrossFit™ Connection Note Not suitable for direct ceramic veneering. A minimum height of 3 mm above the mucosa margin of the abutment must be maintained in order to maintain proper stability of the abutment. The cement margin must not be more than 2 mm below the mucosa. Use a new basal screw for the final insertion of the abutment. 6. Restoration Lab procedure: p. 49–53 Prosthetic procedure: p. 54 1a 1b 1c 49 6.2.1 Anatomic (and Meso) Abutment – Lab procedure The following case describes the fabrication of a cement-retained single crown by using the anatomic abutment. 6. Restoration Lab procedure Step 1 – Fabricating the master cast and wax-up Fabricate the master cast i pp ncluding a gingiva mask with the corresponding implant analog (see instructions in chapter 5، p. 34). ppFor optimal esthetic planning، model a full anatomical wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the customized abutment. 2a 2b 50 Step 2 – Preparing the Anatomic or Meso Abutment The anatomic a pp butment and the meso abutment (p. 51) consist of titanium and can be modified as required. Note To maintain proper stability of the abutment، a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. 6. Restoration Lab procedure ppThe anatomic abutment after modification. 2c 2d 2e 51 If the anatomic abutment does not fit your individual demands or if you prefer grinding the mucosa margins yourself، you can use the meso abutment. The processing of the meso abutment corresponds to the one of the anatomic abutment. 6. Restoration Lab procedure 3 52 Step 3 – Fabricating the superstructure Fabricate the superstructure on the modified abutment using the standard modelling،  

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abutments indicate gingiva height), axial alignment and screw axis of the potential restoration. Lab procedure Prosthetic procedure 47 6.1.3 Cleaning and sterilizing PLAN abutments Clean the PLAN abutments thoroughly with water o pp r ethanol after intra-oral use. ppAfter cleaning, moist-heat-sterilize (autoclave) PLAN abutments 18 minutes at 134 °C (273 °F). ppRefer to the manufacturer’s specifications for the heat-sterilization device. Note Do not sterilize PLAN abutments more than 20 times. Do not g-sterilize PLAN abutments. Do not sterilize the cassette or its components. 6. Restoration Prosthetic procedure 88 88 48 6.2 Anat omic (and mes o) Abutment Intended use ppCement-retained restorations Characteristics Simple ppLess grinding necessary due to prepared mucosa margins ppAdaptation to natural soft tissue contour due to prepared mucosa margins in different heights ppOval shape resembles emergence profile of a natural tooth Reliable ppCrossFit™ Connection Note Not suitable for direct ceramic veneering. A minimum height of 3 mm above the mucosa margin of the abutment must be maintained in order to maintain proper stability of the abutment. The cement margin must not be more than 2 mm below the mucosa. Use a new basal screw for the final insertion of the abutment. 6. Restoration Lab procedure: p. 49–53 Prosthetic procedure: p. 54 1a 1b 1c 49 6.2.1 Anatomic (and Meso) Abutment – Lab procedure The following case describes the fabrication of a cement-retained single crown by using the anatomic abutment. 6. Restoration Lab procedure Step 1 – Fabricating the master cast and wax-up Fabricate the master cast i pp ncluding a gingiva mask with the corresponding implant analog (see instructions in chapter 5, p. 34). ppFor optimal esthetic planning, model a full anatomical wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the customized abutment. 2a 2b 50 Step 2 – Preparing the Anatomic or Meso Abutment The anatomic a pp butment and the meso abutment (p. 51) consist of titanium and can be modified as required. Note To maintain proper stability of the abutment, a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. 6. Restoration Lab procedure ppThe anatomic abutment after modification. 2c 2d 2e 51 If the anatomic abutment does not fit your individual demands or if you prefer grinding the mucosa margins yourself, you can use the meso abutment. The processing of the meso abutment corresponds to the one of the anatomic abutment. 6. Restoration Lab procedure 3 52 Step 3 – Fabricating the superstructure Fabricate the superstructure on the modified abutment using the standard modelling, casting and veneering methods. Place the modified abutment o pp n the polishing aid/analog and hand-tighten the screw using the SCS screwdriver. ppWax an individual resin cap onto the abutment. ppContour a wax model according to the anatomical circumstances of the individual cast. ppCheck the wax-up with the silicone key. 6. Restoration Lab procedure 4a 4b 53 Step 4 – Casting and veneering Cast the framework using th pp e standard casting methods. ppVeneer the superstructure. 6. Restoration Lab procedure ppCheck the framework with the silicone key before veneering. 54 6. Restoration 6.2.2 Anatomic Abutment – Prosthetic procedure Step 2 – Final insertion Position the cleaned abutment i pp n the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. ppCement the superstructure to the abutment. ppRemove superfluous cement. The final restoration is delivered to the doctor’s office on the master cast. Step 1 – Preparation ppRemove the healing cap or temporary restoration. ppRemove the superstructure from the master cast and unscrew the abutment from the analog. ppClean and dry the interior of the implant and the abutment thoroughly. Prosthetic procedure 88 88 55 6.3 Gold Abutment for cr own Intended use ppScrew-retained or cement-retained crowns ppCement-retained bridges via mesostructure (custom abutment technique) ppTelescopic crowns and telescopic bridges Characteristics Simple ppEasy wax-up and protection of the screw channel due to modelling aid (burn-out polymer) ppEasy-to-achieve esthetics due to individual contouring of the emergence profile and adaptation to the margin of the gingival contour Reliable ppSuperfluous cement easily removable by raising the cement margin using an individually designed mesostructure ppCrossFit™ Connection Note Not suitable for direct splinting with other gold abutments. For screw-retained bridges the gold abutment for bridge must be used (see instructions in chapter 6.4, p. 67). Use a new basal screw for the final insertion of the abutment. Do not shorten the gold abutment for crown by more than 1.5 mm. 6. Restoration Lab procedure: p. 56–65 Prosthetic procedure: p. 66 1a 1b 1c 56 6.3.1 Gold Abutment for crown – Lab procedure The following case describes the fabrication of a cement-retained single crown by utilizing the custom abutment technique. Step 1 – Fabricating the master cast and wax-up Fabricate the master cast i pp ncluding a gingiva mask with the corresponding implant analog (see instructions in chapter 5, p. 34). 6. Restoration ppFor optimal esthetic planning, model a full anatomical wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the customized abutment. Lab procedure 2c 2a 2b 2d 57 Step 2 – Preparing the Gold Abutment Place the gold abutment o pp n the analog and hand-tighten the screw using the SCS screwdriver. 6. Restoration ppShorten the modelling aid to the height of the occlusal plane according to the individual circumstances. Working with the modelling aid ensures a clean and sharp-edged finish of the screw channel. ppAttach the gold abutment to the polishing aid for easier handling during manipulation outside of the model. Lab procedure 3d 3a 3b 3c 58 Step 3 – Wax modelling Contour a wax-up shape a pp ccording to the individual anatomical situation. The silicone key shows the exact space for the cement-retained crown, which will be made over the customized abutment. Note The picture displays the optimal configuration of a customized abutment, showing an ideal emergence profile. This configuration ideally adapts the crown contours to the margin of the gingival contour. For reasons of hygiene, the cement margin must not be more than 2 mm below the gingival level. 6. Restoration ppMake sure that the wax layer on the abutment is sufficiently thick (at least 0,7 mm). Do not cover the delicate margin of the abutment with wax. Lab procedure ppCheck the wax-up with the silicone key. 4 59 Step 4 – Investment Invest the customized abutment a pp ccording to standard methods without using wetting agents. Note In order to avoid overflow of the cast-on alloy, thoroughly clean the abutment prior to investment (removal of wax particles, insulating agents with a cotton pellet or brush moistened with alcohol). Always do the cast with the modelling aid. Otherwise, the dental casting alloy will not or only too thinly flow out at the upper coping rim. Ensure that there is no wax on the delicate margin. The use of investment materials for rapid heating methods (speed investment materials) is not recommended. When processing the investment material, follow the manufacturers’ instructions. Observe the recommended mixing ratio and preheating time exactly. 6. Restoration Lab procedure 5b 5a 5c 60 Step 5 – Casting and devestment ppCast the customized abutment. ppGently devest the customized abutment with ultrasound, water jet, pickling acid or a glass fiber brush. Note For the devestment of the gold abutment with sandblasting (maximum pressure: 2 bars; maximum alumina particle size: 50 μm), the inner configuration has to be protected from infiltration with sand with the polishing aid. ppThe wax-fixed polishing aid allows better fixation and protects the pre-polished part of the gold abutment. 6. Restoration Lab procedure 5e 5d 61 The gold a pp butment after sandblasting. Note Do not sandblast the inner configuration of the gold abutment. 6. Restoration Lab procedure 6a 6b 7a 62 Step 6 – Polishing After trimming, polish the finished c pp ustomized abutment. ppThe customized abutment is now ready for the fabrication of the cement-retained single crown. 6. Restoration Lab procedure Step 7 – Fabricating the cement-retained single crown ppBlock out the screw channel and wax the framework directly over the customized abutment. ppThe silicone key shows the spatial relations for the restoration. 7b 7c 63 Cast the framework in the conventional ma pp nner. After trimming the cast, the metal crown fits precisely on the customized abutment. 6. Restoration Lab procedure ppThe silicone key shows the spatial relations for veneering. ppVeneer the superstructure. 64 6. Restoration Lab procedure Note The long-term success of the prosthetic work depends on the accurate fit of the restoration. The entire procedure has to be repeated if… p … trimming through the cast-on alloy prohibits the Ceramicor®surface from being covered with ceramic veneering material (Ceramicor® is a non-oxidizing alloy and does not allow ceramic bonding). Ground down to abutment level Failed casting Casting beads and overflow of alloy … the cast-pp on gold did not flow out entirely. pp…intruded casting metals and casting pearls cannot be removed from the connection part of the gold abutment. Casting errors and incorrect handling 6. Restoration 65 Lab procedure Using alloys with castable Ceramicor® components Ceramicor® is only suitable for cast-on procedures Ceramics can not be bonded directly to cast-on Cermicor® components as this alloy does not form bonding oxides. When selecting the casting alloy, ensure that it is compatible with the high-fusing alloy of the Ceramicor® components. The melting range of the casting alloy must not exceed a liquidus temperature of 1350 °C/2462 °F. Ceramicor® must not be cast on with base metal casting alloys because gold in combination with nickel or cobalt destroys the components. Suitable dental casting alloys ppHigh noble alloys ppPrecious metal alloys with a minimum content of gold and platinum group metals of 25% ppPalladium-based alloys with a minimum content of palladium of 50% ISO standard alloy types Alloy types according to the following ISO standards are suitable for cast-on procedures to the prefabricated Cermicor® component: ppISO standard 9693 ppISO standard 1562 ppISO standard 8891 Note The alloy manufacturer’s recommendation must be followed. Due to diffusion at the alloy and the cast-on coping interface, components made from an unsuitable alloy may form phases with low-strength, reduced corrosion resistance or a lower melting range. Ceramicor® is a registered trademark of Cendres & Métaux SA (Biel-Bienne, Switzerland). 66 6. Restoration 6.3.2 Gold Abutment for crown – Prosthetic procedure Step 1 – Preparation Remove the healing cap or t pp emporary restoration. ppRemove the superstructure from the master cast and unscrew the abutment from the analog. ppClean and dry the interior of the implant and the abutment thoroughly. Option B: Cement-retained crown ppPosition the cleaned abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the customized abutment in case a crown replacement is required. ppCement the crown to the mesostructure. ppRemove superfluous cement. Step 2 – Final insertion Option A: Screw-retained crown ppPosition the cleaned abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the customized abutment in case a crown replacement is required. The final restoration is delivered to the doctor’s office on the master cast. Note The figure displays the optimal configuration of a customized abutment, showing an ideal emergence profile. This configuration ideally adapts the crown contours to the margin of the gingival contour. For reasons of hygiene, the cement margin must not be more than 2 mm below the gingival level. Prosthetic procedure 88 88 67 6.4 Gold ab utment for bridge Intended use ppScrew-retained bridges ppScrew-retained customized bars Characteristics Simple ppEasy wax-up and protection of the screw channel due to modelling aid (burn-out polymer) ppEasy-to-achieve esthetics due to individual contouring of the emergence profile and adaptation to the margin of the gingival contour Reliable ppNo cement gap ppOne-screw solution Note Not suitable for single crowns. For single crowns the gold abutment for crown must be used (see instructions in chapter 6.3, p. 55). Use a new basal screw for the final insertion of the abutment. Do not shorten the gold abutment for bridge by more than 2.5 mm. 6. Restoration Lab procedure: p. 68–75 Prosthetic procedure: p. 76 1b 1a 1c 68 Step 1 – Fabricating the master cast and wax-up Fabricate a master cast i pp ncluding a gingiva mask with the corresponding analogs (see instructions in chapter 5, p. 34). 6. Restoration 6.4.1 Gold abutment for bridge – Lab procedure The following case describes the planning of a screw-retained bridge. ppFor optimal esthetic planning, model a full anatomical wax-up. ppMake a silicone key over the full anatomical wax-up in order to define the optimal shape of the customized bridge. Lab procedure 2b 2a 2c 69 Step 2 – Preparing the gold abutments Place the gold abutments f pp or bridge on the analogs and hand-tighten the screws using the SCS screwdriver. 6. Restoration Lab procedure ppTo avoid a deformation of the conical design of the connection it is highly recommended to always attach the gold abutment to the polishing aid while working outside of the model. ppShorten the modelling aids to the height of the occlusal plane according to individual circumstances. Working with the modelling aid ensures a clean and sharp-edged finish of the screw channel. 3a 3b 70 Step 3 – Wax modelling Contour a wax-up shape a pp ccording to the individual anatomical situation. ppMake sure that the wax layer on the abutment is sufficiently thick (at least 0,7 mm). Do not cover the delicate margin of the abutments with wax. ppCheck the spatial conditions before casting the bridge framework with the silicone key of the wax-up. 6. Restoration Lab procedure 4 71 Step 4 – Investment Check that the wax framework o pp f the bridge is absolutely tension-free before investing the framework. This is accomplished according to commonly known bridge techniques. ppInvest the bridge framework according to standard methods without using wetting agents. Note In order to avoid overflow of the cast-on alloy, thoroughly clean the abutments prior to investment (removal of wax particles, insulating agents with a cotton pellet or brush moistened with alcohol). Ensure that there is no wax on the delicate margin. The use of investment materials for rapid heating methods ( speed investment materials) is not recommended. When processing the investment material, follow the manufactures’ instructions. Observe the recommended mixing ratio and preheating time exactly. 6. Restoration Lab procedure 5b 5a 5c 72 Step 5 – Casting and devestment ppCast the bridge framework. Note The long term success of the prosthetic work depends on the accurate fit of the restoration. The entire procedure will have to be repeated, if casting errors occur, similar to the examples on p. 64. 6. Restoration Lab procedure ppAllow for enough cooling time of the casted bridge before the devestment. ppGently devest the bridge framework with ultrasound, water jet, pickling acid or a glass fiber brush. For the devestment of the gold abutments with sandblasting (maximum pressure: 2 bars; maximum alumina particle size: 50 μm), the inner configuration has to be protected from infiltration from sand with the polishing aid. ppThe wax-fixed polishing aid allows better fixation and protects the pre-polished part of the gold abutments. 5e 5d 5f 6. Restoration 73 Note To help ensure success of the restoration, a perfect prosthetic fit in the internal connection of the implant is mandatory. Take particular care not to let the bridge reconstruction fall down onto any surface. Due to the weight of the bridge construction, this might have a negative impact on the high precision connection of the gold abutment. If the construction falls down at anytime, repeat the entire procedure. Lab procedure ppDo not sandblast the inner configuration of the gold abutment. 6b 6a 6c 74 Step 6 – Preparation before veneering Remove the sprues a pp nd smooth the removal areas. ppCheck the spatial conditions with the silicone key. 6. Restoration ppControl tension-free fitting on the master cast ( Sheffield test). If the bridge is not tension-free and therefore wiggles, cut the bridge and resplint it in a tension-free manner. Note In order to take the bridge off the master cast, all basal screws need to be removed first. Lab procedure 7 6d 6. Restoration 75 Step 7 – Veneering ppVeneer the superstructure. Lab procedure ppDo an additional try-on of the tension-free fit of the framework in the mouth of the patient. 76 Step 1 – Preparation Remove the healing abutment or t pp emporary restoration. ppRemove the superstructure from the master cast and unscrew the bridge from the analogs. ppClean and dry the interior of the implants and the bridgework thoroughly. ppCheck the tension free fit of the bridgework before tightening it in the mouth of the patient. Note Do not insert the bridge in case of movements due to tensions in the bridgework. Step 2 – Final insertion ppPosition the cleaned bridgework in the implants. ppTighten the screws to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screws with cotton and sealing compound (e.g. gutta-percha or composite). This allows later removal of the bridge work if needed. 6. Restoration 6.4.2 Gold abutment for bridge – Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. Prosthetic procedure 88 88 77 6.5 CARES ab utment Intended use ppCement-retained crowns ppCement-retained bridges via mesostructure ppScrew-retained crowns (ceramic abutments only) Characteristics Simple ppAnatomic emergence profile ppGingival situation visible on the screen ppFast scan and design process ppCost and time savings in the dental lab Reliable ppCrossFit™ Connection ppHigh performance materials ppStraumann® warranty for CARES components1 6. Restoration Lab procedure: p. 79–86 Prosthetic procedure: p. 82, 87–89 1 Terms of the CARES warranty are located at the following link: /CARES 78 6.5.1 Technical Requirements For the use of Straumann® CARES, the dental lab and/or the doctor needs the following components: Scanners inLab1 The multifunctional inLab CAD/CAM system includes a compact grinding unit with integrated laser scanner2, controlled by a standard PC with sufficient computing power. inEos1 The scanner records the data from single-tooth models, dye models, complete jaw models as well as the opposing jaw for the occlusion. The scan of the dental model serves as the basis for designing the abutment with the inLab 3D software. 3D Camera of the Cerec1 3 Unit The Cerec 3 system is well suited to record the implant position directly in the patient’s mouth. Scanbody To record the implant position during the scan process a scanbody is required. The scanbody consists of a scan post, which is directly screwed into the implant/ implant analog, and a scan cap. A scanbody (scan post and scan cap) is included in each CARES set. InLab 3D Software The abutment 3D software for designing the abutment shape is part of the inLab 3D software, available from authorized dental equipment distributors. Internet connection A broadband connection is recommended. 1 inLab, inEos and Cerec are registered trademarks of Sirona Dental Systems GmbH, D-64625 Bensheim, Germany. 2 With the inLab system, only the scanner can be used. The abutments can be produced only in the Straumann production center. 6. Restoration 1c 1a 1b 79 Step 1 – Fabricating the scan model Fabricate a master cast with th pp e corresponding analog (see instructions in chapter 5, p. 34). Option A: Fabricate a duplicate model made from scan plaster1. Option B: Cast the master cast directly by using scan pl aster. ppFor optimal esthetic planning, model a full anatomical wax-up and scan it too. ppTo determine the spacing available for further processing, the silicone key can be viewed on-screen. For more details, see chapter 6.5.2.3. 6. Restoration 6.5.2 CARES abutment – Lab procedure 6.5.2.1 Fabricating the model 1 Information on suitable plasters can be obtained from Sirona Dental Systems GmbH, D-64625 Bensheim, Germany (http://) or authorized dental equipment distributors. Lab procedure 1 2 80 Step 1 – Preparing the scan – duplicate model Position th pp e scan post in the implant analog. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. ppDuplicate the master cast including scanbody to produce a scan model made from scan plaster. ppAdjust the sector to be scanned to the available space on the model holder of the inLab. Note For an accurate scan, the scanbody must point upward vertically, i.e. it must be visible without undercuts. The model must be mounted onto the model holder in such a way, that it points towards clamping shank in the mesial direction. With a correctly positioned scanbody, there is no gap and no rotation between the scan post, implant analog, scan cap and scan post. Scanbodies are intended for single use only, to ensure optimal fit and precision. 6. Restoration 6.5.2.2 Scanning of the model situation Option A: Scanning with the inLab unit Step 2 – Scanning ppPut the scan model in the inLab and scan it with the laser scanner. distal mesial Lab procedure 1 6. Restoration 81 Step 1a – Preparing the scan – duplicate model ppPosition the scan post in the implant analog. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. ppDuplicate the master cast including scanbody to produce a scan model made from scan plaster. Step 1b – Preparing the scan – scan spray ppSpray the model. ppPosition the scan post in the implant analog of the master cast. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. Note Avoid direct spraying of the implant analog. Insert the scanbody into the master cast after spraying the model. With a correctly positioned scanbody, there is no gap and no rotation between the scan post, implant analog, scan cap and scan post. Scanbodies are intended for single use only, to ensure optimal fit and precision. Step 2 – Scanning ppAdjust the model to be scanned on the model holder. ppPut the scan model under the camera of the inEos. Option B: Scanning with the inEos scanner Lab procedure 1a 1b 2 82 Step 1a – Preparing the scan – without scan spray Remove the healing cap or t pp emporary restoration. ppPosition the scan post in the implant. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. 6. Restoration Option C: Scanning with the Cerec 3 Unit 3D Camera Step 2 – Scanning ppScan with the 3D Camera. Step 1b – Preparing the scan – with scan spray To improve the contrast of the virtual impression, a scanspray may be used. ppRemove the healing cap or temporary restoration. ppSpray the situation. ppPosition the scan post in the implant. ppInsert the screw and hand-tighten it. ppSnap the scan cap on top of the post. ppAssure that the parts are placed correctly. Prosthetic procedure Note Avoid direct spraying of the implant. Insert the scan post and the scan cap into the mouth after spraying the site. With a correctly positioned scan post and scan cap, there is no gap and no rotation between the scan post, implant, scan cap and scan post. Scanbodies are intended for single use only, to ensure optimal fit and precision. 6. Restoration 83 ppShape the CARES abutment on screen, using the abutment 3D software. This software is part of the inLab 3D design software. Design guidelines ppYou can choose between 0 and max. 2 mm when setting the cement line of the abutment. Menu: Settings – Parameter – Gingival depth ppYou can view the virtual silicone key via the scanned full wax-up. Menu: View – Antagonist ppFurther information and a step-by-step manual for designing CARES abutments can be found at the following Straumann link: http:// /CARES 6.5.2.3 Designing the abutment shape Lab procedure 84 6. Restoration After you have finished th pp e design, send your data over the internet to the Straumann production center at the following link: http://cares.straumann.com ppAfter the data transmission is completed, an email confirmation is sent. ppAs soon as the data is tested and validated, you will receive an order confirmation. Note Before the CARES abutment is fabricated at the Straumann production center, the data is subjected to an incoming inspection. If the data record is found to contain errors or is incomplete, a message is sent to you for corrections to be made. A definitive order confirmation will be sent by Straumann only after completing this step. 6.5.2.4 Online ordering Lab procedure 6. Restoration 85 6.5.2.5 Manufacturing and delivery Fabricating the abutment at Straumann ppBased on the design data, the customized CARES abutment is manufactured at the Straumann production center. Delivery to the dental laboratory ppThe CARES abutment is immediately delivered after production. ppIn just a few working days, the dental laboratory receives the order. Delivery of the CARES abutment is available through the following service providers: ppInternational: DHL () ppSwitzerland: Swiss Post () After the order has left the Straumann production center, you will receive an order tracking number together with the delivery notification. With this number you can check the status of your order on the “track & trace” website of the corresponding service provider. Lab procedure 86 6. Restoration 6.5.2.6 Product completion at the dental laboratory CARES ceramic abutment Fabricate a screw-retained c pp rown with a ceramic synchronized to the thermal expansion coefficient of zirconia. ppCARES ceramic abutments made of zirconia have a thermal expansion coefficient of 10,5 2 10-6/K (25 °C – 500 °C, 77 °F – 932 °F). Note Particular attention must be given to an even layer thickness of the porcelain veneered on the abutment. ppMount the CARES ceramic abutment on the implant anal og. ppUse a standard procedure to fabricate the cement- retained single crown. ppVeneer the structure. CARES titanium abutment The procedure for the CARES titanium abutment is the same as the procedure for the cement-retained CARES ceramic abutment, ZrO2, option B. Lab procedure Option A: Screw-retained crown Option B: Cement-retained crown 1 6. Restoration 87 Step 1 – Preparation ppRemove the healing cap or temporary restoration. ppRemove the superstructure from the master cast and unscrew the abutment from the analog. ppClean and dry the interior of the implant and the abutment thoroughly. Note Use transfer aids if the model contains more than one abutment. Never use cement when the abutment is inserted into the implant. CARES abutments made from zirconia are not autoclavable and must not be cleaned by steam blasting. Prosthetic procedure 6.5.3 CARES abutment – Prosthetic procedure The final restoration is delivered to the doctor’s office on the master cast. 88 6. Restoration Step 2 – Final insertion CARES ceramic abutment Option A: Screw-retained crown Position the cleaned CARES c pp eramic abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. Option B: Cement-retained crown ppPosition the cleaned CARES ceramic abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. ppCement the superstructure to the abutment. ppRemove superfluous cement. Note Use only the special basal screws provided for the CARES ceramic abutment. Prosthetic procedure 6. Restoration 89 Step 2 – Final insertion CARES titanium abutment Option B: Cement-retained crown ppPosition the cleaned CARES titanium abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppClose the SCS configuration of the screw with cotton and sealing compound (gutta-percha). This allows a later removal of the customized abutment in case a crown replacement is required. ppCement the superstructure to the abutment. ppRemove superfluous cement. Note Direct ceramic veneering is not possible. Use only the basal screws provided for the CARES titanium abutment. Prosthetic procedure 88 88 90 6. Restoration 6.6 Cementable ab utment Intended use ppCement-retained crowns and bridges Characteristics Simple ppFlexible impression taking on implant or abutment level ppEasy handling of prefabricated copings ppReduce adjustment work (e.g. height adjustment) ppEasy choice of components thanks to color-coding Reliable ppCrossFit™ Connection ppPerfect fit due to prefabricated components ppProper fit of abutment level impression cap verified by clear-cut response Note Cement margin must be no more that 2 mm below the gingiva. A minimum height of 3 mm above the mucosa margin of the abutment must be maintained to ensure proper stability and retention of the restoration. Lab procedure: p. 98–102 Prosthetic procedure: p. 92–97, 103–104 GH 4 mm AH 5,5 mm 1 mm 2 mm 3 mm D 6. Restoration 91 6.6.1 Cementable abutment coding Narrow CrossFit™ Regular CrossFit™ Diameter (D) 3,5 mm (blue coding) 5 mm (yellow coding) 5 mm (grey coding) 6,5 mm (brown coding) AH 4 mm (black marking) AH 5,5 mm (white marking) D = Diameter AH = Abutment Height GH = Gingiva Height 1a 1b 92 Prosthetic procedure Option A: Impression taking on abutment level – Prosthetic procedure Step 1 – Abutment insertion Select the appropriate s pp ize of the cementable abutment using the PLAN set (see instructions, in chapter 6.1, p. 45). 6. Restoration ppThoroughly clean and dry the interior of the implant. ppPosition the abutment in the implant. Tighten the screw to 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). 2 93 Prosthetic procedure Step 2 – Customizing the abutment Make height adjustments a pp ccording to the individual situation. This can be done down to the bottom of the black/white ring. Note The abutment level impression does not carry any information of potential customizations. In this case, the abutment level impression has to be taken without any auxiliaries. We recommend taking the impression on implant level, and then ask the technician to customize the abutment according to the individual situation. We recommend customizing the abutment right before the final crown is integrated, if the spatial surroundings allow it (no chewing forces against the abutment). Ask your dental lab to supply you with a grinding template. 6. Restoration 3a 3b 94 Step 3 – Impression taking on abutment level Click the impression c pp ap onto the abutment. ppThe white ring on the abutment indicates the abutment height (AH). It corresponds to the white arrowon top of the impression cap and the white clicking mechanism inside of the impression cap. ppTake the impression using an elastomeric impression material (polyvinyl siloxane or polyether rubber). Prosthetic procedure 6. Restoration Note Due to its low tensile strength, hydrocolloid materials are not suitable for this application. 4a 4b 95 Prosthetic procedure 6. Restoration Chairside temporization of the abutment Using the temporary coping* Step 4 – Preparation Snap the temporary c pp oping onto the abutment in the mouth of the patient. ppMark the appropriate height according to the individual situation and shorten the coping as necessary. ppIf you intend to provisionalize a bridge, remove the rotational feature of the temporary coping. Note Do not use Vaseline (aliphatic isolation agent) for insulation of the abutment. Temporary coping Protective cap * Using the protective cap look at step 4, p. 97 5a 5b 5c 96 Prosthetic procedure 6. Restoration Step 5 – Creating the provisional Use a standard procedure to f pp abricate the provisional (e.g. prefabricated crown form or vacuum-formed sheet technique). The retention rings ensure proper mechanical bonding of the veneering material to the coping. The plateau of the coping helps to prevent the veneering material from flowing under the abutment. ppAfter the polymerization is completed, take the provisional out of the mouth and place it on the analog. ppGrind down and polish the emergence profile of the coping and the restoration to achieve an even profile. To avoid tissue irritation, the interface needs to be smooth and flush with the restoration. 4 6 97 Prosthetic procedure 6. Restoration Step 6 – Inserting the provisional Close the SCS configuration o pp f the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the provisional. ppApply temporary cement to the inner part of the coping and cement it onto the abutment. Note Keep the temporary restoration out of occlusion. Use temporary cement in order to remove the temporary restoration in due time. Temporary copings must not be kept longer than 28 days in the mouth. Using the protective cap Step 4 – Cementing the protective cap ppClose the SCS configuration of the screw with cotton and sealing compound (e.g. gutta-percha). This allows a later removal of the provisional. ppApply temporary cement 
برچسب ها: abutments indicate gingiva height)، axial alignment and screw axis of the potential restoration. Lab procedure Prosthetic procedure 47 6.1.3 Cleaning and sterilizing PLAN abutments Clean the PLAN abutments thoroughly with water o pp r ethanol after intra-oral use. ppAfter cleaning، moist-heat-sterilize (autoclave) PLAN abutments 18 minutes at 134 °C (273 °F). ppRefer to the manufacturer’s specifications for the heat-sterilization device. Note Do not sterilize PLAN abutments more than 20 times. Do not g-sterilize PLAN abutments. Do not sterilize the cassette or its components. 6. Restoration Prosthetic procedure 88 88 48 6.2 Anat omic (and mes o) Abutment Intended use ppCement-retained restorations Characteristics Simple ppLess grinding necessary due to prepared mucosa margins ppAdaptation to natural soft tissue contour due to prepared mucosa margins in different heights ppOval shape resembles emergence profile of a natural tooth Reliable ppCrossFit™ Connection Note Not suitable for direct ceramic veneering. A minimum height of 3 mm above the mucosa margin of the abutment must be maintained in order to maintain proper stability of the abutment. The cement margin must not be more than 2 mm below the mucosa. Use a new basal screw for the final insertion of the abutment. 6. Restoration Lab procedure: p. 49–53 Prosthetic procedure: p. 54 1a 1b 1c 49 6.2.1 Anatomic (and Meso) Abutment – Lab procedure The following case describes the fabrication of a cement-retained single crown by using the anatomic abutment. 6. Restoration Lab procedure Step 1 – Fabricating the master cast and wax-up Fabricate the master cast i pp ncluding a gingiva mask with the corresponding implant analog (see instructions in chapter 5، p. 34). ppFor optimal esthetic planning، model a full anatomical wax-up. ppMake a silicone key over the full wax-up in order to define the optimal shape of the customized abutment. 2a 2b 50 Step 2 – Preparing the Anatomic or Meso Abutment The anatomic a pp butment and the meso abutment (p. 51) consist of titanium and can be modified as required. Note To maintain proper stability of the abutment، a minimum height of 3 mm above the mucosa margin of the abutment must be maintained. 6. Restoration Lab procedure ppThe anatomic abutment after modification. 2c 2d 2e 51 If the anatomic abutment does not fit your individual demands or if you prefer grinding the mucosa margins yourself، you can use the meso abutment. The processing of the meso abutment corresponds to the one of the anatomic abutment. 6. Restoration Lab procedure 3 52 Step 3 – Fabricating the superstructure Fabricate the superstructure on the modified abutment using the standard modelling،  

تاریخ : پنجشنبه 31 اردیبهشت 1394 | 05:28 ب.ظ | نویسنده : sinister | نظرات

آموزش ایمپلنت با سیستم ITI

BASIC INFORMATION ON THE prosthetic procedures Straumann® Bone Level Implant Line The ITI (International Team for Implantology) is academic partner of Institut Straumann in the areas of research, development and education. Content 1. Straumann® Bone Level Implant – Straumann expertise applied at bone level 3 2. General information 4 2.1 CrossFit™ Connection 4 2.2 Prosthetic options 6 2.3 Abutment overview 8 2.4 Coding 10 3. Preoperative planning 12 3.1 Wax-up/Set-up 12 3.2 X-ray template with reference spheres 12 3.3 Custom-made drill template 13 3.4 T hermoplastic drill template 14 4. Soft tissue management 15 4.1 Soft tissue management solutions 15 4.2 Prefabricated Healing Abutment 16 4.3 Customizable Healing Abutment 25 4.4 T emporary Abutment 27 5. Impression taking 34 5.1 O ptions for impression taking 34 5.2 O pen tray impression 35 5.3 Closed tray impression 39 5.4 Bite registration 43 6. Restoration 45 6.1 CrossFit™ PLAN Set/PLAN Abutment 45 6.2 Anatomic (and Meso) Abutment 48 6.3 Gold Abutment for crown 55 6.4 Gold Abutment for bridge 67 6.5 CARES Abutment 77 6.6 Cementable Abutment 90 6.7 Multi-Base Abutment 105 6.8 Abutment for bars 123 6.9 LOCATOR® Abutment 133 7. Aids and instruments 149 7.1 SCS Screwdriver 149 7.2 Polishing Aid 150 7.3 Ratchet and Torque Control Device 151 7.4 Assembling the Ratchet and the Torque Control Device 153 7.5 T ightening an abutment to 35 Ncm 155 8. About sterilization 157 9. Important guidelines 158 10. Index 159 88 88 2 Purpose of this guide This guide describes the essential steps required for the fabrication and insertion of prosthetic restorations for Straumann® Bone Level implants. For detailed information regarding implantation and soft tissue management see “Straumann® Bone Level Implant Line: Basic information on the surgical procedures” (Art. No. 152.754). See also DVD „Surgical and Prosthetic Procedures with the Straumann® Bone Level Implant“ (Art. No. 150.760) for additional information. Note Different procedures apply for dental technicians and prosthodontists. Such procedures are marked with a color code in the respective chapters of this guide: Purpose of this guide Lab procedure Prosthetic procedure Not all products shown are available in all markets. 3 The Straumann® Bone Level Implant provides you with a solution for all bone level treatments, with Straumann expertise and quality built in. Its design is based on the latest technology and scientific know-how in implant dentistry. Moreover, it respects key biological principles, brings predictable esthetic results and offers simple handling in all indications. 1. Stra umann ® Bone Level Implant – Stra umann expertise applied at bone level Bone Control Design™ The unique Bone Control Design™ is based on key biological principles and thorough scientific research to support crestal bone preservation and stable soft tissue margins. It features the following strengths: Fast o pp sseointegration with the SLActive surface technology ppOptimal transmission of forces into the bone through the biomechanical implant design ppConsideration of the biological distance with a horizontal distance of micro gap to bone ppReduction of micro movements while controlling the micro gap through a conical connection Consistent Emergence Profiles™ The prosthetic components of the Straumann ® Bone Level Implant line are designed to facilitate highly esthetic restorations that perfectly mimic natural teeth. These implant line components, designed to match the abutment profiles, allow you to easily attain esthetic results through soft tissue management. CrossFit™ Connection The prosthetic connection is intuitive, self-guiding and easy to grasp. The CrossFit™ Connection ppprovides a clear-cut insertion through the guidance by 4 grooves and the deep, conical connection. ppensures precision against rotation through orthogonal fit between implant and abutment. ppgives prosthetic flexibility with mechanical long-term stability through its conical connection. 1. Straumann® Bone Level Implant – Straumann expertise applied at bone level Consistent Emergence Profiles™ Experience simplified soft tissue management from start to finish Bone Control Design™ Optimize crestal bone preservation by adhering to biological principles CrossFit™ Connection Feel the fit of the self-guiding connection 4 2. General information 2.1 crossFit™ Connection The Straumann® Bone Level Implant features a new intuitive implant-abutment connection that is self-guiding and enables simple positioning. It allows clear-cut insertion with all components and provides outstanding protection against rotation as well as long-term stability. Precision and simplicity: 4 grooves The CrossFit™ Connection features 4 grooves for the repositioning of prosthetic components. This configuration is characterized by: ppsimple implant alignment ppclear-cut and guided component insertion ppflexibility in the placement of angled prosthetic components ppoptimal protection against rotation ensured by orthogonal implant-abutment fit Figure 1: Internal connection viewed from above, showing the 4 internal grooves. Figure 2: Abutment insertion, step 1. The abutment is placed on the 4 grooves in the implant. 2. General information 5 Figure 3a: Abutment insertion, step 2. The abutment is turned in until it is aligned with the 4 implant grooves. Figure 3b: Abutment insertion, step 3. The abutment then falls into the final position. Figure 4: Abutment in place, showing the precise orthogonal fit between implant and abutment. Reliability and flexibility: Conical connection The CrossFit™ Connection features a cone with improved mechanical properties, providing more flexibility for prosthetic treatments. The conical prosthetic connection provides: reduced micro movements a pp nd minimized microgap ppoutstanding mechanical long-term stability and optimized stress distribution ppexact implant-abutment fit ppsimplified impression taking even with divergently positioned implants 2. General information 6 Gold Abutment, for crown 2.2 Prosthetic opti ons Single crown Screw-retained Cement-retained Anatomic Abutment Gold Abutment, for crown Meso Abutment 2. General information CARES Ceramic Abutment CARES Ceramic Abutment CARES Titanium Abutment Cementable Abutment Bridge Screw-retained Cement-retained Anatomic Abutment Gold Abutment, for crown Meso Abutment Gold Abutment, for bridge CARES Ceramic Abutment CARES Titanium Abutment Cementable Abutment Multi-Base Abutment 2. General information 7 LOCATOR® Abutment Removable overdentures Retentive anchor Abutment for Bars, Gold Bar Abutment for Bars, Titanium Customized bar Gold Abutment, for bridge Anatomic Abutment Meso Abutment Gold Abutment, for crown Telescope Multi-Base Abutment 8 2.3 Abutment Over vie w Anatomic Abutment Meso Abutment Gold Abutment, for crown Gold Abutment, for bridge CARES Ceramic Abutment Single crown Screw-retained v v Cement-retained v v v v Bridge Screw-retained v Cement-retained v v v v Removable overdentures Telescope v v v Retentive anchor Bar v Impression Implant level v v v v v Abutment level Material* Titanium Titanium Ceramicor® Ceramicor® Zirconia Page 48 48 55 67 77 *See information on sterilization conditions on page 157. 2. General information 9 CARES Titanium Abutment Cementable Abutment Multi-Base Abutment Abutment for Bars, Gold Abutment for Bars, Titanium LOCATOR® Abutment v v v v v v v v v v v v v v v v v v Titanium Titanium Titanium alloy Ceramicor® Titanium Titanium alloy 77 90 105 123 123 133 2. General information 10 2.4 Coding The Straumann® Bone Level Implant line has a simple and thorough color coding and laser marking approach, which enables the quick and precise identification of secondary parts, surgical instruments and auxiliaries. This concept simplifies the communication substantially between the individuals involved in the treatment process. The following scheme illustrates the above mentioned approach: 2. General information Connection Implant Ø Instruments Implant Closure screw Narrow CrossFit ™ (NC) 3,3 mm Regular CrossFit ™ (RC) 4,1 mm 4,8 mm Laser marked (NC/RC) v v Color-coded v 2. General information 11 Healing abutment Impression post Implant analog Temporary abutment Abutment v v v v v v v Screw head Screw head 12 3. Preoperative planning Careful treatment planning is of utmost importance. A comprehensive pre-implantation diagnosis, evaluation and plan are an absolute prerequisite to ensure treatment success. The implant forms the apical extension of the restoration and is thus the planning basis for the surgical procedure aiming at a specific prosthetic result. Close communication between the patient, dentist and dental technician is imperative to achieve excellent implant-borne restorations. 3.1 Wa x-up/Set -up To determine the topographical situation, axial orientation and choice of implants, making a wax-up/set up using the previously prepared study cast is recommended. Subsequently, the type of superstructure can be defined. The wax-up/set-up can later be used as the basis for a custom-made X-ray or drill template and for a temporary restoration. Abutments should always be loaded axially. Ideally, the long axis of the implant is aligned with the cusps of the opposing tooth. Extreme cusp formation should be avoided as this can lead to unphysiological loading. 3.2 X-ra y te mplate wit h reference spheres For easier determination of bone availability, the use of an X-ray template with X-ray reference spheres is recommended. First, mark the selected implant positions on the study cast. Then fix the X-ray reference spheres at the marked points and make the vacuum-formed template with the spheres. The subsequently taken X-ray or computer tomography (CT) gives information on bone availability, quality and mucosal thickness. Based on these properties the number of implants, the exact implant positions, diameters and lengths can be determined. The X-ray reference sphere has a diameter of 5 mm. The image of the sphere on the X-ray provides the reference value for the magnification scale. 3. Preoperative planning 13 3.3 Custom-made drill te mplate A custom-made drill template can facilitate planning and the preparation of the implant bed and enables precise use of the cutting instruments. The basis of planning when making this surgical template should be the desired prosthetic result. With these components, a surgical drill template can be produced in the usual manner: Art. No. Article Dimensions 049.810V4 Drill sleeve with collar height 10 mm outside Ø 3,5 mm inside Ø 2,3 mm 049.818V4 Stepped pin for 049.810 height 16 mm Ø 2,2/3,5 mm 049.816V4 Pin for 049.810 height 16 mm, Ø 2,2 mm 049.817V4 Pin for 049.810 height 10 mm, Ø 2,2 mm 049.819V4 Pin for 049.810 height 16 mm, Ø 3,5 mm The Straumann brochure “Surgical fabrication and use of a custom-made drilling template“ (Art. No. 152.290) contains two fabrication methods with step by step instructions. Vacuum-formed template with integral pins as X-ray reference. Vacuum-formed template with integrated drill sleeve as drilling template. 3. Preoperative planning 14 3. Preoperative planning Art. No. Article Dimensions Material 040.526 Thermoplastic Drill templates set, single tooth, contents: Thermoplastic drill template for single-tooth sites (V5) sleeve height 10 mm, inner-Ø 2,3 mm titanium/polymer Guide pin (V5) length 20 mm, Ø 2,3 mm stainless steel Drill for dental laboratory Ø 2,3 mm steel 040.527 Thermoplastic drill templates set, free-end situation, contents: Thermoplastic drill template for free-end situations (V5) sleeve height 10 mm, inner-Ø 2,3 mm titanium/polymer Guide pin (V5) length 20 mm, Ø 2,3 mm stainless steel Drill for dental laboratory Ø 2,3 mm steel V5 = 5 components per pack For more detailed information, refer to the package insert “Thermoplastic Drill Template Sets” (Art. No. 150.902). 3.4 Ther moplastic drill te mplate Drill a hole in the previously determined implant position and axis in the plaster anatomic cast. Then insert the pin into the drilled hole in order to check the implant position. Subsequently, heat the template in water until it is soft and transparent. Place the template on the guide pin and press it onto the plaster teeth. After it has cooled and been disinfected, the thermoplastic drill template determines exactly how the pilot drill (Ø 2,2 mm) is to be guided. Drill hole template for single tooth gap Drill hole template for free end saddle 15 Healing Abutment Prefabricated healing abutment (titanium) p. 16–18 Customizable healing abutment (polymer) p. 25–26 Temporary Abutment (polymer with titanium inlay) p. 27–33 The Straumann® Bone Level Implant line puts a strong emphasis on esthetic considerations. It offers tailormade solutions that allow for natural soft tissue shaping and maintenance in all indications. A versatile portfolio of healing and temporary abutments is available, including customizable products made of polymer for easy and fast processing. 4. Soft tiss ue management 4.1 Soft tiss ue management solutions 4. Soft tissue management Esthetic results are crucially determined by successful soft tissue management. To optimize the soft tissue management process, various components with Consistent Emergence Profiles™ are available in the prosthetic portfolio of the Straumann® Bone Level Implant. This applies for all healing abutments, the temporary abutment and the abutments for the final restoration. Thus, the emergence profiles are uniform throughout the treatment process (for optimal healing abutment selection see p. 19–24). Healing abutment Temporary restoration Final restoration 88 16 4.2 Prefabricated healing ab utment Intended use ppSoft tissue management ppClosure of implant connection for submerged and non-submerged healing Characteristics Simple ppOne-piece design ppColor-coded and laser-marked ppAnatomically shaped emergence profiles, matching impression post and final abutments (for optimal healing abutment selection see p. 19–24) Reliable ppTight connection 4. Soft tissue management Prosthetic procedure: p. 17–18 1 2 17 4.2.1 Prefabricated Healing Abutment – Prosthetic procedure Step 1 – Insertion Insert the healing abutment w pp ith the SCS screwdriver. The friction fit secures the healing abutment to the instrument during insertion and ensures safe handling. ppHand-tighten the healing abutment. The cone-in-cone design provides a tight connection between the two components. 4. Soft tissue management Step 2 – Wound closure ppAdapt the soft tissue and suture it back tightly around the abutment. Prosthetic procedure 18 The bottle-shaped healing abutment pre-shapes the soft tissue by allowing for a slight excess of mucosa during healing. The insertion of the final restoration pushes the formed tissue outward, supports the creation of a naturally shaped peri-implant soft tissue. 4. Soft tissue management Optional: Bottle-shaped and Customizable Healing Abutment Prosthetic procedure The customizable healing abutment allows for individual soft tissue management. Note Do not use the customizable healing abutment for longer than 6 months. Healing abutments are delivered non-sterile and can be sterilized prior to use (see instructions, p. 157). 19 Anatomic Ø 4.0 mm LOCATOR® Ø 3.8 mm Art. No. 022.2102 022.2104 022.2502 022.2503 022.2505 022.2152 022.2154 022.2504 022.2506 Art. No. GH 2.0 mm 3.5 mm 2.0 mm 3.0/4.0 mm 5.0/6.0 mm Conical Ø 3.6 mm 024.2222 2.0 mm 024.2224 3.5 mm 024.2226 5.0 mm 024.2242 2.0 mm Conical Ø 4.8 mm 024.2244 3.5 mm 024.2246 5.0 mm Bottle shape Ø 3.3 mm 024.2234 3.5 mm 024.2236 5.0 mm Temporary Ø 5.0 mm 024.2370 – GH = Gingiva Height Note The corresponding healing abutments for the Meso, gold, and customized abutments depend on the emergence profile of the final restoration! The above illustration should be understood as a recommendation by Straumann on the optimal use of the “Consistent Emergence Profiles” concept. = ideal combination = best fit Overview of Bone Level abutments and corresponding healing abutments Which healing abutments suit which abutments? Straumann® Bone Level Implant Line – NC Platform 4. Soft tissue management 20 GH = Gingiva Height = ideal combination = best fit 4. Soft tissue management Cementable Ø 3.5 mm Cementable Ø 5.0 mm Art. No. 022.2311 022.2312 022.2313 022.2321 022.2322 022.2323 022.2325 022.2326 022.2327 Art. No. GH 1.0 mm 2.0 mm 3.0 mm 1.0 mm 2.0 mm 3.0 mm Conical Ø 3.6 mm 024.2222 2.0 mm 024.2224 3.5 mm 024.2226 5.0 mm 024.2242 2.0 mm Conical Ø 4.8 mm 024.2244 3.5 mm 024.2246 5.0 mm Bottle shape Ø 3.3 mm 024.2234 3.5 mm 024.2236 5.0 mm Temporary Ø 5.0 mm 024.2370 – Straumann® Bone Level Implant Line – NC Platform Note The corresponding healing abutments for the Meso, gold, and customized abutments depend on the emergence profile of the final restoration! The above illustration should be understood as a recommendation by Straumann on the optimal use of the “Consistent Emergence Profiles” concept. 21 GH = Gingiva Height = ideal combination = best fit 4. Soft tissue management Multi-Base Ø 3.5 mm Multi-Base Ø 4.5 mm Multi-Base Ø 4.0 mm Art. No. 022.2731 022.2732 022.2734 022.2741 022.2742 022.2744 022.2782 022.2786 Art. No. GH 1.0 mm 2.5 mm 4.0 mm 1.0 mm 2.5 mm 4.0 mm 2.5 mm Conical Ø 3.6 mm 024.2222 2.0 mm 024.2224 3.5 mm 024.2226 5.0 mm Konisch Ø 4.8 mm 024.2242 2.0 mm 024.2244 3.5 mm 024.2246 5.0 mm Bottle shape Ø 3.3 mm 024.2234 3.5 mm 024.2236 5.0 mm Provisorium Ø 5.0 mm 024.2370 – Straumann® Bone Level Implant Line – NC Platform Note The corresponding healing abutments for the Meso, gold, and customized abutments depend on the emergence profile of the final restoration! The above illustration should be understood as a recommendation by Straumann on the optimal use of the “Consistent Emergence Profiles” concept. 22 GH = Gingiva Height = ideal combination = best fit 4. Soft tissue management Anatomic Ø 6.5 mm Locat or® Ø 3.8 mm Art. No. 022.4102 022.4104 022.4501 022.4503 022.4505 022.4152 022.4154 022.4502 022.4504 022.4506 Art. No. GH 2.0 mm 3.5 mm 1.0/2.0 mm 3.0/4.0 mm 5.0/6.0 mm 024.4222 2.0 mm Conical Ø 4.5 mm 024.4224 4.0 mm 024.4226 6.0 mm 024.4242 2.0 mm Conical Ø 6.0 mm 024.4244 4.0 mm 024.4246 6.0 mm Bottle shape Ø 4.4/4.7 mm 024.4234 4.0 mm 024.4236 6.0 mm Temporary Ø 7.0 mm 024.4370 – Straumann® Bone Level Implant Line – RC Platform Note The corresponding healing abutments for the Meso, gold, and customized abutments depend on the emergence profile of the final restoration! The above illustration should be understood as a recommendation by Straumann on the optimal use of the “Consistent Emergence Profiles” concept. X 23 Straumann® Bone Level Implant Line – RC Platform GH = Gingiva Height = ideal combination = best fit 4. Soft tissue management Cementable Ø 5.0 mm Cementable Ø 6.5 mm Art. No. 022.4321 022.4322 022.4323 022.4331 022.4332 022.4333 022.4325 022.4326 022.4327 022.4335 022.4336 022.4337 Art. No. GH 1.0 mm 2.0 mm 3.0 mm 1.0 mm 2.0 mm 3.0 mm 024.4222 2.0 mm Conical Ø 4.5 mm 024.4224 4.0 mm 024.4226 6.0 mm 024.4242 2.0 mm Conical Ø 6.0 mm 024.4244 4.0 mm 024.4246 6.0 mm Bottle shape Ø 4.4/4.7 mm 024.4234 4.0 mm 024.4236 6.0 mm Temporary Ø 7.0 mm 024.4370 – X X = with modifications Note The corresponding healing abutments for the Meso, gold, and customized abutments depend on the emergence profile of the final restoration! The above illustration should be understood as a recommendation by Straumann on the optimal use of the “Consistent Emergence Profiles” concept. 24 GH = Gingiva Height = ideal combination = best fit 4. Soft tissue management Multi-Base Ø 4.5 mm Multi-Base Ø 6.5 mm Multi-Base Ø 4.0 mm Art. No. 022.4741 022.4742 022.4744 022.4761 022.4762 022.4764 022.4782 022.4786 Art. No. GH 1.0 mm 2.5 mm 4.0 mm 1.0 mm 2.5 mm 4.0 mm 2.5 mm Conical Ø 4.5 mm 024.4222 2.0 mm 024.4224 4.0 mm 024.4226 6.0 mm Conical Ø 6.0 mm 024.4242 2.0 mm 024.4244 4.0 mm 024.4246 6.0 mm Bottle shape Ø 4.4/4.7 mm 024.4234 4.0 mm 024.4236 5.0 mm Temporary Ø 7.0 mm 024.4370 – Straumann® Bone Level Implant Line – RC Platform Note The corresponding healing abutments for the Meso, gold, and customized abutments depend on the emergence profile of the final restoration! The above illustration should be understood as a recommendation by Straumann on the optimal use of the “Consistent Emergence Profiles” concept. 88 25 4.3 Customizable Healing Abutment Intended use ppIndividual soft tissue management for esthetic cases ppClosure of implant connection during healing phase Characteristics Simple ppPolymer material allows for easy and quick chair-side modification ppEasy-to-achieve esthetics due to gingiva-colored and modifiable polymer material Reliable ppCrossFit™ Connection Note Do not use for longer than 6 months. The customizable healing abutment can be shortened vertically no more than 5 mm. 4. Soft tissue management Prosthetic procedure: p. 26 1a 1b 26 4.3.1 Customizable Healing Abutment – Prosthetic procedure Step 2 – Insertion Hand-tighten the healing a pp butment in the implant with the SCS screwdriver and temporarily seal the screw channel (e.g. with composite). 4. Soft tissue management Prosthetic procedure Step 1 – Customizing ppIndividualize the healing abutment on an analog according to the mouth situation. Heatless wheels and new cross-toothed millers are recommended for grinding. ppTo avoid smearing of the polymer, adjust the bur speed properly (low rpm number, little pressure). 88 88 27 4.4 Temporar y Abutment Intended use ppIndividual soft tissue management for esthetic cases ppScrew- or cement-retained temporary crowns ppCement-retained temporary bridges Characteristics Simple ppPolymer material allows for easy and quick chair-side modification ppEasy-to-achieve esthetics due to tooth-colored and modifiable polymer material Reliable ppPrecise fit and high stability due to reinforcement with titanium inlay ppConnexion CrossFit™ Note Do not use for longer than 6 months. Place temporary restoration out of occlusion. The temporary abutment can be shortened vertically no more than 6 mm and in the lower end be reduced radially no more than 0,5 mm (NC temporary abutment) and 1 mm (RC temporary abutment) respectively. 4. Soft tissue management Lab procedure: p. 28–33 Prosthetic procedure: p. 28–33 1a 1b 28 4.4.1 Temporary Abutment – Procedure Option A: Screw-retained temporary crown Step 1 – Customizing Individualize the temporary a pp butment on an analog according to the mouth situation. Heatless wheels and new cross-toothed millers are recommended for grinding. ppTo avoid smearing of the polymer, adjust the bur speed properly (low rpm number, little pressure). Note For optimal adhesion of the temporary veneering material, roughen or sandblast the upper section of the abutment or integrate a means of retention. 4. Soft tissue management Lab procedure Prosthetic procedure 2a 2b 2c 2d 29 Step 2 – First insertion Hand-tighten the temporary a pp butment in the implant/implant analog with the SCS screwdriver and temporarily seal the screw channel (e.g. with cotton). ppUse a standard technique to fabricate the temporary restoration (e.g. prefabricated crown form or vacuumformed sheet technique as shown here). 4. Soft tissue management Lab procedure Prosthetic procedure 3 4 30 Step 3 – Finishing Remove excess acrylic, r pp eopen the screw channel and finish the temporary restoration. 4. Soft tissue management Step 4 – Final insertion ppClean the polished temporary restoration, place it on the implant and tighten the screw with a torque between 15 Ncm and 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppCover the screw head with absorbent cotton or gutta- percha and seal the screw channel with temporary veneering material (e.g. composite). Lab procedure Prosthetic procedure 1a 1b 31 Option B: Cement-retained temporary crown Step 1 – Customizing Individualize the temporary a pp butment on an analog according to the mouth situation. Heatless wheels and new cross-toothed millers are recommended for grinding. ppTo avoid smearing of the polymer, adjust the bur speed properly (low rpm number, little pressure). 4. Soft tissue management Note For optimal adhesion of the cement-retained temporary crown, roughen or sandblast the upper section of the abutment. Lab procedure Prosthetic procedure 2a 2b 32 Step 2 – Fabricating the cement-retained temporary single crown Use a standard procedure t pp o fabricate the cement- retained single crown (e.g. grind out a prefabricated plastic tooth). 4. Soft tissue management Lab procedure Prosthetic procedure 3a 3b 4 33 Step 3 – Placing the customized abutment Place the abutment o pp n the implant and tighten the screw with a torque between 15 Ncm and 35 Ncm using the SCS screwdriver along with the ratchet and the torque control device (see instructions in chapter 7.5, p. 155). ppCover the screw head with absorbent cotton or guttapercha and seal the screw channel temporarily (e.g. with absorbent cotton). 4. Soft tissue management Step 4 – Cementing the temporary single crown ppCoat the internal configuration of the crown with temporary cement and cement it on the temporary abutment. Lab procedure Prosthetic procedure 34 5. impression ta king 5. Impression taking Open tray technique Closed tray technique 5.1 Opti ons for impressi on taking Impressions for the Straumann® Bone Level Implant can be taken by either of the two following procedures: Straumann® Bone Level Implant The technique used depends on the user’s preference and the clinical situation. Both techniques are described in the following chapters. p. 35–38 p. 39–42 88 88 35 5.2 Open tra y impressi on Intended use ppOpen tray impression technique Characteristics Simple ppColor-coded components corresponding to prosthetic connection ppSlender emergence profile accommodates space limitations ppGuide screw can be tightened either by hand or with the SCS screwdriver Reliable ppHigh precision impression components give an exact replica of the intraoral situation ppClear-cut tactile response from the prosthetic connection verifies proper seating of components Note Open tray impression procedure requires a custom-made tray with perforations. Impression posts are intended for single use only to ensure optimal fit and precise impression taking for each patient. 5. Impression taking Prosthetic procedure: p. 36–37 Lab procedure: p. 38 1 36 5.2.1 Open tray impression – Prosthetic procedure Step 1 – Positioning the impression post Ensure sufficient access t pp o the implant site in order to avoid pinching in the gingival tissue. Be aware that the sulcus may collapse rapidly once the healing components have been removed. ppClean the internal configuration of the implant thoroughly from blood, tissue, etc. prior to the impression procedure. ppPlace the impression post accurately into the implant and hand-tighten the guide screw. ppIn case of occlusal space limitation, the length of the impression post can be reduced by one retention ring after the guide screw has been removed. 5. Impression taking Prosthetic procedure 2c 2d 2a 2b 5. Impression taking 37 Prosthetic procedure ppUncover the screws before the material is cured. ppOnce the material is cured, loosen the guide screws and remove the tray. Step 2 – Impression taking ppMake perforations in the custom-made impression tray (light cured resin) according to the individual situation so that the positioning screw of the impression post sticks out. ppTake the impression using an elastomeric impression material (polyvinyl siloxane or polyether rubber). Note Due to its low tensile strength, hydrocolloid is not suitable for this application. 1a 1b 1c 2 38 5.2.2 Open tray impression – Lab procedure Step 2 – Fabricating the master cast Fabricate the master cast u pp sing standard methods and type 4 dental stone (DIN 6873). A gingival mask should always be used to ensure that the emergence profile of the crown is optimally contoured. 5. Impression taking Note When tightening the screw, grasp the retentive section of the analog securely to prevent the impression post from rotating. This is especially important with a shortened post. Lab procedure Step 1 – Analog repositioning and fixing ppReposition and fix the analog in the impression using the guide screw. To avoid inaccuracies when connecting, the analog must be positioned exactly in line with the grooves of the impression post before screwing in. 88 88 5. Impression taking 39 5.3 Closed tra y impressi on Intended use ppClosed tray impression technique Characteristics Simple ppColor-coded components corresponding to prosthetic connection ppSlender emergence profile to accommodate space limitations ppNo additional preparation (i.e. perforation) of tray required Reliable ppHigh precision impression components give an exact replica of the intraoral situation ppClear-cut tactile response from the prosthetic connection verifies proper seating of components Note Impression posts are intended for single use only to ensure optimal fit and precise impression taking for each patient. Prosthetic procedure: p. 40–41 Lab procedure: p. 42 1a 1b 40 Prosthetic procedure 5. Impression taking 5.3.1 Closed tray impression – Prosthetic procedure Place the polymer impression c pp ap on top of the fixed impression post. Ensure that the color of the cap corresponds to the color of the positioning screw in the post and that the arrows are aligned with the oral- vestibular direction. ppPush the impression cap in apical direction until it clicks. The impression cap is now firmly seated on the impression post. Step 1 – Positioning the impression post ppEnsure sufficient access to the implant site in order to avoid pinching in the gingival tissue. Be aware that the sulcus may collapse rapidly once the healing components have been removed. ppClean the internal configuration of the implant thoroughly from blood, tissue, etc. prior to the impression procedure. ppPlace the impression post accurately into the implant and tighten the guide screw hand-tight (using the SCS screwdriver). Note Ensure that the lateral planar areas of the post are facing mesial and distal. 2a 2b 2c 41 Unscrew and remove th pp e impression post and send it together with the impression tray to the dental technician. Step 2 – Impression taking ppTake the impression using an elastomeric impression material (polyvinyl siloxane or polyether rubber). Note Due to its low tensile strength, hydrocolloid is not suitable for this application. ppOnce the material is cured, carefully remove the tray. The impression cap remains in the impression material and therefore is automatically pulled off from the impression post with the removal of the tray. Prosthetic procedure 5. Impression taking 1a 1b 1c 2 42 5.3.2 Closed tray impression – Lab procedure Step 2 – Fabricating the master cast Fabricate the master cast u pp sing standard methods and a type 4 dental stone (DIN 6873). A gingiva mask should always be used to ensure that the emergence profile of the crown is optimally contoured. 5. Impression taking ppReposition the impression post in the tray. ppSmoothly push the impression post until you feel the tactile response of engagement. It is now firmly seated on the impression cap in the impression tray. Lab procedure Step 1 – Analog fixing and impression post repositioning ppMount the impression post on the analog using the guide screw. To avoid inaccuracies when connecting, the analog must be positioned exactly in line with the grooves of the impression post before screwing it in. Note Ensure that the color code of the guide screw corresponds to the color code of the analog and that the color code of the analog corresponds to the color code of the polymer cap in the impression material. 1 5. Impression taking 43 Step 1 – Insertion ppInsert the bite registration aids into the implants. Each component is fitted with a snap mechanism that holds it in the internal configuration. Note Protect the components against aspiration (e.g. use a throat pack or a thread). 5.4 Bite registrati on To simplify bite registration after impression taking, plastic bite registration aids are available in various heights. For repositioning on the master cast, the bite registration aids have a flat side laterally. Prosthetic procedure 2b 3 2a 44 Step 3 – Positioning To transfer the bite, put the bite r pp egistration in the analogs on the master cast. Fix the bite wax model and mount the maxilla and mandible casts on the articulator. Step 2 – Shortening ppShorten the bite registration aids (if needed) and apply the bite registration material. To ensure the repositioning from the mouth to the master cast, the occlusal area and the lateral flat side of the bite registration aids must be adequately surrounded with the registration material. Note Bite registration aids must be shaped out of the mouth. If they need to be shortened occlusally due to lack of space, ensure that the lateral flat side is not ground off. 5. Impression taking Prosthetic procedure 88 88 45 6.1 CrossFit™ PLAN SET/PLAN ab utment Intended use ppIntra- and extra-oral planning of prosthetic restoration Characteristics Simple ppColor-coded, well-marked and easily readable PLAN abutments ppComprehensive PLAN set containing all PLAN abutments arranged clearly ppEasy handling with the SCS screwdriver Reliable ppProper seating of PLAN abutments verified through the clear-cut response from the prosthetic connection ppPLAN abutments fabricated of sterilizable polymer material Note Clean and moist-heat-sterilize PLAN abutments after intra-oral use. Do not sterilize the cassette or its components. Replace non-functional PLAN abutments. 6. Restoration Lab procedure: p. 46 Prosthetic procedure: p. 46–47 6. Restoration 1a 1b 2 46 6. Restoration 6.1.2 CrossFit™ PLAN Set/PLAN abutment selection Step 2 – Ordering the stock abutment Once the best fitting P pp LAN abutment is determined, order the corresponding stock abutment (titanium, gold) using the allocation chart on the PLAN set inlay card. Step 1 – Selecting the right abutment ppOpen the PLAN set, pick up a PLAN abutment and secure it with the SCS screwdriver (empty mold for instruments built in). The Straumann® CrossFit™ PLAN Set allows for optimal planning of the restoration in the mouth and on the model. It gives the dentist and the dental technician greatest flexibility in cooperative planning and minimizes the quantity of stock abutments. The PLAN set contains all PLAN abutments available for the Straumann® Bone Level Implant (anatomic, cementable, gold, Multi-Base, LOCATOR®). ppPlace the PLAN abutment on the implant (intra-oral use) or implant analog (extra-oral use). This will aid in checking dimensions (rings on PLAN 
برچسب ها: BASIC INFORMATION ON THE prosthetic procedures Straumann® Bone Level Implant Line The ITI (International Team for Implantology) is academic partner of Institut Straumann in the areas of research، development and education. Content 1. Straumann® Bone Level Implant – Straumann expertise applied at bone level 3 2. General information 4 2.1 CrossFit™ Connection 4 2.2 Prosthetic options 6 2.3 Abutment overview 8 2.4 Coding 10 3. Preoperative planning 12 3.1 Wax-up/Set-up 12 3.2 X-ray template with reference spheres 12 3.3 Custom-made drill template 13 3.4 T hermoplastic drill template 14 4. Soft tissue management 15 4.1 Soft tissue management solutions 15 4.2 Prefabricated Healing Abutment 16 4.3 Customizable Healing Abutment 25 4.4 T emporary Abutment 27 5. Impression taking 34 5.1 O ptions for impression taking 34 5.2 O pen tray impression 35 5.3 Closed tray impression 39 5.4 Bite registration 43 6. Restoration 45 6.1 CrossFit™ PLAN Set/PLAN Abutment 45 6.2 Anatomic (and Meso) Abutment 48 6.3 Gold Abutment for crown 55 6.4 Gold Abutment for bridge 67 6.5 CARES Abutment 77 6.6 Cementable Abutment 90 6.7 Multi-Base Abutment 105 6.8 Abutment for bars 123 6.9 LOCATOR® Abutment 133 7. Aids and instruments 149 7.1 SCS Screwdriver 149 7.2 Polishing Aid 150 7.3 Ratchet and Torque Control Device 151 7.4 Assembling the Ratchet and the Torque Control Device 153 7.5 T ightening an abutment to 35 Ncm 155 8. About sterilization 157 9. Important guidelines 158 10. Index 159 88 88 2 Purpose of this guide This guide describes the essential steps required for the fabrication and insertion of prosthetic restorations for Straumann® Bone Level implants. For detailed information regarding implantation and soft tissue management see “Straumann® Bone Level Implant Line: Basic information on the surgical procedures” (Art. No. 152.754). See also DVD „Surgical and Prosthetic Procedures with the Straumann® Bone Level Implant“ (Art. No. 150.760) for additional information. Note Different procedures apply for dental technicians and prosthodontists. Such procedures are marked with a color code in the respective chapters of this guide: Purpose of this guide Lab procedure Prosthetic procedure Not all products shown are available in all markets. 3 The Straumann® Bone Level Implant provides you with a solution for all bone level treatments، with Straumann expertise and quality built in. Its design is based on the latest technology and scientific know-how in implant dentistry. Moreover، it respects key biological principles، brings predictable esthetic results and offers simple handling in all indications. 1. Stra umann ® Bone Level Implant – Stra umann expertise applied at bone level Bone Control Design™ The unique Bone Control Design™ is based on key biological principles and thorough scientific research to support crestal bone preservation and stable soft tissue margins. It features the following strengths: Fast o pp sseointegration with the SLActive surface technology ppOptimal transmission of forces into the bone through the biomechanical implant design ppConsideration of the biological distance with a horizontal distance of micro gap to bone ppReduction of micro movements while controlling the micro gap through a conical connection Consistent Emergence Profiles™ The prosthetic components of the Straumann ® Bone Level Implant line are designed to facilitate highly esthetic restorations that perfectly mimic natural teeth. These implant line components، designed to match the abutment profiles، allow you to easily attain esthetic results through soft tissue management. CrossFit™ Connection The prosthetic connection is intuitive،  

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of base metal in the solder, which may vaporize when the gap between the components is too narrow or when the solder is overheated. 4. Strong. Solder should be as strong as the alloy with Solder Joints and Other Cor. which il is used. The hardness of the solder decreases as the fineness (gold content) increases. 5. Free-flowing. The solder should flow freely. Silver in the solder tends to make it adhere to metal and to flow more freely. Copper, on the other hand, makes it more sluggish. Solders that melt at higher temperatures have a lower surface tension and flow easily through narrow gaps. Low-fusing solders flow poorly through narrow gaps 5 6. Same color. The color of the solder should match that of the alloy being soldered. As is the case with many aspects of dentistry and life in general, soldering is much more complicated today than it was a relatively few years ago. Crowns and fixed partial dentures were made of a gold alloy, solders were gold, fluxes were borates, and, at least from a dental perspective, it was a fairly simple process. With the nearly 1,500 alloys available for use in dentistry today, a dentist cannot be proficient in every aspect of soldering. However, soldering is still not in the exclusive domain of the dental laboratory. There are occasions when being able to solder in the office can be a great convenience for dentist and patient alike. An otherwise acceptable gold restoration may not have an adequate proximal contact. Adding that proximal contact is a simple procedure that can and should be done in the office It usually does not require investing. If a fixed partial denture must be sectioned because it does not seat completely, or if it was constructed in segments for intraoral try-in, the dentist must at least be able to index the components to insure that the technician who does the actual soldering will have an accurate starting point. The components that are to be joined with solder must be stabilized in soldering investment to maintain the exact relationship throughout the soldering process. The soldering procedures to be considered are: • Gold alloy fixed partial denture soldering • Adding proximal contact • Repairing casting voids • Breaking solder joints • Preveneer metal-ceramic alloy soldering • Postveneer metal-ceramic alloy soldering Gold Alloy Fixed Partial Denture Soldering There are two ways in which a three-unit fixed partial denture can be fabricated. It can be made as a single casting, with the pontic wax pattern attached to that of each of the retainers. The fixed partial denture may be cast as two units, with the pontic wax pattern attached to that of one of the retainers and cast with it. The two units are then assembled by soldering. Single-Piece Casting Certainly it is possible to achieve an accurately fitting fixed partial denture by use of a single-piece casting.6 If this is to be attempted, a one-piece die in which the abutment preparations have not been separated from each other offers the greatest accuracy. (Refer to Chapter 26 for a discussion of this type of die.) To achieve maximum accuracy, the wax pattern should be invested in a largediameter casting ring (60 mm or larger) to assure uniform expansion.7 Either a round or an oval casting ring can be used. Both investment expansion and pattern distortion can affect the accuracy of multiunit castings & There is less pattern distortion when investment is allowed to bench set rather than using the hygroscopic technique.8 As the length of a single-piece fixed partial denture casting increases, so does its inaccuracy9"11 Distortion is three-dimensional, as though the pattern has elongated and twisted. Schiffleger et al found the discrepancies greatest at the mesiogingival aspect of the anterior retainer and the distolingual aspect of the posterior retainer.11 Four- and five-unit fixed partial dentures joined by soldering have better-fitting margins than do onepiece castings of the same length.12 Any fixed partial denture larger than three units should still be cast in two pieces and soldered.13 A single-piece casting must be tried in the mouth with an awareness of some of the problems inherent in the technique The single-piece casting offers no opportunity to verify the fit of the individual retainers. In an effort to make a nonfitting casting seat, there is a tendency to relieve the internal surfaces of the retainers so drastically that all retention is lost. In that event, the fixed partial denture cannot be saved even if it is later separated, indexed, and soldered. If the fixed partial denture will not seat totally after routine adjustments have been made, use a thin (0.009 inch or 0.23 mm) separating disc (Ultra Thin Abrasive Disks, Dedeco International, Long Eddy, NY) to cut through one connector and then try the separate pieces of the fixed partial denture back in the mouth. Indexing A two-piece casting can be used to fabricate a fixed partial denture with a solid pontic, such as a hygienic. The technique described is used for soldering three-unit posterior fixed partial dentures. The pontic is cast with the smaller retainer. Then the retainer-pontic unit is soldered to the larger retainer, utilizing an index of the relationship of the fixed partial denture components in the patient's mouth. This provides for the most accurate relationship between the retainers and between each retainer and its abutment tooth. The index must accurately maintain that relationship until the parts of the fixed partial denture have been embedded in soldering investment. Numerous materials have been described for transferring the relationship of Gold Alloy Fixed Partial Denture Soldering the fixed partial denture components from mouth to laboratory bench: plaster,14 ie sticky wax.317 autopolymerizing acrylic resin (Duralay),18 4-META adhesive resin,'9 and zinc oxide-eugenol,ao which has been shown to be a highly accurate material for indexing.20 If plaster is used, the most accurate and consistent results will be obtained if the castings are not removed from the index prior to investing.21 Resin indices (Duralay, Reliance Dental Manufacturing Co, Worth, ll_) are as accurate as those made of plaster if the components are separated from and reseated in the plaster However, excess bulk of a resin index will diminish accuracy because of additional polymerization shrinkage.?? Armamentarium 1. Plaster bowl, spatula 2. Impression plaster 3. Bite registration paste, mixing pad 4. Index tray or tongue blade 5. Petrolatum 6. Laboratory knife with no. 25 blade 7. PKT (Thomas) waxing instruments: no. 1, no. 2 8. Straight handpiece, no. 8 round bur 9. Explorer 10 Sticky wax. utility wax, boxing wax 1. Soldering investment 2. Vibrator 3 No. 2 pencil 4 Fisher burner, matches 5. Tripod, screen 16. Solder (650 fine), soldering flux Blowpipe, casting tongs 8. Toothbrush Remove the provisional restoration from the patient's mouth and make certain that there are no traces of temporary cement left on the tooth preparations. Try in the single retainer first and then the retamer-pontic combination. On the first try-in for each, do not leave the other unit in place. Verify the marginal fit of each retainer first. Make sure that there is a small gap between the pontic and the retainer to which it has not yet been soldered. Adjust the occlusion with green stones or other appropriate abrasives. Perform preliminary finishing procedures on the retainer margins, if they are accessible, Smooth off the occlusal surface with a rubber sulci disk. The rough surface left on the casting by a green stone could create problems in seating the castings into the index. Do not polish the castings at this point, since polishing rouge is iron oxide, a specific antiflux for soldering. Mix a small amount of fast-setting impression plaster. Place it on a plastic index tray (Index Tray, Crown Enterprises, Oklahoma City, OK) or a thoroughly wet tongue depressor (Fig 27-1). Arrange the index material on the carrier so that a sharp ridge of material runs the length of the depressor (Fig 27-2) or tray. This ridge facilitates getting index material into the central grooves of the casting. Carefully position the index on the occlusal surface of the castings, vibrating it gently as you seat it (Fig 27-3). Solder Joints and Other Cor / cCFt! Fig 27-5 Excert piaster jround [he I h"L> imprint i> trimmed nfr wilh Fig 27-8 When the [wo surfaces to be soldered are parallel, ther is less likelihood ot di&torhon. OtclLfsal view (topi and facial viev (bottom). Gold Alloy Fixed Partial Demure Soldering When the material has set, remove the index. If the castings come out with it, so much the better (Fig 27-4). A plaster index is most accurate when the crowns stay in it.21 Carefully trim it with a laboratory knife with a no. 25 blade so that all margins are exposed by at least 1.0 mm (Fig 27-5). The index should extend at least 3.0 mm mesially and distally past the crowns being soldered. This guarantees a symmetric, uniform bulk of investment surrounding the units to be soldered and should minimize distortion.15 The plaster index should be approximately 6 mm (0.25 inch) thick. If the crowns separate from the index when it is removed from the cast, trim off excess that might prevent the castings from seating completely back into the imprints. Trim the area around the imprints enough so that a substantial part of the axial walls will be covered by investment (Fig 27-6). Then clean the index thoroughly with compressed air. The slightest bit of debris between the index and crown will keep the crown from seating in the index and will make the relationship inaccurate. Scrub the occlusal surfaces of the crowns and clean them in the ultrasonic cleaner before repositioning them in the index Place the index on the bench and carefully try the castings in their respective imprints. If the castings touch, there is a likelihood of increased distortion.31423 For this reason, it has been suggested that there be a gap of at least 0.005 inch (0.13 mm) between the pontic and the retainer.3'14 A conflict arises in determining the proper gap dimension for a solder joint. The wider the solder joint gap, the stronger the joint, apparently because there is less porosity in the joint.13 Therefore, a gap width of 0.012 inch (0.30 mm) is recommended for strength. In another study, however, it was determined that increased gap width produces an increase in distortion. A gap width of 0.006 inch (0.15 mm) is recommended for greatest accuracy.24 Obviously there is a need for some compromise. A gap width of 0.008 inch (0.20 mm) would appear to be optimum, since it is intermediate between the narrow, undistorted joint and the wide, strong joint. Indeed, some investigators have used this distance as a standard.?5 Furthermore, it can be determined easily by inserting a business card into the gap (Fig 27-7), since the average card is 0.008 inch thick. The opposing surfaces of the retainer and pontic on either side of the solder joint should parallel each other {Fig 27-8). If these surfaces diverge, the resulting wedge shape of the solder joint may produce distortion.?6 In addition, wherever there is contact, there will not be space for the solder and there will be no bonding. On the other hand, if the gap is too wide, it will be harder to solder, since capillary action is more difficult to achieve. As a result, solder will be more likely to stick to one surface or the other, instead of filling the gap and adhering to both surfaces. Investing Pontics and retainers that have come off the index should be luted back on the index with sticky wax. it is often necessary to use a no. 8 round bur to cut a small "well" on the facial and lingual edges of each imprint in the index (Fig 27-9). This permits space lor a bulk of sticky wax without forcing it over the margins. Separate the tongue depressor from the index if they have not already come apart. Use a cast trimmer to remove excess from the edge of the index, leaving approximately 3.0 mm all around the perimeter (Fig 27-10). Allow the index to dry, and apply sticky wax to each casting using the PKT no. 1 instrument (Fig 27-11). Do nol allow the sticky wax to cover occlusal margins (if any) on the facial surfaces. Fig 27-9 Wells are cut along the edges of the L imprints to provide space for sticky wax. Fig 27-10 The periphery of the plaster index is trimmed on the cast trimmer so that there will be a 3.0-mm apron around the imprint of the FPD. Solder Joints and Other Cor Fig 27-12 A triariguldr-shaped piece of utility wax is extended facially and lingually from the solder joint area. There must be no gaps. Flow utility wax into the joint with a PKT no. 2 instrument to prevent the joint area from being filled with investment. The waxed area should be slightly larger than the solder joint will be. Any margin covered by wax at this point will not be covered by soldering investment. This could cause the margin to melt when heated by the blowpipe during soldering. Run a triangular-shaped extension of utility wax from the lingual side of the solder joint area of the index (Fig 27-12). There should be a slightly smaller one on the facial. These wax wedges will be narrower in the solder joint area than at the edge of the index. Check again to make sure that the castings are completely seated. A separating medium (Super-Sep, Kerr Dental Manufacturing Co, Romulus, Ml) may be painted over the index outside the castings to insure easy separation later. Place boxing wax around the index (Fig 27-13). There should be 3.0 mm of space between the castings and the boxing wax. Mix a small amount of soldering investment (Soldering Investment, Whip Mix Corp, Louisville, KY] . Paint it into the castings and carefully vibrate it into the boxed area (Fig 27-14). Hold the index so that there is a finger between it and the vibrator. Overzealous vibrating could jar one of the castings loose. Gold Alloy Fixed Partial Denture Soldering %S£ Allow the investment to set for 1 hour and then remove the boxing wax (Fig 27-15). Run hot water over the investment and index to soften the sticky wax. Separate the index and the investment with a heavy laboratory knife (Fig 27-16). Inspect the block of investment containing the fixed partial denture castings (Fig 27-17). The investment should measure 2.5 cm (1.0 inch thick) top to bottom. If it is more, trim off the excess from the bottom on a cast trimmer (Fig 27-18). Use a laboratory knife with a no. 25 blade to cut a V-shaped notch buccal and lingual to the solder joint (Fig 27-19). The wax extension placed on the lingual earlier will facilitate this step. The lingual notch is larger than the facial, because the solder will be fed into the joint area from the lingual The facial notch is necessary to gain access for healing the castings during soldering. If either of these notches is not placed, an incomplete solder joint is likely to result. Flush out the remaining wax with boiling water Solder Joints and Other Conne Fig 27-20 Pei face of the castings. from a boil-out tank. Use a no. 2 pencil to draw a heavy line across the marginal ridges adjacent to the solder joint area (Fig 27-20). This will act as an ant if lux and will prevent solder from flowing onto the occlusal surfaces. While the castings are still warm, add flux paste with an explorer (Fig 27-21). It will melt, and capillary action will draw it through the entire solder joint. If flux is applied later when the castings are hot, it will bubble up and stick where it is applied rather than flowing into the joint where it is needed. Also, surface oxidation may occur before the protective flux is applied. Soldering The invested castings should be preheated to insure even heating. If the castings are not preheated, the uneven heat distribution that will occur when the blowpipe is applied to a cold block may produce distortion of the finished joint.14'23 The investment block can be placed in an oven and brought from room temperature to 815°C (1,500°F).|7 In an alternative method of preheating the invested castings, they are set on a tripod and screen over a Fisher burner. Continue to preheat the castings for 10 to 15 minutes (Fig 27-22). Begin heating with the blowpipe, and brush the flame over the entire investment block repeatedly until it is so hot that the castings glow red when the flame is held on them for 2 or 3 seconds (Fig 27-23). Leave the burner on throughout this process. Wedge two or three pieces of solder, 2 x 3 mm, covered with flux, into the lingual embrasure of the joint area (Fig 27-24). They will be melted by the heat of the castings, and not by the blowpipe. If too much solder is used, it may run onto the occiusal surface, and a larger bulk of solder is more likely to produce distortion. Gold Alloy Fixed Partial Denture Soldering Fig 27-25 Hie flan If the blowpipe is used to melt the solder directly, the following difficulties can be expected: the solder will "ball up" and not flow at all, or it will not flow through the entire joint. Aim the blowpipe obliquely at the investment, since an obliquely directed flame results in more even heating and less distortion.14 Concentrate the tip of the blue cone on the buccal side of the block near the open space between retainer and pontic (Fig 27-25). The solder on the lingual side of the castings will flow toward the source of heat on the facial. When the solder starts to flow, direct the torch into the buccal notch and keep it there while the solder flows through the joint. Leave the flame there a few seconds longer while the solder shimmers and appears to "roll" in the joint. Turn off the flame (Fig 27-26). Remove the investment block from the tripod with casting tongs and place it someplace where there is no chance of someone picking it up and getting burned. The bottom of a casting well is good for this purpose (Fig 27-27). If you must place it on a benchtop, select an area where there is little traffic and be sure the surface is heat resistant. Leave a conspicuous sign to warn off "lab lizards" who wander around picking up other people's work. Do not quench immediately. Quenching shortly after soldering will produce thermal stresses that will result in distortion.26 On the other hand, allowing the investment block to cool slowly to room temperature may produce excessive recrystallization and gram growth.3 The resulting solder joint will be weaker. If the invested fixed partial denture is allowed to bench cool for 5 minutes and is then quenched, distortion should be minimized This allows time for the gold and solder to respond to an ordering heat treatment, which will increase hardness and strength while reducing elongation. Place the invested block in water and remove the Solder Joints and Other Connectors Fig 27-28 The investment is removed after pi investment (Fig 27-28). That which does not flake off should be picked off with a sharp instrument and an old toothbrush (Fig 27-29). Examine the solder joint to make sure that it is pit free. Evaluate its size (Fig 27-30). If it is too bulky, it can be trimmed down with a carborundum disc. Inadequate bulk or the presence of pits requires reinvestment and resoldering. Air abrade the castings with 50 urn aluminum oxide. The fixed partial denture is ready to be finished and tried in the patient's mouth. Adding Proximal Contacts The addition of solder to a proximal contact area is done to build up a contour that may be deficient for any number of reasons. It can easily be done freehand on a single restoration A fixed partial denture must be invested before the addition. Fig 27-30 The solder joint farrow) is inspected for ploteness. Armamentarium 1. Straight handpiece 2. 5/8-inch Burlew disc 3. Bunsen burner, matches 4 No. 2 pencil 5. Locking soldering pliers 6. Solder (650 fine), soldering flux Finish the proximal area to be soldered with a Burlew disc. Outline the interproximal surface to be soldered with a no. 2 pencil. The area to be soldered must be wider than the contact. It should extend across the entire proximal surface, just apical to the marginal ridge. The periphery of this new bulk will be blended into the contours of the crown, rather than being a pimple on the side of the crown. A 1.5-cm-long piece of ceramic ring lining material can be rolled and packed into the restoration, leaving some to overlap the crown margins.27 This step will be of greater benefit for smaller crowns. Bend one tip of a pair of locking soldering pliers so that a crown can be held by its axial wall without the pliers touching the margin (Fig 27-31). Grasp the crown with the locking soldering pliers The bent beak should be inside the casting, and there should be no contact at any other point (Fig 27-32). Wrap a wet paper towel around the handle of the soldering pliers. Warm the casting slightly and place a small drop of soldering flux on the contact to be soldered, staying within the pencil outline. Dip a 2 x 4-mm piece of solder (± depending on the size of the casting) into the flux. Place the solder on the proximal surface (Fig 27-33). Holding the soldering pliers with the wet towel, place the casting over the burner, keeping the casting in the blue reducing tip of the flame (Fig 27-34). Keep it there until the casting glows a bright red, allowing the solder to melt and adapt itself to the casting. Repairing Casting Voids Fig 27-31 Soldering pliers Remove the casting from the flame. Allow a gold alloy casting to cool until the metal loses its glow and then quench it in water. Air abrade it with 50 fim aluminum oxide. If the casting is made of a base metal alloy, allow it to cool for at least 5 minutes before quenching it. Clean it with aluminum oxide abrasive. Then finish it to the proper contour and return it to the mouth for final adjustment of the contact area. Repairing Casting Voids There are some deficiencies in casting that can be repaired by soldering. "Blow holes" or voids extending all the way through a casting on an axial surface, or pits that do not extend all the way through, are candidates for solder repairs. Solder should not be used to repair: 1. Deficient margins It is impossible to get an acceptably adapted margin by adding solder, 2. Occlusal holes. Holes in the occlusal surface cannot be successfully soldered because of the risk of solder running over the entire surface. Aside from the technique difficulties, the presence of a hole on the occlusal surface of a crown is usually symptomatic of , te presece of ol symptomat inadequate occlusaf reduction in the preparation. Efforts to "patch" poor castings of this variety result in a compromise at best (and more often in a casting that is Solder Joints and Other Cor still poor). Inordinate amounts of time can be expended to salvage a restoration of questionable value when that same time could have been spent in remaking it properly. A remake is never a satisfying effort, but as Forrest Gump


برچسب ها: of base metal in the solder، which may vaporize when the gap between the components is too narrow or when the solder is overheated. 4. Strong. Solder should be as strong as the alloy with Solder Joints and Other Cor. which il is used. The hardness of the solder decreases as the fineness (gold content) increases. 5. Free-flowing. The solder should flow freely. Silver in the solder tends to make it adhere to metal and to flow more freely. Copper، on the other hand، makes it more sluggish. Solders that melt at higher temperatures have a lower surface tension and flow easily through narrow gaps. Low-fusing solders flow poorly through narrow gaps 5 6. Same color. The color of the solder should match that of the alloy being soldered. As is the case with many aspects of dentistry and life in general، soldering is much more complicated today than it was a relatively few years ago. Crowns and fixed partial dentures were made of a gold alloy، solders were gold، fluxes were borates،  

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of "making do" with a deficient ridge. There are nonetheless situations in which a more conservative approach may be desired. The patient's inability to undergo surgery, or an unwillingness to consider it, will force the consideration of an alternative form of pontic. In ridges with severe defects, where two or more pontics must be used to fill the space, it is not uncommon to eliminate gingiva! embrasure spaces between the pontics. "Black triangles" can be very unesthetic (Fig 26-20), and they serve no useful purpose. They collect plaque, interfere with the passage of floss, and may reduce the rigidity of the pontic span,3940 Pink porcelain can be added to the gingival embrasure area of the pontic to simulate interdental papilla (Fig 26-21),4142 although the shade rarely matches the particular hue of the patient's gingiva. The gingival extension of porcelain must be supported by the metal framework. If not, all of the gingival porcelain, as well as much of the facial porcelain, is at risk of fracturing.43 Elimination of interpontic gingival embrasures in a multitooth pontic may limit or eliminate soft tissue proliferation.44 Embrasure spaces filled with porcelain can be satisfactory when replacing mandibular molars39 and mandibular incisors,4043 where the gingival area is not subject to close scrutiny. However, it is more difficult to achieve an esthetic result simply by modification of the embrasure spaces in a high-profile area such as the maxillary incisor region (Fig 26-22). In the presence of a large deformity, an unmodified pontic would leave large, unsightly gingival embrasures (Fig 26-23), and the addition of a gingival flange may be too conspicuous (Fig 26-24). One solution used in the restoration of large ridge defects, particularly in the anterior segment, is the Andrews bridge system.45 It utilizes fixed retainers that are connected by a rectangular bar that follows the curve of the ridge under it (Fig 26-25). The prosthesis consists of teeth set in a patient-removable flange of gingiva-colored acrylic resin that clips over and is stabilized by the rectangular bar. Unfortunately, the flange is a food and plaque trap that is difficult to keep clean. In spite of its drawbacks, it still may be the best way of handling some large ridge defects.* Ponlics and Edentulous Ridges Fig 26-22 This large ridge defect in the maxillary anterior region is Fig 26-23 An ordinary pontic in this defect space will result ir not a good candidate for pontic modification. elongated pontic with large, highly visible embrasures. ig 26-25 In some cases, larger anterior defects may be better lanaged by an Andrews bridge system with a removable acrylic nsert that clamps down over a bar linking the abutments. Surgical Correction Ri igmentation can be accomplished by the addition of either soft or hard tissue, although filling a ridge defect with bone is not essential unless the ridge is to be used for implants.46 Excellent esthetic results in Class I defects can be obtained by connective tissue plastic surgery,47 in the form of a subepithelial or submucosal conr e tissue graftA The technique for a connective tissue graft is based on procedures described by Langer and Calagna48 and Kaldahl et al.47 A horizontal incision is made on the palate 1.0 mm apical to the free gingival margin of the molars. The length of the incision is dependent on the size of the defect being repaired. Vertical releasing incisions are made at both ends of the incision to allow the reflection of a split-thickness flap from the underlying connective tissue. The connective tissue base is dissected from the flap and removed for later use as the donor material. The Incisions are made 1 0 mm on either side of the defect in the edentulous ridge. An incision paralleling the crest of the ridge joins them (Fig 26-26). A partial-thickness pedicle flap is dissected to a depth of 1.5 to 2.0 mm in the palatal area. On the facial it can remain a partialthickness flap,47 or it can become a full-thickness flap (Fig 26-27).48 The donor tissue is placed into the defect under the base of the flap on the facial side of the ridge The Edentulous Ridge is placed at the base of the flap. (Fig 26-28) until the defect is filled. The flap is sutured, stabilizing the donor material in position (Fig 26-29). Unfortunately, apicccoronal Class II and III defects cannot be adequately treated by a pouch type of ridge augmentation. This type of defect is better treated using an onlay graft, which Seibert describes as a "thick free gingival graft."•l5'49 The surface of the edentulous ridge is planed with a no. 15 scalpel blade to remove as much epithelium as possible (Fig 26-30), followed by parallel striations cut into the exposed lamina propria 1.0 mm apart and perpendicular to the curvature of the alveolar ridge (Fig 26-31 ).3(i These cuts create bleeding, which is highly desirable for the graft to "take." Anesthetic for the procedure should be of a type providing minimal vasoconstriction and as far from the surgical site as possible, so as not to interfere with bleeding. The full-thickness donor tissue is harvested from the gingival zone or the palatal area of the tuberosity. The more fatty tissue that is included, the more the graft will shrink over time as the tissue is resorbed. The premolar/first molar vault area is an excellent donor source. It provides the greatest volume, and the gingiva there is pliable and easily adapted.50 The graft is placed over the prepared area and sutured in place (Fig 26-32). The procedure is limited by donor site availability. Ridges with s lay require more Ly. I l U ^ l jO V VI LI I OUVC IJ JCTI^^IO II ICly IWI^UHV i r i u i i ' MIL^II U I IV surgery, allowing 8 weeks before repeating the proce- ->• 'eii49 The patient should be forewarned of this possiPontics and Edentulous Ridges Fig 26-34 Pontics over the • !6-35 Excessive Ringiwl tissuf ad|ai ent tu the edentulou e (A) is removed by electrosurRerv before the fixed partial der Pontic Fabrication bility before the first surgery. Alter the graft has healed (Fig 26-33), the final fixed partial denture can be fabricated with a natural-looking pontic (Fig 26-34). If the facial contour of a ridge has a convex shape or irregularities that will prevent the use of a convex pontic, the soft tissue may be recontoured surgically to provide an easily cleanable and esthetic pontic. Another problem frequently encountered is a large "cuff" of tissue adjacent to the edentulous space. If left there, this tissue will force the connectors to be made too small occlusogingivally and will probably result in uncleanable embrasures under the solder joints after the fixed partial denture is seated (Fig 26-35, A). This roll of gingival tissue should be removed before the impressions are made for fabrication of the fixed partial denture (Fig 26-35. B). Pontic Fabrication Following are the techniques for waxing (1) an all-metal mandibular posterior fixed partial denture with a hygienic pontic and (2) a metal-ceramic maxillary posterior fixed partial denture3-1 with a modified ridge lap pontic. Armamentarium 1 Sable brush 2 Plaster bowl 3. Spatula 4. Quick-setting plaster 5. Bunsen burner and mat 6. PKT (Thomas) waxing ir no. 4, no. 5) 7. Beavertail burnisher 8. No. 7 wax spatula 9. Inlay casting wax 10. Die lubricant 11. Zinc stearate 12. Cotton pliers 13. Hollow plastic sprue All-Metal Hygienic Pontic Fabrication Pour the full-arch impression, filling the prepared teeth and one tooth on either side of them to a height of 3.8 cm (1.5 inches) off the tabletop (Fig 26-36). Trim the die to an overall height of about 3.2 cm (1.25 inches). Leave the dies attached with a common base, whioti will retain the exact relationship of the two preparations. Trim away the stone 1 2 cm (0 5 inch) apical to the finish line (Fig 26-37) to produce a U-shaped die. Coat the dies with cement spacer and lubricant. Fig 26-37 An unirimmed die should rr inches from preparation to base (A). E teeth is trimmed from the poured cast ( between preparations is reduced to 3 from an apical direction (Cl. ie prepared IUS segment Pontics and Edentulous Ridges Fig 26-38 The wax copi ping the die into molten can be started by dipparted by adding wax spatula. Place wax on ihe lubricated dies either by dipping them in a small container of molten wax (Fig 26-38) or adding dollops of wax with the large end of a no. 7 wax spatula (Fig 26-39). Use a warm beavertail burnisher to trim off excess wax beyond the retainer margins on the die (Fig 26-40). Place the wax patterns on the working cast and correct axial contours as needed (Fig 26-41). Replace the retainer patterns onto the die and connect them with a short stick of inlay wax (Fig 26-42) With a hot beavertail burnisher, carve wax off the "top" (occlusal aspect) of the stick of wax connecting the two retainers (Fig 26-43). Turn the die over and deposit the molten wax on the undersurface of the pontic (Fig 26-44). Carve the undersurface of the pontic to produce the totally convex "fish belly" (Fig 26-45). Smooth and round the undersurface of the pontic with instruments and a clean cotton roll dipped in die lubricant (Gator Die Lube. Whip Mix Corp, Louisville, KY) (Fig 26-46). Fig 26-43 Excess wax is removed from the occlusal aspect of the stick wax "pontic:" with a hot beavertail burnisher. Fig 26-44 Wax removed in the previous step is added to the underside of the pontit. Fig 26-45 A PKT no. 4 is used to define the gingival embrasure to smooth the undersurface of the pontic. Fig 26-46 Die luhncant on a cotton roll is used to finish smoothing the underside of the pontic. Parities and Edentulous Ridge Fig 26-47 The pattern is plated on the working cast, and the tours of the pontic are checked one last time. Fig 26-48 A runny mix of qui undcrsurfacc of the pontic. Plaster Matrix. Place the fixed partial denture wax pattern on the working cast and evaluate the configuration of the underside of [he pontic in relation to the edentulous ridge (Fig 26-47). Check for clearance with the ridge, impingement on the interdental papilla adjacent to the edentulous space, smoothness, and degree of curvature on the undersurface of the pontic. If any aspect requires adjustment, remove the wax pattern from the working cast and make the necessary changes. Then replace the patte n the c Lubricate the area of the cast adjacent to the edentulous ridge with a light coating of petrolatum. Construct a matrix on the facial and lingual surfaces of the cast with quick-setting plaster. Use a sable brush or instrument to place the plaster in the embrasure spaces around the lingual (Fig 26-48) and facial aspects of the wax pattern to insure complete support of the pontic and connectors later. Apply a thin mixture of plaster over the facial surface of the cast and the pontic (Fig 26-49). Be sure to wash the brush before the plaster sets on it. When the plaster has set on the cast, remove the wax pattern and trim the matrix so that none of it overlaps the prepared teeth (Fig 26-50). The edge of the matrix should be about 1.0 mm below the occlusal edge o! the pontic. With the wax pattern on the cast, close the articulator and reproduce all functional mandibular movements to test opposing cusp relationships. The occlusal surface is developed by the placement of cones and ridges, as are utilized for the waxing of any occlusal surface (Fig 26- 51). If the fixed partial denture is to be cast as two pieces with assembly following after try-in, saw through the larger connector with a piece of 3-0 suture silk (Fig 26-52). Finish the margins on the U-shaped die (Fig 26-53). Investing and Casting. Attach a 10-gauge hollow plastic sprue to a nonfunctional cusp of each of the fixed partial denture retainer wax patterns. Place one sprue on each of the pontic nonfunctional cusps (Fig 26-54). Connect the free ends of the multiple sprues with sticky wax. Remove the wax pattern from the die by grasping the facial and lingual surfaces of the pontic wax pattern between the thumb and forefinger (Fig 26-55). Do not use Pontic Fabrication surface is built up with a wax-added tech- Fig 26-52 If the fixed partial denture is to be cast in two pie< 3-0 suture silk can be used to saw through the connector Fig 26-54 One sprue is attached to each of the pontic. • and to each cusp Fig 26-55 The pattern is removed by grasping the gual surfaces of the pontic. Poritics and Edentulous Ridges partial dension requires bolstered by the sprue as a handle to loosen the pattern from the die. Carefully take the wax pattern by the sprue between the thumb and forefinger oi the left hand. The lips of the lingers should support the pattern without distorting it. Attach the sprues to the crucible former. Do not try to hold the pattern by the proximal surfaces. Invest and cast the fixed partial denture wax pattern in the usual manner. Remember to use more casting alloy than would be used for crowns, since the pontic is solid. After the casting is retrieved from the investment, scrub it clean. Cut off the sprues and finish the casting. Remove the plaster matrix from the working cast and place the casting on the working cast. It is now ready for try-in Metal-Ceramic Fixed Partial Dentures Metal frameworks or copings for metal-ceramic fixed partial dentures should be constructed with these requirements in mind: (1) there must be an adequate bulk of metal to insure rigidity for strength and (2) porcelain should be of nearly equal thickness throughout to avoid the possibility of weakening the porcelain through uneven stress concentrations. To meet these requirements, there should be a continuous strip of exposed metal on the lingual surface, extending from the metal portion of one retainer, across the lingual of the pontic, to the metal portion of the other retainer. The incisal configuration of the lingual aspect of the coping may be straight, if occlusion permits (Fig 26-56, A), or scalloped (Fig 26-56, B).s' The scalloped or "trestle" design is indicated when the connector is diminished in its faciolingual dimension to allow for the porcelain in the embrasures. By increasing the height of the strut incisogingivally, the strength of the connector will increase.52 This provides a bulk of metal for rigidity in the connector areas between the pontic and the respective retainers; if soldering should be necessary, it provides adequate metal for a strong solder joint. Porcelain coverage of the retainers is the same as that for single units, except in the area adjacent to the pontic. The porcelain veneer on the pontic is continuous with the porcelain veneering of the retainers. It covers the incisal portion of the lingual surface, the labial surface, and the entire area adjacent to or contacting the ridge. Porcelain terminates against the metal on the lingual surface, about 1.0 mm incisal to the ridge (Fig 26-57). Porcelain tissue contact allows for better esthetics and removes the potentially rough porcelain-metal junction from contact with the tissue, where it could cause irritation.53 The metal coping on the underside or gingival aspect of the pontic follows the same contours that the porcelain will, rather than being just a straight bar of metal between the retainer copings. This makes the pontic esthetically similar to the retainers in the gingival area and provides support for the porcelain. The tissue contact of the porcelain should be a modified ridge lap on the facial aspect of the ridge. There must be no saddle contact. An exception to the recommended porcsurface is built up with a wax-added tech- Fig 26-52 If the fixed partial denture is to be cast in two pie< 3-0 suture silk can be used to saw through the connector Fig 26-54 One sprue is attached to each of the pontic. • and to each cusp Fig 26-55 The pattern is removed by grasping the gual surfaces of the pontic. Poritics and Edentulous Ridges partial dension requires bolstered by the sprue as a handle to loosen the pattern from the die. Carefully take the wax pattern by the sprue between the thumb and forefinger oi the left hand. The lips of the lingers should support the pattern without distorting it. Attach the sprues to the crucible former. Do not try to hold the pattern by the proximal surfaces. Invest and cast the fixed partial denture wax pattern in the usual manner. Remember to use more casting alloy than would be used for crowns, since the pontic is solid. After the casting is retrieved from the investment, scrub it clean. Cut off the sprues and finish the casting. Remove the plaster matrix from the working cast and place the casting on the working cast. It is now ready for try-in Metal-Ceramic Fixed Partial Dentures Metal frameworks or copings for metal-ceramic fixed partial dentures should be constructed with these requirements in mind: (1) there must be an adequate bulk of metal to insure rigidity for strength and (2) porcelain should be of nearly equal thickness throughout to avoid the possibility of weakening the porcelain through uneven stress concentrations. To meet these requirements, there should be a continuous strip of exposed metal on the lingual surface, extending from the metal portion of one retainer, across the lingual of the pontic, to the metal portion of the other retainer. The incisal configuration of the lingual aspect of the coping may be straight, if occlusion permits (Fig 26-56, A), or scalloped (Fig 26-56, B).s' The scalloped or "trestle" design is indicated when the connector is diminished in its faciolingual dimension to allow for the porcelain in the embrasures. By increasing the height of the strut incisogingivally, the strength of the connector will increase.52 This provides a bulk of metal for rigidity in the connector areas between the pontic and the respective retainers; if soldering should be necessary, it provides adequate metal for a strong solder joint. Porcelain coverage of the retainers is the same as that for single units, except in the area adjacent to the pontic. The porcelain veneer on the pontic is continuous with the porcelain veneering of the retainers. It covers the incisal portion of the lingual surface, the labial surface, and the entire area adjacent to or contacting the ridge. Porcelain terminates against the metal on the lingual surface, about 1.0 mm incisal to the ridge (Fig 26-57). Porcelain tissue contact allows for better esthetics and removes the potentially rough porcelain-metal junction from contact with the tissue, where it could cause irritation.53 The metal coping on the underside or gingival aspect of the pontic follows the same contours that the porcelain will, rather than being just a straight bar of metal between the retainer copings. This makes the pontic esthetically similar to the retainers in the gingival area and provides support for the porcelain. The tissue contact of the porcelain should be a modified ridge lap on the facial aspect of the ridge. There must be no saddle contact. An exception to the recommended porcelain coverage on the gingival aspect of a pontic occurs in those situalions where an all-porcelain occlusal surface is used and the occlusogingival space is limited. To ensure rigid support for the porcelain, the gingival aspect of the pontic should remain in metal, with the porcelain-metal junction located on the gingivofacial aspect of the pontic. An attempt at producing an esthetic posterior fixed partial denture will require the use of all-porcelain occlusal surfaces, especially in the mandibular arch, since only the occlusal aspect of premolars and molars is seen, if, in fact, any part is seen. Any time that an all-porcelain occlusal surface is used on a pontic, a judgment must be made regarding the occlusogingivaf thickness of the metal in the pontic. To insure adequate rigidity, the undersurface of the pontic may have to be metal to compensate for the metal removed from the occlusal (Fig 26-58) Fixed Partial Denture Coping Wax Pattern. Portions of any metal-ceramic fixed partial denture will remain unveneered and, in the posterior region, unveneered metal may constitute the majority of the surface area of the fixed partial denture. To produce a continuous contour between metal and porcelain and to provide a uniform thickness of porcelain, it is important to fabricate the wax pattern to full contour and then cut it back. Fabricate copings on the lubricated die of the abutment preparations with a no. 7 wax spatula. Trim the excess from the margins and transfer the copings to the working cast. Form the axial contours facially, lingually, and interproximally. On posterior teeth, develop the occlusion in the usual manner (see Chapter 19). Cut off a short section of a stick of blue inlay wax and heat one end of it in a Bunsen burner flame until the wax has been softened. Place the piece of wax into the edentulous space on the cast, pressing the softened end against the lubricated edentulous ridge. When the wax has hardened, flow wax into the interproximal areas to attach it to the retainer wax pattern on either side of it. Using wax addition and carving, produce the desired axial contours in the pontic. Check the alignment of the pontic in a mesiodistal direction to prevent any "leaning" (Fig 26-59). Remember Fig 26-58 A pontic with a short occlusogingival dimension may be loo weak with a ceramic ridge contacl (upper left); it could be strengthened by changing the ridge contact to metal (upper right). A pontic may be weakened by covering the occlusal surface with porcelain (lower left). The loss of meial bulk can he compensated by using a metal ridge contact (lower right). 1I Correct Ifii Mesial i / J Distal Fig 26-59 Tile mesrodisMl inclination of the facing must be in harmony with that of the adjacent teeth. Pontics and Edentulous Ridges Fig 26-60 The facial profile should be cor Ih thai of Ihe other teeth in the quadra: also to check the alignment of the occlusal two-thirds of the facial surface to make sure that it is in harmony with the facial surfaces of the other teeth in the arch (Fig 26- 60). Remove the assembled wax pattern to carve the tissue side of the pontic to produce the desired open embrasures in the mesiogingival, distogingival, and linguogingival aspects. In the appearance zone, the pontic should be a modified ridge lap design. When completed, duplicate the full-contour wax pattern with a resilient impression putty material, such as condensation silicone. This impression can be poured to produce a stone cast, providing a visual guide to the desired contours, or it can be sectioned horizontally to allow assessment of the amount and contours of the cutback. Replace the pattern on the working cast and sketch the outline of the area to be veneered with a no. 25 blade in a laboratory knife (Fig 26-61). Place the mark as far to the lingual as possible in the interproximal areas, Remove the fixed partial denture wax pattern from the working cast and place it on the single-piece die of the abutment preparation. Use a discoid carver to place a groove ad|acent to the outline of the boundaries of the veneering area Place the groove just buccal to the proximal contact on a pattern for a posterior tooth so that the contact will be on metal. On a pattern for an anterior tooth, place the groove lingual to the contact so that the contact will be on porcelain. Use a discoid carver to place grooves on the facial surface of the pontic and on any retainers that are to be veneered (Fig 26-62). These grooves should be 0.7 to 1.0 mm deep. With grooves it is possible to gauge the depth of the wax that will be removed from the veneering area to make room for porcelain. A similar groove is placed on the lingual surface of the pontic to mark the Imguogingival porcelain-metal junction line (Fig 26-63) Use a sharp no 25 blade to remove the bulk of wax left between the grooves (Fig 26-64). Leave a 1-mm-wide collar of wax at the gingival margin to insure an adequate bulk to be invested and cast accurately. The collar will be thinned markedly after casting. Use the discoid carver to blend in all cuts made near the porcelain-metal junction line (Fig 26-65). The cutback of the pontic should follow the general contours of the original full-contour wax-up, with a bulk of wax underlying the cusp tip and gingival tip of the pontic so that the porcelain which will ultimately be placed over those contours will be supported by metal (Fig 26-66, A). On maxillary posterior teeth, be sure that there is a ledge of smoothly contoured wax underlying the eventual location of the buccal cusp tips on both the pontic and retainers (Fig 26-66, B). Poritic Fabrication 0% Fig 26-61 Proximal extensions of the porcelain-mi are marked on the wax pattern with a knife tip. g 26-62 Orientation grooves are cut with a discoid carver on all irfaces of the retainer and ponlic that are to be veneered. Fig 26-63 An orientation groove is carved along the location ofthe Fig 26-64 Wax remaining between the orientation gro linguogingival porcelain-metal junction line on the pontic. removed with a sharp knife. •ith a Fig 26-66 Proximal views of the components of a wax pattern for a maxillary posterior metal-ceramic fixed partial denture. A, the pontic; B, the retainer. 3ncl Edentulous Rid; There should not be any sharp angles in the area to be veneered. The porcelam-metal junction line should have the configuration of a deep chamfer with a crisp 90- degree angle in the wax pattern at the porcelain-metal junction. Smooth the veneering area with a cotton pellet dipped in die lubricant. Wash off the excess and blow dry. Place the pattern of the fixed partial denture on the working cast and carefully inspect the area to be veneered from the facial (Fig 26-67, A), the occlusal (Fig 26-67, B), and the lingual (Fig 26-67, C) aspects. Be sure that all angles which will be covered with porcelain are rounded, all contours are smoothed, and all aspects of the porcelain-metal junction line are sharply defined. Return the pattern to the freshly lubricated die and readapt the margins. Prepare the pattern for investing by attaching the sprues (see Chapter 21). References i. J Prosthet Dent sthet Dent Fig 26-67 Wax pattern for a maxillary posterior metal-ceramic fixed partial denture from the facial (A), the occlusal (B), and the lingual (C) aspects. 1. Parkinson CF Schaberg TV: Pontic design of posterior fixed partial prostheses: Is it a microbial misadventure? J Prosthet Denl 1984; 51:51-54. 2. Stein RS. Pontic-residual ridge relationship: A research report. J Prosthet Denf\ 966; 16:251-285. 3. Henry PJ, Johnston JF, Mitchell DF1 Tissue changes beneath fixed partial dentures. J Prosthet Dent 1966; 16:937-947. 4. Podshadley AG: Gingival response to pontics. J Prosthet Dent 1968; 19:51-57. 5. Smith DE, Potter HR: The pontic in fixed bridgework. Dent Digest 1937; 43:16-20. 6. Klaffenbach AO: Biomechanical restoration and maintenance of the permanent first molar space. J Am DentAssoc 1952; 45.633-644. 7. Boyd HR: Pontics in fixed par 1955, 5:55-64. 8. Harmon CB. Pontic design. J Pro 8.496-503. 9. Cavazos E1 Tissue response to fixed partial denture pontics. J Prosthet Dent-1968, 20:143-153. 10. Eissmann HF, Radke RA, Noble WH: Physiologic design criteria for fixed dental restorations Dent Clin North Am 1971, 15:543-568. 11. Johnson GH, Leary JM: Ponlic design and localized ridge augmentation in fixed partial denture design. Dent Clin North Am 1992; 36591-605. 12. Schield HW: The influence of bridge pontics on oral health. JMich DentAssoc 1968; 50:143-147. 13. Reynolds JM: Abutment selection for fixed prosthodontics. J Prosthet Dent^ 968; 19:483-488 14. Hirshberg SM. The relationship of oral hygiene to embrasure and pontic design—A preliminary study. J Prosthet Dent 1972; 27:26-38. 15. Tjan AH: Biologic pontic designs. Gen Denf 1983; 31:40-44. 16. Johnston JF1 Pontic form and bridge design: A new survey (Parti) MDenM 1956; 25:272-279. 17. Roid GH, Wilson LG, Grenfell J, Ueno H: Bridging the Gap- An Instructional Program in Pontic Design. Monmouth, OR Teaching Research, 1973, p 16. 18. Silness J, Gustavsen F. Mangernes K: The relationship between pontic hygiene and mucosal inflammation in fixed bridge recipients. J Penodont Res 1982; 17.434-439. 19. Tripodakis A-P, Constantinides A: Tissue response under hyperpressure from convex pontics. Int J Periodont Rest Dent 1990; 10:406-414. 20. Becker CM, Kaldahl WB: Current theories of crown contour, margin placement and pontic design. J Prosthet Dent 1981; 45:268-277. 21 Clayton JA, Green E: Roughness of pontic materials and dental plaque. J Prosthet Dent 1970; 23:407-411 ?2. Ante JH. Construction of pontics. J Can DentAssoc 1936; 23. Tjan AHL: A sanitary "arc-fixed partial denture"1 Concept and technique of pontic design. J Prosthet Dent 1983; 50338-341. 24. Yamashita A: Practical construction procedure for a new type of bridge pontic. Quintessence Int 1985; 16:743-753. 25 Garber DA, Rosenberg ES: The edentulous ridge in fixed prosthodontics. Compend Contin Educ Dent 1981; 2.212-224. i. Perel ML A modified sanitary pontic J Prosthet Dent 19721 28:589-592. '. Hood JA. Stress and defection of three different pontic designs. J Prosthet Dent 1975; 33:54-59. 1. Tinker ET: Sanitary dummies. Dent Rev 1918; 32:401-408 t Dobson NJ. The value of porcelain in artificial root insertion Dent Cosmos 1921; 63.247-248. ). Budde CC: Porcelain baked toots in tixed bridgework. J Am Dent Assoc 1928; 15.1914-1916. I. Bowles RO: Fixed bridges with special reference to tissue contact pontics and inlay abutments. J Am Dent Assoc 1931; 18:1521-1537 '. Dewey KW, Zugsmith R: An experimental Study of tissue reactions about porcelain roots. J Dent Res 1931, 13:459-472 i. Boyd HB: Pontics in fixed partial dentures. J Prosthet Dent 1955; 5:55-64 r Shooshan ED' The reverse pin-porcelain facing. J Prosthet Dent1959; 9:284-301. ;. Seibert JS: Reconstruction of deformed, partially edentulous ridge, using full thickness onlay grafts. Part I. Technique and wound healing. Compend Contin Educ Dent 1983; 4:437-^)53. ' Hawkins CH, Sterrett JD, Murphy HJ, Thomas JC; Bidge contour related to esthetics and function. J Prosthet Dent 1991; 66:165-168. i. Abrams H, Kopczyk RA, Kaplan AL: Incidence of anterior ridge deformities in partially edentulous patients J Prosthet Dent 1987; 57:191-194. i Behrend DA: The mandibular posterior fixed partial denture J Prosthet Dent 1977; 37:622-638. -colored ceramic powder 31; 3:245-252. > Vryonis P: Esthetics and funct Quintessence Dent Technol 191 j. Porter CB: Anterior pontic design: A logical progression. J Prosthet Den(1984; 51.774-776. I Crispin BJ: Tissue response to posterior denture base-type pontics. J Prosthet Dent 1979; 42:257-261. ',. Siebert JS, Cohen DW: Periodontal considerations in preparation for fixed and removable prosthodontics. Dent Clin NorthAm1987: 31:529-555. i. Siebert JS, Nyman S: Localized ridge augmentation in dogs: A pilot study using membranes and hydroxy apatite. J Periodontol 1990; 61:157-165. '. Kaldahl WB, Tussing GJ, Wentz FM, Walker JA: Achieving an esthetic appearance with fixed prosthesis by submucosal grafts. J Am Dent Assoc 1982; 104:449-452. { Langer B, Calagna L: The subepithelial connective tissue graft. J Prosthet Dent 1980; 44:363-367. I Siebert JS: Bidge augmentation to enhance esthetics in fixed prosthetic treatment. Compend Contin Educ Dent 1991; 12:548-560. ). Orth CF: A modification of the connective tissue graft procedure for the treatment of type II and type III ridge deformities. Int J Periodont Rest Dent 1996; 16:267-277. Stein RS, Kuwata M: A dentist and a dental technologist analyze current ceramo-metal procedures. Dent Clin North Am 1977; 21:729-749. I. Miller LL: Framework design in ceramo-metal restorations. Dent Clin North Am 1977; 21:699-716. i. Hobo S, Shillingburg HT: Porcelain fused to metal1 Tooth preparations and coping design. J Prosthet Dent 1973; 30:28-36. I Chapter 27 Solder Joints and Other Connectors Soldering is the joining of metal components by a filler metal, or solder, which is fused to each of the parts being joined. Strictly speaking, if the filler metal has a melting temperature greater than 450"C (840°F), the process is brazing.^ The term soldering, as commonly used in dentistry, will be used in this chapter. Bonding is contingent on welting of the joined surfaces by the solder, and not on melting of the metal components. When a solder joint is done properly, there should be no fusion or alteration of the two components joined.2 Soldering differs in that respect from welding, another means of joining metals. In fusion welding, the pieces that are joined are melted or fused together, without solder. Solder can be used for joining, as in the fabrication of a fixed partial denture, or it can be used for building, as when an addition is made to the proximal surface of a crown. Cleanliness is the prime prerequisite of soldering,3 inasmuch as the soldering process depends on wetting of the surface to achieve bonding. Corrosion products, such as oxides and sulfides, that are present as a result of the casting process or that occur on the surface of metals when they are heated, interfere with bonding. Flux is placed on the surfaces to be soldered before they are heated. Fluxes may provide surface protection, reduce oxides, or dissolve oxides.1 Flux is displaced by solder, which then can form an interface with and bond to the surface being soldered. Soldering fluxes for noble metals are based on borate compounds. They form lowfusing glasses that protect the metal surface, and they also reduce oxides such as copper oxide. They often are too fluid for preceramic soldering.1 Fluorides are used on base metal alloys to dissolve the stable oxides of chromium, cobalt, and nickel. In addition to acting as solvents, these fluxes also serve a protective role.1 Flux is more easily applied if it is in paste form. While a flux paste can be made with alcohol, the most popular form for use with noble metal alloys employs petrolatum as a vehicle, since it is more easily handled. It keeps air from the flux, and when heated, the petrolatum burns off without leaving any residue. Fluxes made from common borax, or pastes made with water, tend to effloresce when they are heated, producing pits in the solder joint Antiflux is a material used to outline the area to be soldered in order to restrict the flow of solder. The most common antiflux is the mark of a soft graphite pencil, which works best on surfaces that do not have a high polish. Polishing rouge (iron oxide) suspended in chloroform can also be painted around the area of the solder joint to prevent undesired spread of the solder. Gold solders are classified by fineness and by carat. Fineness refers to parts per thousand of the solder that is gold. For example, a 600 fine solder would be 600 parts gold per 1,000, or 60% gold. When used to designate a casting alloy, carat refers to parts per 24 of a metal that are gold. As an example, an alloy that is 18 K is 18 parts gold per 24, or 75% gold. When used with solder, however, carat has a different meaning. A solder that is designated as 18 K does not have a 75% content of gold. Instead, the 18 K designation means that it was formulated to be used with 18 K casting alloys. The actual noblemetal content of the solder would be given by its fineness rather than by its carat. The higher the fineness of a solder, the higher will be its melting range and the greater its corrosion resistance. While a solder with a lower fineness has a lower melting range, it also has poorer flow characteristics.^ Dental solder should be4: 1. Corrosion resistant. Restorations, such as fixed partial dentures, which are permanently placed in the mouth require the use of a solder of high fineness to resist corrosion. The minimum fineness that should be used is 580 fine, and a higher number would be better for preventing tarnish and discoloration. 2. Lower tusmg than alloy. The solder should possess a fusion temperature that is about 60°C (100 to 150T) below that of the metal being soldered.3 3. Nonpitling. Pitting in solder is not desirable. More pitting occurs when there is an increased amount 
برچسب ها: of "making do" with a deficient ridge. There are nonetheless situations in which a more conservative approach may be desired. The patient's inability to undergo surgery، or an unwillingness to consider it، will force the consideration of an alternative form of pontic. In ridges with severe defects، where two or more pontics must be used to fill the space، it is not uncommon to eliminate gingiva! embrasure spaces between the pontics. "Black triangles" can be very unesthetic (Fig 26-20)، and they serve no useful purpose. They collect plaque، interfere with the passage of floss،  

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technique, mark the shoulder finish line on the die using Fig 25-45 "Die facial shoulder finish lii A red pencil. the side o! a red pencil (Fig 25-45). Then seal the porous surface of the gypsum die by brushing on a special sealing material (Cera-Seal, Belle de St Claire, Chatsworth. CA) or by squeezing a thin layer of cyanoacrylate cement (Permabond 910 Adhesive, Buffalo Dental Mfg Co, Brooklyn, NY) onto the finish line area of the die (Fig 25- 46). Blow off the excess liquid with compressed air to insure a uniformly thin layer of sealant (Fig 25-47). Apply a special lubricant, or porcelain release agent (Cera-Sep, Belle de St Claire), to the facial shoulder of the sealed die with a brush (Fig 25-48). Then seat the opaqued coping on the die. Shoulder porcelain powder should be mixed with distilled water or the manufacturer's recommended liquid. There are techniques utilizing hightemperature investment liquid as the binder for direct-lift porcelain margins. The investment liquid hardens as the wet porcelain mixture dries on the die, making it easier to remove the coping from the die without fracturing the margin. However, after firing, residual silica particles act as inclusions in the porcelain, weakening it and making it more prone to fracture.50 Add the initial increment of shoulder porcelain to the facial shoulder; it should extend approximately 2 to 3 mm onto the coping (Fig 25-49). Condense the porcelain and blot it dry with tissue (Fig 25-50). Carve the porcelain with a large spoon excavator or a small cleoid (Fig 25-51) to produce a slight bevel or undercontour. This produces space for a narrow layer of dentin porcelain over the shoulder porcelain. Lightly smooth the shoulder porcelain at the margin with a no. 10 sable condensing brush (Fig 25-52). Carefully tease the coping from the die (Fig 25-53). Inspect the inside of the casting for any specks of porcelain and remove any found (Fig 25-54). Although they can be ground out after firing, they are more easily seen and removed in the prefired state. Gently place the coping on a sagger tray (Fig 25-55). Fig 25-46 Cyanoac applied to seal the die facial shoulder. Porcelain Addition :ial shoulder to prevent porcelain from sticking to the die. Fig 25-49 The first shoulder porcelain is applied to the shoulder of the die with a brush. It should extend 2 to 3 mn the metal coping. Fig 25-50 The porcelain is condensed by blotting it dry with ti until no more liquid comes to the surface- 25-51 A large spoon excavator or a discoicJ carver is used t< •ove the excess "green" shoulder porcelain. Onty the materia sctly over the shoulder and a slight extension (1.0 mm or les< j the coping is left in place. Metal-Ceramic Restoratii gently teased off the die. and the shoulder porcelain is inspected for defects. Fig 25-54 Any porcelain visibI on .1 sapger tray and dried in front Thoroughly dry the porcelain in front of the furnace. Then fire it under vacuum at a temperature approximately 30DC higher than the corresponding dentin and enamel porcelains. When the initial increment of shoulder porcelain is inspected on the die after firing, a small opening may be apparent at the facial margin (Fig 25- 56) More shoulder porcelain can be added to the discrepancy with the crown seated on the die. Vibrate it into the opening with a small vibrating sable brush. Some ceramists prefer to add a very small amount of shoulder porcelain of a runny consistency to the gingival aspect of the fired margin to correct the discrepancy (Fig 25-57). Place the coping back onto the die, alternately applying firm seating pressure (Fig 25-58) and vibrating the die. Be sure that the metal margin on the lingual of the casting seats completely. If it doesn't, remove the coping from the die and scrape away some of the newly added "correction porcelain." Condense and smooth the porcelain (Fig 25-59). Use the same firing cycle for the correction bake as used in the initial application. When the margin is satisfactory (Fig 25-60), proceed with the dentin and enamel buildup. Porcelain Addition Fig 25-57 A uniform layer of shoulder porcelain is applied wit brubh to the underside of the already fired porcelain. Fig 2S-6O The marginal gap between the shoulder porcelain and the finish lint must be dosed before proceeding. Fig 25-62 Buildup of the dentin porcelain is continued with the brush while holding a piece of tissue behind the incisal edge If absorb water. slightly beyond the intend- Dentin and Enamel Porcelain Application Mix dentin porcelain to a creamy consistency with distilled water or the manufacturer's recommended liquid. Then apply it over the opaque with a sable brush or small spatula, starting at the gingivofacial of the coping, which is seated on the working cast (Fig 25-61). First develop the full contour of the crown in dentin porcelain with a brush. Vibrate the porcelain to condense it, absorbing the liquid with tissue (Fig 25-62). Then brush it with a no. 10 sable condensation brush (Fig 25-63). The completed buildup should be overcontoured (Fig 25-64). When the porcelain is condensed and dried to a consistency of wet sand, carve the dentin back to allow the placement of the enamel porcelain. The desired translucency pattern dictates the amount and design of the cutback. It will commonly produce some form of bevel on the incisofacial segment of the buildup in dentin porcelain (Fig 25-65). Frequently the cuts at the incisoproximal corners overlap in the center (Fig 25-66). Apply the enamel porcelain to restore the full contour of the restoration (Fig 25-67). Use carving instruments or brushes to shape the porcelain to its final contours (Fig 25-68). Condense the porcelain by blotting from the lingual (Fig 25-69, A) and the facial (Fig 25-69, B). Commercially available porcelains exhibit significant linear firing shrinkage, with a typical central incisor metalceramic crown shrinking 0.9 mm at the incisal edge.57 When completed, the restoration should be slightly larger incisally to compensate for this shrinkage (Fig 25-70). Fig 25-65 The dentin porcelain is cut back to allow placemen! of the incisal porcelain (A). The ai 3no extent are dictated by the transluccncy pattern desrred for Erie restoration. It could reouiro the re of nothing more than the corners (B). Fig 25-67 Enamel porcelain is added with a brush to the cutback areas: frontal view iA) and Metal-Ceramic Res Fig 25-68 The enamel porcelain is carried The lingual fossa is shaped with a brush. Fig 25-70 The enamel porcelain is slightly overbuilt to compor for shrinkage during firing. Fig 25-71 Facial view of completed porcelain buildup on the Porcelain Additior Overall, make the crown about one-fifth larger than the desired size to compensate for the 20% shrinkage that will occur during firing (Fig 25-71). Cautiously remove the restoration from the working cast and add porcelain to the interproximal areas (Fig 25- 72). Blend the proximal addition into the surrounding contours of the crown (Fig 25-73). Remove excess porcelain from the unveneered metal at the porcelain-metal junction (Fig 25-74). Tease the crown off the die by placing the tip of a sharp instrument under the lingual metal margin (Fig 25-75). Avoid any ceramic margin while removing the Complete the condensation by vibrating the forceps holding the crown with the serrations on a Roach carver (Fig 25-76). Blot up any moisture brought to the surface by this process. With a brush, remove any bits of porcelain that may have strayed into the crown (Fig 25-77). The initial buildup is dried in front of the furnace for several minutes, and then it is fired under vacuum and carried to the temperature specified by the manufacturer of that porcelain. Try the restoration back on the working cast and evaluate contours. The proximal contacts will often be open (Fig 25-78). insufficient contours can be corrected by adding the appropriate porcelain Remove the crown from the die, and grasp it on the unveneered metal in the beaks of a modified mosquito hemostat, which prevents damage to the margin.58 Add porcelain to the proximal contacts and blend in the contours (Fig 25-79). Fire the restoration at a temperature about 10 to 20°C lower than the initial bake. The higher-fusing porcelain forming the facial margin should not be affected by these subsequent firings. Metal-Ceramic Restoratioi Fig 25-76 The condensation of the porcelain is completed, using a tissue to absorb the excess moisture. Fig 25-79 A small amount of porcelain is added to the pr Fig 25-80 Following the correction bake, be necessary, such as the he^vy proximo here. ling and Cementation 3& Fig 25-81 A dean green stcv to reconiour the porcelain. jr diamond is used Following the correction bake, the crown may not seat completely, or it may have other minor deficiencies (Fig 25-80). Adjustments are made on the porcelain with diamond discs, aluminum oxide stones, or carborundum stones (Fig 25-81). Porcelain Surface Treatment Once the desired contours and occlusion have been achieved, the restoration must receive a surface treatment. Three commonly used treatments include: (1) natural or autoglaze, (^applied overglaze, or (3) polishing. Commercially available kits of rubberized abrasives and polishing compounds are available to polish porcelain. Porcelain has the ability to glaze itself when held at its fusing temperature under air for 1 to 4 minutes. Many ceramists prefer this treatment, feeling that it preserves the surface character and texture of the porcelain. Applied overglaze is a low-fusing clear porcelain that is painted on the surface of the restoration and fired at a fusing temperature much lower than the fusing temperature of the dentin and enamel porcelains. Since porcelain loses its ability to form a natural glaze after multiple firings, an applied overglaze may be indicated on large restorations that have required numerous corrections. However, caution must be exercised not to overfire the porcefain. It may return to a more crystalline state and become milky or cloudy in appearance, a condition known as devitrification. Devitrification causes a loss of natural appearance, and no surface treatment can revive the porcelain. Polishing lends itself to use on relatively small areas of adjustment such as proximal contacts and limited areas of occlusal contact. Traditionally, polished porcelain has been regarded as a rougher surface than glazed porcelain. 59 However, recent qualitative and quantitative evaluations of polished porcelain surfaces indicate that an acceptable surface may be obtained by using a commercially available system (Truluster, Brasseler USA, Savannah, GA; Porcelain Adjustment Kit, Shofu Dental Corp, Menlo Park, CA).60 Jacobi et al showed polished porcelain to be less destructive of tooth structure in the opposing arch than glazed porcelain M Finishing and Cementation The metal portion is adjusted and finished as described on page 397. Ceramic portions are handled much the same as afl-ceramic restorations. If the contours or shade will be modified substantially during try-in, the restoration can be left unglazed until after the adjustments are made Insufficient proximal contacts and marginal gaps may be corrected at chairside or the restoration may be returned to the laboratory. Shade Modification If the shade of a metal-ceramic crown is too dark (its value too low) it is almost impossible to lighten it by custom staining without making the tooth appear too opaque. However, if it is too light (its value too high), it can be modified. Fracture lines and areas of discoloration also can be simulated to give a more natural appearance. References . Chrisiensen GJ: The use of pofcelain-fused-to-metal restorations in current dental praclice. A survey. J Proslhet Den/1986; 56:1-3. '. Jochen DG, Caputo AA, Matyas J: Effect of metal surface 55:186-188. I. Carpenter MA, Goodkind RJ: Effect of varying surface texture on bond strength of one semi-precious and one nonprecious ceramo-alloy. J Prosthet Dent 1976: 42;86. .. Gavelis JR, Urn SB, Guckes AD, Morency JD, Sozio RB A comparison of the bond strength of two ceramometal systems J Prosthet Dent 1982; 48'424-428. i. McLean JW, Seed IR: Bonding of dental porcelain to metal—I. The gold alloy/porcelain bond. Trans Br Ceram Soc 1973; 72:229-233. Irength of dental porce- 3; 45:1047-1051. '. Anusavice KJ, Horner JA. Fairhurst CW: Adherence controlling elements in ceramic- metal systems. I Precious alloys. JDenr Res 1977, 56:1045-1052 1. von Radnoth MS, Lautenschlager EP: Metal surface changes during porcelain firing. J Dent Res 1969: 481 321-324. I Dent RJ, Preston JD, Moffa JP, et al: Effect of oxidation on ceramometal bond strength. J Prosthet Dent 19821 47- 59-62. ). Vickery RC, Badinelli LA: Nature of attachment forces in porcelain-gold systems. J Dent Res 1968; 47:683-689. I. Shell JS, Nielson JP: Study of the bond between gold alloys and porcelain. JDentRes 1962; 41:1424-1437. I Phillips RW: Skinner's Science of Dental Materials, ed 9. Philadelphia, WB Saunders Co, 1991, p 505-527. S. Council on Dental Materials, Instruments, and Equipment. Classification system for cast alloys. J Am Dent Assoc 1984;109:838~850. I. Moffa JP, Guckes AD, Okawa MT, Lilly GE: An evaluation of nonprecious alloys for use with porcelain veneers. Part II. Industrial safety and biocompatibility. J Prosthet Dent niZ- 30:432-441. i. Kelly JR, Rose TC: Nonprecio prosthodontics' A literature rev 49:363-370. '. Tai Y, De Long R, Goodkind RJ, Douglas WH' Leaching of nickel, chromium and beryllium ions from base metal alloy in an artificial environment. J Prosthet Dent 1992, 68692-697. i. Naylor WP; Introduction to Metal Ceramic Technology. Chicago, Quintessence Publishing Co, 1992, pp 33-34. i. Fisher RM, Moore BK, Swartz ML, Dykema RW: The effects of enamel wear on the metal-porcelain interface J Prosthet Denf1983, 50:627-631 etal storatio Dent . Weiss PA. New design parameters. Utilizing the properties of nickel-chromium superalloys. Dent Clin North Am 1977; 21 769-785. !. Monasky GE, Taylor DF: Studies on the wear of porcelain enamel and gold. J Prosthet Dent 1971; 25:299-306 !. Mahalik JA, Knap FJ, Weiter EJ/ Occlusal wea dontics. J Am Dent Assoc 1971; 82.154-159 k Jacobi R, Shillingburg HT, Duncanson MG: A cc the abrasiveness of six ceramic surfaces ; Prosthet Dent 1991; 66:303-309. 26. Craig RG, El-Ebrashi MK, Peyton FA: Stress distribution in porcelain-fused-to-gold crowns and preparations constructed with photoelastic plastics. J Dent Res 1971; 50.1278-1283 27. Woods JA, Cavazos E; Effec angulation on porcelain frai 54:501-503 28. Craig RG, El-Ebrashi MK, Farah JW: Stress distribution in photoelastic models of transverse sections of porcelainfused- to-gold crowns and preparations. J Dent Res 1973; 52:1060-1064. 29. Hobo S, Shillingburg HT. Porcelain fused to metal: Tooth preparation and coping design. J Prosthet Dent 1973; 30:28-36. 30. Marker JC, Goodkind RJ, Gerberich WW: The compressive strength < unprec s fra o R, Cwynar R, Schlimmer margin placement vs time 1986:55:560-567. I. Weir D, Staffer W, Irvin D, Na\ S, Morris H: The stability of era [abstract 1154], J Dent Res V. I. Waerhaug, J: Histologic considerations which govern where the margins of restorations should be located in relation to thegingiva. Dent Clin North Am 1960; 4:161-176. !. Silness J: Periodontal conditions with patients with dental bridges III: The relationship between the location of the crown margin and the periodontal condition. J Periodont Res 1970; 5:225 I. Silness J: Fixed prosthodontics and periodontal health. Dent Clin North Am 1980; 24:317-329. j. Loe H' Reactions of marginal tissue to restorative procedures. Int Dent J 1968; 18759-775. >. Goodacre CJ, Van Roekel NB. Dykema RW, Ullmann RB: The collarless metal ceramic crown. J Prosthet Dent 1977; 38:615-622. '. Schneider DM, Levi MS, Mori DF' Porcelain shoulder adaptation using direct refractory dies. J Prosthet Dent 1976; 36:583-587 I. Sozio RB, Riley EJ: A precision ceramic-metal restoration with a facial butted margin. J Prosthet Dent 1977; 37517-521. ). Vryonis P: A simplified approach to the complete porcelain margin. J Prosthet Dent 1979; 42:592-593. . Vryonis P: A Manual for the Fabrication of the Complete Porcelain Margin. Adelaide, Stock Journal Publishers Ply, 1982, p 27. '. Kessler JC, Brooks TD, Keenan MP: The direct lift technique for constructing porcelain margins Quint Dent Technol 1986; 10'U5-150. !. Prince J, Donovan T: The esthetic metal ceramic margin. A comparison of techniques. J Prosthet Dent 1983: 50:185-192. I. Belser UC, MacEntee Ml, Ftichter WA. Fit of three porcelainfused- to-metal marginal designs in vivo: A scanning electron microscope study J Prosthet Dent 1965; 5324-29. i. Hunt JL, Cruickshanks-Boyd DW, Davies EH The marginal characteristics of collarless bonded porcelain crowns produced using a separating medium technique. Quint Dent Technol 1978; 2(9):21-26. >. West AJ, Goodacre CJ, Moore BK. Dykema BW: A comparison of four techniques for fabricating collarless metal ceramic crowns J Prosthet Dent 1985; 54:636-643 '. Arnold HN. Aquilino SA: Marginal adaptation of porcelain 59:409-417. 1. Wanserski DJ, Sobczak KP, Monaco JG, McGivney GP: An analysis of margin adaptation of all-porcelain facial margin ceramometal crowns. J Prosthet Dent 1986, 56:289-292. I. Boyle JJ, Naylor WP, Blackman BB: Marginal accuracy of metal ceramic restorations with porcelain facial margins. J Prosthet Dent 1993; 69:19-27. ). Bracket! SE, Leary JM, Turner KA. Jordan BD' An evaluation of porcelain strength and the effect of surface treatment. J Prosthet Dent-1989; 61:446-451. Scheu R: Kunstoff ersetztwachs-Rationelle fromebung fur stumpf- and kronenhulsen Zahntecnik (Zurj 1970, 28 359-362. 52. Hauser HJ: Technical fabrication of caps for crown preparation (II). Quint Dent Technol 1978, 2(3)'43-47. 53. El-Sherif MH, Shillingburg HT. Smith KS: A plastic shell technique for fabricating porcelam-fused-to-metal coping patterns. Quint Dent Technol 1987; 11.383-38B. 54. Stein BS. Kuwata M. A dentist and a dental technologist analyze current ceramo-metal procedures. Dent Clin North Am-\977; 21:729-749. 55. McLean JW: The Science and Art of Dental Ceramics, Volt. The Nature of Dental Ceramics and the Clinical Use. Chicago, Quintessence Publishing Co, 1979, p 71. 56. McLean JW: The Science and Art of Dental Ceramics, Vol II. Bridge Design and Laboratory Procedures in Dental Ceramics. Chicago, Quintessene Publishing Co, 1980, p 242. 57. Bosenstiel SF: Linear firing shrinkage of metal ceramic restorations. Br Dent J1987; 162.390-392. 58 Brooks TD: Instrumentation that facilitates porcelain restoration construction. J Prosthet Dent 1983; 49:446. 59. Klausner LH, Cartwright CB, Charbeneau GT: Polished versus auto-glazed porcelain surfaces J Prosthet Dent 1982; 47:157-162. 60. Goldstein GR, Barnhard BR, Penugonda B. Profilometer, SEM, and visual assessment of porcelain polishing methods. J Prosthet Dent 1991; 65:627-634. Chapter 26 Pontics and Edentulous Ridges The pontic, or artificial tooth, is the raison d'etre of a fixed partial denture. Its name is derived from the Latin pons, meaning bridge. It is not a simple replacement, because placing an exact anatomic replica of the tooth in the space would be hygienically unmanageable. The design of the prosthetic tooth will be dictated by esthetics, function, ease of cleaning, maintenance of healthy tissue on the edentulous ridge, and patient comfort.1 Pontics may be metal-ceramic, cast metal, or, less commonly today, resin processed to metal (Fig 26-1). Several clinical studies have indicated that all materials used for pontics are tolerated equally, although some inflammation can occur in the gingival tissue in response to any of them.2-1 Porcelain has been observed to be easily cleanable and hygienic,34 and many clinicians have advocated glazed porcelain as the preferred, or only, material that should touch the edentulous ridge.5"10 Because of the porous nature of resin, and the difficulty in maintaining a highly polished surface on it, resins should not be used on pontics near the tissue.11 Glazed or highly polished porcelain and gold with a mirror-like finish are preferred for tissue contact. Proper design is more important to cleanability and good tissue health than is the choice of materials.12 The surrounding tissues change with the loss of a tooth so that a pontic cannot exactly duplicate the lost tooth. Alveolar resorption and remodeling reshapes the edentulous area, rounding over sharp edges and filling the socket itself. If there is trauma or periodontal disease associated with the loss of the tooth, the final healed ridge shape may be an even greater departure from the original configuration. Because some of the supporting tissues are lost when the tooth is removed, and because the pontic lies over the tissue instead of growing from it, modifications must be made in basic tooth morphology to insure that the pontic will be cleanable and noninjurious to soft tissues. The contours in the apical half of the facial surface cannot match those of the tooth that originally occupied the space, or of the remaining natural teeth (Fig 26-2). If they do, the facial surface will be too long and it will look artificial (Fig 26-3). The pontic must be shortened apically, but it cannot simply be clipped off, as the result would be an uncleanable gingivofacial ledge (Fig 26-4). The facial surface must be altered to curve gently from the gingivofacial angle to the middle of the facial surface (Fig 26-5). Tissue Contact The extent and shape of the pontic contact with trie ridge is very important. Excessive tissue contact has been cited as a major factor in the failure of fixed partial dentures. 5 There is widespread agreement that the area of contact between the pontic and the ridge should be small (Fig 26-6, A),a 9 " 1 3 and the portion of the pontic touching the ridge should be as convex as possible. 2^914 However, if there is contact along the gingivofacial angle of the pontic. there must be no space between pontic and soft tissue on the facial side of the ridge (Fig 26-6, A}. If the tip of the pontic extends past the mucogmgival junction,15 an ulcer will form there (Fig 26-7, A). The pontic should contact only attached keratinized gingiva (Fig 26-7, B).5'5 The once-popular practice of scraping the ridge on the cast to obtain close adaptation of the pontic with tissue compression is not indicated, because the resultant pressure on the ridge is likely to cause inflammation.9 It is generally accepted that the pontic should exert no pressure on the ridge.2^1G One author has gone so far as to suggest that the contact be with the film of saliva on the ridge.13 Others flatly state that the pontic should not contact the tissue at all.1217 However, pontics not contacting the ridge at the time of insertion of a prosthesis may become surrounded by hypertrophied tissue after a time in the mouth.18 Although one study has shown that the tissues under a pontic can be maintained in an inflammation-free state if the patient flosses vigorously at least once a day,19 there will be an imprint, or "footprint," of the pontic on the ridge even without inflammation. There is an increased risk of clinical failure if success depends too much on a patient's cooperation. Pontics and Edentulous Rid< Fig 26-1 Proximal views of a metal-cer ic pontic (A), an all-metal pontic (B), and Fig 2&-2 Facial (left) and proximal (right) views of the a maxillary second premolar. Fig 26-3 Because a ridge resoros after extraction of a tooth, an attempt to follow the exact contours of the original tooth will result in an elongated pontic. Dotted area shows contours of tooth and soft tissue before extraction. Fig 26-4 Cutting off the apical end of the pontic would wive the Fig 26-5 Modifying the apical segment of the facial surfdt. length problem liul an unacceptable debris-trapping shelf would will help the. pontic bJend in without compromising hygiene c result eahelics. Postinsertion Hygiene Fig 26-6 Poniic ccrta.. \ith If ridge shnjld be compact, facial to the cte.f u> 'ht ridge I ghtly wider mesiodistally at the facial, and narrower at the lingual aspect (A). Contact with the tissue should not fall just along the gingivofacial fine angle; if there is a space between it and the crest, a debris trap will result (B). Postinsertion Hygiene The mesial, distal, and lingual gingival embrasures of the pontic should be wide open to allow the patient easy access for cleaning,3^.12.'620 and the contact between pontic and tissue must allow the passage of floss from one retainer to the other. After the fixed partial denture is cemented, teach the patient appropriate technique(s) that can be mastered. Motivate the individual to practice good hygiene around and under the pontic with dental floss (Fig 26-8), interproximal brushes (Fig 26-9), or pipe cleaners. The method used will depend on embrasure size, accessibility, and patient skill. Give the patient time to learn the techniques and demonstrate the ability to clean the underside of the pontic and the adjacent areas of the abutment teeth. Evaluate home care at each appointment and reinforce the necessity for good hygiene and the skills to accomplish it. Even the smoothest pontic surface must be cleaned well and often to prevent the accumulation of plaque.21 If cleaning is not done at frequent, regular intervals, the tissue around the pontic wili become infiamed.18 Pontics designed for placement in the appearance zone (areas of high visibility [Richter WA; personal communication, July 1973]) must produce the illusion of being teeth, esthetically, without compromising cleanand Edentulous Ridges Fig 26-8 Floss h fed through the gingival embi the pontics and connectors by ihe patient. If the spa monofilament floss threader can be used. jnunde 5 tight, ; c saddle, or ridge lap pontic (A). A linguogingi- >r extension past the crest of the ridge, although institutes a saddle (B). ability. Those pontics placed in the nonappearance zone (usually mandibular posterior replacements) are there to restore function and prevent the drifting of teeth. Since esthetics is usually a minor consideration in this area of the mouth, it may not be necessary to utilize materials or contours that suggest the presence of a tooth. The pontic should be on as straight a line as possible between the retainers to prevent any torquing of the retainers and/or abutments. The pontic will be slightly narrower than the natural tooth, partly because of the effort to place it on the interabutment axis. The pontic may also be somewhat narrower at the expense of the lingual surface in an effort to avoid the formation of an uncleanable, overhanging shelf m the pontic overlying the lingual aspect of ihe ridge. However, no attempt is made to make the pontic narrower by a set percentage (eg, 10% per pontic). Doing so does not alter the plaque index.1 Narrowing the pontic is not practical if an effort is being made to maintain occlusal contacts on cusps or in fossae. Pontic Designs There are several designs available for our use in situations requiring pontics in the fabrication of fixed partial dentures. These include: saddle (ridge lap), modified ridge lap, hygienic, conical, ovate, prefabricated pontic facings, and metal-ceramic pontics. Saddle This pontic looks most like a tooth, replacing all the contours of the missing tooth. It forms a large concave contact with the ridge (Fig 26-10, A), obliterating the facial, lingual, and proximal embrasures. It is also called a ridge lap, because it overlaps the facial and lingual aspects of the ridge. A contact with the ridge that extends beyond the midiine of the edentulous ridge, or a sharp angle at the linguogingival aspect of the tissue contact, constitutes a ridge lap (Fig 26-10, B). This design has long been recognized as being unclean and uncleanable.^ It still is.2324 The saddle is impossible to clean, because floss cannot traverse the tissue-facing area of the pontic because it bridges across the linguogingival and faciogingival angles of the pontic. The saddle causes tissue inflammation, and it should not be used.25 Pontic Designs gj% Fig 26-11 Modified ridge lap ponlics: A, maxillary; B, mandibular. Fig 26-12 Hyg Fig 26-13 Floss passes over a smooth, surface and sharp angles (B). Modified Ridge Lap This design gives the illusion of a tooth, but it possesses all or nearly all convex surfaces for ease of cleaning. The lingual surface should have a slight deflective contour to prevent food impaction and minimize plaque accumulation. 14 There may be a slight faciolingual concavity on the facial side of the ridge, which can be cleaned and tolerated by the tissue as long as the tissue contact is narrow mesiodistally and faciolingually. Ridge contact must extend no farther Imgually than the midline of the edentulous ridge, even on posterior teeth. Whenever possible, the contour of the tissue-contacting area of the pontic should be convex, even if a small amount of soft tissue on the ridge must be surgically removed to facilitate it. This design, with a porcelain veneer, is the most commonly used pontic design in the appearance zone for both maxillary and mandibular fixed partial dentures (Fig 26-11). Hygienic The term hygienic is used to describe pontics that have no contact with the edentulous ridge (Fig 26-12). This pontic design is frequently called a "sanitary pontic," which in years past was the trade name for a prefabricated, convex facing with a slot back, used for mandibular molar pontics. The hygienic pontic is used in the nonappearance zone, particularly for replacing mandibular first molars. It restores occlusal function and stabilizes adjacent and opposing teeth If there is no requirement for esthetics, it can be made entirely of metal. The occlusogingival thickness of the pontic should be no less than 3.0 mm, and there should be adequate space under it to facilitate cleaning. The hygienic pontic is frequently made in an all-convex configuration, faciolingually and mesiodistally. Making the undersurface of the pontic round without angles allows for easier flossing (Fig 26-13, A). It is more Pontics and Edentulous Ridt al ("fish belly"); B, modified (Perel). g incorrectly ping embras p y th a broad, flat ridge (B). Arro re spaces. ridge (A) ^n te debris-tra Fig 26-16 The round-end ovate pontic fits into a depressio ridge. ly to be visible: the occlusal surface and the occlusal half of the facial surface, which happens to be all of the facial surface on this pontic. This design has been called an "arc-fixed partial denture,"23 a "modified sanitary pontic," 27 or simply a "Perel pontic." Conical The conical pontic is rounded and cleanable, but the tip is small in relation to the overall size of the pontic. It is well suited for use on a thin mandibular ridge (Fig 26-15, A). However, when used with a broad, flat ridge, the resulting large triangular embrasure spaces around the tissue contact have a tendency to collect debris (Fig 26- 15, B).10 This pontic is related to the "sanitary dummy" described by Tinker in 1918.™ Its use is limited to replacement of teeth over thin ridges in the nonappeardifficult to get floss to pass over a flat undersurface evenly, or to get over sharp faciogingival and linguogingival line angles (Fig 26-13, B). The round design has been described as a "fish belly" (Fig 26-14, A). An alternative design, in which the pontic is made in the form of a concave archway mesiodistally (Fig 26-14, B), has been suggested The undersurface of the pontic is convex faciolingually, giving the tissue-facing surface of the pontic the configuration of a hyperbolic paraboloid. There is added bulk for strength in the connectors, and access for cleaning is good.?6 Stress is reduced significantly in the connectors, and deflection is diminished in the center of the pontic, with less gold used.27 An esthetic version of this pontic can be created by veneering with porcelain those parts of the pontic that are like- Ovate The ovate pontic is a round-end design currently in use where esthetics is a primary concern." Its antecedent was the porcelain root-tipped pontic,^M-^ which was used considerably before 1930 as an esthetic and sanitary substitute for the saddle pontic. The tissue-contacting segment of the ovate pontic is bluntly rounded, and it is set into a concavity in the ridge (Fig 26-16) It is easily flossed. The concavity can be created by placement of a provisional fixed partial denture with the pontic extending one-quarter of the way into the socket immediately after extraction of the tooth It also can be created surgically at some later time.2ii This pontic works well with a broad, flat ridge, giving the appearance that it is growing from the ridge Prefabricated Pontic Facings At one time, preformed porcelain facings were popular for fabricating pontics.33 They required adaptation to a specific edentulous space,1634 after which they were reglazed. Some, such as Trupontics, Sanitary pontics, and Steeles facings (Franklin Dental Co, Columbus, OH), relied on a lug in a custom cast metal backing to engage a slot in the occlusal or lingual surface of the facing (Fig 26-17, A), The large bulk of porcelain could result in a thin gold backing susceptible to flexing. Harmony and Trubyte facings used horizontal pins that fit into the gold backing (Fig 26-17, B). They were difficult to use in patients with limited occlusogingival space, and refitting the pins into a backing after casting was demanding. Porcelain denture teeth also were modified to use as pontic facings. Multiple pin holes, 2.0 mm deep, were made with a drill press in the lingual surface of the reverse pin facing (Fig 26-18).34 The pins came out of the backing, providing retention where a deep overbite would have overshortened conventional pins. Unfortunately, the pin holes in the facing were stress points that led to fracture. Metal-Ceramic Pontics With the widespread use of metal-ceramic restorations, metal- ceramic pontics have replaced other types of pontics employing porcelain. Metal-ceramic pontics have the greatest esthetic potential as prosthetic replacements for missing teeth.35 Additionally, metal-ceramic pontics are stronger, since the porcelain is bonded to the metal substrate rather than cemented to it. They are easier to use because the backing is custom made for a space (no need to adapt a premade porcelain facing to the space) The Edentulous Ridge Before a fixed partial denture is undertaken, the edentulous ridge should be examined carefully. The type and amount of destruction will play a role in selecting the pontic to be used and also may indicate the necessity for reshaping the ridge surgically. Ridge deformities have been grouped into three categories by Siebert (Fig 26-19),36 and this classification has been widely accepted1137' • Class I. Loss of faciolingual ridge width, with normal apicocoronal height. • Class II. Loss of ridge height, with normal width. • Class III. Loss of both ridge width and height. If a "normal" classification (Class N) with minimal deformity is added, there are four classes of ridge contours In a study of 416 diagnostic casts, Abrams et al28 showed Class I defects to constitute 32.4% of the edentulous ridges, with 2 9% being Class II, 55.9% being Class III, and only 8 8% having no defects. Ponlics and Edentulous Ridges Fig 26-19 Tlie three types of ridge deformities described by Siebert1'- plus the normal category The Edentulous Ridge Fig 26-20 Lingual view of open gingival embrasures ("black triangles") on a fixed partial denture replacing mandibular incisors. Pontic Modification Al one time it was common to modify a pontic to fit an edentulous space, no matter what the esthetic consequences were. Developments in surgical techniques have made it simpler to change the configuration of a ridge to create a more esthetic and a more easily cleanable shape. It has become more common to modify the ridge than to suffer the rigors 
برچسب ها: technique، mark the shoulder finish line on the die using Fig 25-45 "Die facial shoulder finish lii A red pencil. the side o! a red pencil (Fig 25-45). Then seal the porous surface of the gypsum die by brushing on a special sealing material (Cera-Seal، Belle de St Claire، Chatsworth. CA) or by squeezing a thin layer of cyanoacrylate cement (Permabond 910 Adhesive، Buffalo Dental Mfg Co، Brooklyn، NY) onto the finish line area of the die (Fig 25- 46). Blow off the excess liquid with compressed air to insure a uniformly thin layer of sealant (Fig 25-47). Apply a special lubricant،  

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was once thought.5 Although the molecular attraction makes only a minor contribution to overall bond strength, it is significant in the initiation of the most important mechanism, the chemical bond. Chemical bonding is indicated by the formation of an oxide layer on the metal,87 and by bond strength that is increased by firing in an oxidizing atmosphere.89 When fired in air, trace elements in the gold alloy, such as tin, indium, gallium, or iron, migrate to the surface, form oxides, and subsequently bond to similar oxides in the opaque layer of the porcelain. A gold alloy containing minute amounts of tin and iron creates a significantly stronger bond with porcelain than a pure gold alloy does.10 The bond strength of true adhesion is such that failure or fracture will occur in the porcelain rather than at the porcelain-metal interface." The clean separation of porcelain from the metal coping is evidence of bond failure from contamination of the coping surface, or an excessive oxide layer. Base metal alloys readily form chromium oxides that bond to the porcelain without the addition of any trace elements. Alloys Used for Fabricating Metal-Ceramic Restorations High noble Gold-platinum-palladium Gold-palladium-silver Gold-palladium Noble Palladium-silver High palladium Predominantly base Nickel-chromium Nickel-chromium-beryllium Cobalt-chromium Alloys Used The properties of the porcelain cannot be considered alone. The porcelain and metal used for a restoration must have compatible melting temperatures and coefficients of thermal expansion. Conventional gold alloys have a high coefficient of thermal expansion (14 x 10-6°C) while conventional porcelain possesses a much lower value (2 - 4 x 1f>6°C). A difference of only 1.7 x 10-6°c can produce sufficient shear stress to produce failure of the bond." The optimum difference between the two would be no greater than 1 x 10-6°C. The coefficient of thermal expansion of porcelain can be increased to as much as 7 - 8 x 10-6°C by the addition of an alkali such as lithium carbonate. At the same time, the coefficient of the metal can be lowered to 7 - 8 x 10-6°C by adding palladium or platinum. The melting range of the alloy used in the coping must be 170 to 280°C (300 to 500°F) higher than the fusing temperature of the porcelain applied to it. A similar melting range of the two materials would result in the distortion or melting of the coping during the firing and glazing of the porcelain. The greater the difference, the fewer the problems that are encountered during firing. A noble metal coping is subject to flow, or creep, when it is heated to 980°C (1,800°F).'2 The porcelain used must not require that the metal be heated much beyond this point. Porcelains most commonly used for this purpose have a fusing temperature of nearly 980°C (1,800°F), and noble alloys melt at near 1,260°C (2,300°F). Many alloys have been used for metal-ceramic restorations A classification system proposed by the American Dental Association is based on noble metal content (see box above).13 High noble alloys have a noble metal (gold, platinum, palladium) content greater than 60%, with at least 40% gold. Noble alloys have a noble metal content r of at least 25%, and predominantly base alloys have less than 25% noble metal content. Major constituents also are used to further describe an alloy, eg, a gold-palladium alloy. The choice of an alloy will depend on a variety of factors, including cost, rigidity, castability, ease of finishing and polishing, corrosion resistance, compatibility with specific porcelains, and personal preference. No alloy system is superior in all aspects. Alloys that have proven most satisfactory for metalceramic crowns and fixed partial dentures are composed of gold (44% to 55%) and palladium (35% to 45%) with small amounts of gallium, indium, and/or tin. Disadvantages most often attributed to gold-palladium alloys are cost and incompatibility with certain types of porcelains. Other systems developed over the past 20 years also have been successful. The choice of an alloy must be made after weighing all factors. The skyrocketing cost of gold in the late 1970s stimulated the development of alloys containing little or no gold. A logical transition was the application of materials commonly used in the fabrication of removable partial denture frameworks to fixed prosthodontics. These alloys possess desirable properties such as low cost, increased strength and hardness, high fusion temperatures, and greater resistance to distortion during porcelain firing. However, there are inherent problems with these alloys when used as an integral part of a metal-ceramic system. The disadvantages include excessive oxide formation, difficulty in finishing and polishing, and questionable biocompatibility. Beryllium, which is added to alloys to control oxide formation, is a carcinogen. It can pose a hazard to laboratory personnel who may inhale it as dust in improperly ventilated work areas 14 Approximately 5% of the general population is sensitive to nickel, and that sensitivity is 10 times as prevalent in women as in men.15 Contact dermatitis from nickel-containing prostheses appears to be a risk to some patients.1fi Dissolution and occlusal wear affect the amount of nickel and beryllium released in an artificial oral environment.17 Nickel sensitivity should be considered in the diagnosis of any soft tissue changes that occur after crown placement.16 Another cost-cutting alternative to traditional alloys is the modification of existing noble metal alloys by using less-expensive metals, such as copper or cobalt, in the alloy. Unfortunately, the addition of these elements caused dark oxide formation and poor high-temperature strength.19 Subsequent formulations replaced the copper or cobalt with a small amount of gold and silver. One of the most common disadvantages of the silver-containing alloys is the potential of porcelain discoloration, most commonly described as "greening." No system is without disadvantages, whether they be financial or technical. Coping Design The metal coping is an important part of the metalceramic restoration, and one that unfortunately is often overlooked. Its design can have an important effect on the success or failure of the restoration. To provide structural integrity in function, the coping must reflect the unique relationship of the two dissimilar materials used to fabricate metal-ceramic restorations. Since the kaolin content must be reduced to allow translucency, dental porcelains may behave more like glass than a true ceramic. Like glass, dental porcelains are significantly stronger in compression than in tension. The coping must allow the porcelain to remain in compression by supporting the incisal region, the occlusal table, and the marginal ridges. Otherwise, occlusal forces will create a situation similar to applying a load to a pane of glass suspended between two sawhorses. Without any underlying support, the glass would break— and so will unsupported porcelain on a restoration. There are four features of importance to be considered when designing the metal coping for a metal-ceramic restoration: . Thickness porcelain ;rlying and adjoining the 3. Extensions of the area to be veneered for porcelain 4. Design of the facial margin Thickness of Metal Porcelain should be kept at a minimum thickness that is still compatible with good esthetics. Relatively thin porcelain, of uniform thickness and supported by rigid metal, is strongest. The absolute minimum thickness of porcelain is 0 7 mm, and the desirable thickness is 1.0 mm. Deficiencies in the incisal edge, interproximal areas, or occlusal surface of the tooth preparation that have been caused by caries or previous restorations should be blocked out in the preparation or compensated for with extra thickness of the coping in those areas. An evenly flowing convex contour of the veneering area distributes stress best. Sharp angles and undercuts should be avoided. The outer junction of porcelain to metal should be at a right angle to avoid burnishing of the metal and subsequent fracture of the porcelain. An acute angle of metal at the metal-porcelain interface is more likely to produce porcelain crazing than an angle of 90 or 135 degrees.19 On the other hand, if the edge of metal at the porcelain-metal junction line is beveled or rounded, the porcelain will end in a feathered edge, through which the oxidized metal or opaque will show. Maximum restoration strength and longevity is achieved by coping rigidity. The metal must not flex during seating or under occlusal forces, because flexure places the porcelain in tension and leads to its shearing. The metal Fig 25-2 Metal c gual surface of a n may fr* icisally. must be as hard as practical, and the coping design must insure an optimum bulk for rigidity. For adequate strength and rigidity, a noble metal coping should be at least 0.3 to 0.5 mm thick.20 A base metal alloy with a higher yield strength and elevated melting temperature may be as thin as 0.2 mm.21 The thickness of the coping may vary, depending on the configuration of the preparation. These values are only minimum thicknesses for different alloy systems The ultimate goal of achieving a uniform thickness of approximately 1.0 mm of porcelain will dictate the thickness of the metal coping Occlusal and Proximal Contacts If the coping is designed to place occlusal contacts on unveneered metal surfaces, their location and the area covered by ceramic can be more precisely controlled, with less resultant wear on opposing teeth. Studies and clinical experience have documented the highly abrasive nature of dental porcelain and its deleterious effects on enamel or gold.22 2& Jacobi et a)'4 found that glazed porcelain removes 40 times as much opposing tooth structure as gold. Therefore, occlusal contacts should occur on metal whenever possible, well away from the porcelain-metal junction line. Contact near the junction can lead to metal flow and subsequent porcelain fracture. The porcelain-metal junction should be placed 1.0 mm from occlusal contacts at the position of maximum intercuspation (Fig 25-2). To minimize stress resulting from occlusal contacts on the lingual surface of maxillary anterior restorations, the porcelain-metal junction should not be placed in the vicinity of those contacts with the mandibular teeth.26 The porcelain-metal junction must not be placed too close to the incisal edge. Incisal translucency will be destroyed and the chances of porcelain fracture will be increased greatly because the porcelain is no longer supported by metal. When occlusal forces are exerted, the porcelain will be placed in tension, a condition that it does not resist well (Fig 25-3). When there is inadequate vertical overlap to place the contact on metal, the porcelain-metal junction is placed far enough gingivally for the contact to occur on porcelain close to the junction line (Fig 25-4). A constant application of increasing compressive force on the porcelainmetal junction line, irrespective of its angulation, produces failure less readily than a load applied to porcelain 1.0 or 2.0 mm from the junction.27 Anterior metal-ceramic restorations with guidance in lateral excursions and protrusion on porcelain will abrade opposing natural teeth. The patient should be cautioned that the opposing teeth eventually will require restorations. The collar of exposed metal on the lingual should be at least 3.0 mm wide incisogingivally. Wherever there will be porcelain on the lingual surface, there must be greater tooth reduction. Proximal contacts for anterior teeth should be on porcelain, which the dentist must facilitate during the tooth preparation by adequate reduction of the interproximal areas. The cosmetic effect is improved by placing the metal lingually, so that proximal porcelain has greater depth and translucency. Interproximal metal tends to darken the unrestored proximal surfaces of adjacent teeth. An optimum stress distribution also occurs when the porcelain-metal junction is lingual to the proximal contact areas.29 Fig 25-7 Proximal views of a maxillary po (B) proper metal support under the facial ci Extent of Veneered Area To place occlusal contacts in metal, the porcelain on the facial surface extends over the cusp tip and about half of the way down the lingual incline of the facial cusp on maxillary premolars (Fig 25-5) and molars (Fig 25-6).^ There must be a rounded ledge of metal under the facial cusp to support the porcelain (Fig 25-7, A). Without a supporting ledge, the ceramic will fracture (Fig 25-7, B). This configuration will satisfy the cosmetic requirements of most patients and provide longevity if the porcelainmetal junction is kept away from the occlusal contacts This design is more resistant to fracture than those in which the porcelain extends to the central groove or covers the entire occlusal surface.30 Variants for maxillary teeth include porcelain coverage of the mesial marginal ridge up to the middle of the triangular ridge (Fig 25-8), or for those patients who demand absolute esthetics, complete coverage with porcelain of the occlusal surface of premolars (Fig 25-9) and molars (Fig 25-10). Mandibular first premolars will require complete porcelain coverage of the occlusal surfaces of metal-ceramic crowns placed on them (Fig 25-11). The degree of porcelain occlusal coverage on metal-ceramic crowns for Fig 25-8 Me views of a r design for a •sial (top) and occlus nodified metal-cerai maxillary premolar. ;al (bottom! •nic coping Fig 25-9 Mesial ic coping des (top) and ary prem ign with Fig 25-10 Mesial (top) and occlusal ft ceramic coping design with full purcel Fig 25-11 Occlusal (top) and mesial (bottom) views of a mandibular premolar metalceramic coping design (standard for first premolar, optional for second premolar]. Fig 25-12 Occlusal (top) and mesial (bottom) views of a standard mandibular second premolar metal-ceramic coping design. mandibular molars and second premolars will be dictated by patient wishes, occlusal restoration of the opposing arch, and the presence or absence of bruxism. The distal half of premolars (Fig 25-12) and molars (Fig 25- 13) can be unveneered to allow more occlusal contacts to be on metal, if the patient can be satisfied with a toothcolored veneer on the mesial marginal ridge, proximal contact, fossa, and cusp incline. If the patient is extremely concerned about esthetics, the occlusal surfaces of mandibular molars can be covered with porcelain (Fig 25-14). A 1.0- to 2.0-mm-wide metal collar can be used on the facial surface to minimize the destruction of tooth structure for a facial shoulder. The patient should be informed of the potential damage to opposing teeih and the necessity for a more destructive crown preparation to provide adequate Fig 25-13 Occlusal (lop) ar torn) views of a standard rr Fig 25-14 Occlusal (top) and mesial (bottom) views of an optional mandibuiar first molar metal-ceramic coping dcstgn. space for the porcelain. In the final analysis, it is the patient's mouth, and the final decision is the patient's. Be sure that it is an informed one. A posterior crown with porcelain occlusal coverage should have a 3.0-mm metal collar on the lingual, with metal support under the marginal ridges. Although the greater portion of the crown will be veneered with porcelain, it should still be waxed to a full contour and then cut back to insure a uniform thickness of porcelain and correct contours. A "thimble" coping may result in unsupported, fracture-prone porcelain. Facial Margins For many years, the conventional facial margin for a metal-ceramic crown was a narrow metal collar. To avoid an unesthetic display of metal on highly visible teeth, the facial finish line often was placed subgingivally, which serious periodontal problems. Gingival recession may occur from the trauma of tooth preparation, impressionmaking, or an improperly contoured provisional restoration. Following cementation, 60% of subgingival margins become visible within a 2-year period.31 The association of subgingival crown margins and detrimental effects on the periodontium is well-documented.^-^ To avoid showing an unsightly band of metal, porcelain was extended onto the collar itself. This can create an overcon toured gmgival margin; thin, fracture-prone porcelain; or an undetected open margin. Frustration with the esthetics of the conventional metal collar led to the use of the all-porcelain facial margin, which can be even with the gingiva or even slightly supragingival. An improvement in periodontal health was an unexpected bonus. Improved esthetics and periodonial health made the all-porcelain margin popular, and the demand spawned many ways of fabricating one. The first was a transition from a technique used for porcelain jacket crowns, in which a platinum foil matrix supports the porcelain margin during firing.3" Another technique employs a refractory die to support the porcelain margin during firing.37'38 In an effort to simplify the fabrication of all-porcelain shoulders even more, direct-lift techniques were tried. Correction porcelain was added to the margin, after a full-contour buildup of the crown. The porcelain was condensed by compression and fired to produce the final margin.39 In 1979 Vyronis40 described a method which required a tooth preparation with a 90-degree shoulder finish line and a metal coping that terminated at the gingivoaxial line angle. Opaque porcelain was applied to the metal coping and the shoulder on a sealed stone die, forming the margin. After obtaining a satisfactory margin, dentin and enamel porcelains were added to complete the crown. A blend of dentin and enamel porcelains was substituted to form the margin.41 However, margins of conventional porcelain tend to round or slump during subsequent firings because the fusion temperatures are identical. To correct this problem, manufacturers created special shoulder porcelains containing aluminous porcelain that fuse at temperatures 30 to 80°C higher than the dentin or enamel porcelains. The higher-fusing porcelain allows repeated firings of the crown buildup with no effect on the completed margin.42 In addition to stability during the firing cycle, shoulder porcelains are stronger Metal-Ceramic Restorations full-contour wax pattern; B, coping w pattern cut back; Q porcelain additr to metal coping. Fig 25-16 If the coping pattern (Al is the first step in fabrication, the porcelain veneer on the final restoration may have contours that are not continuous with those of the unveneered coping (B). binders indicates that the quality of the margins is directly related to the skill of the ceramist. If a talented and conscientious ceramist is not available, all-porcelain facial margins are definitely contraindicated. Single Coping Wax Pattern Before a coping can be fabricated for a metal-ceramic crown, the wax pattern should be made to the complete contour of the finished restoration (Fig 25-15). Then the areas to be veneered with porcelain are cut back. Only by following this procedure can there be a smooth continuation of the lingual and proximal contours between the unveneered metal and the porcelain. If only the portion of the wax pattern that later will be unveneered metal is made, it is difficult to be sure that the contours of the unveneered portion of the coping will match the contours of the porcelain (Fig 25-16). in flexure than conventional porcelains, making the margin more resistant to fracture.43 A number of studies have shown the accuracy of allporcelain margins to be quite acceptable.44"48 Early studies utilized conventionai porcelains for the margins. Recent studies using shoulder porcelains and the directlift technique have produced a consistent level of marginal adaptation with mean marginal openings of 15 to 23 urn49 and 8 to 11 urn.50 The demonstration of acceptable porcelain margins with a wide assortment of techniques, porcelains, and Waxing Armamentarium 1. PKT (Thomas) waxing instruments (nos. 1,2, 3, 4, and 5) 2. Beavertail burnisher 3. No. 7 wax spatula 4. Discoid carver 5. Large spoon excavator 6. Sable brush 7. No. 2 pencil Single Coping Wax Patte, Fig 25-17 Theproxi with a sharp knife tip Fig 25-18 Frc al portion of the pattern, 1.5 n 8. Laboratory knife with no. 25 blade 9. Iwanson thickness gauge 10. Cotton pliers Bunsen burner and matches 12. Inlay casting wax Zinc stearate Die lubricant All-Wax Technique Wax is first applied to the lubricated die with a hot no. 7 wax spatula. Trim the wax back from the margins and transfer the wax thimble to the articulated working cast. Build up the axial contours, including the proximal contacts, in harmony with the adjacent teeth. Establish the proper occlusal relationships with the opposing teeth. If the wax pattern is for a posterior tooth, use the PKT instruments to build up the occlusal surface with cones and ridges to obtain good occlusion (see Chapter 19). When the full-contour wax pattern is completed, make an impression of it with a resilient condensation silicone putty impression material- This impression can be poured to produce a stone cast, providing a visual guide to the desired contours, or it can be sectioned horizontally to allow assessment of the amount and contours of the cutback. The first step in forming the veneering area is sketching of the outline of that area on the wax pattern. Place the no, 25 blade on the proximal surface of the adjacent tooth. Using this guide, scratch a line on the proximal surface of the pattern, placing it as far lingual as possible (Fig 25-17), After drawing the outline on the pattern, place it on the die. Remove 1.5 mm from the incisal portion of an anterior pattern with the knife (Fig 25-18). Place the proximal porcelain-metal junction 0.5 mm to the lingual of the proximal contacts (which will be nearly 1.0 mm lingual to the proximal line drawn earlier). Use a discoid carver to finish the wax that will form the porcelain-metal junction on the proximal surface. Carve a vertical groove in the center of the labial surface with the discoid carver (Fig 25- 19). Cut similar grooves on the mesial anddista!. From an incisal view, these grooves should be about 1.0 mm deep. They are used to gauge the depth of wax to be removed from the veneering area. Metal-Ceramic Restorat Fig 25-20 Wax is removed with a sharp knife to the desired depth. an all-porcelain shoulder erids at the gingivofacial angle (z The design of the facial margin must be decided before preparing the tooth, because it will be dictated by the facial finish line. For a metal collar, the bulk of the wax is removed with the knife, leaving a collar of wax 1.0 mm wide at the facial margin to reinforce it during investing and to insure an adequate bulk to cast the margin (Fig 25-20). The collar will be narrowed to approximately 0.3 mm in metal. For an all-porcelain facial margin, the wax pattern terminates at the junction of the facial axial wall and the facial shoulder (Fig 25-21). Adapt the margins with a warm beavertail burnisher. Check the thickness of the wax pattern with a thickness gauge. It should be 0.4 to 0.5 mm thick in the veneering area. It will be thinned to about 0.3 mm after it has been cast. If it is made too thin at this point, it may not cast completely. Plastic Shell Technique Thinning the wax in the areas to be veneered with porcelain can create problems. The wax becomes very fragile and breaks easily, forces generated during the cutback may distort the adaptation of the wax, and it is difficult to judge the thickness of the coping wax pattern. The use of a plastic shell coping can overcome the problems encountered in fabricating wax patterns for single units and fixed partial dentures. Techniques utilizing plastic shells to form the underlying structure of coping patterns have been in use for nearly 25 years. Shells for multiple dies can be made with the use of machines to apply compressed air to the plastic shell51 or vacuum-forming machines. Shells for single dies can be formed in hand-held frames without the need for machines.52 Another convenient and reliable method for making a plastic shell coping is to compress a plastic sheet to fit a die (Adapta, BEGO GmbH & Co, Bremen, Germany). This technique is especially useful in small laboratories or in training programs, where the volume of work does not require large numbers of copings to be made at once. The commercially available kit contains sheets of coping material, thinner sheets of material used as a cement spacer, a frame for holding the materials during heating, and a molding apparatus containing silicone putty. Plastic Shell Armamentarium In addition to items listed for waxing 1. 4.0-cm spacer disks 2. 4.0-cm coping disks 3. Wire holding frame 4. Putty-filled jar 5. Iris scissors i The technique63 is simple and easily mastered. Lay a 4.0-cm-diameter spacer disk, 0.1 mm thick, over a 4.0-cmdiameter disk of coping material, 0.6 mm thick (Fig 25-22). Place the coping material and spacer disks onto a wire holding frame (Fig 25-23). Heat the disks slowly and evenly by holding them, approximately 10 cm (4 inches) above a Bunsen burner flame (Fig 25-24). The plastic sheets are flammable, so heat the material cautiously The material will first buckle and then slump, becoming transparent. Place the heated coping disk and spacer over the mouth of the molding apparatus, a plastic jar filled with silicone putty. The spacer should be facing upward {Fig 25- 25). Press the trimmed die forcefully against the softened spacer and coping disks until the finish line of the preparation is completely submerged (Fig 25-26). This closely adapts the two disks over the tooth preparation. Continue to exert pressure against the disks with the die until the sheet becomes cloudy, which will take approximately 10 seconds. The heating and adaptation of the coping disk stretches it to the desired thickness of 0.3 mm. Single Coping Wax Pattern Fig 25-22 A spacer disk is placed over the coping disk. Fig 25-23 Both disks are placed in the holding frarr Fig 25-26 The die of the tooth preparation is plunged into the heat-softened disks over the putty. Melal-Ceramic Restoratioi Fig 25-27 Three cuts are made in the unadapted skirt of the disks with a pair of iris scissors. I Fig 25-29 The spacer disk is peeled out of the toping shell. Single Coping Wax Patte, Fig 25-30 Excess border material is above the preparation finish line. Fig 25-31 The tri coping are aboirl !he shell and finish li Remove the die with the adapted spacer and coping disks from the silicone putty in the molding apparatus with a sharp movement. Use a small, sharp-nosed scissors with straight blades to make three or four lateral cuts in the unadapted skirt of the coping disk (Fig 25-27) Remove the adapted coping and spacer disks from the die (Fig 25-28). Because the coping material is welladapted to the tooth preparation, it will offer some resistance to removal. Separate the spacer from the inside of the coping (Fig 25-29). Use cotton pliers or a hemostat, if necessary, to accomplish the task. This is an important step, not only because the spacer provides room for the cement in the completed restoration, but also because it will not burn out. Use the scissors to trim the margin of the coping shell (Fig 25-30). At this point the margin should be about 1.0 mm short of the gingival finish line when the coping is replaced on the die (Fig 25-31). Add wax to the gap between the edge of the coping and the preparation finish line (Fig 25-32). If any of the wax runs under the coping, remove the plastic shell from the die and scrape it clean. The only wax in contact with the die should be the 1.0-mm-wide band immediately occlusal to the finish line. Any other contact defeats the relief provided previously by the spacer disk. The welladapted coping is now ready for the application of wax. Complete the full-contour wax pattern in the usual fashion (Fig 25-33) and make a silicone index Determine and mark the outline of the cutback area on the wax pattern. Use a PKT no. 4 carver to remove the wax down to the level of the plastic shell on those areas of the pattern where porcelain is to be applied later (Fig 25-34). A large spoon excavator is ideally suited for creating the deep chamfer at the porcelain-metal junction line around the area to be veneered with porcelain (Fig 25-35). If there is to be an all-porcelain shoulder on the finished crown, shape [he porcelain-metai ji carefully remove the wax collar at the gingival area of the facial surface using a laboratory knife with a no. 25 blade (Fig 25-36). The benefit of using the plastic shell coping becomes apparent during the cutback stage. The plastic coping provides rigidity and resists distortion during the removal of wax. When the cutback is complete, use the silicone index of the full-contour wax pattern to verify the adequacy of the cutback Adapt the margins with a warm beavertail burnisher (Fig 25-37) and smooth the wax pattern. Carefully inspect the wax pattern, paying particular attention to the lingual margins (Fig 25-38). Then sprue and invest the pattern in the customary manner. The resulting casting should be well-adapted internally, with a uniform relief for cement. Alloy Surface Treatment The surfaces of a coping that are to receive porcelain must be properly finished to assure a strong bond and an esthetic restoration. Surface irregularities and small particles of investment may be embedded in the surface of Single Coping Wax Pattern Fig 25-38 The lingual surface of ihe completed pattern is checked for marginal adapthe casting. Finishing can remove much of this residue while producing uniform striations in one direction to decrease the possibility oi gas entrapment during the initial firing cycles. Surface Treatment Armamentarium 1. Straight handpiece 2. Carborundum separating disc on mandrel 2. Aluminum oxide separating disc on mandrel 3. Aluminum oxide stones 4. Craytex disc on mandrel 5. Burlew disc on mandrel 6. Fine cuttle disc on mandrel Place the casting on the die. Remove the sprue with a carborundum separating disk. To linish the veneering area, use only new, clean burs and noncontaminating stones and discs. Instruments that have been previously used on other types of metal will contaminate the veneering area. Use aluminum oxide stones (Forum Brown Abrasives, Unitek Corp, Monrovia, CA; or Lab Series Coral Stones, Shofu Dental Corp, Menlo Park, CA) for rough finishing of the veneering area (Fig 25-39). If a disc must be used, it also must be aluminum oxide since it will not contaminate the veneering area (Dura-Thtn Disc, National Keystone Products Co, Cherry Hill, NJ). The demarcation line between the veneered and unveneered areas of the coping should be distinct, with an external angle of 90 degrees and a rounded internal angle. Metal-Ceramic Restoration T Fig 25-39 The veneering area is prepared with nxide Fig 25-40 Tiic coping thickness is checked with ai ness gauge. Check the thickness of the metal to be veneered with a thickness gauge (Fig 25-40). On noble metal castings it should measure at least 0.3 mm, while on base metal copings it can be 0.2 mm. Narrow the cervical collar, if there is one, from 1.0 mm to about 0.3 mm. Be careful not to run over the margin. Use Craytex and Burlew discs on the unveneered area, and finish the face of the collar with a fine cuttle disc. Do not use any polishing compounds, as they may contaminate the surface of the metal to be veneered later. Novices would be wise to try the casting in the patient's mouth. Experienced operators will usually bypass this step unless there are a large number of single castings being done at one time, or a long-span fixed partial denture. Check the marginal adaptation of the casting and make any occlusal or contour adjustments that are necessary. Heat Treatment Any remaining investment or abrasive particles embedded in the surface of the casting could oxidize and release gases during firing. Oils from the skin left during handling of the casting are another serious form of contamination. "Live steam" is effective in removing residual contamination caused by surface deposits of abrasive particles.54 The coping is ready for the oxidation cycle. Metal surface treatments are unique for each porcelain-alloy combination, and manufacturer's recommendations should be followed. Bond strength varies with the surface treatment. Unaltered, as cast, gold-palladium and silver-palladium specimens produce low bond values.2 Typically, a coping is placed in a furnace at a relatively low temperature and the temperature is raised 300 to 400°C at a Porcelain Additioi Fig 25-42 The veneering surface of the toping is wetted with di^ tilled water or special liquid recommended by the manufacturer. Fig 25-44 Aflcr the first layer of opaque is fired, a second coat is applied lo completely cover [he metal. designated rate of climb. The atmosphere (air or vacuum) during this heating process, as well as the length of time at temperature, is dictated by the alloy. Heat treatment of noble metal alloys causes the trace quantities of tin, gallium, indium, and zinc in the alloy to form oxides that enhance bonding with the porcelain.^ Base metal alloys, on the other hand, readily oxidize, so oxide formation must be carefully controlled. Following oxidation, most alloys require air abrasion with 50 |im aluminum oxide to reduce the layer of oxide (Fig 25-41), as excess oxide weakens the porcelain-to-metal bond. Oxidation is only one of the functions of the initial firing. During casting, hydrogen gas is incorporated into the molten alloy. This gas, if left in the coping, can weaken the bond between porcelain and metal,5 causing the formation of bubbles in the porcelain.66 The hydrogen is released during the oxidation cycle, degassing the alloy as well as forming the important oxide layer. Porcelain Addition The buildup of porcelain is a skill that requires a great deal of practice to develop Therefore, only a brief description for the sake of familiarization is given here Opaque Porcelain Application The casting is now ready for the actual placement of porcelain. Opaque porcelain is applied first to mask the metal, to give the restoration its basic shade, and to initiate the porcelain-metal bond. The prepared coping is painted with a thin coating of distilled water or special liquid (Fig 25-42). A small amount of the appropriate opaque powder is mixed with distilled water or the specially formulated liquid, forming a thin wash which is applied with a brush (Fig 25-43). No attempt should be made to thoroughly mask the metal with this initial application. It is intended to completely wet the metal and penetrate the striations created by finishing. The coping is dried and fired under vacuum to a specific temperature. The vacuum is broken and the coping held at the temperature under air for 1 minute. The second application of opaque porcelain should mask the metal (Fig 25-44). The powder and liquid are mixed to a creamy consistency and applied to the coping with a brush in a vibrating motion. The opaque layer should be applied as thinly as possible to still mask the metal. The coping is gently vibrated to condense the porcelain, and excess water is removed with a dry tissue. The second layer of opaque is fired using the same firing cycle The opaque layer of porcelain should be approximately 0-3 mm thick. All-Porcelain Margin Fabrication Restorations with a metal collar facial margin are now ready for the application of dentm and enamel porcelains following opaque application. For restorations with an allporcelain facial margin, a few extra steps are necessary at this point. The additional time and skill required to fabricate a direct-lift porcelain margin will often translate into a higher laboratory fee for the restoration. To fabricate an all-porcelain margin using the direct-lift 
برچسب ها: was once thought.5 Although the molecular attraction makes only a minor contribution to overall bond strength، it is significant in the initiation of the most important mechanism، the chemical bond. Chemical bonding is indicated by the formation of an oxide layer on the metal، 87 and by bond strength that is increased by firing in an oxidizing atmosphere.89 When fired in air، trace elements in the gold alloy، such as tin، indium،  

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Dent Assoc 1992; 72:10-12. t. Yamamoto M: Metal-Ceramics: Principles and Methods of Makato resist vertical loads.61 For most patients, coverage of the incisal edge will be the preferred design. The multiple-wheel diamond bur (Model 834-021, Brasseler USA) is used to make 0.5-mm-deep orientation grooves in the incisal edge (Fig 24-26). The wheels will penetrate the enamel until the shaft touches the incisal edge. Remove tooth structure between the grooves with a round-end tapered diamond (Fig 24-27). The diamond parallels the incisal edge of the tooth, maintaining that configuration. With the same diamond, complete the facial reduction (Figs 24-28). Lingual Reduction. Create the lingual finish line with the round-end tapered diamond. Hold the instrument parallel to the lingual surface, with its end forming a slight chamfer 0.5 mm deep. The finish line should be approximately one-fourth the way down the lingual surface, preferably 1.0 mm from centric contacts, and connecting the two proximal finish lines (Fig 24-29). The creation of the lingual finish line often produces a notch at the mesial and distal incisal corners (Fig 24-30). Besides placing the porcelain in compression, extension onto the lingual surface will enhance mechanical retention and increase the surface area for bonding. Placement of the lingual finish line for a laminate veneer will depend on the thickness of the tooth and the patient's occlusion. Whenever possible, the finish line should be placed on the lingual surface. An extremely thin tooth may require that the finish line be on the incisal edge. Placing it on the lingual surface may expose dentin and overshorten the tooth preparation Finishing the Preparation. Be sure to remove any sharp angles that might serve as a focal point for stress concentration, particularly at the junction of the incisal angle and the lingual surface (Fig 24-31). At the completion of the lingual reduction, use the round-end tapered diamond to remove the sharp features that may have formed where the facial, proximal, and lingual planes of reduction meet. The completed preparation has no sharp angles (Figs 24-32). Provisional Restorations Since the preparation remains in enamel, most patients will not require a provisional restoration.43 For patients who insist upon a "temporary" veneer, light-activated microfilled composite resins may be utilized.56 Place one or two dots of etchant on the facial surface, then build up the lost tooth structure with composite resin with or without the use of a clear stint. Be very careful to avoid the finish line when removing excess composite resin. Provisional restorations for veneer preparations are timeconsuming, and the results can be disappointing. Avoiding provisional restorations in this situation will decrease frustrations. Impression Gingival retraction is usually necessary for making an impression of laminate veneer preparations because the cervical finish line is terminated at or slightly below the gingival margin. Some patients may require anesthesia for cord placement, while others will tolerate the procedure without it. This is an individual judgment. Small-diameter retraction cord will reduce or eliminate discomfort. Any impression material suitable for fixed prosthodontics can be employed. If the impression will be sent to the laboratory for pouring, a stable material such as polyvinyl siloxane or polyether should be used, in most cases, porcelain laminate veneers will play a role in some aspect of the patient's occlusal scheme by providing protrusive or lateral guidance For this reason, the casts should be made from full-arch impressions and they should be articulated. Fabrication of Working Casts and Dies Many laboratories use a removable die system that is a modification of a plastic tray with internal orientation grooves and notches (eg, Accutrak, JF Jelenko. Armonk, NY). Pour the impression in die stone, with a minimum base of 20 mm. After the stone has set, remove the cast from the impression and trim it to a height of 15 mm and a faciolingual width of 10 mm on a model trimmer and arbor band. The trimmed cast should fit loosely in the tray. Score the base of the die stone. Mix stone and vibrate it into the assembled tray. Seat the trimmed cast with a jiggling motion until the cervical areas of the teeth are approximately 5.0 mm above the edge of the tray. Remove excess stone and allow the stone to set until it is hard and dry. Next the tray is disassembled to allow separation of the die(s). Use a saw to separate the die from the base of the cast to avoid damage to the interproximal finish lines (Fig 24-33). The saw cut should extend through the inierdenFig 24-34 Packets of duplicating paste, liquid, emptied into the plastic cup. Fig 24-35 Duplicating paste is mixed in the cup. tal papillae and stop 1.0 mm short of the interproximal finish line. Uss finger pressure to break the die and attached teeth from the cast by squeezing the two pieces together. Repeat the process to separate the die from the teeth attached to it. Trim the die and mark the finish line with a red pencil. Apply a minimum of two coats of cement spacer to the die, staying 1.0 mm away from the finish line. Then reassemble the die and working cast in the tray. Fabrication of the Refractory Die Use low-viscosity polyvinyl siloxane duplicating materia (Vita Hi-Ceram Duplicating Material, Vident) to reproduce the die(s); the low viscosity allows registration of minute details It is supplied in packets of paste, liquid, and catalyst (Figs 24-34) that are mixed in a clear plastic cup (Fig 24-35). Adapt putty to the working cast and die(s) to limit the flow of the mold material. It should extend several teeth beyond the die(s) and beyond the edge of the tray on both the facial and lingual sides {Fig 24-36). To avoid air entrapment, fill the putty reservoir by pouring the mixture (Fig 24-37). The duplicating material should be at least 3.0 mm thick, and it should extend 3.0 mm beyond the incisal edges of the teeth to provide adequate support for the refractory material. The setting time may vary due to room temperature and humidity, but the minimum time before separation is 30 minutes (Fig 24-38). When the duplicating medium has set, remove the silicone putty reservoir (Fig 24-39) and disassemble the plastic tray (Fig 24-40). By applying Porcelain Laminate Venee Fig 24-36 A strip of putty is wrapped around the part of the cast that contains the die of the prepared tooth. All-Ceramic Restoratioi is poured through openings in the Fig 24-44 The refractory die duplicates the ITO to oiher teeth as well as in con figuration. pressure to the base of the tray, the master cast is loosened with the duplicating material intact (Fig 24-41). The master die of the prepared tooth can then be removed from the cast (Fig 24-42) and then from the duplicating material. At this point it is easy to see that the larger the area duplicated, the greater the stability of the cast in the duplicating material. The plastic tray is reassembled without the bottom articulating plate. The absence of this plate allows access for pouring the refractory material in the area of the missing die(s), while maintaining the stability and orientation of the cast in the duplicating material. A number of refractory investments suitable for porcelain laminate veneer fabrication are commercially available. Selection witl depend on porcelain compatibility and personal preference. The refractory material should be mixed according to the manufacturer's directions, and the recommended liquid-powder ratio must be followed. Deviation from this precise ratio may cause uncontrolled expansion or shrinkage during setting and possibly a weakened die. Mix and carefully vibrate the refractory die material through the opening in the base of the tray to fill the space vacated by the die (Fig 24-43). Since the orientation and stability of the die depend on the grooves and notches of the tray, the entire opening must be filled with refractory material. Allow the refractory die to set for the manufacturer's recommended time, which is usually 1 to 2 hours. When the duplicating mold is removed, the refractory die(s) should occupy the exact location and orientation of the master die(s) (Fig 24-44). Porcelain Laminate Veneers Preparation of the Refractory Die Prior to porcelain application, degas the refractory die to eliminate ammonia and sulfur gases that would contaminate the porcelain. These noxious gases also can contaminate the muffle of a porcelain furnace. Therefore, the initial stage of the degassing process is completed in a casting burnout oven Place the die in a room-temperature oven, and heat and hold it to a specified temperature. Then transfer the die to a preheated porcelain furnace and continue the heating cycle without vacuum (Fig 24- 45) Allow the refractory die to cool to room temperature. Following burnout, the refractory die should appear uniform in color with no dark-gray streaks. Mark the finish line with an underglaze clay pencil. Soak the die in water until no more bubbles are emitted. To seal the die, apply a thin wash of half glaze, half dentin porcelain to it and fire (Fig 24-46). Two applications of this mixture may be necessary to completely seal the die. Without a sealant. the porous refractory material will absorb water from the porcelain, making it difficult to apply and shape the porcelain. Porcelain Application To produce a natural-looking porcelain laminate veneer, the technician must have information regarding the shade of the unprepared tooth, the desired shade, and the location of discolored areas. Discoloration associated with intrinsic staining often appears more intense following tooth preparation, The technician should receive diagrams and photographs of the teeth prepreparation and postpreparation to facilitate the fabrication of customized porcelain veneers.62 Perhaps one of the greatest challenges of porcelain veneers is maintaining a natural appearance while masking discolorations. Opaque porcelains or luting agents can be used to mask the colors but produce a dull, whitish result There are two methods of adding color to porcelain veneers: (1) by adding color and characterization to the porcelain itself, or (2) by adding tints to the luting agents The addition of tints to the luting agents requires knowledge of the subtractive color system and the use of complements to "neutralize" the discolored areas.6263 The tinted resin is applied directly to the tooth in thin layers, followed by enhancers to raise the value. A cement spacer must be applied to the master die to allow for this additional luting agent. The use of complementary colors to mask discolorations also has been applied to porcelain addition. Special complementary-color porcelain (a mixture of dentin and modifier porcelain) neutralizes the existing prepared tooth color. This produces a grayish tone that requires a white modifier to increase the value.64 Another technique utilizes a masking dentin porcelain to block the color of the underlying tooth structure before dentin, enamel, and translucent porcelains are added. The masking dentin is effective in a very thin layer (0 1 mm) and acts as internal shading and light diffuser.65 The other porcelains continue to develop the color and translucency of the restoration The dentist and technician must communicate to select the technique of color modification. With a cooperative effort, the desired esthetic result can be achieved The application of the porcelain is similar to a layered buildup of a conventional ceramic restoration. First apply the dentin porcelain (Fig 24-47) and then build it up to the full contour Use a sable brush or spatula to apply and shape the porcelain to the desired contour (Fig 24-48). All-Ceramic Restoration Fig 24-47 Dentin porcelain is applied first Fig 24-48 Dontin porcnl.iin is hui Using a tissue and a slight amount of condensation, remove the excess moisture. The porcelain should remain slightly damp, but it should carve easily. Finalize gingival contours and use a sharp blade to cut back the incisal one-third to one-half to allow for the enamel porcelain (Figs 24-49 and 24-50). The desired amount of translucency determines the depth and extent of the cutback. The enamel porcelain should be supported by the dentin porcelain. If the outback is straight across the incisal edge without any supporting dentin. the fired porcelain will be too translucent and it will lack color and vitality as well. Like dentin porcelain, enamel porcelain is applied with either a damp sable brush or a spatula (Fig 24-51). It should be blended with the dentin porcelain on the facial, and the incisal edge should be slightly overbuilt to compensate for shrinkage. Use a tissue and a small amount of condensation to remove any excess moisture Finalize and smooth the axial contours of the porcelain (Fig 24- 52). Remove the die from the working cast and add porcelain to the proximal contours Carefully examine the margins and remove even the slightest amount of excess porcelain. Place the refractory die with the porcelain buildup on a sagger tray in front of the muffle to dry. Then fire the porcelain according to manufacturer's recommendations. Allow the die to cool completely to room temperature. Then reseat it in the working cast. After evaluating the contours and occlusion of the fired porcelain, corrections may be made by grinding with a fine-grit diamond or green stone or by adding an appropriate porcelain and retiring at a slightly lower temperature. When the desired contours, margins, and occlusion have been produced, glaze the porcelain veneer on the Cementation and Finishing of All-Ceramic Restorations refractory die. After cooling, carefully remove (he die from the veneer by glass-bead air abrasion on the die Confirm marginal integrity of the veneer on the original stone die. Place the veneer in a jar in the ultrasonic cleaner (Fig 24-53). The veneer should rest on a piece of gauze to prevent its fracture against the hard glass bottom of the jar. To bond the porcelain laminate veneer to the composite resin luting agent, it is necessary to acid-etch the internal aspect of the glazed veneer Apply 5% hydrofluoric acid solution and let it remain in contact with the porcelain for 30 seconds. A gel etchant is easily confined to the internal aspect of the veneer. If a liquid etchant is used, the glazed porcelain should be protected. When applied to porcelain. the acid produces microstructural pits that enhance the mechanical interlocking with the composite resin Fig 24-53 The the jar is placed inl Cementation and Finishing of All-Ceramic Restorations The techniques for adjusting, cementing, and finishing all-ceramic crowns, labial veneers, and inlays vary significantly from those used for metal restorations. A tight proximal contact will not produce a visible burnished area on porcelain. A thin coating of a pressure indicator such as Occlude (Pascal Co, Bellevue, WA) can be applied to these materials before seating to reveal the exact location of the contact. To avoid fracture, only gentle forces should be used for inserting and testing ceramic restorations. Internal support for a ceramic crown or onlay can be provided during occlusal adjustment by temporarily "cementing" the restoration to the tooth with a low-viscosity elastomeric impression material. Broad, relatively flat surfaces are best reduced extraorally with a large, smooth-cutting Busch Silent stone (Pfingst & Co, South Plainfield, NJ), while grooves and ridges are reshaped with smaller pointed diamond stones and green stones. Instruments that have been used on metals should not be used on porcelain. Metal particles become embedded in pores in the porcelain and cause discoloration. When working near an acute edge of porcelain, apply the stone so that it is moving from the edge toward the greater bulk to prevent chipping the fragile edge. This is opposite of the technique used in finishing metal margins. It is best to postpone minor grinding adjustments on thin veneers and inlays until after they are permanently bonded to the tooth- Roughened ceramic surfaces are smoothed with clean white stones and polished with rubber wheels of progressively finer grit such as those found in the Ceramiste Porcelain Adjustment Kit (Shofu Dental Corp, Menlo Park, CA), or diamond-impregnated wheels and points (Dialite, Brasseler USA). Grit in the Ceramiste kit is indicated by stripes around the shank of the instrument: no stripe is coarse, one yellow stripe is medium, and either two yellow stripes or one white stripe is fine. Pastes containing diamond dust are available for use on cups and brushes. Porcelain also may be reglazed after i! is polished. At try-in, have the patient moisten the ceramic and adjacent teeth with saliva. Evaluate Hie shade under incandescent, fluorescent, and natural light. To minimize the effects of metamerism, it is better to accept a shade that matches reasonably well under all lighting conditions than one that matches perfectly under natural light but appears discolored under artificial light. Allow the patient to look at the completed restoration in a wall mirror and approve it before cementation. Crown Cementation Ceramic crowns may be cemented with zinc phosphate, glass ionomer. or a dual-polymerizing resin cement such as Enforce with Fluoride (LD Caulk Div, Dentsply International, Milford, DE). The cement comes in four shades (A2, C2, B1, and B3), permitting some influence on the final shade of transluscent crowns. Ceramic crowns that have been etched internally and bonded with a composite resin cement are 50% stronger than similar crowns cemented with zinc phosphate cement.66 The crown should be clean, etched, and silaned. Remove any organic debris with ethanol or acetone, followed by placing the restoration in an ultrasonic cleaner. Further cleaning can be accomplished by applying liquid phosphoric acid etchant If the crown was not silaned at the laboratory, it can be done at this time with Silane Coupling Agent (LD Caulk). Dispense one drop of Silane Primer and one drop of Silane Activator into a dappen dish. Stir the liquid in the dish for 10 to 15 seconds with a brush. Set the mixture aside for no less than 5 minutes. nor more than 10 minutes before application. Apply it to the internal surface of the crown, and gently air dry. Repeat once. Avoid application of the activated silane to the external surface of the crown by covering the outside of the crown with wax. Remove the cement and mixing dish from the refrigerator and allow it to warm to room temperature. Rinse the crown and dry it with compressed air. Clean the tooth preparation with a rubber cup and flour of pumice. Then wash and dry it. Etch enamel on the preparation for 30 seconds with 37% phosphoric acid on a foam pellet. Dab, do not rub. Rinse for 20 seconds and air dry the tooth. Apply ProBOND Primer to dentin and keep moist for 30 seconds. Air dry. Apply a thin layer of ProBOND adhesive over the entire preparation with a brush. Thin the bonding agent with compressed air for 15 seconds. Use a second clean brush to remove excess adhesive. Polymerize the adhesive for 20 seconds with a light Do not apply any primer or adhesive to the crown. Dispense equal amounts of Enforce base from the syringe and catalyst from the tub. Mix for 10 to 20 seconds with a flat-ended plastic mixing stick. Apply a thin layer of cement to the internal surfaces of the crown. Seat the crown and remove excess cement from the marginal areas with an explorer and a clean brush. Leave a slight excess to avoid ditching the cement at the margin. Aim the light cure at marginal areas from facial, lingual, and occlusal directions for 40 seconds. When light activation is not utilized, allow 6 minutes for autopolymerization. Adjust bulky margins or premature occlusal contacts with a fine diamond stone. Polish occlusal surfaces with wheels from a porcelain adjustment kit. Veneer Cementation Ceramic veneers and inlays should be etched, silaned, and bonded to the underlying enamel with a selected shade of dual-polymerizing hybrid composite resin cement such as Vita Lummbond (Vident). This type of composite resin has a superior coefficient of thermal expansion, low water absorption, and a surface smoothness similar to microfilled composite resins The luting agent comes in several shades coordinated with the shade of porcelain selected. Other kits that include colored modifiers and opaque modifiers may be used for special needs. This not only provides better retention and color control, but it makes the ceramic material less fragile than if it were cemented with nonresin cement.68 Clean the prepared tooth with nonfluoride pumice and try in the porcelain veneers. Verify the marginal fit. A drop of water or glycerine will help the veneer stay in place on the tooth during the try-in. If there is an overhang, trim it with a fine-grit diamond. After verifying the marginal fit, evaluate the proximal contacts. The final appearance of a veneer is affected by the shade of cement used. Isolate the teeth with Mylar strips. Determine the correct shade or blend of shades by seating the veneer or inlay on the unetched tooth with resin cement Avoid exposure to high-intensity light to prevent bonding at this time. After try-in and shade determination, clean the veneer with a solvent such as acetone. Pumice the teeth to remove any traces of polymerized composite resin. Apply a 30% phosphoric acid etchant gel to the prepared tooth and allow it to remain 1 minute. Thoroughly rinse the tooth with a steady stream of water for 30 seconds and dry with air. Check that the tooth surface has the dull, frosted-white appearance of properly etched Apply the silane coupling agent or primer to the internal surface of the veneer and allow it to remain in contact with the etched porcelain for 1 minute. At the end of that time, dry the veneer with an air syringe by blowing the air parallel to and slightly above the veneer. Apply a small amount of the previously selected composite resin luting agent to the internal surface of the veneer and use a brush to evenly distribute it over the surface. Carefully seat it on the dry. etched tooth. In the case of an inlay, place the cement into the cavity The plastic interproxtmal strips may be left in place if they do not interfere with seating of the restoration. Using finger pressure, gently seat the veneer from the labial surface. Excessive pressure at this time could fracture the veneer. When the veneer is positioned correctly, hold it gently against the tooth with a finger and apply a visible-light curing unit for 10 seconds. Verify that the veneer is placed correctly on the tooth. After the initial set, the flash may be carefully removed before the resin is completely polymerized. Continue polymerizing for an additional 45 to 60 seconds, directing the light from the lingual (through the tooth) so that shrinkage will occur toward the tooth. Then direct the light from the labial (through the veneer) for an additional 60 seconds. Once the luting agent is polymerized, fine-grit flame diamonds may be used to trim excess composite resin. The occlusion should be checked and adjusted only after the veneer is bonded to the tooth. Final finishing procedures can be accomplished with porcelain polishing agents, including rubberized abrasives and diamond polishing paste. The proximal areas can be finished with finishing strips (Fig 24-54). References 1. McLean JW1 The Science and Art of Dental Ceramics, vol I: The Nature of Dental Ceramics and Their Clinical Use. Chicago, Quintessence Publ Co, 1979, p 30-37. 2. Phillips RW: Skinner's Science of Dental Materials ed 9 Philadelphia, WB Saunders Co, 1991, p 505-527. 3. Land CH: A new system of restoring badly decayed teeth by means of an enamelled coating, independent Pract 1886; 7:407. 4. McLean JW, Hughes TH: The reinforcement of dental porcelain with ceramic oxides. Br Dent J 1965, 119:251-267. j. McLean JW. Seed IR. The bonded alumina crown Part I Bonding of platinum to aluminous porcelain using tin oxide coating. Aust Dent J 1976: 21.119-127. >. Seed IR, McLean JW, Hotz P: The strengthening of aluminous porcelain with bonded platinum foils. J Dent Res 1977, 56:1067-1069. ' Munoz CA, Goodacre CJ. Moore SK, Dykema RW: A comparative study ot the strength of aluminous porcelain jacket crowns constructed with the conventional and twin foil techniques. J Prosthet Dent 1982; 48:271-281. i Green DJ: Mic roc racking mechanisms in ceramics. In: Bradt RC, Evans AG, Lange FF, Hasselman DP (eds); Fracture Mechanics of Ceramics, vol 5. New York: Plenum Press, 1983, pp 457-478. ). Green DJ, Hannink RHJ, Swain MV: Transformation Toughening of Ceramics. Boca Raton, Fl: CRC Press, 1989, pp 57-91. >. Seghi RR, Sorensen JA: Relative flexural strength of six new ceramic materials. Int J Pmsthodont-\995; 8:239-246. . Adair PJ, Grossman DG: Esthetic properties of lost tooth 1025]. JDentHes 1982; 61:292. !. Hobo S, Iwata T Castable apatite ceramics as a new biocompalible restorative material. I. Theoretical considerations. Quintessence Int 1985; 16135-141. l. Sozio RB, Rjley EJ: The shrink-free ceramic crown. J Prosthet Dent 1983, 49:182-187. !. Riley EJ, Sozio RB, Shkiar G, Krech K: Shrink-free ceramic crown versus ceramometal: A comparative study in dogs. J Prosthet Dent 1983; 49:766-771. ». WainD: Porcelain casting. Br Dent J 1923, 44'1364 ;. MacCulloch WT: Advances in dental ceramics. Br Dent J 1968; 89:361-365. '. Adair PJ, Grossman DG. The castable ceramic crown. Int J Periodont Rest Dent 1984; 4(2):32-45 !. Malament KA, Grossman DG1 The cast glass-ceramic restoration. J Prosthet Dent 1987; 57:674-683. i. Grossman DG. Cast glass ceramics. Dent Clm North Am 1985; 29:725-739 i. Hobo S, Iwaia T: Castable apatite ceramics as a new biocompatible restorative material. II. Fabrication of the restoration. Quintessence Int 1985; 16:207-216. . Seghi RB, Rosenstiel DF: Relative fracture toughness and hardness of new dental ceramics. J Prosthet Dent 1995; 74:145-150. !. Wohlwend A, Scharer P; The Empress technique: A new technique for the fabrication of full ceramic crowns, inlays and veneers. QuintessenzZahntech 1990; 16966-978. i. Nixon RL: IPS Empress: The ceramic system of the future. S/priafure 1994: Fall: 10-15. • Myers ML, Ergle JW, Fairhurst CW, Ringle RD: Fatigue failure parameters of IPS-Empress porcelain. Int J Pmsthodont 1994, 7549-553. i. Probster L: Compressive strength of two modern all-ceramic crowns. Int J Prosthodont 1992; 5:409-414. i. Levy H, Daniel X; Working with the In-Ceram porcelain system. Prothese Dentaire 1990; 44-45.1-11. ' Probster L, Diehl J: Slip-casting alumina ceramics for crown and bridge restorations. Quintessence Int 1992; 23:25-31. i Giordano RA, Pelletier L, Campbell S, Pober R: Flexural strength of an infused ceramic, glass ceramic, and feldspathic porcelain. J Prosthet Dent 1995; 73:411-418. 29. Castellani D, Bact crowns. Int J Prosthodc . Kelly JR, Tesk JA, Son T, Giovannoni A, Bernaedmi UD. ice to fracture of metal ceramic and all-ceramic Int J Prosthodont 1994; 7:149-154. M, Derand T Fracture strength of all-ceramic 1994:7:329-338. ;n JA: Failure of all-ceramic fixed <ivo: Analysis and modeling. J. >. Scotti R, Catapano S, D'Elia A: A clinical evaluation of In- Ceram crowns. Int J Prosthodont 1995; 8:320-323. 3. Probster L: Survival rate of In-Ceram restorations Int J Prosthodont 1993; 6259-163. X. Ironside JG: Light transmission of a ceramic core material used in fixed prosthodontics. Quintessence Dent Technol 1993; 103-106. i. Sieber C: Illumination in anterior teeth. Quintessence Dent Technol 1992; 15:81-88. 5. Paul SJ, Pietrobon N, Scharer P: The new In-Ceram Spinell system—A case report. Int J Periodont Rest Dent 1995- 15:521-527. '. Claus H: VITA In-Ceram: A new system for producing aluminum oxide crown and bridge substructures. Qumtessenz Zahntech 1990: 16:35-46. 3. PeraP, GilodiS, Bassi F, 1994; 72:585-590. i. Carrier DD, Kelly JR: In-Ceram failure behavior and coi veneer interface quality as influenced by residual infiltrati glass. J Prosthod 1995; 4:237-242. ). Horn HR Porcelain laminate veneers bonded to etch. enamel. Dent Clin North Am 1983: 27671-684. I. McLaughlin G Porcelain fused to tooth—A new esthetic ai >. Ibsen RL, Strassler HE: An innovative method for fi rior tooth replacement utilizing porcelain Quintessence tof 1986; 17:455-459. i. Goldstein R: Diagnostic dilemma. To bond, la crown? Int J Periodont Rest Dent 1987; 5:9-29. •. Faunce FR: Tooth restoration with preformed laminate veneers. Dent Survey 1977; 1:30-32 i. Boyer DB, Chalkley Y: Bonding between acrylic laminates and composite resin. J Dent Res 1982: 61:489-492. '. Horn H: A new lamination: Porcelain bonded to enamel NY State Dent J 1983; 49:40 H 0 3 . 1. Calamia JR: Etched porci ment modality based on si JDent 1983, 53:255-259. 49 Simonsen RJ. Calamia JR. Tensile bond strength of etched porcelain [abstract 1154], J Dent Res 1983: 62:297. 50. Stangel I, Nathanson D, Hsu CS1 Shear strength of the composite bond to etched porcelain J Dent Res 1987, 66' 1460-1465. 51. Hsu CS, Stangel I, Nathanson D: Shear bond strength of resin to etched porcelain [abstract 1095], J Dent Res 1985: 64:296. 52. Calamia JR, Simonsen RJ: Effect of coupling agents on bond strength of etched porcelain [abstract 79]. J Dent Res 53. Calar leof ihea 54. Siacey G: A shear i ess analysis of the bonding of porce- •I J Prosthet Dent-[993; 70:395-402. i. Wall JG, Reisbick MH, Johnston WM: Incisal-edge strength Int J Prosthodont 1992; 5:441-446. ;. Jordan RE: Esthetic Composite Bonding. Philadelphia, DC Decker Inc. 1987, Ch 3. '. Quinn F, McConnell RJ, Byrne D. Porcelain laminates: A review 8r Dent J1986; 161:61-65. \ Lacy AM, Wada C, Du W, Watanabe LP- In vitro microleakage at the gingiva! margin of porcelain and resin veneers. J Prosthet Dent 1992; 67:7-10. >. Shillingburg HT, Grace CS. Thickness of enamel and dentm. JSouth Call!DentAssoc 1973, 4133-36. ). Karlsson S, Landahl I. Stegersjo G, Milleding P: A clinical evaluation of ceramic laminate veneers Int J Prosthodont 1992:5:447-451. . Highton R, Caputo AA, Matyas J: A photoelastic study of stresses on porcelain laminate veneers. J Prosthet Dent 1987; 58:157-161 !. Robbins JW' Color characterization of porcelain veneers Quintessence Int 1991: 22:853-656. i. Reid JS: Tooth color modification and porcelain veneers. Quintessence Int 1988; 19:477-^81. . Yamada K Porcelain le mentary color sneers for discolored teeth Int J Prosthodont 1993; slain U itific and clinic; 9vidence. NY >. Hobo S: Porcelain laminate veneers with three-dimensional shade reproduction. Int Dent J 1992: 42:189-198. i Ludwig K, Joseph K: Untersuchungen zur Bruchfestigkeit von I PS-Empress-Kronen in Abhangigkeit von den Zementiermodalitaten. QuintessenzZahntech 1994; 20247-256. ' Qvist V, Stolze K, Qvist J: Human pulp reactions to resin restorations performed with different acid-etch restorative procedures. Ada Odontol Scand 1989: 47:253-263. i. Derand T: Stress analysis of cemented or resin-bonded loaded porcelain inlays. Dent Mater 1991: 7:21-24. r Chapter 25 Metal-Ceramic Restorations Metal-ceramic restorations combine the strength and accuracy of cast metal with the esthetics of porcelain. Their use has grown markedly in the last 30 years as a result of technical improvements. However, restraint should be exercised in the selection of this type of restoration, as there is a tendency to overuse it. Metal-ceramic restorations should not be substituted for less destructive types of restorations when the latter will serve as well. A 1986 survey of 80 dentists revealed that 70% of them placed metal-ceramic crowns on their patients' posterior teeth 70% to 100% of the time, but the same dentists indicated a preference for partial veneer gold crowns in their own mouths.1 The metal-ceramic crown has gone by a variety of names since its introduction to dentistry nearly four decades ago. It was called, at different times and in different parts of the US, a "Ceramco crown" (for one of the first brands of porcelain used for fabricating this type of restoration), a "porcelain veneer crown" (PVC), "porcelain fused to gold" (PFG), as well as "porcelain fused to metal" (PFM), a term commonly used in the dental literature during the 1970s and '80s. Metal-ceramic is a more precise term scientifically, and it is compatible with the terminology used to describe allceramic crowns, inlays, veneers, etc. Because there seems to be a proclivity in the English language for threeletter abbreviations (rhythm, trinity connection, who knows?), MCR appears to be a reasonable abbreviation for metal-ceramic restoration. The metal-ceramic restoration is composed of a metai casting, or coping, which fits over the tooth preparation and ceramic that is fused to the coping. The coping may be little more than a thin thimble, or it may be clearly recognizable as a cast crown with some portion cut away. The contours in the area that has been cut away will be replaced with porcelain that will mask or hide the metal coping, produce the desired contours, and make the restoration esthetically pleasing. The metal coping in a metal-ceramic restoration is covered with three layers of porcelain (Fig 25-1): 1 Opaque porcelain conceals the metal underneath, initiates the development of the shade, and plays an important role in the development of the bond between the ceramic and the metal. Unveneered Metal ired Metal 2. Dentin, or body, porcelain makes up the bulk of the restoration, providing most of the color, or shade. 3. Enamel, or incisal, porcelain imparts translucency to the restoration. Other porcelains, such as opaque or dentin modifiers, or clear porcelain, are utilized within the three basic layers for special effects and characterization. There are two principal reasons for the acceptance of metal-ceramic restorations. First, they are more resistant to fracture than the traditional all-ceramic crown, the porcelain jacket crown (PJC), because the combination of ceramic and metal bonded together is stronger than the ceramic alone. The strength of metal-cerarnic restorations depends on the bond between the ceramic and the metal substructure, the design and rigidity of the metal coping, and the compatibility of the metal and the porcelain. Second, the MCR is the only dependable means of fabricating an esthetic fixed partial denture when full coverage is required on one or both retainers. Bonding Mechanisms Four mechanisms have been described to explain the bond between the ceramic veneer and the metal substructure: 1. Mechanical entrapment 2. Compressive forces 3. Van der Waal's forces 4. Chemical bonding Mechanical entrapment creates attachment by interlocking the ceramic with microabrasions in the surface of the metal coping, which are produced by finishing the metal with noncontaminating stones or discs and air abrasion. When compared with unprepared metal, surface finishing enhances the metal-ceramic bond.2 Air abrasion appears to enhance wettability, provide mechanical interlocking, and increase the surface area for chemical bonding.3 The use of a bonding agent, such as platinum spheres, 3 to 6 um in diameter, also can increase bond strength significantly." Compressive forces within a metal-ceramic restoration are developed by a properly designed coping and a slightly higher coefficient of thermal expansion for the metal coping than for the porcelain veneered over it. This slight difference in coefficients of thermal expansion will cause the porcelain to "draw" toward the metal coping when the restoration cools after firing. Van der Waal's forces comprise an affinity based on a mutual attraction of charged molecules. They contribute to bonding, but they are a minor force that is not as significant as 
برچسب ها: Dent Assoc 1992; 72:10-12. t. Yamamoto M: Metal-Ceramics: Principles and Methods of Makato resist vertical loads.61 For most patients، coverage of the incisal edge will be the preferred design. The multiple-wheel diamond bur (Model 834-021، Brasseler USA) is used to make 0.5-mm-deep orientation grooves in the incisal edge (Fig 24-26). The wheels will penetrate the enamel until the shaft touches the incisal edge. Remove tooth structure between the grooves with a round-end tapered diamond (Fig 24-27). The diamond parallels the incisal edge of the tooth، maintaining that configuration. With the same diamond، complete the facial reduction (Figs 24-28). Lingual Reduction. Create the lingual finish line with the round-end tapered diamond. Hold the instrument parallel to the lingual surface، with its end forming a slight chamfer 0.5 mm deep. The finish line should be approximately one-fourth the way down the lingual surface، preferably 1.0 mm from centric contacts،  

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Yamamoto. Chicago. Quintessence Publishing Co, 1985, p 350 I. Bell AM, Kurzeja R, Gamberg MG: Ceramometal crowns and bridges Focus on failures. Dent Clin North Am 1985; 29.763-778. ! Kessler JC: Dentist and laboratory: Communication for success. J Am Dent Assoc 1987: 11597E-102E i. Sorensen JA, Torres TJ: Improved color matching of metal ceramic restorations. Part II Procedures for visual communication. J Prosthet Dent 1987; 58:669-677. ical illus s in dentistry J i. Seluk LW, Laionde TD. Esthetics and communication with a custom shade guide. Dent Clin North Am 1985, 29.741-751. ). Yamamoto M: Metal-Ceramics: Principles and Methods of Makato Yamamoto. Chicago, Quintessence Publishing Co, 1985, p 240. }. Sorensen JA,Torres TJ' Improved color matching of metalceramic restorations. Part I: A systematic method for shade determination. J Prosthet Dent 1987; 58:133-139. I O'Keefe KL, Stnckler ER, Kerrin HK: Color and shade matching: The weak link in esthetic dentistry. Compend Contin Educ Den! 1990; 11:116-120. Chapter 24 All-Ceramic Restorations Dental porcelains play an important role in the fabrication of the most esthetic fixed restorations. Translucency, light transmission, and biocompatibility give dental ceramics highly desirable esthetic properties. However, the brittle nature of dental porcelains, which are basically noncrystall!ne glasses composed of structural units of silicon and oxygen (SiO4 tetrahedra), limit the use of these materials. Several properties are necessary for their use in the fabrication of dental restorations': 1. Low fusing temperature 2. High viscosity 3. Resistance to devitrification These properties are obtained by the addition of other oxides to the basic structure. The fusing temperature is lowered by reducing the cross linkages between oxygen and silicon with glass modifiers, such as potassium oxide, sodium oxide, and calcium oxide. Unfortunately, these modifiers or fluxes also lower the viscosity. Dental porcelains require a high resistance to slumping so that restorations will maintain their basic shape during firing. This is accomplished by the use of an intermediate oxide, aluminum oxide, which is incorporated into the silicon-oxygen lattice. If too many modifiers are added to the porcelain to disrupt the SiO4 tetrahedra, the glass tends to devitrify, or crystallize This becomes a special problem in porcelains with an increased coefficient of thermal expansion, because alkalis are introduced to interrupt the silicon oxygen lattice and raise the expansion. When a porcelain is fired too many times, it may devitrify, becoming milky and difficult to glaze. Porcelain can be classified by firing temperature^. 1. High-fusing: 1,290 to 1,370°C (2,350 to 2.500T) 2. Medium-fusing: 1,090 to 1,260cC (2,000 to 2.300T ) 3. Low-fusing: 870 to 1,065DC (1,600 to 1,950°F) High-fusing porcelain is usually used for the manufacture of porcelain teeth, although it has been used to some extent for porcelain jacket crowns. The typical high-fusing porcelain is composed of feldspar (70% to 90%), quartz (11% to18%), and kaolin (t% to 10%) The main Table 24-1 Constituents of Dental Porcelains' Boric o Calciur Lithium oxide Magnesium oxide Phosporous pento constituent of feldspar is silicon dioxide, present in the form of Na2O AI2O3 6SiO;j and K2O AI2O3 6SiO2. When it fuses, it forms a glassy material that gives the porcelain its translucency. It acts as a matrix for the high-fusing quartz (SiO2), which in turn forms a refractory skeleton around which the other materials fuse. It helps the porcelain restoration maintain its form during firing. Kaolin, a clay, is a sticky material that binds the particles together when the porcelain is "green" or unfired. Low- and medium-fusing porcelains are manufactured by a process called fritting. The raw constituents of porcelain are fused, quenched, and ground back to an extremely fine powder. When fired again in the fabrication of the restoration, the powder fuses at a lower temperature and undergoes no pyrochemical reaction. The constituents of typical low- and medium-fusing porcelains are shown in Table 24-1.' The addition of certain metallic oxides (zirconium oxide, titanium oxide, and tin oxide) will make the porcelain opaque. A layer of opaque porcelain is used to mask the metal coping of a metal-ceramic restoration. Certain other metallic substances are added to the frit during manufacturing to produce color in the porcelain1: indium (yellow); chromium, tin fpink); iron oxide (black); cobalt salts (blue). All-Ceramic Restorations Dentin ~ \ 1 Mrr ~ Aluminuus Core Fig 24-1 The layers of an aluminous porcelain jack McLean and Hughes4). All-Ceramic Crowns The first all-ceramic crown was developed by Land3 in 1886 and was known as the porcelain jacket crown fPJC). For many decades it was the most esthetic full-veneer restoration dentistry had to offer. The PJC was once made from high-fusing porcelains utilizing platinum foil for support during firing. It relied on the support of the underlying tooth preparation during function. Because of the tendency of this type of restoration to fracture, its use usually is limited to single anterior teeth, primarily incisors. As the demand for more natural-looking crowns has increased in recent years, dentists and porcelain manufacturers have investigated a variety of methods to reinforce ceramics with the ultimate goal of a ceramic material that possesses not only a high level of esthetics and soft tissue acceptance, but sufficient strength to allow the fabrication of fixed partial dentures. In 1965 McLean and Hughes developed a porcelain jacket crown with an inner core of aluminous porcelain containing 40% to 50% alumina crystals to block the propagation of cracks (Fig 24-1).4 The reinforcing inner core of the restoration that surrounds the preparation is layered with conventional porcelain, resulting in a restoration approximately twice as strong as the traditional PJC. The use of this type of reinforcement revived the use of porcelain jacket crowns. Unfortunately, the strength was still insufficient for anything but single anterior crowns. Fracture resistance in the aluminous porcelain jacket crown was improved by a technique in which the platinum matrix was left in the completed restoration.56 The strength of the crown was augmented even more by the "twin foil" technique 7 The platinum foil matrix not only provided additional support of the porcelain, it allowed a chemical bond between the tin-plated foil and oxides in the porcelain. However, the residual platinum foil did decrease the amount of light transmitted, which diminished somewhat the esthetic advantage of an all-ceramic restoration. In the last two decades, research has focused on strengthening dental ceramics by modification of the porcelain's microstructure. The typical "glassy" matrix of feldspathic porcelain is manipulated to include a unique crystalline structure that alters both optical and mechanical properties of the ceramic. Strength and fracture toughness can be directly compared in materials with similar surface flaws.8 Three mechanisms strengthen ceramics, and they all require incorporation of a second phase of heat-generated crystal production to increase the energy necessary for crack propagation: 1. Crack-tip interactions. Obstacles in the microstructure impede crack motion by reorienting or deflecting the plane of fracture. 2. Crack-Up shielding. Events triggered by the high stresses in the crack tip region act to reduce the stress; le, transformation toughening (often associated with zirconium) and microcrack toughening, 3. Crack bridging. Second-phase crystalline structure acts as a "bandage" to prevent a crack from opening further.910 The 1980s saw the introduction of several "new" all-ceramic restorations that relied on the introduction of a second-phase crystalline structure to reinforce the porcelain. They included two castable glass-ceramics (Dicor, Dentsply International, York, PA," and Cerapearl, Kyocera, San Diego, CA'?) and a shrink-free ceramic crown (Cerestore Non-Shrmk Alumina Ceramic, Coors Biomedical Co, Lakewood, CO"."). These systems were appealing because they used the lost wax technique in crown fabrication. Their esthetics were better than metal-ceramic restorations, and the reinforcement method offered the potential of greater strength. Unfortunately, the improvements they offered were not great enough to outweigh the disadvantages of each system. A big problem was the necessity of purchasing expensive equipment and materials, which in turn necessitated charging higher laboratory fees to the dentist. The ceramics were not strong enough for fixed partial dentures, so each system essentially became another way of doing a PJC—at a higher cost. Coupled with cost were technique sensitivity and high fracture/failure rates. These systems of fabricating all-ceramic crowns have fallen victim to the demands of the market. In the Cerestore system, a core, or coping, was waxed for marginal integrity and porcelain support. Following investing, a ceramic material with a high alumina crystal content was melted and flowed into the mold. The mold was heated overnight, the core was divested, and conventional porcelain was applied to the core. The core could distort during firing of the porcelain veneer, and esthetics could be compromised by the opaque nature of the core, especially in the marginal area. The idea of casting ceramics is not new. In 1923 Wain described a method for casting glass in a refractory mold similar to the lost wax technique of casting gold.15 In 1968 MacCulloch fabricated denture teeth from a glass-ceramic used to make cookware (Pyrosil) and suggested the possibility of using glass-ceramics for inlays and crowns.16 The strength of certain glasses can be increased by adding a small amount of nucleating agent (metal phosphate) to the molten glass and heating the glass after solidification. During the reheating phase, ceramming, crystals form on the small metal nuclei, greatly increasing the strength of the ceramic. The Dicor system, utilizing a castable glass-ceramic, was introduced in the 1980s This glass-ceramic material was composed of SiO2> K2O, MgO, fluoride from MgF3, minor amounts of AI2O3 and ZtO2 incorporated for durability, and a fluorescing agent for esthetics.17'18 The fluoride acts as a nucleating agent (as a source of fluoride ions), a necessary agent in the crystalline phase, and it improves the fluidity of the molten glass.17 Fabrication of Dicor restorations was immediately familiar, since it was built around waxing the crown to full anatomic contour with precise control of the occlusion and axial contours.19 The wax pattern was invested in a phosphate-bonded investment, burned out, cast in molten glass, and divested following solidification. The casting was embedded in investment and reheated to allow nucleation and growth of the crystalline phase. After ceramming, the material is approximately 55% crystalline and contains tetrasilicic fluormica crystals ( K M S O Table 24-2 Reinforcing Crystals Used in Brands of Dental Porcelain These crystals are similar to mica, and the microstructure consists of many small, interlocking, randomly oriented crystals The cerammed casting is achromatic, and shade is developed by adding external colorants. Although the lack of internal color was criticized, its translucency led to a variation in which Dicor was used as a coping material. Conventional porcelain was applied to achieve the desired contours and color. Despite significant start-up costs, Dicor experienced popularity for partial veneer and complete-coverage restorations in all areas of the mouth. Unfortunately, a high failure rate in the posterior regions of the mouth, as well as the development of other materials, led to the phasing out of this product. Cerapearl, another castable glass-ceramic, also employed the lost wax technique to produce the initial stage of the restoration and a reheating phase to develop a crystalline microstructure. The micrestructure in this ceramic contained CaPj,O5SiO5, a crystal similar to the hydroxyapatite of enamel.1220 The brief availability of this system made it relatively unknown in the United States. Perhaps the greatest contribution of glass-ceramics was reinforcement of the microstructure by the secondary crystalline phase. In the newest generation of high-strength ceramics for all-ceramic restorations, crystalline- reinforced composite materials employ a variety of reinforcing crystals (Table 24-2). Two materials, I PSEmpress (Ivolclar North America, Amherst, NY) and In- Reinforcing crystal Alumina Alumina and Leucite Magnesium aluminous spinel Samdine Zirconia whiskers Brand Vitadur-N core In-Ceram In-Ceram (recent) Cerinate IPS-Empress Optec HSP Vita VMK 68 In-Ceram Spinel! Mark II Mirage II fiber Manufacturer Vident, Brea, CA Vident Vident Den-Mat Corp, Santa Maria. CA Ivolclar North America, Amherst, NY Jenenc/Pentron Wallinglord, CT Vident Vident Vident Myron International Kansas City, KS Ceram (Vident. Brea, CA), stand out for their unique technology and popularity. The IPS-Empress system is indicated for inlays, onlays, veneers, and complete-coverage crowns. The system relies on a leucite-reinforced glass-ceramic that is heat-pressed into a phosphate-bonded investment, forming either a core or a completed restoration. Unlike previous glass-ceramics, the IPS-Empress system does not require a second heating cycle to initiate the crystalline phase of leucite crystals Instead, they are formed within the glass matrix of feldspathic porcelain throughout various temperature cycles.?l When the restoration is retrieved from the investment, heavily pigmented colorants and glaze can be painted on the surface of the achromatic material to form the completed restoration. A popular option uses an Empress core or "dentin structure" veneered with ceramic. A wide range of shades and translucency similar to natural tooth structure provide excellent esthetics.?2 Fatigue parameter testing indicates that IPS-Empress is less fatigue-susceptible and has a greater 12-year failure stress than feldspathic porcelain.23 However, it exhibits lower compressive strength than metal-ceramic crowns or In-Ceram crowns.34 In comparisons of flexural strength of current ceramic materials, IPS-Empress exhibited less fracture resistance and less fracture toughness than alumina-reinforced ceramics.10'25 Low flexural strength precludes IPS-Empress from consideration for fixed partial dentures, but it offers considerable versatility for single-tooth restorations with high translucency. In-Ceram shows promise for all-ceramic crowns and fixed partial dentures. This system has evolved from research by Sadoun25 in 1985. using alumina as the core material. A suspension of finely ground material (slip) mixed to a thin, creamy consistency, is brushed onto the die in a method called slipcasting. The alumina is fired, or sintered, in a furnace, fusing particles together without completely melting them.2 In a second firing process, glass is applied to the surface of the porous core and is infused, or absorbed into the porous core material, by capillary action. The densely packed alumina crystals limit crack propagation, and glass infiltration eliminates residual porosity.21 A comparison of the flexural strength of alumina core material, infusion glass, the infused alumina core, feldspathic porcelain (VMK 68), and glass-ceramic (Dicor) revealed that the infused alumina core was 2.5 times stronger than glass-ceramic and feldspathic porcelain.ss Although the sintered alumina core is relatively weak, there is a marked elevation of strength following glass infusion.23 The design of the core resembles the coping of a metal-ceramic restoration. It provides a strong substructure that resists flexure and supports the veneer. Conventional porcelain (Vitadur-N or Alpha porcelain, Vident) is applied to the core to develop the final contours and color. Research in Europe and the United States confirms the desirable physical properties of In-Ceram. When uniform premolar crowns were loaded in a "crushing" manner on axial surfaces, In-Ceram crowns demonstrated greater fracture resistance than two other all-ceramic systems (Hi-Ceram and veneered glass-ceramic), Although the fracture resistance of the In-Ceram did not differ significantly from the metal-ceramic restorations (control), the authors had standardized the number of firings between groups by eliminating the application of opaque porcelain in the control group.29 Another study compared the compressive strength of In-Ceram and IPS-Empress to that of metal-ceramic crowns. This study found tiiat In-Ceram possessed greater compressive strength than IPS-Empress, but less than the metal-ceramic control.21 Evaluations of flexural strength and fracture toughness appear more relevant to clinical performance. In comparing flexural strength of six new-generation ceramics, all of the In-Ceram core materials (alumina reinforced, alumina and zirconia reinforced, and magnesium aluminous spinel) were significantly stronger than all other ceramic systems. A spinel is a natural oxide of magnesium (Mg++) and aluminum (AI+++) in which other metals can be substituted for the two named here. These compounds are commonly used for refractory purposes. Crack deflection appears to be the principle strengthening mechanism in the highly crystalline materials. 10 In evaluating fracture toughness and hardness, alumina was the most effective reinforcing agent.?1 Ceramic strength is influenced by flaw size, number, and distribution, especially in areas of high tensile stress. Voids and flaws at the interface between the core and porcelain would allow crack propagation and failure, leaving the core intact30 Due to its high strength and toughness, In-Ceram has been used to fabricate fixed partial dentures, but the manufacturer recommends only short-span (three-unit) anterior restorations. In a study evaluating 20 experimental (in vitro) and 9 clinical (in vivo) unsuccessful fixed partial dentures, failure occurred in the connector areas of all specimens. Approximately 70% to 78% originated from the coreveneer interface.31 All of the experimental restorations and the majority of the clinical examples replaced posterior teeth, supporting the manufacturer's suggested use on anterior fixed partial dentures only. The development of the newest core material with 33% zirconia may strengthen the core material sufficiently for use in posterior fixed partial dentures. Early evaluations of In-Ceram restorations were more anecdotal than scientific. However, initial longitudinal clinical studies are favorable. In one study, 63 In-Ceram crowns were observed over 24 to 44 months {average time of 37.6 months). In this time frame, the success rate was 98.4%, with one crown failing due to improper tooth preparation.32 Another study included a total of 76 restorations distributed over single crowns and fixed partial dentures. Single-tooth restorations did very well over the 35-month trial period. Failures occurred only in fixed partial dentures. It is interesting to note that as a result of "extensive tooth preparation," 3 of 68 teeth required endodontic treatmentM One disadvantage of metal-ceramic restorations is the absence of light transmission due to the metal coping. The improved esthetics of all-ceramic restorations is partially due to the ability of porcelain to transmit light. Recent developments in all-ceramic crowns have greatly improved this esthetic requirement. When light transmission was measured in a variety of dimensions and shades of In-Ceram discs, there was an inverse relationship between thickness and light transmission. Light transmission also decreased as shade intensity increased.34 Alumina-reinforced ceramic systems significantly improve the light reflection characteristics of crowns when compared to conventional metal-ceramic restorations. 3« However, opaque aluminum oxide diminishes translucency when compared to leucite-reinforced systems (Optec, IPS-Empress). To improve light transmission and reflection in single anterior crowns where maximum strength is not required, a magnesium aluminous spinel may be utilized. The transilluminating qualities seem to be similar to those of natural teeth.36 With a variety of core materials for diverse clinical situations, and reported strength and longevity, In-Ceram is a system worthy of consideration when all-ceramic restorations are planned for a patient. A description of the fabrication of a typical restoration follows. Strict adherence to instructions and specified materials is essential to the success in the clinical application of the system v Fig24-3 Undercuts are blocked 01 Fig 24-4 Die spacer is applied to the prepatat slaying away from the fin'"u l:— Crown Fabrication All-ceramic crowns demand a significant amount of tooth reduction to allow for a minimum thickness of core material, development of internal shade characterization, and the ability to maintain biologically acceptable contours. Tooth preparation for In-Ceram restorations should provide a minimum overall reduction of 1.0 mm.27 However. 1.5 mm on the facial and 1.5 to 2.0 mm on the occlusal aspects are preferred. All line and point angles should be rounded.2e-ze (See Chapter 10 for a complete description of the tooth preparation for an all-ceramic crown.) The finish line is a 1 0-mm-wide radial shoulder on the facial and 0.5 to 0.7 mm in other areas (Fig 24-2).w A study comparing the marginal adaptation of In-Ceram crowns with varying finish lines found that all three of the configurations tested (chamfer, 50-degree shoulder, and 9-degree shoulder) yielded acceptable results.38 Following the impression of the prepared tooth, a master cast with removable dies is constructed. Trim the dies and block out any undercuts (Fig 24-3). Apply cement spacer to the dies, staying 0.5 to 1.0 mm from the finish line (Fig 24-4). An addition silicone impression material is utilized in duplicating the master cast (Fig 24-5) and All-Ceramic Restorations poured in a specially formulated stone (Fig 24-6). The expansion of this stone corresponds to the contraction of the slipcasting material during the initial sintering process. After trimming the duplicate dies, mark the finish line (Fig 24-7). Apply a sealant , which will act as a surface wetting agent, decreasing absorption of liquid slip by the die (Fig 24-8). An ultrasonic device (Vitasonic, Vident) is utilized for the preparation of the aluminous oxide slip material (Fig 24-9). Liquid, alumina powder, and an additive are combined and mixed on a vibrator (Fig 24-10) until becoming an homogenous mass. The slip should exhibit rheopex properties; ie, the liquid mass stiffens under pressure. This property may cause the ceramist a few moments of frustration and require some additional practice. Rapidly apply the slip with a synthetic brush, building up the desired coping configuration (Fig 24-11). The die readily absorbs the fluid, aiding the condensation of alumina particles. The consistency of the applied slip materials resembles wax and carves easily. Use a scalpel and other carving instruments for initial shaping of the coping (Fig 24-12). Allow the completed aluminous oxide coping to dry for 30 minutes. Then apply a liquid stabilizer to the framework to facilitate corrections after firing. Fig 24-9 C ing fluid. added to the container, the mixture is vibrated. The framework is sintered in a furnace designed lor long-duration firing (Fig 24-13). During the 10-hour firing cycle temperatures reach 1,120°C. When the cycle reaches its maximum temperature, the copings are held at 1,120°C for 2 hours to allow the development of aluminous oxide crystals. During the sintering process the duplicate dies shrink, making the removal of the copings extremely easy (Fig 24-14). Final shaping of the framework is accomplished with rotary stones and diamond burs. Glass infiltration provides the coping with its final shade, translucency, and strength. The glass powders are coordinated with the shades in the Vita-Lumin shade guide. Mix ihe desired shade of glass powder with distilled water. Generously apply the mixture to the coping (Fig 24-15), leaving a small area uncovered to facilitate an escape of air as the glass fills the porosities. Place the coping on platinum foil in preparation for firing (Fig 24- 16). The infiltration firing cycle at 1,100°C requires 4 hours for single crowns and 6 hours for fixed partial den- During this cycle the glass infiltrates the alumina core materials via capillary action, very much like coffee soaks into a lump of sugar. When infiltration is complete, reAll- Ceramic Restorations move excess bulk of glass with diamond burs (Fig 24- 17) Then air abrade the coping (Fig 24-18). Excess infiltration glass (0.1 to 0.3 mm) on the surface of the core does not appear to adversely affect the compressive strength of In-Ceram crowns.39 However, it could increase the chroma of the restoration and decrease light transmission. Following glass infiltration, conventional porcelain (Vitadur-Alpha) is added to the coping, restoring the correct anatomic form and occlusal function (Fig 24-19). Cut back the incisai area in "green" porcelain (Fig 24-20). Add back to full contour with incisai porcelain (Fig 24- 21). After necessary correction bakes, the crown is glazed and ready for cementation. Porcelain Laminate Veneers The laminate veneer is a conservative alternative to full coverage for improving the appearance of an anterior tooth.40 Laminate veneers have evolved over the last several decades to become one of esthetic dentistry's most popular restorations. A porcelain laminate veneer is an extremely thin shell of porcelain applied directly to tooth structure.41 This restoration may be used to improve the color of stained teeth, alter contours of misshapen teeth, and close interproximal spaces. Tooth preparation is minimal, remaining within enamel. The restoration derives its strength from the ability of a composite resin luting agent, with a silane coupling agent, to bond with etched porcelain and etched enamel. The idea of porcelain veneers is not new. In the 1930s and 1940s Dr Charles Pincus used thin porcelain veneers to improve the esthetics of movie stars' teeth.42 Unfortunately, he had to use denture adhesive to hold the veneers in place The development of bis-GMA and composite resin restorative materials provided innovative opportunities to restore discolored or malposed teeth. In the mid-1970s and early 1980s the composite resin laminate veneer, with or without a facing, evolved. At first composite resin was added directly to the facial surface of a tooth to restore fractured, discolored, and malformed permanent incisors in a procedure commonly known as "bonding."43 The early composite resin bonding presented several problems, including a monochromatic appearance, with staining and a loss of luster occurring over time. Early composite resin veneers typically did not employ any tooth preparation, and a bulk of material was necessary to obtain a pleasing appearance.44 Unfortunately, the overcontoured restorations contributed to gingival inflammation. The second evolution of veneers involved the development of preformed veneers or crown forms that were joined to the etched tooth structure. Constructing a veneer (without regard to the material) and bonding it to etched tooth structure is referred to as "laminating."44 Indications for these laminate veneers included use as an interim restoration for esthetic improvement of badly discolored anterior teeth, especially in young patients.45 The application of preexisting facings became a popular practice. The three types of facings commonly used were hollow-ground denture teeth, preformed stock laminates, and custom-fabricated laminates of processed acrylic resin.4046 The preformed veneers were a definite improvement over bonding. However, color instability, surface staining, loss of surface luster, low abrasion resistance, biologic incompatibility, and a poor bond between the veneer and the tooth still persisted.47'43 The bond between the acrylic resin laminate and the composite resin was weak, allowing the veneer to be removed easily or simply to fall off. Surface pretreatments helped, but the effectiveness was technique sensitive46 These problems eventually led to the diminished use of acrylic resin and/or composite resin veneers. Glazed porcelain is nonporous, resists abrasion, possesses esthetic stability, and is well-tolerated by gingiva. 47'43 In the early 1980s a method of bonding porcelain to acid-etched enamel was developed. Etching the porcelain, usually with hydrofluoric acid or a derivative, is the most important factor in determining bond strength between the composite resin luting agent and the porcelain veneer.49'50 The mechanical retention obtained by etching the porcelain increases the shear bond strength by a factor of four when compared to unetched porcelain. 51 The application of a silane coupling agent also improves the bond strength.52 The silane coupling agent initiates a weak chemical bond53 between the SiO2 of the porcelain and the bis-GMA polymer of the composite resin.40 Scanning electron microscope examination of the porcelain-resin interface exhibits a smaller gap when the etched porcelain is treated with a silane coupling agent.51 Thermocycling does not significantly reduce the strength of etched enamel/composite/etched porcelain bonding when a silane coupling agent is first applied to the porcelain.511 The improved shear bond strength of etched porcelain/ silane/resin/etched enamel permits an expanded use of veneers, but sufficient enamel must remain to achieve an adequate bond. Indications for porcelain laminate veneers include enamel hypoplasia, tooth discoloration, intrinsic staining (such as tetracycline staining), fractured teeth, closure of diastemas, and correction of anatomically malformed anterior teeth.43 Porcelain laminate veneers can be considered a conservative approach to restoring anterior guidance, especially on worn mandibular incisors. An increase in incisal length up to 2.0 mm does not significantly change the fracture resistance of either the restoration or the tooth.55 The popularity of this restoration has increased significantly over the last several years. Tooth Preparation Porcelain laminate veneers require preparation of the tooth. Although this preparation is minimal and limited to the enamel of the tooth, sufficient enamel thickness must be removed to provide adequate space for a correctly contoured restoration.56 The preparation should provide a reduction of approximately 0.5 mm.ft3-S657 Ideally, the finish line should be a slight chamfer placed within enamel at the level of the gingival crest or slightly subgingival. Enamel provides a better seal and more effectively diminishes marginal leakage than a finish line in either cementum or glass ionomer.58 Due to the relatively thin enamel in the gingival half of the labial surface of most anterior teeth,59 the desired reduction in that area is 0.3 mm. The minimal thickness for a porcelain laminate veneer is 0.3 to 0.5 mm. The required uniform reduction can be achieved by following an orderly progression of Facial Reduction. Since the amount of enamel decreases at the cementoenamel junction,59 some teeth (eg, mandibular incisors) permit less reduction at the gingival finish line. The standard reduction is 0.3 mm. The optimal reduction for the incisal half of the labial surface and incisal edge is 0.5 mm. Tooth preparation is facilitated by using instruments designed specifically for the task. A diamond depth cutter with three 1.6-mm-diameter wheels mounted on a 1.0-mm-diameter noncutting shaft (Model 834-016, Brasseler USA, Savannah, GA) creates the correct depth-orientation grooves in the gingival half of the labial surface. The radius of the wheel extending from the noncutting shaft is 0.3 mm. If the wheels are made to penetrate the enamel until the shaft is flush with the tooth surface, a depth-orientation groove of 0.3 mm is produced (Fig 24-22). A second three-wheeled diamond depth cutter (Model 834-021, Brasseler USA) produces the correct reduction in the incisal half of the facial surface (Fig 24-23) The wheels extend from the noncutting shaft to a diameter of 2.0 mm, with a 0.5-mm radius from the shaft to the perimeters of the wheels. Once again, the wheels cut through the enamel until the shaft is flush with the surface, and 0.5-mm-deep grooves are created. Remove tooth structure remaining between the depthorientation grooves with a round-end tapered diamond (Model 856-016, Brasseler USA) This completes the gingival portion of the facial reduction while the tip of the diamond establishes a slight chamfer finish line at the level of the gingiva (Fig 24-24). Proximal Reduction. Proximal reduction is simply an extension of facial reduction. Using the round-end tapered diamond, continue the reduction into the proxiPorcelain Laminate Vene Fig 24-22 Depth-orientation grooveb (Rinsival half); three-wheel diamond depth cutte ( Fig 24-23 Depth-orientation grooves (incisal half): three-wheel diamond depth cuttor (0.5 mm). Fig 24-24 Facial reduction (pingiv; round-end tapered dial mal area, being sure to maintain adequate reduction, especially at the line angle (Fig 24-25). As the diamond is carried into the interproximal embrasure, it is easy to lift the instrument slightly toward the incisal, creating a "step" at the gingival. This "step" should be eliminated, since that tooth structure, although small, could create an unsightly dark shadow when the veneer is placed. To correct an uneven finish line, make sure the diamond is parallel with the long axis of the tooth. This will guarantee that the gingival extension in the interproximal area is equal to the reduction of the proximal surface at the incisal. The proximal reduction should extend into the contact area, but it should stop just short of breaking the contact. When multiple adjacent teeth are prepared for veneers, the contacts should be opened to facilitate separation of the dies without damaging the interproximal finish line. Incisal Reduction. There are two techniques for placement of the incisal finish line. In the first, the prepared facial surface is terminated at the incisal edge. There is no incisal reduction or preparation of the lingual surface. In the second technique, the incisal edge is slightly reduced and the porcelain overlaps the incisal edge, terminating on the lingual surface. In a retrospective clinical evaluation of 119 veneers, the two techniques were used equally and provided clinically acceptable results for an average period of 18 months.60 Faciolingual thickness of the tooth, the need for esthetic lengthening, and ocdusal considerations will help to determine the design of the incisal edge. Porcelain is stronger in compression than in tension. Wrapping the porcelain over the incisal edge and terminating it on the lingual surface places the veneer in compression during function. A slight incisal overlap provides All-Ceramic Rsstorat Fig 24-26 Uepth-orif jnd-end Fig 24-28 Facial reduction (i round-end tapered diamond. Fig 24-29 Lingual reducti tapered diamond. a vertical stop that aids in the proper seating of the veneer.48 Photoelastic studies indicate that the stress concentration within the laminate veneer is diminished by covering the incisal edge, providing a wide vertical stop to 
برچسب ها: Yamamoto. Chicago. Quintessence Publishing Co، 1985، p 350 I. Bell AM، Kurzeja R، Gamberg MG: Ceramometal crowns and bridges Focus on failures. Dent Clin North Am 1985; 29.763-778. ! Kessler JC: Dentist and laboratory: Communication for success. J Am Dent Assoc 1987: 11597E-102E i. Sorensen JA، Torres TJ: Improved color matching of metal ceramic restorations. Part II Procedures for visual communication. J Prosthet Dent 1987; 58:669-677. ical illus s in dentistry J i. Seluk LW، Laionde TD. Esthetics and communication with a custom shade guide. Dent Clin North Am 1985،  

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JDentRes 1984; 63:171. !. McLean JW: Clinical applications of glass-ionomer cements. Oper Denti 992; 17:184-190. '. Mount GJ, Makinson OF: Clinical characteristics of a a glass ionomer cement. Br Dent J 1978; 14:67. studies •elated t< ,. Oper 5. White SN, Kipnis V: Effect of adhesive luting agents on the marginal seating of cast restorations. J Prosthet Dent 1993; 69:28-31. ). Qvist V, Stoltze K, Qvist J: Human pulp reactions to resin restorations performed with different acid-etch restorative procedures. Ada Odontol Scand 5 989; 47-253-263. I. Tjan AHL, Dunn JR, Brant BE. Marginalleakage of cast gold crowns luted with an adhesive resin cement. J Prosthet Dent 1992; 67:11-15. i. Cox CF: Effects of adhesive resi cements on the pulp. Oper DenM9 '. Pashley DH, Michelich V, Kehl T: Dentin permeability: Effects of smear layer removal J Esthet Dent 1981; 46:531-537. ;. Fusayama T, Nakamura M, Kurosaki N, Iwaku M: Non-pressure adhesion of a new adhesive restorative resin. J Dent Res 1979, 58 1364-1370. m of adhesive material. Oper 1. Kanca J: Dental adhesion and the All-Bond system. J Esthet Denf 1991; 3:129-132. I. Blosser RL, Bowen RL: Effects of purified ferric oxalate/nitric acid solutions as a pretreatment for the NTG-GMA and PMDM bonding system. Pent Materials 1988; 4:225-231. I Hosoda H, Fujitani T, Negishi T, Hirasawa K: Effect of a series of new cavity treatment on bond strength and wall adaptation of adhesive composite resins. Jpn J Conserv Dent 1989; 32:656-665. i. Nakabayashi N, Ko|ima K, Masuhara E: The promotion of adhesion by the infiltration of monomers into tooth substrates J Biomed Mater Res 1982; 16:265-273. I Retief DH, Austin JC, Fatti LP: Pulpal response to phosphoric acid. J Oral Patflo/1974; 3:114-122. i. Macko DL, Rutberg M, Langeland K. Pulp response lo me application of phosphoric acid to dentin. Oral Surg 1978; 45:930-940. >. Kanca J: An alternative hypothesis to the cause of pulpai inflammation in teeth treated with phosphoric acid on the dentin. Quintessence Int 1990; 21:83-86. '. Brannstror its prevent 1. Brannstrom M: Infection beneath composite resin restorations. Can it be avoided? Oper Dent 1987, 12-158-163. i. Cox CF, Keall CL, Keall HJ, Ostro E, Bergenholtz G: Biocompatibility of surface-sealed dental materials against exposed pulps. J Prosthet Dent 1987; 57:1-8. I. Koyano E, Iwaku M, Fusayama T: Pressuring techniques and cement thickness for cast restorations. J Prosthet Dent 1978,40-544-548. I Oliviera JF, Ishikinama A, Vieira DF, Mondelli J; Influence of pressure and vibration during cementation. J Prosthet Dent 1979; 41:173-177 I Smith DC1 Dental cements. Current status and future prospects. Dent Clm North Am 1983; 27.763-792 Finishing and Cementatior 1 Karipidis A, Pearson GJ: The effect of seating pressure and powder/liquid ratio of zinc phosphate cement on the retention of crowns. J Oral Rehabil 1988; 15:333-337. .. Hembree JH, George TA, Hembree. ME: Film thickness of cements beneath complete crowns. J Prosthet Dent 1978; 39533-535. i Jargensen KD: Factors affecting the film thickness of zinc phosphate cements. Ada Odontol Scand 1960; 18: 479-490. '6. Van Nortwick WT, Gettleman L: Effect of internal relief, vibration, and venting on the vertical seating of cemented crowns. J Prosthet Denti 981; 45.395-399. •7. Ishikiriama A, Oliveira JF, Vieira DF, Mondelli J: Influence of some factors on the fit of cemented crowns. J Prosthet DenM981; 45:400-404 •8. Webb EL, Murray HV, Holland GA, Taylor DF: Effects of preparation relief and flow channels on seating full coverage castings during cementation. J Prosthet Dent 1982; 49:777-780. 9. Miller, GD, Tjan, AHL: An internal escape channel. A simplified solution to the problem of incomplete seating of full cast-gold crowns. J Am Dent Assoc 1982; 104:332-335. 10. Brose MO, Woelfel JB, Rieger MR, Tanquist RA: Internal channel vents for posterior complete crown. J Prosthet DenM 982; 51:755-760. H. FeltonD, Madison S, Kanoy E, KantorM, Maryniuk G: Long term effects of crown preparation on pulp vitality [abstract 1139], J Dent Res 1989; 68:1009. i2. Norman RD, Swartz ML, Phillips RW, Sears CR : Properties of cements mixed from liquids with altered water content. J Prosthet Dent 1970; 24:410-418. 6. Tan K, Ibbetson RJ: The effect of cement volume on crown seating [abslract 169]. J Dent Res 1995; 74:422. i4. Swartz ML, Sears, C, Phillips RW: Solubility of cement as related to time of exposure in water J Prosthet Dent 1971 26:501-505. j. Button GL, Moon PC. Barnes RF, Gunsolley JC: Effect of preparation cleaning procedures on crown retention. J Prosthet Dent 1988; 59:145-148. i. Council on Dental Materials, Instruments, and Equipment: Using glass ionomers. J Am Dent Assoc 1990; 121: 181-186. '. Tamura N, Lim HD, Carroll TD, Woody RD, Nakajima H, Okabe T: Retentive strength of crown by different cleaning procedures [abstract 537], J Dent Res 1990; 69:176. i. Hewlett ER, Caputo AA, Wrobel DC: Concentration of smear removal agents vs. glass ionomer bond strength [abstract 558], J Dent Res 1989; 68:251. ). Billington R, Williams J, Pearson G. Glass ionomers: Practice variation in powder/liquid ratio [abstract 629], J Dent Res 1989; 68:945. I. Nikaido T, Inai N, Satoh M, et al: Effect of an artificial oral environment on bonding of of 4-META/MMA-TBB resin to dentin. Jpn J Conserv Dent 1991, 34.1430-1434. . Barghi N, Knight GT, Berry TG. Comparing two methods of moisture control in bonding to enamel: A clinical study. Oper DenM 991; 16:130-135. >. Suh Bl: All-Bond—Fourth generation dentin bonding system. JEsthet DenM991; 3:139-147 1. Jacobi R, Shillingburg HT: A method to prevent swallowing or aspiration of cast restorations J Prosthet Dent 198V 46:642-645. k Goldman M, DeVitre R, Tenca J. Cement distribution and bond strength in cemented posts. J Den? Res 1984; 63:1392-1395. j. Ludwig K, Joseph K: Untersuchungen zur Bruchfestigkeit von IPS-Empress-Kronen in Abhangigkeit von den Zementiermodalitaten. Quintessenz Zahntech 1994; 20:247-256. >. Derand T: Stress analysis of cemented or resin-bonded loaded porcelain inlays. Dent Mater 1991; 7:21-24. Chapter 23 Esthetic Considerations ^ ^ h e analysis of natural dentitions and the develop- I ment of the concept of dental esthetics have been I used in the arrangement of denture teeth. To contribute to a pleasing facial appearance, particularly when the patient smiles, contours, size, incisal edges, occlusal plane, and midline must be in harmony. Many of these principles can be applied to fixed restorations in the appearance zone (Richter WA. Personal communication, July 1973), that part of the mouth where high visibility requires a restoration or tooth replacement to simulate the appearance of a tooth. Appearance Zone A 1984 study of 454 smiles,1 using both men and women aged 20 to 30 years, noted that when a person smiles, the individual typically displays the maxillary anterior and premolar teeth. The zone frequently also includes maxillary first molars. It varies from person to person, depending upon mouth size, smile width, tooth length, lip size and tightness, and perhaps most importantly, the patient's self-image. The smile line or incisal curve is composed of the incisal edges of the maxillary anterior teeth and parallels the inner curvature of the lower lip.'-3 It is parallel with the interpupillary axis/ and it is perpendicular to the midline (Fig 23-1). Nearly 80% of the young subjects in the study by Tjan et al displayed the entire length of the maxillary anterior teeth.1 Women show nearly twice as much maxillary central incisor as men (3.4 to 1.9 mm, respectively) with the upper lip at rest,4 and men are 2 4 times more likely to have a low smile line than women.' The length of maxillary incisors cannot be established by esthetics alone, since they play an important role in both anterior guidance and phonetics. If the length is correct, having the patient sound the letter "F" should place the maxillary incisal edges against the inner edge of the vermilion border (the "wet-dry line") of the lower lip (Fig 23-2).3 The incisal edges of mandibular incisors are established both by occlusal contact with the maxillary incisors and by their position 1.0 mm behind and 1.0 mm ig 23-1 The incisal curve should be perpendicular to ihe midline, which is in the middle of the face, and parallel with the interbelow the edges of the maxillary teeth when pronouncing an "S" (Fig 23-3). => Relatively little is seen of mandibular central incisors in people under the age of 30, and the relationship between men and women is the opposite of that seen in the maxillary incisors (1.2 to 0.5 mm. respectively). As time and gravity win out, the tissues surrounding the mouth sag. The length of maxillary incisors exposed diminishes, and the amount of mandibular incisor that is seen increases (Fig 23-4). At the age of 60, the length of maxillary central incisor showing below the upper lip is 0.0 mm, while nearly 3.0 mm of the mandibular incisors is exposed.4 The crowns of teeth in "nonorthodontic normal occlusion," from a study of 120 casts of subjects who had not received orthodontic treatment and did not need it, were angled so that the incisal portions of the long axes of the crowns were more mesial than the gingival segments (Fig 23-5).5 There is likewise a lingual inclination of the incisal or occlusal segment of the facial surfaces of canines, premolars, and especially molars (Fig 23-6).s This esthetic requirement necessitates biplanar facial Esthetic Considerations Fig 23-2 The incisal edge; of the maxillary inci touch the inner edge of the vermilion border ol lower lip when making the "F" sound: frontal v (left) and midsagittal view (right). s 23-3 The incisal edges of the mandibular cisors are 1.0 mm inferior and 1.0 lingual to the cisal edges of the maxillary incisors when makg the "S" sound: frontal view (left) and midsagitview (right). mandibular incisors individual ages (B). T Fig 23-8 There should be slight irregulai midline, even though the teeth are similai reduction in tooth preparations for all-ceramic or metalceramic crowns on anterior or posterior teeth (described in Chapter 10). The midline, which is centered on the face,6 is perpendicular to the interpupillary line.™ It is the focal point of the smile. Total symmetry is rare, and if compromises must be made, the midline of the smile should correspond to the features nearest ii, such as the column of the nose or the philtrum (Fig 23-7).? The teeth on either side of the midline should be balanced. Perfect horizontal symmetry occurs when all anterior teeth have the same shape, looking more or less like central incisors.^ It is monotonous, and it appears artificial. If the teeth have different shapes, but the left side is a mirror image of the right, radiating symmetry results. A more natural appearance can be produced by introducing slight variations to each side (Fig 23-8).9 Dentists prefer more irregularities than patients do, and dentists tend to prefer more elongated incisors. Variety in arrangement and shape unquestionably produces a more natural appearance. However, the dentist must discuss the concept beforehand to develop in the patient an appreciation for the role played by subtle irregularities in the creation of a more natural appearance. The patient may have desired "straight, white teeth" for a lifetime Teeth that do not meet this long-held vision of dental perfection could be rejected by the patient if they suddenly appear in the mouth without warning. It is also quite possible that they may be rejected even if you do attempt to prepare the patient. Esthetic Considerattoi £\ A B Fig 23-9 When viewed from the facial aspect of each tooth (A), the canines are second in width to ihe central incisors. However, when viewed from the midline, each tooth is narrower than the tooth mesial to it (8). It is suggested that the apparent width be 60% of the apparent width of the tooth n-iru>i-kl tft • 4 Maxillary central incisors are positioned at the middle of the smile, making them the most prominent teeth. They have crowns that are the widest of the anterior teeth.10'11 Canines are the next widest, and lateral incisors are the narrowest (Fig 23-9, A).1"'11 However, Irom a irontal view, the apparent sizes of teeth should become progressively smaller from the midline distally (Fig 23-9, B) It has been suggested that this apparent reduction in size should approximate the proportion of the golden ratio (0.618) as a guide for dental compositions.7.'^13 Starting at the midline, this geometric formula of proportionality would require that each of the anterior teeth should be slightly less than 40% narrower than the tooth immediately mesial to it.14 The ratio of 1.618 to 1.0 is a constant that is designated as 0 (phi). Golden mean,*5 golden section,™ golden rectangle,^' golden proportion,2 and divine proportion™ are all terms that have been used to describe various aspects of this proportion. The ratio has been celebrated as the standard of visual esthetics since ancient times. In 1876 Fechner found that 75.6% of the subjects that he tested expressed a preference for rectangles with ratios ranging from 0.57 to 0.67, with 35% selecting the golden rectangle (with a ratio of 0.62) as the most pleasing visually (Fig 23-10). 15.1B The dimensions of the Parthenon, built in Athens in the fifth century BC, fit within the golden rectangle (Fig 23-11).^'a Phi is related to sequences of numbers that are called Fibonacci series, in which each number is the sum of the two numbers preceding it: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34. 55, 89... (n, + n2 = n3). The ratio between any number and the number preceding it approximates 1.618 or 0, (eg, 34/21 = 1.6190). Conversely, the ratio of any number and the number following it approximates the reciprocal ig 23-12 Incisal edges of central incisors an the same curved line, with the ini rs being about 1.0 mm above that sam Fig 23-13 Interproximal situated progressively c\ located from the midlim ^r to the gingiva the more distal they are of 1.618, which is 0.618 (eg, 21/34 = 0.6176). As the numbers m a series become larger, their ratios more closely approximate 1.618 or 0.618. The series appeared as a "brain teaser" in a book, Liber abaci, published in 1202 by the mathematician Leonardo of Pisa, also known as Fibonacci19 The book eventually came to be regarded as the most influential work on the introduction of the Hindu-Arabic decimal number system to Christian Europe.19 This series is one that is seen in nature, occurring in the intertwining equiangular left- and right-handed spirals of a sunflower, in which the number of clockwise and counterclockwise spirals most commonly are the adjacent Fibonacci numbers, 21 and 34. Similar opposing spirals that are also Fibonacci numbers are found in pine cones (5, 8) and pineapples (8,13).^ The series is seen again in phyllotaxis, or the arrangement of leaves on the stems of plants, and in the number of petals of common flowers l 5 ' ia It would appear that the series is connected to patterns of growth, making it an underlying factor in morphology.20 The incisal edges of the maxillary central incisors and the cusp tips of the canines should be on the same gently curved horizontal line, with the lateral incisors approximately 1 0 mm above the line (Fig 23-12). Beginning with the mesial of the central incisors, the interproximal contacts of the maxillary anterior teeth are situated successively more gingivally, all the way to the distal of the canines {Fig 23-13). As the contacts become located farther gingivally, the incisal embrasures become larger, creating a more dynamic and youthful smile (Fig 23-14). With age and increased wear, the incisal embrasures become minimal (Fig 23-15). Solicit Ihe patient's input for which "look" to try to achieve. In the majority of anterior restorative situations, fewer Esthetic Considerations Fig 23-16 If a patient ace be moderate amounts of critically that will not be mI j i _ \ Fig 23-18 Looking at the teeth in how the restored tooth will look tc tional distance. Fig 23-19 Using a hand mirror held only ir allows the patient to see the teeth as no one problems will be encountered if the patient's original tooth position is approximated. However, when the original positions of anterior teeth have been lost through disease or trauma, or if significant changes are to be made for the sake of esthetics, the new tooth position should first be tried in the provisional restoration, Patient satisfaction can be strongly influenced by comments made away from the office by friends or family members. Only after the provisional restoration has passed this "trial by fire" should the changes be incorporated into a final restoration. Ideal esthetics vary between cultures, generations, and gender, and the dentists view of esthetics must not be the only determinant of the final result.14 It is important that the patient's esthetic expectations be discussed and understood before a restoration is fabricated. "Absolute esthetics" require that there be no metal visible, even if one were to look carefully. A restoration containing surface metal that is not visible in normal conversation will satisfy "conversational esthetics" (Fig 23-16). On the other hand, if there is metal that can be seen when the Fig 23-20 The thret lip is retracied and a strong light shone in the mouth, the restoration or replacement does not meet the requirements of "absolute esthetics" (Fig 23-17). It may be maddening for the dentist if a patient objects to metal being present even if it is normally not visible. A dentist will do well to remember that the patient is the ultimate judge of an "esthetic" crown or fixed partial denture. 12 It is the patient's mouth, and it is the patient's definition of the appearance zone that must be used. It is far better to learn its boundaries before the restoration is Try, if at all possible, to discuss esthetic requirements in front of a wall mirror (Fig 23-18) and not at chairside, with the patient wielding a hand mirror under a dental unit light (Fig 23-19). Second molars, maxillary or mandibular, are rarely in the appearance zone, and the dentist should be as persuasive as possible to get the patient to permit full metal crowns on these teeth. They are usually short, and reducing them enough to permit a metal-ceramic crown may leave very little tooth structure, with an attendant loss of retention. This could be especially critical if the molar is to serve as a fixed partial denture abutment. The dentist has a responsibility to inform the patient of the disadvantages associated with the use of ceramic materials (greater tooth reduction, increased risk of fracture, and increased abrasion of opposing teeth) to secure a truly informed consent. Shade Selection To provide the patient with an esthetic restoration, the dentist must consider the scientific basis of color as well as the artistic aspects of shade selection. Color is a phenomenon of light (red, green, brown, yellow) or visual perception that permits the differentiation of otherwise identical objects. There are three factors upon which color is dependent: (1) the observer, (2) the object, and (3) the light source.21 Each of these three factors is a variable and, when any one is altered, the perception of color changes. Many individuals have some form of color-blindness and are incapable of seeing certain colors. It is well documented that color vision deficiency is more common in men than in women, with a recent study finding 9.3% of the men deficient and 0% of the women.23 At the 1981 ADA convention, color vision testing of 670 dentists (635 males; 35 females) was included in the Health Assessment Program. Sixty-five (9.8%) men and one (0.1%) woman demonstrated color vision deficiency, and individuals with a red-green deficiency showed lower color vision scores in the yellow region of the visible light spectrum. 23 Since the majority of the dentists in the United States are male, it is important that a dentist be aware of this condition if it exists in himself. If the condition is severe, the dentist can have a laboratory technician or a well-trained assistant match shades. The object being viewed modifies the light that falls on it by absorbing, reflecting, transmitting, or refracting part or all of the light energy, thereby producing the quality of color. Furthermore, different parts of the same object can exhibit varying amounts of these phenomena. Perception of the object can be influenced by scattered or reflected light from operatory walls, cabinets, and furniture. The walls in a room used for shade selection should be a neutral color, and intense colors should be avoided in selecting cabinets and furniture for this room. The light source utilized can have a definite effect on the perception of color. There are three light sources commonly found in the dental office: natural, incandescent, and fluorescent (Fig 23-20). The visible portion of the electromagnetic spectrum lies between 380 and 750 jjm Each light source will produce a distinctive distribution of color in the light that it emits. Esthetic Consideratioi Natural sunlight itself is extremely variable. The sky appears blue at noon when the sun has less atmosphere to penetrate. There is an uneven distribution of colors in the morning or evening, when the shorter blue and green rays are scattered by the atmosphere surrounding the earth, and the longer red and orange rays of the spectrum are able to penetrate the atmosphere without being scattered. The sky appears red or orange as a result Artificial light sources are also lacking in an equal distribution of color. Incandescent light is predominantly red-yellow and lacking in blue. This type of light tends to make reds and yellows stronger and blues weaker. Conversely, under a cool-white fluorescent light source that is high in blue-green energy and low in red, blues are strong and reds are weak. There are special lights that are "color corrected" to emit light with a more uniform distribution of color. Initial shade selection should be made using color-corrected lights, but any shade should be matched under more than one type of light to overcome the problem of metamerism.?1 Metamerism is the phenomenon of an object appearing to be different colors when viewed under different light sources. The different spectrophotometric curves in the light from the surface of a porcelain restoration and from the enamel of an intact tooth may give the appearance of similar colors when viewed under a light source with a particular color distribution. However, they may appear to be different colors when viewed under a light source with a different color distribution. It is better to select a compromise shade that looks reasonably good under all three types of light than to choose one that may look nearly perfect in sunlight, for example, but appear to be badly mismatched in the patient's home or office. The three characteristics of color are hue, chroma, and value.2' To facilitate communication with ceramists, the dentist should be thoroughly familiar with these terms and their definitions. Hue is that quality which distinguishes one color from another. It is the name of a color, such as red, blue, or yellow. Hue may be a primary color or a combination of colors. Chroma is the saturation, intensity, or strength of a hue. For example, a red and a pink may be of the same hue. The red has a high chroma, while the pink, which is actually a weak red, has a low chroma. Value, or brightness, is the relative amount of lightness or darkness in a hue. Value is the most important color characteristic in shade matching. If it is not possible to achieve a close match with a shade guide, a lighter shade should be selected since it can be stained more easily to a lower value. It is impossible to stain a tooth to obtain a lighter shade (higher value) without producing opacity. If major changes are attempted in the hue or chroma, there will be an accompanying decrease in value. A number of related factors must be incorporated in ceramic restorations to achieve natural-appearing results. These factors include: color, translucency, contour, surface texture, and luster.25 Selecting the basic shade or color of the restoration is merely the first step. Commercially available shade guides do not adequately cover the entire range of tooth color as seen in nature.26"29 These guides are made of porcelain without a metal backing, and the thickness of the porcelain is much greater than the veneer on a metal-ceramic restoration. The porcelain used for the shade tab is different from that used for fabricating restorations.30 It is often a higher-fusing porcelain used for denture teeth with extrinsic colorants to develop the desired shade.3132 It is easy to see why the color is simply a starting point; natural teeth are much more complicated than shade tabs, and all the individual variations cannot be covered by a commercial guide with approximately 16 selections. To successfully reproduce natural teeth in ceramic restorations, the various patterns of translucency must be recognized.33 The translucency pattern contributes to the shade by affecting value: with increasing translucency the value decreases. The amount, location, and quality of translucency varies with individuals and with age. Young teeth often exhibit a great deal of incisal translucency, with the enamel appearing almost transparent at times. Over years of function, the incisal edges wear and this highly translucent enamel is lost. From daily functions such as eating and toothbrushing, the facial enamel layer becomes thinner allowing the dentin to dominate the shade. In general, older individuals exhibit teeth that are lower in value and higher in chroma than are commonly seen in young adults,12'1425 The pattern of translucency will dictate the depth and extent of the enamel and translucent porcelains built into the restoration.35 Since tooth color occurs in a very narrow range of the visible light spectrum, the form and contours of the restoration play a major role in esthetics. Matching the outline form is just as important as matching the shade correctly.36 There can be a slight mismatch in color, but with proper contours, the crown will blend \r\.2b The contralateral tooth can provide valuable information regarding the proper contours, embrasure form, and subtle characterizations of the facial surface. The surface texture of a tooth or a ceramic restoration influences esthetics by determining the amount and direction of light reflected off the facial surface. To harmonize with the natural dentition, the surface texture of a crown must be designed to simulate the reflectance pattern of the adjacent natural teeth.35'36 Typically, young teeth exhibit a great deal of surface characterization including stippling, ridges, striations, and evidence of developmental lobes. These surface features are gradually worn away with daily function, leaving older teeth with a much smoother, highly polished surface.37 Communicating the amount and quality of surface texture is very difficult. Some authors suggest the use of sterilized extracted teeth or custom shade tabs as a guide.36 The key to the success of natural-appearing restorations is a team approach by the dentist and the technician. Often the ceramist does not participate in the shade selection, making it imperative that the dentist communicate detailed information to the technician. The methods utilized to relay the different factors include a written work Shade Selection Fig 23-22 The patient should tions before a shade match is performed. authorization with the patients age and gender, a detailed shade diagram, diagnostic and working casts, and photographs.35 Custom shade tabs can also aid in the determination of the shade, internal characterization, and surface texture.^^ Since ceramists rarely get to see the iinal result, it is extremely important for the dentist to provide feedback, both positive and negative. Shade Selection Sequence There are a few simple guidelines that should be followed by novice and experienced practitioners alike While following them will not guarantee a perfect match every time, it will eliminate many sources of error and help to standardize the process. Use the shade guide that matches the porcelain your technician is using (Fig 23-21). Every porcelain is different, and best results are obtained if you use the same guide the manufacturer used in designating the colors of the product. This is preferred to making the technician resort to conversion charts The shade should always be matched prior to preparation of the tooth to be restored. Not only can teeth become dehydrated and change color during preparation, but the debris generated in the form of enamel, metal, and cement grindings can coat everything in the mouth. Ask the patient to remove all distractions before attempting to match a shade. Lipstick in particular should be removed (Fig 23-22). Large, bright items, such as earrings or glasses, can also distract the eye from the intended focus of attention on the teeth. Heavy facial makeup, such as rouge, could also interfere with an accurate match and would need to be removed or masked. Be sure that the teeth are clean and unstained before attempting to match a shade. Perform a quick rubber cup and paste prophylaxis in the area of the mouth where the Esthetic Considerations Fig 23-24 When matching a shade, ihe operator should stand between the patient and the light source. Fig 23-25 The matching pro begun by quickly scanning the gi shade is to be matched (Fig 23-23). Rinse the area thoroughly to remove any traces of the prophy paste; otherwise, the prophylaxis will do more harm than good. Seat the patient in an upright position with the mouth at the operator's eye level (Fig 23-24). Position yourself between the patient and the light source. Observations should be made quickly (5 seconds or less) to avoid fatiguing the cones in the retina.3^0 The longer the observer's gaze is held, the less ability there is to discriminate, and the cones will become sensitized to the complement of the observed color. Since blue fatigue accentuates yellow sensitivity, the dentist should glance at a blue object (wall, drape, card, etc) while resting the eyes. The shade should be matched by value, chroma, and hue, in that order. Scan the entire shade guide quickly, selecting those tabs that are the worst match first and eliminating them (Fig 23-25) By process of elimination, this will leave the few tabs that are the closest matches. Moisten them as they are used. If a decision cannot be made between two tabs, hold them on either side of the tooth being matched (Fig 23- Fig 23-26 The tabs are held on either side of the tooth when making a choice between two closely matching shade 26). If no tab will permit a good match, then resort to matching the gmgival portion of the shade tabs with the gingival area of the tooth (Fig 23-27). The necks of the shade tabs often exhibit a great deal of extrinsic colorants. Remove the necks of the tabs to eliminate this very artistic but distracting aspect prior to matching the gingival one-third to one-half of the tooth.'10'11 Complete the matching process by comparing the incisal segments of those tabs which most nearly match with the incisal portion of the tooth (Fig 23-28). Initially select the shade using a color-corrected light (color rendering index of 90 or greater), then repeat the process under at least one other light source to minimize metamerism. Since value is the most important dimension of color when selecting porcelain shades, try viewing the tabs through half-closed eyes. Although this decreases the ability to discriminate color, it increases the ability to match value. Arranging the shade guide according to value may also facilitate the correct selection of the tooth's relative lightness or darkness. Carefully examine the tooth and determine the pattern of translucency and any unique characterizing features Esthetic Consideratioi DENTAL LABORATORY WORK AUTHORIZATION Fig 23-29 The prescription should be precise and detailed in ils description of the restoration to be fabricated. Fig 23-30 Shade tabs should be placed in a disinfecting solut when the shade matching has been completed. such as craze lines, areas of hypocalcification, etc. Use a periodontal probe or other millimeter measuring device to establish the location and extent of these distinguishing features Developing color, translucency, and characterizations within the porcelain will create a more lifelike restoration than simply applying extrinsic colorants after the porcelain is fired. Make a drawing of the facial surface of the tooth in the patient's chart, and record all pertinent information graphically. Indicate different shades if more than one is selected for different parts of the tooth. Transfer this information to the laboratory work authorization, making it as complete as possible (Fig 23-29). It is a good idea, whenever possible, to send the shade tab, a cast including the contralateral tooth, and a photograph to the dental laboratory. Before putting the shade guide away, disinfect it (Fig 23-30). Since parts of most shade guides are made of plastic heat. g ther pr g ade esses involving References fstheiic ictors in a !. Moskowitz ME, Nayyar A: Determinanls of dental esthetics: A rationale for smile analysis and treatment. Compend Contin Educ Dent 1995; 16:1164-1186. !. Heinlein WD: Anterior teeth: Esthetics ant) function. J Prosthet Dent 1980: 44:389-393. i. Andrews LF: The six keys to normal occlusion. Am J Orthod 1972; 62:296-309. :. Powell N, Humphreys B: Proportions of the Aesthetic Face. New York, Thieme-Stratton, 1984, pp 2, 4-9, 50. '. Lombardi RE: The principles of visual perception and their clinical application to denture esthetics J Prosthet Dent 1973; 29:358-382. i. Cipra DL, Wall JG: Esthetics in fixed and removable prosthodontics. The composition of a smile. J Tenn Dent Assoc 1991; 71:24-29. !. Brisi patit 1 Black GV: Descriptive Anatomy of the Human Teeth Philadelphia, Wilmington Dental Mfg Co, 1890, p 14-15. 1 Shillingburg HT, Kaplan MJ, Grace CS: Tooth dimensions— A comparative study. J South Calif Dent Assoc 1972; 40:830-839. ?. Brisman A, Hirsch SM, Paige H, et al: Tooth shade preferences in older patients. Gerodontics 1985; 1:130-133. i. Levin El: Dental esthetics and the golden proportion. J Prosthet Den!1978; 40:244-252. artistry. j. Barratt K: Logic and Design in Art, Science and Mathematics. New York, Design Books, 1980, p 108-111. >. Ricketts RM. The golden divider J Clin Orthod 1981 15:752-759. '. Pedoe D: Geometry and the Visual Arts. N York, Dover Publications, 1983, pp 69, 70. 1. Huntley HE: The Divine Proportion—A Study in Mathematical Beauty. New York Dover Publications 1970 pp23, 62, 64, 161. ). Gardner M: The multiple fascinations of the Fibonacci sequence. Scientific Amer 1969; 220:116-120. 1. Ricketts RM: Divine proportion in facial esthetics J Clin Orthod-\98-\\ 15:752-59. y. Part III Color con- 3-154. on and dentistry. i. Moser JB, Wozniak WT, Naleway CA, Ayer WA. Color vision in dentistry A survey. J Am Dent Assoc 1985; 110:509-510. I. Sproull RC: Color matching in dentistry. Part I. The threedimensional nature of color. J Prosthet Dent 1973; 29:416-424. i Winter RR: Achieving esthetic ceramic restorations. J Calif Dent Assoc 1990; 18:21-24. i. Clark EB: Tooth color selection J Am Dent Assoc 1933; 20:1065-1073. '. Sproull RC: Color matching in dent applications of the organizatic 1973; 29 556-566. I Preston JD: The metal-ceramic restoration: The problems remain. Int J Periodont Rest Dent 1984, 4(5):9-23. i. Miller LL: Organizing color in dentistry. J Am Dent Assoc 1987; 115:26E-40E. I. Preston JD: Current status of shade selection and color matching. Quintessence Int 1385; 16:47-58. Bergen SF- Color in esthetics. N Y State Dent J 1985; 51:470-471 !. Wall JG, Cipra DL. Esthetics in fixed and removable prosthodontics. Shade selection in metal-ceramics. J Tenn 
برچسب ها: JDentRes 1984; 63:171. !. McLean JW: Clinical applications of glass-ionomer cements. Oper Denti 992; 17:184-190. '. Mount GJ، Makinson OF: Clinical characteristics of a a glass ionomer cement. Br Dent J 1978; 14:67. studies •elated t<، . Oper 5. White SN، Kipnis V: Effect of adhesive luting agents on the marginal seating of cast restorations. J Prosthet Dent 1993; 69:28-31. ). Qvist V، Stoltze K، Qvist J: Human pulp reactions to resin restorations performed with different acid-etch restorative procedures. Ada Odontol Scand 5 989; 47-253-263. I. Tjan AHL، Dunn JR،  

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the patient to open wider to apply seating force, which could cause discomfort in the temporomandibular joint. Anterior crowns and crowns that occlude on only one corner might become tipped by pressure from the opposing teeth even on a cementation wafer. In these cases it is better to apply force with a finger padded by a cotton roll. The force must be sufficient to seat the crown completely. Vibration can be applied by gently tapping the side of a crown or the wafer with a mirror handle. Vibration will produce more complete seating than static force alone.91 Check that the restoration is completely seated by palpating a supragingival margin with an explorer through the soft extruded cement, or by removing the bite stick and having the palient close with shim stock between nearby teeth. This must be done quickly and with cotton rolls in place to avoid contamination of the cement by saliva. If the restoration is not completely seated, remove it before the cement hardens, thoroughly clean both restoration and tooth, and try again. If the restoration cannot be removed intact, it may be ground into occlusion to serve temporarily while a new restoration is fabricated. At the following appointment the unintentional "temporary" restoration will have to be sectioned and removed. After the restoration is completely seated, keep the field dry until the cement has hardened. The solubility of zinc phosphate is greatly increased by premature contact with moisture.104 If the patient salivates heavily, the suction device must be left in place during seating of the restoration and hardening of the cement. This makes it necessary to place a thicker object, such as a wooden stick on top of a bite wafer, to maintain pressure on the restoration without allowing the anterior teeth to strike the suction device. No attempt should be made to remove excess cement while it is still soft. The excess helps protect the margins during setting. Furthermore, large masses of hardened cement will break away more easily and cleanly than will thin, smeared films. Once the cement has completely set, remove all excess with a sealer, explorer, and knotted dental floss. Cement left in the gingival crevice can be very irritating to the tissue. The entire crevice should be checked with an explorer several times to insure that all of the cement has been removed. Cementation With Polycarboxylate Cement Use cotton rolls to isolate the quadrant containing the tooth being restored. The tooth should be thoroughly clean. Drying can be accomplished by blotting, since absolute dryness is not required. Following try-in, wash the restoration in water and dip it in alcohol to remove all contaminants. Sandblast the inside of the casting to insure maximum retention. Coat the outside of the casting to be cemented with petrolatum to prevent the cement from sticking where it is not needed. The powder-liquid ratio for this type of cement is 1.5 parts powder to 1.0 part liquid, which can be dispensed with some degree of accuracy. Dispense one measure of powder for each restoration to be cemented. Pick up the powder by pressing the measuring stick, scoop down, into the bottle of powder. Scrape off the excess and place the powder on a glass slab or a special impermeable mixing pad provided with the cement. Do not use a standard, porous parchment pad. Express 1.0 mL of liquid from the graduated syringe for each measure of powder and begin mixing immediately. The powder should be incorporated quickly (Fig 22-43) Finishing and Cementation 7 Fig 22-43 Powder is added quickly, in large qu, and the spatulation should be completed within 30 seconds. Because the liquid has a honey-like consistency, the cement may seem loo viscous. This is normal, and it is not a matter of concern. Coat the inside of the casting with cement, and place some on the tooth while the cement is still glossy. Place the casting on the tooth with firm finger pressure. Then instruct the patient to bite on a plastic wafer or a wooden stick. If the cement becomes dull in appearance before the casting is cemented, remove the cement from the casting and repeat the procedure. There is approximately 3 minutes of working time after the 30-second spatulation is completed. Clean the instruments and the slab with water before the cement has set. Remove cement from the casting in the mouth before it becomes rubbery, or after it has set. Removing the cement while it is in its elastic, semi-set stage may pull some out from under the margin of the restoration, leaving a void in the cement near the margin. Keep the restored tooth isolated and dry until the cement has set completely Cementation With Glass lonomer Cement Complete isolation and protection from moisture is also essential with this type of cement. Isolate the quadrant well with cotton rolls and a saliva ejector or svedoptor. If a dry field cannot be adequately maintained in this way, place a rubber dam. The outside of the crown may be coated with petrolatum to make the hardened cement easier to remove, but care must be taken not to allow any lubricant to contaminate the internal surface. Clean and dry the tooth. Clean the tooth preparation with wet flour of pumice on a rubber cup (Fig 2?-44). It will improve the retention somewhat.1Q6 Rinse the pumice away (Fig 22-45) and then dry the tooth preparation (Fig 22-46). Do not remove the smear layer with acids as is sometimes done prior to application of the more viscous glass ionomer filling materials.1™ This might have an untoward effect on the pulp, and it has been shown to produce little or no improvement in retention.ios.io7.ios QQ not apply varnish to the tooth, as that would negate the benefit of the cement's adhesiveness. Those accustomed to mixing zinc phosphate cement lend to mix glass ionomers too thin, with resultant decreased strength and increased solubility.109 The manufacturer's prescribed powder-liquid ratio should be rigidly observed. For Ketac Cem (ESPE-Premter) the powder-liquid ratio is 3.4.1 by weight, or one level scoop of powder for two drops of liquid. Shake the powder bottle and then place two level scoops of powder and four drops of liquid onto a glass slab. Mix the cement as quickly as possible. Glass ionomer cement, unlike zinc phosphate, liberates very little heat during mixing and therefore can be mixed more rapidly over a smaller area. The mix must be completed within 60 seconds and should have a creamy consistency. At first, a properly proportioned mixture will appear too thick, but as the particles dissolve it will become less viscous. Resist the temptation to add more liquid. Too thin a mix may lead to microleakage and washout.66 Glass ionomer cements are also available in sasured capsules for mixing on machines designed for n xing a Apply the cement to the restoration with a brush. It has been theorized that placing a smaller amount of cement in the crown will prevent a buildup of hydrostatic pressure from excess cement.66 Seat the crown as described for zinc phosphate cement. Working time is 3 minutes from the start of the mix, so move quickly. If the cement becomes thick or starts to form a skin before the restoration is seated, remove it and start over. The cement must be kept dry until it is hard. Keep the suction device in place and replace cotton rolls as necessary. When the excess cement extruded around the margins has become doughy, cover it with petrolatum to prevent it from dehydrating and cracking. Wait until the excess cement has become brittle, but before it achieves its full hardness. The excess may then be removed using a sealer, explorer, and floss. The material must be protected from moisture during its early stages of set to prevent weakening To provide extended protection, cover the margins with the sealing material provided with the cement, varnish, or petrolatum before dismissing the patient. Cementation With Resin Cements There are many types of resin cement and each has specific mixing instructions that should be reviewed before use. If resin cement hardens under a restoration that is improperly seated, it is almost always necessary to destroy the restoration in order to remove it. Furthermore, the tooth surface will usually have to be reprepared to Fig 22-45 The tooth prepat, a water syringe. remove resin tags projecting into the etched enamel and dentinal tubules. Therefore, it is imperative that the dentist have a clear understanding of the necessary steps and carry them out in an efficient, deliberate manner. Use of a chairside assistant is highly recommended. The techniques for cementing metal restorations with two autopolymerizing resin cements are described here. Use of a dual-curing cement under translucent ceramic restorations will be discussed in Chapter 24. Although bonding can be accomplished while using cotton roll isolation,73 it does require immediate placement of the bonding agent. A delay of as little as 1 minute can reduce the bonding strength by 50%.110 Barghi et alMI demonstrated superior results using a rubber dam. Even i! the system utilized will tolerate moisture, better control is maintained through the use of a rubber dam The first technique is for C&B Metabond (Parkell, Farmingdale. NY), a popular material among practicing dentists. Keep the material and the mixing dish in the refrigerator until time to use them. Air abrade the inside of the crown with 50 jim aluminum oxide at 80 psi or more. Then rinse it, and dry with compressed air Clean the tooth preparation with pumice, wash, and dry it Etch any enamel in the preparation for 30 seconds with a plastic foam pellet saturated with red enamel etchant. Dab; do not rub. Rinse and dry the tooth. Apply green dentin activator to the dentin for 10 seconds, and then rinse and dry lightly. Do not desiccate the dentin. Place four drops of base into one of the three wells in the chilled (16 to 22°C, or 61 to 72°F) ceramic mixing dish Add one drop of catalyst from the syringe. Recap each container immediately after its use to prevent evaporation. Mix the two liquids for no more than 5 seconds. Paint both the tooth preparation and the inside of the restoration with the mixture. Repeat the mixing of four drops of base to one drop of catalyst in a second well of the mixing dish Use more for a larger casting or for multiple retainers on a fixed partial denture, always maintaining the 4:1 base-catalyst ratio. Again, stir the solution gently for no more than 5 seconds. Finishing and Cementation Add two level scoops of powder for every unit of liquid (4 drops of base + 1 drop of catalyst). Stir gently for 5 to 10 seconds to produce a creamy mixture. Apply the cement to the restoration. If the restoration or the tooth are no longer wet, apply more liquid to them from the first well before placing the mixed cement into the restoration. Seat the restoration Quickly, as the normal working time is slightly less than 1 minute. To increase working time to 2.0+ minutes, the base and mixing dish, but not the etchants, can be chilled further in the freezer for 15 minutes. Although the material has a very short working time, it takes at least 10 minutes to set and should be held during that time. Wipe off excess while it is soft with a cotton pellet wetted with a drop of base liquid. Do not remove cement from the casting once it becomes rubbery, because you will tear it out from under the margin of the restoration, creating voids under the margin. Cement remaining after setting must be removed with a sealer. The second technique described utilizes a bonding agent, All-Bond 2, that works well with most resin luting materials,112 and a resin cement, All-Bond C&B (Bisco, Itasca, IL). Air abrade the inside of the crown, rinse it, and dry with compressed air. Treat superficial dentin with a dentin bonding agent, while deeper dentin may be protected with a glass ionomer base. Apply 10% phosphoric acid gel (All-Etch, Bisco) to dentin and enamel for 15 seconds, agitating the etchant over the enamel with a brush. Rinse off the acid thoroughly with a water spray. Then air dry very briefly to remove excess moisture, without desiccating the dentin. This particular bonding agent tolerates the presence of some moisture. However, this does not mean that contamination by saliva is acceptable. Mix primer A and B and brush five coats onto enamel and dentin with a disposable brush. Do not dry between any of the five coats. With an air syringe, dry all surfaces for 5 seconds to remove any remaining solvent or water. The tooth surface should have a glossy appearance. Light cure for 20 seconds. If the dentin bonding agent has been used as a cavity sealer for a nonresin cement, eliminate the following step If the bonding agent is being used as part of an all-resin luting, brush on a thin layer of Pre-Bond Resin (LD Caulk) immediately before cementation. Blow off excess resin, but do not light cure. Brush two coats of primer B on the inside of the crown and dry with an air syringe. Mix the base and catalyst of an autopolymerizing resin cement (All-Bond C&B) and quickly spread a thin layer on the inside of the crown. Seat the restoration with gentle pressure and then wipe excess resin from the margin with a cotton roll or cotton pellets. It should be obvious from these two descriptions that techniques vary widely from one brand to another. In the interest of obtaining the best possible result, it is essential that the instructions for the material being used be followed precisely. Special Considerations Following is a discussion of the special requirements for inserting gold inlays, custom cast dowel cores, allceramic restorations, metal-ceramic crowns, and fixed partial dentures. Gold Inlays Because of their smaller size, inlays are more difficult to handle and more readily aspirated by the patient than are crowns. Therefore, trial insertion and cementation should be carried out with a rubber dam in place. Intraoral refinement of occlusal anatomy and margins can be accomplished simultaneously by extending the natural grooves onto the metal with a cone-shaped white stone under heavy pressure. Where space permits, hold the iniay firmly in place with a small blunt instrument. The tip of the stone must be kept sharp by frequently spinning it against a truing stone. Remove the inlay from its preparation by teasing it loose with an explorer. If difficulty is encountered, try a blast of compressed air. If this fails, soften a corner of a Richwil crown remover in hot water, press it against the inlay for several seconds, and remove. Place the inlay back on the die for polishing. Follow the white stone with sharp-tipped brown and green rubber points. Give trie final polish with tripoli on a rotary brush, followed by gold rouge on a separate brush. Before cementation, coat the tooth preparation with varnish or dentin bonding agent. Then fill the cavity preparation with cement before inserting the inlay. The inlay can be safely carried to the mouth by sticking it to a gloved fingertip in the correct orientation with a small piece of double-sided carpet tape or a spot of tray adhesive. 113 After the cement has thoroughly hardened, remove the rubber dam and check the occlusion. If adjustments must be made, repolish the occlusal surface with several grades of progressively finer pumice, followed by Amalgloss on a rubber cup or small brush. Again, be careful not to overheat the tooth. Custom Cast Dowel Cores The casting is cleaned by sandblasting, and any visible casting nodules are removed with a bur. A longitudinal groove should be cut in the side of the dowel to create a cement escape channel, If a dowel core is swallowed during try-in, the risk of intestinal obstruction or perforation is even greater than that associated with a fufl crown. To reduce the risk, a rubber dam can be used As an alternative, about 2.0 mm of the sprue can be left attached to the casting. This g 22-47 A safely knob is formed on a dowel cc attached (A) and notching the stub IB). A floss safety Fig 22-48 To verify that the dowel is as long as the dowel space, the preparation depth is marked on a reamer (A) and this length is compared with that of the dowel i B). stub is notched with a separating disc, and dental floss is tied to it to act as a safety line (Fig 22-47). Insert a rubber dam or gauze throat pack. Remove the provisional restoration. Gently rotate a Peeso reamer in the canal with the fingertips to ensure that no cement remains in the dowel space and to measure its length (Fig 22-48, A). Compare the depth of the dowel space with the length of the dowel to be certain that the casting is complete (Fig 22-48, B). Seat the restoration with light force. Never use heavy force, as the root may be split by the wedging action of the dowel. Remove any areas that prevent complete seating. If the dowel core becomes progressively tighter as it is inserted and resists removal, the interfering area is on the side of the dowel. If it abruptly stops short of seating and offers no resistance to removal, the obstruction is either on the underside of the core or at the tip of the dowel. Once the casting seats completely without binding, remove the safety knob and evaluate the axial and occlusal surfaces. The contours should be those of an ideal crown preparation with adequate occlusal clearance and no undercuts Adjust if necessary, and then clean all surfaces by sandblasting. Do not polish. 6. Zinc phosphate cement 7. Mixing slab and spatula Clean the dowel space with paper points or a wisp of cotton wrapped around a reamer and moistened with Cavilax (ESPE-Premier, Norristown, PA). Make a mix of zinc phosphate cement that is slightly thin. If the mix is too thick, or if it sets too rapidly, the dowel may not seat completely. Spin cement into the dowel space by using a lentulo spiral. This has been shown to provide twice as much retention as merely coating the dowel with cement m Seat the dowel core slowly to allow excess cement to escape without building up hydraulic pressure that might "blow out" the apical seal or crack the root When the cement is hard, remove the excess and place a provisional crown. All-Ceramic Restorations Full crowns, labial veneers, and inlays are sometimes made entirely of ceramic materials. The techniques for adjusting, cementing, and finishing these vary significantly from those used for metal restorations and are described in detail in Chapter 24. Armamentarium for Dowel Cores 1 High-speed handpiece 2. Straight handpiece 3. Separating disc 4. Cavilax 5. Lentulo spiral Armamentarium for All-Ceramic Restorations 1. Busch Silent Stone on SHP mandrel 2. Fine diamond stones 3. Carborundum stones 4. Porcelain finishing kit Finishing and Cementation Fig 22-49 Rotation of a stone toward the greatest bulk of porcelain prevents chipping (A). Rotating away from the bulk can lead lo A light proximal contact will not produce a visible burnished area on porcelain. A thin coating of a pressure indicator such as Occlude (Pascal Co, Belleview, WA) can be applied to these materials before seating to reveal the exact location of the contact. Only gentle forces should be used when inserting and testing ceramic restorations, as fracture may result if forces are too heavy. Internal support for a ceramic crown or onlay can be provided during occlusal adjustment by temporarily "cementing" the restoration to the tooth with a low-viscosity elastomeric impression material. Broad, relatively flat surfaces are best reduced extraorally with the large, smooth-cutting Busch Silent stone (Pfingst & Co. South Plainfield, NJ ), while grooves and ridges are reshaped with smaller pointed diamond stones and green stones. Instruments that have been used on metals should not be used on porcelain, lest particles of metal become imbedded in pores within the porcelain and cause discoloration. When working near an acute edge of porcelain, hold the stone so that it is always moving from the edge toward the greater bulk to reduce the danger of chipping the fragile edge (Fig 22- 49). This is the opposite of the technique used in finishing metal margins. It is best to postpone minor grinding adjustments on thin veneers and inlays until after they are permanently bonded to the tooth. Any roughened ceramic surfaces are smoothed with clean white stones and polished with rubber wheels of progressively finer grit such as those found in the Ceramiste Porcelain Adjustment Kit (Shofu Dental Corp, Menlo Park, CA). These grits are indicated by stripes around the shank of the instrument: no stripe (coarsest), one yellow stripe (medium), and either two yellow stripes or one white stripe (finest). Diamond-impregnated Dialite wheels and points (Brasseler USA, Savannah, GA) may also be used for this purpose. Pastes containing diamond dust are also available for use on cups and brushes. Porcelain may also be reglazed after it is polished. It is often desirable to leave grooves and ridges on labial surfaces to simulate the texture of young enamel, but surfaces touching the gingiva and opposing teeth should be made as smooth as possible. Have the patient moisten the ceramic and adjacent teeth with saliva and reevaluate the shade. Always allow the patient to see the completed restoration in a mirror and express approval before cementing it. Ceramic crowns may be cemented with zinc phosphate, glass ionomer, or composite resin cements. Ceramic crowns that are etched internally and bonded with a composite resin cement have been shown to be 50% stronger than similar crowns cemented with a conventional zinc phosphate cement.115 Ceramic veneers and inlays should be etched, silaned, and bonded to the underlying enamel with resin cements. This not only provides better retention and color control, but makes the ceramic material less susceptible to fracture than if it were cemented with nonresin cement.116 Cement ceramic veneers and inlays with a selected shade of a dual-cure composite resin cement such as Dicor Light-Activated Cement (Dentsply International, York, PA). Store resin cements in a refrigerator to prolong shelf life. Remove the cementation kit from the refrigerator before the appointment lo allow it to approach room temperature. The final appearance of an all-ceramic restoration is affected by the shade of cement used. Determine the correct shade or blend of shades by seating the veneer or inlay on the unetched tooth with water-soluble Dicor try-in paste (white syringe). Opacity can be controlled by varying the proportions of opaque and translucent cataSpecial Considerations lyst. Record the shade or blend of try-in paste selected and clean the veneer thoroughly with a stream of water. Isolate the tooth and clean it with a mixture of pumice and water. Rinse and dry. Place thin plastic strips interproximally. A piece of heavy black silk suture placed into the sulcus will help prevent contamination by sulcular fluid and will limit the entrance of cement into the sulcus. Etch the enamel for 30 seconds with a phosphoric acid gel. Wash with a stream of water for 15 seconds and dry thoroughly. If areas of exposed dentin are present, a dentin bonding agent should be applied as a very thin layer to seal the tubules 70 Place equal amounts of Dicor Light-Activated Cement catalyst (translucent or opaque) and the selected shade of resin cement base from a black syringe onto a paper mixing pad. Mix the components with a clean plastic spatula. Avoid contact with metal instruments. Mix thoroughly to ensure that there are no isolated portions of base or catalyst. Load the veneer with the mixture and carefully seat it on the dry, etched tooth. The plastic interproximal strips may be left in place if they will not interfere with seating of the restoration. Excessive pressure at this time could fracture the veneer. In the case of an inlay, place the cement into the cavity. Remove the excess cement with cotton pellets, explorer, and floss, leaving a slight amount at the margin to accommodate the oxygen-inhibited layer. Hold the veneer gently against the tooth with a finger and harden the cement with a curing light, first directing the light from the lingual (through the tooth) for 60 seconds so that shrinkage will occur toward the tooth, then directing it from the labial (through the veneer) for an additional 60 seconds. Adjust any overbulked margins or premature occlusal contacts with a fine diamond stone. If suture material was placed in the sulcus, remove it. Proximal margins of veneers can be polished with fine finishing strips. Polish occlusal surfaces with the rubber wheels and points of a porcelain adjustment kit. Finish the cement margins with carbide finishing burs, fine paper discs, and porcelain polishing paste on a rubber cup. Metal-Ceramic Crowns The metal portion is adjusted and finished in the same manner as a full gold crown, except that it is somewhat harder than type III gold. The porcelain portions are handled much the same as all-ceramic restorations, except that there is less risk of breakage and the shade is unaffected by the cement. Normally, ceramic restorations will be received from the laboratory with a glazed surface. If it is anticipated that the contours and color will be modified substantially during try-in, they can be left unglazed until after these adjustments are made. Check the internal fit in the mouth to be sure there are no heavy contacts on axial walls near porcelain cervical margins Undue pressure here can cause flaking of the porcelain, either during cementation or later during function. Insufficient contact areas and marginal gaps may be corrected at chairside by adding the appropriate shade of porcelain and firing it in a glazing oven. As an alternative, the restoration can be returned to the laboratory. If the defects are not apparent on the cast, or if the cast has been altered or damaged, new impressions may be necessary. Each porcelain manufacturer provides a shade modification kit for its porcelain, permitting the alteration of shades at chairside if there is a staining furnace nearby. If any shade modification or glazing is required, repolish the exposed metal with rubber wheels, beginning with a coarse one, such as Cratex, to remove the black oxide layer. If a film of shading porcelain or glaze extends over the metal surface, it must be removed with a stone before the metal can be polished. Metal-ceramic crowns are cemented in the same manner as gold crowns. Do not have the patient bite on a hard object to seat the crown, as the porcelain may fracture. Fixed Partial Dentures Procedures for adjusting, polishing, and cementing a fixed partial denture are the same as for a single crown, except for a few special considerations. A piece of dental floss should be tied around one of the connectors to act as a safety line during try-in and cementation If the restoration fails to seat properly after removal of internal nodules and adjustment of the proximal contacts, it should be sectioned with a thin separating disc through the connector of the larger retainer, and the two halves tried in separately. If both retainers fit well after sectioning, the fixed partial denture can be reassembled and soldered using a soldering index (see Chapter 27). References I. Moon PC: Bond strengths o1 the lost salt procei retention method tor resin-bonded fixed pros Prosthet Dent \§&7; 57:435-439. . Gildenhuys RR, Stallard RE: Comparison of plaque accumulation on metal restorative surfaces. Dent Survey 1975: 51:56-59. '.. Keenan MR Shillingburg HT, Duncanson MG, Wade CK: Effects o( cast gold surface tinishing on plaque retention. JPmsthet Dent 1980, 43:168-173. t. Klausner LH, Cartwright CB, Charbeneau GT Polished versus autoglazed porcelain surfaces. J Prosthet Dent 1982; 47:157-162. L Raimondo RL, Richardson JT, Wiedner B: Polished versus autoglazed dental porcelain. J Prosthet Dent 1990; 64:553-557. >. Jacob! R, Shillingburg HT, Duncanson MG: Comparison of the abrasiveness of six ceramic surfaces and gold. J Prosthet Dent 1991; 66:303-309. •>. Phillips RW: Skinner's Science of Dental Materials, ed 7. Philadelphia, WB Saunders Co, 1973, p 631. '. Craig RG. Restorative Dental Materials, ed 8. St Louis, CV Mosby Co, 1969, p 100. i. O'Brien WJ: Dental Materials: Properties and Selection. Chicago, Quintessence Publishing Co, 1989, pp 271, 322, 438. ). Phillips RW: Skinner's Science of Dental Materials, ed 9. Philadelphia, WB Saunders Co, 1991, p 563. ). Lee PW1 Ceramics. New York, Reinhold Publishing Corp, 1961, p 143. I. Cherberg JW. Nicholls Jl Analysis of gold removal by acid etching and electro-chemical stripping. J Prosthet Dent 1979; 42:638-644. >. Campagni WV, Preston JD, Reisbick MH: Measurement of paint on die spacers used for casting relief. J Prosthet Dent 1982; 77:606-611. ). Troxel RR. The polishing of gold castings. J Prosthet Dent 1959; 9:668-675. 1. Jacobi R, Shillingburg HT: A me or aspiration of cast restoratio 46:642-645. ». Kaiser DA, Wise HB: Fitting cast gold restorations with the aid of disclosing wax. J Prosthet Dent 1980; 43.227-228. >. Christensen GJ: Marginal fit of gold inlay. J Prosthet Dent 1966; 16:297-305. '. Eames WB, Little RM. Movement of gold at cavosurface margins with finishing instruments J Am Dent Assoc 1967; 75:147-152. t. Kishimoto M, Hobo S, Duncanson MG, Shillingburg HT. Effectiveness of margin finishing techniques on cast gold restorations. Int J Periodont Rest Dent 1981; 1:20-29. ). Moffa JP, Guckes AS, Okawa MT, Lilly GE: An evaluation of non-precious alloys for use with porcelain veneers. Part II. Industrial safety and biocompatibility. J Prosthet Dent 1973; 30:432-441. i. Kohli S. Levine WA, Grisius UF, Fenster RK The effect of three different surface treatments on the tensile strength of ll J P h t g the resin bond to nickel-c m-beryllium alloy. J Prosthet Dent 1990; 63:4-6. I. Buonocore MG: A simple method of increasing the adhesion of acrylic filling materials to enamel surface. J Dent Res 1955; 34:849-853. !. Simonsen RJ, Calamia JR: Tensile bond strength of etched porcelain [abstract 1154], J Dent Res 1983; 62:297. 19! :9:359. i. Matsumura H, Kawahara M. Tanaka T, Atsuta M: A new porcelain repair system with a silane coupler, ferric chloride, and adhesive opaque resin. J Dent Res 1989; 68:813-818. i. Kerby RE, Knobloch L, McMillen K: Physical properties of composite resin cements [abstract 1849]. J Dent Res 1995; 74243. '. Aboush YE, Mudassir A, Elderton RJ: Technical note: Resinto- metal bonds mediated by adhesion promoters. Dent Mater 1991; 7:279-280. I. White SN, Yu Z: Compressive and diametral tensile strengths of current adhesive luting agents J Prosthet Dent 1993; 69:568-572. ). Isidor F, Hassna NM, Josephsen K, Kaaber S1 Tensile bond strength of resin-bonded non-precious alloys with chemically and mechanically roughened surfaces. Dem Mafer 1991; 7 225-229. ). White SN, Yu Z, Kipnis V: Effect of seating force on film thickness of new adhesive luting agents. J Prosthet Dent 1992; 68:476-481. . Nakajima H, Hashimoto H, Hanaoka K, ei al: Static and dynamic mechanical properties of luting cements [abstract 890], J Dent Res 1989; 68.978. '.. Powers JM, Dennison JD: A review of dental cements used for permanent retention of restorations Part II' properties and criteria for selection. J Mich Dent Assoc 19741 56:218-225. t. Powers JM, Farah JW, Craig RG: Modulus of elasticity and strength properties of dental cements. J Am Dent Assoc 1976, 92:588-591. 1 Drummond JL, Lenke JW, Randolph RG: Compressive strength comparison and crystal morphology of dental cements. Dent Mater 1988; 4:38-40. >. Branco R, Hegdahl T: Physical properties of some zinc phosphate and polycarboxylale cements. Actn Odonlol Scandi983; 41:349-353 >. Swartz ML, Phillips RW, Norman RD, Oldham DF: Strength, hardness, and abrasion characteristics of dental cements. J Am Dent Assoc 1963; 67:367-374. '. Richter WA, Mitchem JC, Brown JD. Predictability of retentive values of dental cements. J Prosthet Dent 19701 24:298-303. i. Dennison JD, Powers JM: A review of dental cements used for permanent retention of restorations. Part I: Composition and manipulation. J Mich Dent Assoc 1974; 56:116-121. i. Norman RD, Swartz ML, Phillips RW: Direct pH determination of setting cements. 2. The effects of prolonged storage time, powder-liquid ratio, temperature and dentin. J Dent Res 1966; 45:1214-1219. I. Smith DC: Dental Cements. Dent Clin North Am 1971, 15:3-31. . Grieve AR: A study of dental cements Br Dent J 1969; 127.405-410. !. Langeland K, Langeland LK: Pulp reactions to crown preparation, impression, temporary crown fixation, and permanent cementation. J Prosthet Dent 1965; 15:129-143. I. Brannstrom M, Nyborg H: Bacterial growth and pulpal changes under inlays cemented with zinc phosphate cement and Epoxylite CBA 9080. J Prosthet Dent 1974; 31:556 565. t. BrannstromM, NyborgH Pulpal reaction to polycar boxy late and zinc phosphate cement used with inlays in deep cavity preparations J Am Dent Assoc 1977; 94:308-310. i. Going RE, Mitchem JC: Cements for permanent luting: A summarizing review. J Am Dent Assoc 1975; 91:107-117. j Swartz ML, Phillips RW, Norman RD, Niblack BF: Role of cavity varnishes and bases in the penetration of cement constituents through tooth structure. J Prosthet Dent 1966; 16:963-972. '. Chan KC, Svare CW, Horton DJ: The effect of varnish on dentinal bonding strength of five dental cements- J Prosthet Dent 1976; 35:403-406. i. Anderson JN, Paffenbarger GC: Properties of silicophosphate cements. D Progress 1962, 272-75. ). Wilson AD, Crisp S, Lewis BG. McLean JW: Experimental luting agents based on the glass-ionomer cements Br Dent J1977; 142-117-122. I Hembree JH, George TA, Hembree ME: Film thickness of cements beneath complete crowns. J Prosthet Dent 1978; 39:533-535. I. Smith DC: A new dental cement. Br Dent J 1968; 125:381-384. I Brauer GM, McLaughlin R. Huget EF: Aluminum oxide as a reinforcing agent for zinc oxide-eugenol-o-ethoxy-benzoic acid cements JDentRes 1968; 47:622-628. 1 Phillips RW, Swartz ML, Norman RD, Schnell RJ, Niblack BF: Zinc oxide and eugenol cements for permanent cementation. J Prosthet Dent 1968; 19-144-150. I. Osborne JW, Swartz ML, Goodacre CJ, Phillips RW, Gale EN: A method for assesing the clinical solubility and disintegration of luting cements. J Prosthet Dent 1978; 40.413-417. i. Mesu FP, Reedijk T: Degradation of luting cements measured in vitro and in vivo. JDentRes 1983; 62-1236-1240. >. Wilson AD, McLean JW: Glass-ionomer Cement. Chicago, Quintessence Publishing Co, 1988 '. Jemt T, Stalblad PA, Silo G: Adhesion of polycarboxylatebased dental cements to enamel1 An in vivo study. J Dent Res 1986; 65:885-887. i. Smith DC: Polyacrylic acid-based cements: Adhesion to enamel and dentin. Oper Dent 1992; 17:177-183. i. Behen MJ, Setcos JC, Paleik CJ, Miller CH: Antibacterial abilities of various glass ionomers [abstract 626], J Dent Res 1990; 68312. i. Maldonado A, Swartz ML, Phillips RW: An in vitro study of certain properties of glass ionomer cement. J Am Dent Assoc 1978; 96:785-791. I. McComb D: Retention of casting with glass ionomer cement. J Prosthet Dent 1982; 48:285-288. !. Kent WA, Shillingburg HT, Duncanson MG, Nelson EL: Fracture resistance of ceramic inlays with three luting materials [abstract 2364], J Dent Res 1991; 70:561. i. Smith DC, Ruse ND: Acidity of glass ionomer cements during setting and its relation to pulp sensitivity. J Am Dent ASSOC 1986; 112:654-657. k Simmons JJ: Post-cementation sensitivity commonly associated with the "anhydrous" forms of glass ionomer luting cements: A theory. Tex Dent J1988; 10:7-8. >. Pameijer CH, Stanley HR. Primate response to anhydrous Chembond [abstract 1]. 
برچسب ها: the patient to open wider to apply seating force، which could cause discomfort in the temporomandibular joint. Anterior crowns and crowns that occlude on only one corner might become tipped by pressure from the opposing teeth even on a cementation wafer. In these cases it is better to apply force with a finger padded by a cotton roll. The force must be sufficient to seat the crown completely. Vibration can be applied by gently tapping the side of a crown or the wafer with a mirror handle. Vibration will produce more complete seating than static force alone.91 Check that the restoration is completely seated by palpating a supragingival margin with an explorer through the soft extruded cement، or by removing the bite stick and having the palient close with shim stock between nearby teeth. This must be done quickly and with cotton rolls in place to avoid contamination of the cement by saliva. If the restoration is not completely seated، remove it before the cement hardens، thoroughly clean both restoration and tooth، and try again. If the restoration cannot be removed intact، it may be ground into occlusion to serve temporarily while a new restoration is fabricated. At the following appointment the unintentional "temporary" restoration will have to be sectioned and removed. After the restoration is completely seated،  

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back in your face. Polish the axial surface with rouge on a second soft-bristle brush reserved for this purpose only. This should be done with the restoration on a die to avoid rounding over the thin margins. Until this time, manipulation of the gingival margins has been avoided, but now they must be polished to a high shine, especially where they will lie subgingivally. Polishing of supragingival margins that were finished in the mouth may be postponed until after the restoration is cemented. Occlusal anatomy that has been lost through adjustments is restored with a 171L carbide bur. Then the recreated occlusal grooves are refined with a no. 0 budshaped finishing bur. Cusp ridges may be smoothed with a sulci disc, taking care not to destroy the occlusal contacts so carefully developed earlier, From this point, the occlusal surface can be treated in one of two ways: it can be carefully polished to a high shine, or it can be sandblasted to provide a matte finish. The dull matte surface will enable observation of facets or burnishing produced by occlusal contacts after the casting has been in the s left uncovered IB). Fig 22-31 An ait brush also can be used tc apply 3 matte finish lo the occlusal surfatt of the casting. vng of Base Metal Restorations mouth for a short time. The use of a matte finish in no way implies that the occlusal surface is unfinished or left in a roughly ground condition. When a sandblaster is used to produce the matte finish on the occlusal surface, the polished axial surfaces and margins should be protected by wrapping the casting in 1-inch-wide masking tape (Fig 22-29, A). The edge of the tape should be tightly adapted around the marginal ridges and cusp ridges, since any area not covered by the tape will be sandblasted. The excess width of tape left projecting beyond the margin forms a handle by which the casting can be held in the sandblaster (Fig 22- 29, B). The casting is placed in the sandblaster (Fig 22- 30) and the occlusal surface is given a uniformly dull surface by a stream from the nozzle from a distance of about 3 inches. A less coarse matte finish can be produced by a handheld air abrasion unit with fine aluminum oxide abrasive (Microetcher II, Danville Engineering, San Ramon, CA; or Air Brush, Paasche Air Brush Co, Harwood Heights, IL) (Fig 22-31). Move the nozzle around until all exposed areas of the crown have been dulled to a uniform matte finish. Rinse the restoration in water and dry with air. Make a final check to be sure there are no remnants of polishing agent or abrasive inside the restoration. Postcementation Finishing of Gold Restorations After cementation, the occlusion should be tested again to make sure that there has been no increase in vertical dimension. There also may be excursive prematurities that escaped detection at try-in because of movement of the uncemented restoration. Ask the patient how the restoration feels. Any report of a strange feeling in centric occlusion, or a statement that the restoration "bumps" or "catches" during excursions means that there is a premature contact or an excursive interference. If not corrected, these can cause tooth hypersensitivity, tenderness, and even myofacial disturbances. As a final check of the occlusion on a polished restoration, use Occlusal Indicator Wax as described on page 397. Then remove the wax, refine the anatomy with pointed stones, and repolish all ground surfaces using finegrit rubber points. The white polishing stone lubricated with petrolatum may again be used on the accessible margins of gold castings to reduce any minute projections of gold or enamel. However, after the cement has hardened, no further closing of the margins can be accomplished and the result of attempts to do so is likely to be excessive removal of gold and exposure of even more underlying cement. The white stone may be followed by a fine cuttle disc, which has been lubricated to make it flexible, and several grits of wet pumice on a rubber cup. Final polishing of the gold restoration can be accomplished mtraorally with Amalgloss (LD Caulk) on a rubber cup or brush. An anesthetized tooth can easily be overheated during polishing. To avoid this, use only light intermittent contact and keep one finger resting on the restoration to monitor its temperature. Preliminary Finishing of Base Metal Restorations Base metals have grown in popularity in the last couple of decades because they are significantly less expensive than gold alloys. They also provide greater strength than do gold alloys, making them desirable for long-span prostheses. They are commonly used for resin-bonded fixed partial dentures because they provide a strong bond to resin cements when properly etched. Armamentarium 1. High-speed handpiece 2 Straight handpiece 3. 1.5-inch cutoff disc on mandrel 4. No. 8 coral stone on mandrel 5. No. 330 bur 6. No. 1 round bur 7. Aluminum oxide tapered stone 8. Aluminum oxide inverted cone 9. Blue rubber wheels and mounted points The technique for finishing castings made of a base metal alloy is similar to that employed for gold alloys. The major difference lies in the use of coarser and harder abrasives on base metals If the alloy being finished contains beryllium, standards of the Occupational Safety and Health Administration (OSHA) of the US Department of Labor require that it be ground only where there is adequate exhaust ventilation or if the technician is wearing an approved respirator.19 Use a 1.5-inch-diameter cutoff disc to remove the sprue(s). Complete the contouring of the surfaces where the sprues were attached with a no. 8 aluminum oxide coral wheel on a mandrel. Examine the internal aspect of the casting for small nodules of metal. Remove them with a no. 330 bur in a high-speed handpiece. When all such defects, as well as atl investment, have been removed, try the casting on the working cast. If it binds, remove the casting. Look for particles of stone or smudges of die relief agent on the inside of the restoration and remove them with the no. 330 bur. Reseat the casting for finishing. Smooth the occlusal grooves with a no. 1 carbide bur. Then do the rough finishing on all accessible areas with the no. 8 aluminum oxide coral wheel. Finish occlusal morphologic features (triangular ridges, cusp ridges, Finishing and Cemenlatioi and cusp inclines) with a mounted coral aluminum oxide tapered stone and inverted cone. Smooth the casting with blue rubber wheels and mounied points. Try-in, Adjustment, and Polishing of Base Metal Restorations The fit of a base metal restoration is adjusted in much the same way as for a gold restoration. Because of the greater hardness of base metals, sandblasting will not disclose binding areas; therefore, disclosing paints or sprays must be depended on. Smooth, highly polished axial surfaces are of equal importance in castings made of base metals. Because of the hardness of these alloys, some adjustments in technique and materials are required. Because the long-term success of any restoration is strongly influenced by the quality of the patient's oral hygiene, home care instructions and dispensing of appropriate cleaning aids (floss threaders, interproximal brushes, etc) must be considered an essential par! of the cementation appointment. Cements The gap between an indirect fixed restoration and the tooth is filled with a cement, or luting agent The mechanisms that hold a restoration on a prepared tooth can be divided into nonadhesive (mechanical) luting, micromechanical bonding, and molecular adhesion. In many cases, combinations of these mechanisms are at work. Armamentarium 1 Straight handpiece 2. Blue disc on mandrel 3. White disc on mandrel 4. No. 1 round bur 5. Felt wheels 6. Felt cones 7. Ti-Cor 8. Ti-Hi 9. Mounted Robinson brushes (soft) 10. Tripoli 11. Palladius 12. 1-inch masking tape 13. Airabrader With blue wheels and tips, smooth areas that were roughened during chairside adjustments. Then go over all of the accessible areas with a white rubber wheel. Finish right to the margins by holding the casting so the wheel is running parallel with the margin. The bottom of each groove can be finished with a no.1 carbide bur. Steel burs are not very effective on base metal alloys, so bud finishing burs cannot be used for finishing grooves on base metal castings. The next step will vary depending on the hardness of the metal used. If it is an extremely hard metal, use Ti-Cor (Ticonium Co, Albany, NY) on a felt disc for axial surfaces and on felt cones for occlusal anatomy. Clean the casting thoroughly and apply the high shine with Ti-Hi (Ticonium) on felt discs and cones. If a somewhat softer base metal alloy such as Rexilfium III (Jeneric Industries, Wallmgford, CT) is used, the final polish can be achieved by the use of tripoli on a bristle brush, followed by Palladius (Vident, Baldwin Park, CA) on another bristle brush. Rouge can also be used for the final step, although it is not quite as effective. A matte finish on metal occlusal surfaces can be provided with an air abrasion unit if desired. Protect the polished axial surfaces with masking tape if you do. Bonding Mechanisms Nonadhesive Luting. Originally, as the name implies (Latin lutum = mud), the luting agent served primarily to fill the gap and prevent entrance of fluids. Zinc phosphate cement, for example, exhibits no adhesion on the molecular level. It holds the restoration in place by engaging small irregularities on the surfaces of both tooth and restoration. The nearly parallel opposing walls of a correctly prepared tooth make it impossible to remove the restoration without shearing or crushing the minute projections of cement extending into recesses in the surfaces (Fig 22-32). Micromechanical Bonding. Resin cements have tensile strengths in the range of 30 to 40 MPa,?D which is approximately five times that of zinc phosphate cement. When used on pitted surfaces, they can provide effective micromechanical bonding (Fig 22-33). The tensile strength of such bonds can sometimes exceed the cohesive strength of enamel. This allows the use of less extensive tooth preparation for restorations such as ceramic veneers and resin-bonded fixed partial dentures. The deep irregularities necessary for micromechanical bonding can be produced on enamel surfaces by etching with a phosphoric acid solution or gel21, on ceramics by etching with hydrofluoric acicF; and on metals by electrolytic etching, chemical etching, sandblasting, or by incorporating salt crystals into the preliminary resin pattern.23 Molecular Adhesion. Molecular adhesion involves physical forces (bipolar, Van der Waals and chemical bonds (ionic, covalent) between the molecules of two different substances (Fig 22-34). Newer cements, such as polycarboxylates and glass ionomers, possess some adhesive capabilities, although this is limited by their relatively low cohesive strength. They still depend primarily on nearly parallel walls in the preparation to retain restorations. Fig 22-32 Nonadhesive luting. The crown can be removed only along the path (large arrow) determined by the axial walls of the preparation. Cement extending into small irregularities of the adjoining surfaces {shown magnified in the two large circles) prevents removal along any path more vertical than the sides of the irregularities Limited success has been achieved in attempts to develop resin cements and coupling agents that will exhibit strong, durable molecular adhesion to tooth structure, base metals, and ceramics. Noble metal alloys are not well suited for direct molecular bonding. However, a thin layer of silane can be bonded to a gold alloy with special equipment (Silicoater, Kulzer, Irvine, CA, or Rocatec, ESPE-Premier, Norristown, PA) to serve as a coupling agent by bonding chemically to resin cements. Equally effective is a layer of tin electroplated onto the gold alloy.24 By applying a silane coupler to roughened porcelain, shear bond strengths in excess of the cohesive strength of the porcelain (approximately 30 MPa) have been achieved in the laboratory. However, such bonds lend to become weaker after thermocycling in water.26 At this time, molecular adhesion should be looked upon only as retention and reduce microleakage, rather than as an independent bonding mechanism. Cement Selection There are several types of cement available for the permanent retention of indirect restorations. These include zinc phosphate, zinc silicophosphate, polycarboxylate (zinc polyacrylate), glass lonomer, and composite resin cements. Cements based on zinc oxide and eugenol are not indicated for permanent cementation. The properties of various cements are compared in Table 22-2.?e"37 Table 22-2 Properties of Commonly Used Luting Cements2*-3* Rim thickn (urn) Composite polymerizing) Composite Glass lonomer Composite (Bisco) (Dentsply/Caulk) C&B Metabond (Parkell; Sun Medical) Comspan (Dentsply/Caulk) Panavia (Kuraray) Panavia 21 (Den Mat) Dicor LAC (Dentsply/York) Dicor LAC with Fluoride (Dentsply/York) (Dentsply/Caulk) Infinity (Den Mat) Fuji I (GC America) Glasionomer Type I (Sholu) Ketac Cem (ESPE-Premier) Ketac Cem Capsule Paste/paste Paste/paste Powder/liquid Paste/paste Powder/liquid Paste/paste Paste/paste Paste/paste Paste/paste Paste/paste Paste/paste Powder/liquid Powder/liquid Powder/liquid Powder/liquid Bis-GMA + quartz Urethane dimethacrylate Powder = PMMA Liquid - MMA + 4 META Bis-GMA Powder = silanated silica Liquid = modified bis-GMA + phosphorylated methacrvlate Modified bis-GMA + barium qlass filler Bis-GMA + silica and barium glass Urethane dimethacrylate Urethane dimethacrylate, Bis-GMA, glass with fluoride Modified bis-GMA. hydrophilic resin, bariofluoroaluminosilicate, quartz Powder = fluoroaluminosilicate Liquid = polyacrylic acid, tartaric acid, citric acid Powder = fluoroaluminosilicate glass Liquid = polyacrylic acid Powder = glass fillers, sodium, calcium, aluminum, lanthanum, fluorosilicate, dried copolymer of acrylic + maleic acids Liquid = tartaric acid + water Powder = glass fillers, sodium, 186 2* 60.1* 275.9* 314.1=6 178.5" 255* 290* 117.5" 137.7* (shaded) 251.7* (translucent) 180* 274.5 (auto)* 293.0 (liqht)* 140.7" 225* 186* 122" 196* 162.1" - - 46.9" 45.1" 47* 29.4" 24* (shaded) 34 5* (translucent) 45-48* 42 7 (auto)* 23.1" 13.6* — 17.8" 10* - 20* " • 19* 41.7s9 10-20* - <25* 20 16* <25 0 09* - 0.13* 0.03* 1.4* — 0.15-0.25* - 0.08- " 0.06* 0 30 - lanthanum, fluorosilicate, 124* dried copolymer of 96.8" acrylic + maleic acids Liquid = tartaric acid + water Table 22-2 Continued Type Hybrid (glass ionomer Polycarboxylaie Zinc phosphate Brand Advance (Dentsply/Caulk) Fuji Duel (GC America) Vitremer Luting Cement (3M) Carboxylon (3M) Durelon (ESPE-Premier) Liv Carbo (GC America! Sholu Pol year boxy late Tylok-Plus Fleck's Zinc Cement (National Keystone Products/Mizzy) Lee Smith Zinc (Teledyne) Modem Tenacin (Caulk) DeTrey Zinc Cement Improved (DeTrey) Shofu Zinc Phosphate Form Powder/liquid Powder/I iqu id Powder/liquid Powder/liquid Powder/liquid Powder/liquid Powder/liquid Powder/liquid Powder/liquid Powder/I iquid Powder/liquid Powder/liquid Powder/liquid Compressive Composition strength (MPa] Powder = glass filler Liquid = OEMA + water Powder = silane-treated aluminosilicate glass Liquid = HEMA, polyacrylic acid, proprietary resins Powder = Strontium fluoroaluminosilicate glass Liquid = Water + polycarboxylic acid copolymer + 2-HEMA Powder = zinc oxide Liquid = polyacrylic acid Powder = zinc oxide, tin oxide, stannous fluoride Liquid - 40% polyacrylic acid Powder - zinc oxide + aluminum + polyacrylic acid powder Liquid = polyacrylic acid Powder = zinc oxide Liquid = polyacrylic acid + tannin fluoride Powder = zinc oxide + SnF + dried polyacrylic acid Liquid = water Powder = zinc oxide Liquid = orthophosphoric acid Powder = zinc oxide + magnesium oxide Liquid = orthophosphoric acid Powder = zinc oxide + aluminum phosphate Liquid = orthophosphoric acid Powder = zinc oxide Liquid = orthopticsphoric acid Powder = zinc oxide Liquid = orthophosphoric acid + tannin fluoride 151.7' 155' 132.6* 5631 50 731 7032 53.333 653" 67.42' 79.3" 55.0" 69 4 >69* 11732 56.533 6 2 . 1 " 96.55-110.3^ 77.527 15034 1173? 117* Tensile strength (MPa) 34.5' 24 23.3* e.o31 10* 12.632 15.1" 10.8" >6.9* 9.3?7 4436 9.5?7 4333 8.135 - Film thickness Solubility feim) in water (%) 20* 0-0.07* 10* 0.07' 19" 0* — 13* 21.039 0.1* 13- 0.01-0.03* 19* 0.04* 19* — 10-20* <0.2* 2531 <0.2 — — - - <25* 0.05* Unfortunately, there is no cement that offers superior properties in all areas of concern. Zinc Phosphate Cement. First introduced in 1878,38 zinc phosphate cement possesses high compressive strength (96 to 110 MPa).36 It exhibits a pH of 3.5 at the time of cementation,39 and it has been widely blamed for contributing to pulpal irritation.3a4lM2 Brannstrom and Nyborg,4344 however, found no irritating effect on the pulp from zinc phosphate, per se. Cavity varnishes partially reduce the exposure of the pulp to the cement,45''"3 but unfortunately they also reduce retention.47 Zinc silicophosphate cement, which also has been in use since 1878,46 exhibits a high compressive strength (152 MPa) and a moderate tensile strength (9.3 MPa).49 However, its film thickness can be excessive (88 urn at the occlusal surface under an actual casting),60 and it also has an acidic pH39 that may be harmful to the pulp. Polycarboxylate Cement. While polycarboxylate cement has a higher tensile strength than that of zinc phosphate,33'37 its compressive strength at 24 hours is significantly lower35 Its pH is also low (4.8), but because of the large size of the polyacrylic acid molecule there is apparently little penetration into the dentinal tubules.33 As a result, it seems to cause little pulpal irritation.4551 This cement has shown a moderately high bond strength to enamel (9 MPa) and to dentin (3.3 MPa).51 Polycarboxylate will also bond to stainless steel, but not to gold.41 Zinc Oxide-Eugenol. Cements based on zinc oxide and eugenol cause virtually no pulpal inflammation as long as they make no direct contact with the pulp. They have long been used as temporary cements. Attempts have been made to create more biocompatible permanent cements by adding o-ethoxy-benzoic acid (EBA) to zinc oxide-eugenol and by reinforcing it with aluminum oxide and poly(methyl methacrylate). Based on in vitro tests, this type of cement was reported to have good strength and be less soluble than zinc phosphate cement.52-53 Unfortunately, its clinical performance was much poorer than its laboratory performance, and in vivo studies have shown that it deteriorates much more rapidly in the mouth than do other cements.5455 Zinc oxide-eugenol cements are still used largely for provisional cementation. Glass lonomer Cement. Glass ionomer has many properties of an ideal cement. The powder is composed mainly of a calcium fluoroaluminosilicate glass, with fluoride content ranging from 10% to 16% by weight.se |n some brands the liquid is an aqueous solution of copolymers of polyacrylic acid with itaconic or maleic acid and tartaric acid. In others the polyacrylic acid or copolymer is dried and incorporated into the powder, the liquid consisting only of water or a tartaric acid solution. Glass ionomer has been in general use as a restorative material in Europe since 1975 and in the United States since 1977, and has gradually gained in popularity as a luting agent. Both its compressive strength (127 MPa) and its tensile strength (8 MPa) are quite good.49 Its bond to tooth structure is comparable to that of polycarboxylate. 57 Bonding of both glass ionomer and polycarboxylate cements to the restoration can be produced by tinplating the inner surfaces of the restoration. A tin -polyacrylic acid product overlying the tin layer on the restoration establishes the bond.68 Glass ionomer cement is bacteriostatic during its setting phase,59 is less soluble than zinc phosphate cement,55 and releases fluoride at a greater rate than does silicate cement. This has been shown to reduce the solubility of adjacent enamel and therefore should inhibit secondary caries.60 In one study,61 glass ionomer was found to be 65% more retentive than zinc phosphate cement. In another,6? premolars with inlays cemented with glass ionomer were slightly more resistant to fracture than were premolars with inlays cemented with zinc phosphate. Glass ionomer cement is not without its disadvantages. Its pH is even lower than that of zinc phosphate cement during setting, and some concern has been expressed regarding postcementation hypersensitivity.63'64 Because the molecules of polyacrylic or polymaleic acid used in glass ionomers are large, it is assumed they are less likely than phosphoric acid to penetrate the dentinal tubules, and varnish is not generally recommended. A calcium hydroxide coating should be applied to areas close to the pulp, however.65 Clinical success with glass ionomer cement depends on early protection from both hydration and dehydration. 66 It is weakened by early exposure to moisture, while desiccation, on the other hand, produces shrinkage cracks in the recently set cement67 Therefore, the cement at the crown margins must be protected by a coating of petrolatum or varnish.6*5 Glass ionomer is more translucent than zinc phosphate, and this property often makes the enamel adjacent to metal castings appear slightly gray, particularly on partial veneer crowns This material continues to be improved, but its efficacy is difficult to assess accurately. Tyas63 sums it up: "Because of constant improvements in glass ionomers, there have been too few studies on any one material, and comparisons between studies are further complicated by differences in evaluation criteria." Resin Luting Cements. Resin cements are composites composed of a resin matrix, eg, bis-GMA or diurethane methacrylate, and a filler of fine inorganic particles. They differ from restorative composites primarily in their lower filler content and lower viscosity. Resin cements are virtually insoluble and are much stronger than conventional cements. It is their high tensile strength that makes them useful for micromechanically bonding etched ceramic veneers and pitted fixed partial denture retainers to etched enamel on tooth preparations that would not be retentive enough to succeed with conventional cements. Some of these cements are autopolymerizing for use under light-blocking metallic restorations, while others are either entirely photocured or dual cured (light activated) for use under translucent ceramic veneers and inlays. In dual-cured cements, a catalyst is mixed into the cement so that it will eventually harden within shadowed recesses after a rapid initial hardening is achieved with a curing light. Problems that have been reported with the use of resin cements for luting fuil crowns include excessive cement film thickness,ao69 marginal leakage because of setting shrinkage, and severe pulpal reactions when applied to cut vital dentin The latter may be related more to bacterial infiltration than to chemical toxicity, however. Use of a dentin bonding agent under a resin cement is critical to its success, unless the preparation has been cut in enamel. Dentin bonding agents have been reported to reduce pulpal response, presumably by sealing the dentinal tubules and reducing microleakage.70 Adhesive resin cement was found to produce a better marginal seal than zinc phosphate cement.71 Even if the problems of film thickness and microleakage should be solved, the problem of adequately removing hardened excess resin from inaccessible margins may preclude the use of resin cement for full crowns with subgingival margins. A number of systems have been developed, utilizing different mechanisms for bonding to the dentinal surface^ • Tags in dentinal tubules • Bonding to precipitates on pretreated dentin • Chemical union with inorganic components • Chemical union with organic components • Production of a resin-impregnated layer of dentin In researching the mechanism of attachment to tooth structure, it was found that resin tags in excess of 200 }im were reported when resin was applied to the dentin surface of extracted teeth. However, the resin penetrated only 10 (im into the dentinal tubules of vital teeth, forming a resin-reinforced layer of tooth structure, the hybrid layer.™ Chemical bonds are subject to degradation when they are exposed to the oral environment.71 Microleakage may occur as a result of bond disruption, causing recurrent caries, sensitivity, and pulpal necrosis after restoration placement.75 The smear layer, a 1- to 5-[im-thick/6 grinding debris-laden layer of dentin produced during the tooth preparation, is a critical barrier that protects the tooth from the oral environment. If bonding is attempted directly to the smear layer, however, tensile failure can occur between it and the cement, or within the layer itself. Therefore, to enhance bonding to tooth structure, the tooth preparation is usually etched. This step alters the dentin surface by removing the smear layer, opening the tubules, and increasing the permeability of the dentin.77 If the smear layer is to be removed, an effective dentin bonding agent must be employed, with true adhesion between the restorative material and the tooth,72 The practice of "total etching" (etching dentin as well as enamel) was described by Fusayama et al in 1979.78 Caution has been urged in approaching the pulp with acids, utilizing passive (soaking) rather than active (scrubbing) methods of application and timing them carefully.79 Weaker concentrations of acid not only pose less of a risk to the pulp, but they also may produce greater bond strengths/6 Solutions of 10% phosphoric acid are preferable to those containing nearly 40%.eo Other etchants effectively used include a 2.5% solution of nitric acid81; a 10% citric acid, 20% calcium chloride solution82; and a 10% citric acid, 3% ferric chloride solution, called simply "10-3," which dissolves a thin layer of calcium on the surface of the dentin without affecting the collagen.33 Each system requires a particular acid, so always use the one specified for the dentin bonding agent you are using. There is controversy about the use of acids, because pulpal damage has been attributed to their application near the pulp.84'85 Kanca813 interprets the pulpal irritation as being caused by the eugenoi used as a cavity sealer in earlier studies, rather than by the phosphoric acid itself. Brannstrom87'88 and Cox et al89 also have questioned a link between sensitivity and toxicity. Instead they conclude that it is the result of bacterial infection. Hybrid lonomer Cements. The recently introduced "hybrid cements," or resin-modified potyalkenoate cements, are purported to combine the strength and insolubility of resin with the fluoride release of glass ionomer. They differ from other composite resin cements in that Ihe glass filler particles react with the liquid during the hardening process. The selection of a cement for the placement of a cast restoration is not a clear-cut decision. Zinc phosphate is a strong cement that has proven itself over many years of use, outliving numerous would-be replacements. When depth of the preparation or history of hypersensitivity raises some concern for the vitality of the pulp, a more biologically compatible cement, eg, polycarboxylate, should be used. Cement deteriorates much more rapidly in some patients than in others.54 If a particular patient has a history of rapid failure of previous crowns due to washout of zinc phosphate cement and marginal caries, use of a glass ionomer cement might help prevent recurrence. Resin cements are indicated where micromechanical bonding is desired. They are especially useful when the tooth preparation is largely in enamel and all finish lines are accessible Cementation Regardless of the material used, cementation involves a number of steps which, if not carried out meticulously, can result in early failure of an otherwise technically excellent restoration. Some of the problems that can be caused by improper cementation technique are premature occlusion, pulpitis, loosening of the restoration, and recurrent caries. Many problems are the result of incomplete seating of the restoration. Factors that can influence the completeness of seating are the viscosity of the cement, the morFig 22-35 under crc A >wn ement ti is. The o es hoi i ihe o cape r cclusal • eadily fr ,y then be Fig 22-3b A vertical groove in the tooth preparation provides art internal escape channel for cement without perforating the phology of the restoration, vibration,90 venting, and seating force.30 Mesio-occluso-distal onlays seated an average of 34 tim farther than did full crowns in a study by Oliveira et a l 9 1 In ihe same study, vibration produced an improvement of 27 nm in the seating of full crowns. Seating force must be adequate to ensure complete seating, but excessive force of brief duration may produce elastic strains in the dentin, creating a rebound that dislodges the restoration when the force is relaxed.92 A study by Karipidis and Pearson93 found that crowns seated on preparations in bovine dentin with a force of 300 M/cm2 could be removed more easily than those cemented with half the force; the reverse was true when crowns were cemented on more rigid metal dies. Venting full crowns will facilitate the escape of cement from crowns and allow more complete seating.94"97 Normally, adequate seating can be achieved without venting. Problems can be encountered, however, over preparations with unusually long, nearly parallel axial walls, or multiple fixed partial denture abutments with greater than normal mobility. The most effective venting is provided by drilling a hole in or near the occlusal surface (Fig 22-35), but that leaves a defect in the crown after cementation. Various methods have been proposed for sealing the vent hole, including placement of direct filling materials, metal screws, and cemented plugs. Venting can be achieved without perforating the crown by creating an internal escape channel in the form of an unoccupied vertical groove in the axial wall of the preparation (Fig 22- 36) or in the internal surface of the crown. The groove should begin at the occlusal surface and end short of the finish line.9" ™ Techniques for using zinc phosphate, polyi glass ionomer, and resin cements follow. Cementation With Zinc Phosphate Cement The field must be kept dry during final placement of the restoration and hardening of the cement. The quadrant containing the tooth being restored is isolated with cotton rolls and a suction device such as a saliva ejector for the maxillary arch or a Svedopter for the mandibular arch (Fig 22-37). Inlays should be cemented with a rubber dam in place. If petrolatum was used during finishing of margins, the tooth must be carefully cleaned with Cavilax on cotton pellets. If the tooth is vital, it is customarily protected from the acidity of the cement. It has been reported that nearly 18% of teeth restored with cores and full crowns later experienced pulpal necrosis.101 More often than not, a tooth receiving a crown has already been subjected to multiple insults from caries and previous restorations, in addition to the crown preparation and impression procedures Possible trauma from zinc phosphate cement should be minimized. Partial protection of the pulp can be provided by the application of two thin layers of copal cavity varnish (Copahte, Cooley and Cooley, Houston, TX). It is applied to the dry tooth with cotton pellets and lightly blown dry after each application. This partially seals the dentinal tubules and protects the pulp from the phosphoric acid The fact that the cement is irritating to the pulp is evidenced by the pain an unanesthetized patient sometimes experiences when a crown is cemented over a Fig 22-37 Mandibular isolation with a Svedopter and cotton tolls. vital, unvarnished tooth. Because varnish does reduce the retention of a crown,47 it should not be used on nonvital teeth or with other types of cement A dentin bonding agent can also be used for this purpose. Place powder on one end of a glass slab that has been cooled in tap water and wiped dry. At the center of the slab, measure out approximately six drops of liquid for each unit to be cemented. The composition of the liquid may be altered by prolonged exposure to air. Both the loss and gain of water adversely affect the properties of zinc phosphate cement.102 Therefore, the bottle should be kept capped and the liquid should not be dispensed until just before it is mixed. Bottles that are less than onequarter full of liquid should be discarded, as should bottles in which the color of the liquid has changed. It is not "good to the last drop." Use the spatula to divide the powder into small increments approximately 3 mm on a side. Move one increment across the slab and incorporate it into the liquid, mixing it for 20 seconds across a wide area (Fig 22-38). This will aid in neutralizing the acid and retarding the setting time. Continue to add small increments of powder, mixing each for 10 to 20 seconds using a circular motionthat can unduly accelerate its setting. Therefore, it must be mixed slowly over a wide area on a cool glass slab to insure that a maximum amount of powder can be incorporated into a mix that is still workable. The more powder incorporated into a given amount of liquid, the stronger and less acidic the resulting cement will be.92 On the other hand, If the mixture becomes too thick, the restoration may be prevented from seating completely. The setting time can be controlled by the rate at which powder is incorporated into the mix. If powder is added slowly, the setting time will be prolonged. If powder is added more rapidly, the setting time will be shortened, less powder will be incorporated, and the resultant cemeni will be weaker and more acidic. Check the consistency by slowly lifting the spatula (Fig 22-40). When the consistency is right, it will string out about 10 mm between the spatula and slab before it runs back onto the slab. If it runs quickly off the spatula, it is too thin, and if it must be nudged off the spatula, it is too thick. A mixture that is too thick cannot be salvaged by adding more liquid. Clean the slab and start over. Quickly load the clean, dry restoration with cement. Brush or wipe cement on the inner surfaces of the restoration (Fig 22-41, A and B). Brushed-on cement produces a seating discrepancy one-third less than that resulting from filling the crown half full, and more than two-thirds less than that resulting from filling the crown completely full.103 If there are recessed features on the preparation, such as box forms or grooves, apply some cement directly to the preparation with a plastic applicator (IPPA). Insert cement into pin holes with a small lentulo spiral or the tip of a periodontal probe. Place cement directly into inlay cavity preparations. At this time the tooth should still be dry. If there is persistent contamination from gingival fluids, it may be necessary to place retraction cord in the sulcus for a few minutes and make afresh mix of cement. Seat the restoration on the tooth and, if it is a posterior tooth with uniform occlusion, have the patient apply force to the occlusal surface of the restoration by closing on a plastic wafer (E-Z Bite Cementation Wafers, HAL Products, Westlake Village, CA) (Fig 22-42, A). An orangewood stick also can be used for this purpose (Fig 22-42, B). However, the stick may apply force to only one cusp, causing the crown to be crooked. It also requires 
برچسب ها: back in your face. Polish the axial surface with rouge on a second soft-bristle brush reserved for this purpose only. This should be done with the restoration on a die to avoid rounding over the thin margins. Until this time، manipulation of the gingival margins has been avoided، but now they must be polished to a high shine، especially where they will lie subgingivally. Polishing of supragingival margins that were finished in the mouth may be postponed until after the restoration is cemented. Occlusal anatomy that has been lost through adjustments is restored with a 171L carbide bur. Then the recreated occlusal grooves are refined with a no. 0 budshaped finishing bur. Cusp ridges may be smoothed with a sulci disc، taking care not to destroy the occlusal contacts so carefully developed earlier، From this point، the occlusal surface can be treated in one of two ways: it can be carefully polished to a high shine،  

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547. . Schnell RJ, Mumford GM, Phillips RW: An evaluation of phosphate bonded investments used with a high fusing alloy. J Prosthet DenM963; 13:324-336. i. Saas FA, Eames WB: Fit of unit-cast fixed partial dentures relating to casting ring size and shape. J Prosthet Dent 1980;43:163-167. !. Dental Technology Reference for Fixed Restorations, ed 7. Armonk, NY, JF Jelenko, 1983. p IV-^t. L Wetterstrom ET: An innovation in sprue design for Ceramico castings. Thermotrol Technician 1966; 20:3-4. ;. Weiss PA: New design parameters: Utilizing the properties of nickel-chromium superalloys. Dent Clin North Am 1977; 21:769-785. Chapter 22 Finishing and Cementation The surface of the casting that is retrieved from investment is too rough for use in the mouth. Five preparatory procedures need to be performed on any type of cemented restoration after it has been fabricated in the laboratory: preliminary finishing, try-in and adjustment, precementation polishing, cementation, and postcementation finishing. With skilled laboratory support, adjustments should be minimal, and the polishing may be done before try-in. The internal ftooth-facing) and external aspects of a restoration are handled differently. The correct internal configuration allows a restoration to seat completely without binding, provides space for a film of cement, allows the margins to lie in intimate contact with the finish line of the tooth preparation, and provides an internal surface that is conducive to a strong cement bond Sandblasting leaves a clean, textured surface on metals that is ideal for conventional nonadhesive luting. Special surface treatments are indicated for bonding with resin cements and will be discussed later. The external surface of a cemented restoration must be smooth, and it should create as nearly a perfect uninterrupted transition from restorative material to tooth as possible. A rough surface accumulates plaque that is injurious to the health of the periodontal tissues," and the amount of plaque is directly related to the roughness of the surface (Fig 22-1 }.2 Metallic surfaces may be brought to only a satin finish before try-in, but they must be given a high luster following chairside adjustments. Porcelain that has been roughened by grinding must be polished and may also be reglazed after it is polished, although polishing alone can produce a surface that is as smooth as glazed porcelain34 and slightly less abrasive on opposing enamel.5 Finishing and polishing should be accomplished by following a fixed routine, starting with an abrasive that is coarse enough to remove gross irregularities. The particles in any abrasive leave scratches on the surface. The surface is smoothed with abrasives of progressively smaller particle size, thereby substituting increasingly smaller scratches until the scratches are eliminated or reduced to microscopic size. It has been theorized that as a gold surface is polished, minute amounts of the abraded surface material (possibly even of molecular size) are filled into surface irregularities. This results in a microcrystalline surface layer that is known as the Beilby layer.6 Abrasives and Polishing Materials Abrasives are exceptionally hard materials that develop sharp cutting edges when they are chipped. Polishing materials consist of abrasives and softer materials that are reduced to extremely fine particle size. For maximum cutting efficiency, the abrasive must be appreciably harder than the material on which it is used. The Knoop Hardness Numbers of commonly used abrasives, dental materials, and tooth structure are listed for comparison in Table 22-1.7-10 In determining the effectiveness of an abrasive, factors other than hardness alone can be significant. The toughness of the binder and the ability of abrasive chips to break sharply, rather than rounding, can alter the effectiveness of an abrasive. Some commonly used abrasives and polishing materials are described briefly below: 1. Diamond—Chips are bound to a metal shape by a ceramic bond or by metal electroplating The hardest of all abrasives, diamond should be reserved for use on hard, brittle substances such as enamel or porcelain When used on ductile substances, such as gold, the abrasive particles become clogged with the material being abraded, and the diamond wheel or point becomes inefficient. 2. Silicon carbide—This commonly used laboratory abrasive is the basic material of carborundum. It is pressed into many shapes to form separating discs and the many points and wheels known as green 3. Emery—This hard, black natural mineral is a mixture of aluminum oxide and iron oxide. Bound to paper discs with glue or resins, emery can be used on gold or porcelain 4. Aluminum oxide—A synthetic abrasive produced by purifying bauxite to crystalline form in ovens. Coarse Finishing and Cementation PLAQUE ACCUMULATION ON SIX GOLD SURFACE FINISHES AT 72 HOURS SUR SURFACE FINISHES Fig 22-1 PiTcuntage of metal surface covered by plaque (F < .05). (From Keenan MP, Shillingburg HT, Duncanson MG, Wade CK: Effects of cast gold surface finishing on plaque retention. / Prosthet Dent 1980; 43:168- Table 22-1 Knoop Hardness Number (KHN) of Dental Substances and Materials710 Substance (Material) KHN Gementum 407 Gold alloy (type III) Amalgam Gold-platinum MCR* alloy Gold-palladium MCR* alloy Ni-Cr MCR* alloy Ni-Cr-Be MCR* alloys Pumice Sand (flint) 192s' 230al 2000^ 250OS grit aluminum oxide is the abrasive in the brown, pink, or "coral" stones used for finishing metalceramic copings. A very fine grit (400) is used to manufacture white polishing stones, sometimes called "poly stones." . Garnet —Available in many grits, or particle sizes, this red abrasive is composed primarily of the silicates of aluminum and iron, with some silicates of magnesium, cobalt, and manganese as well. It will cut both metal and porcelain. Garnet is bound to paper discs with glue. 6. Sand— Sandpaper discs are coated with a dense crystalline form of quartz, called flint. Flint is a naturally occurring mineral that chips to form sharp cutting edges It is not as durable or strong as some other abrasives, but it is a useful abrasive in finishing cast gold. It is available in various grits. 7. Cuttle—A fine, relatively soft polishing agent made from the calcified internal shell of the cuttlefish. It is used on paper discs. 8. Tripoli— A fine siliceous polishing powder that is combined with a wax binder to form light brown cakes. Tripoli is used in the initial polishing step of gold on either a cloth buff wheel or a soft bristle brush. 9. Rouge—Composed of iron oxide (Fe2O3), rouge is likewise supplied in cake form. It is the finest of polishing agents used extraorally on gold castings. It is applied with a soft bristle brush or a small muslin buff wheel. Rouge is also used to fabricate crocus discs. 10. Tin oxide—This is used as a fine powder on a brush or rubber cup for final intraoral polishing of metal restorations. It is the chief ingredient in Amalgloss (LD Caulk Div, Dentsply International, Milford, DE). These materials are bonded to a paper backing or mixed with a binder and pressed into various shapes to form stone or rubber wheels, discs, and points for specific processes. They are also incorporated into pastes for use on brushes, cloth wheels, or rubber cups. Some nonly used forms are as follows: Preliminary Finishing of Gold Restorations 1. Separating discs ("Joe Dandy" discs) are stiff and will cut on the edges as well as on the sides. They are useful for removing sprues from castings, for sectioning fixed partial dentures, and for contouring embrasures around pontics. 2. Moore's Discs (EC Moore Co, Dearborn, Ml) are flexible paper discs coated on one side with various grits of garnet, sand, emery, and cuttle, and are used for contouring and smoothing large convex areas on gold and resins Each disc has a square hole for mounting on a special mandrel, which allows them to be rotated in reverse. 3. Meatless stones are extremely coarse stones for bulk oval of etal. 4. Busch Silent Stones (Pfmgst & Co, South Plainfield, MJ) are large, fine-grained stones for reducing broad areas of porcelain. 5. Green stones contain silicon carbide and are manufactured in many different shapes (Fig 22-2). They are permanently mounted to their mandrels and so can be rotated in reverse as well as forward. They are of medium grit and are used for shaping metal and porcelain. 6. Pink stones are made of porcelain-bonded aluminum oxide and are to be used only for finishing the areas of metal copings to which porcelain is to be fired. 7. White stones contain fine-grained aluminum oxide. They are useful for smoothing the rough surfaces left by green stones and for adapting gold margins to enamel intraorally. 8. Rubber wheels and points are used for polishing metals and ceramics. Examples of coarser discs are Cratex (William Dixon Co, Carlstadt, W), Gold Lustre White (JF Jelenko, Armonk, NY), White Flexie and Brown discs (Dedeco International, Long Eddy, NY). Finer discs that will produce a satin finish include Burlew, Sulci, Gold Lustre Blue (all from Jelenko), and Blue discs (Dedeco). Brownies and Greenies (Shofu Dental Corp, Menlo Park, CA) are fine-grit discs that are capable of producing a fairly high polish. Preliminary Finishing of Gold Restorations To minimize the expenditure of valuable chair time, preliminary adjustments using the die and master cast should be completed on the internal and external surfaces of the restoration prior to the cementation appointment. A dentist who can seat a crown that is comfortable with a minimum amount of chairside adjustments will win the confidence of the patient. Fig 22-2 Common shapes of abrasive siones are; cone (CN), flame (FL), cylinder (CY), barrel (BA), wheel (WH), inverted cone (IC), knife edge (KN), round (RD), round edge (RE). Armamentarium 1. High-speed handpiece 2, Straight handpiece 3 Separating disc on mandrel 4. No. 2F Craytex disc on mandrel 5. 5/8-inch Burlew wheel on mandrel 6. Sulci disc on small-head mandrel 7. No. 0 "bud" finishing bur 8. No. 330 friction-grip bur 9. Articulating paper 10. Green stone Inspect the internal portions of the casting under magnification for small nodules or "bubbles" of gold Remove any that are found with a no 330 bur in a high-speed handpiece (Fig 22-3) Trace all of trie negative angles on the inside of the occlusal surface with the tip of the bur. When there are no obvious artifacts in the casting, seat it gently on the die. Then remove the casting and inspect the preparation portion of the die. If there are any small scratches on the surface, examine the corresponding areas of the internal portion of the casting and use the side of the 330 bur to relieve any areas of the casting where small particles of stone or smudges of die spacer are found clinging. Ideally, the casting should touch the die only in the marginal region. There should be a slight gap everywhere else tor the future cement film. The optimum film thickness of zinc phosphate cement is approximately 30 to 40 urn."-is The space allows cement to escape as the crown is seated and provides some thermal insulation under metal crowns. If adequate relief has not been created in the laboratory, it can be added by chemical or electrolytic etching until the restoration can be seated and removed from the die with gentle finger pressure. Mechanical grinding for this purpose must be done judiciously, because it can easily destroy retentive features or create marginal defects. When you are satisfied with the fit on the die, the restoration is ready for finishing of the external surface. The procedure described here for finishing the external surface of a gold alloy is essentially the same as that developed by Tanner and described in detail by Troxell.13 Use a separating disc to cut the sprues from the casting (Fig 22-4). Diagonal cutting pliers may be used, but the stress generated by them could distort a thin casting. Hold the handpiece with a firm palm grasp while cutting the sprue next to the casting. Avoid tipping the discs—if a disc binds in the cut groove, it may flip the casting out of your hand. After removing the sprue, use the separating disc to trim the remaining portions of the sprue attachment on the casting until the contour in that area is continuous with the contour of the restoration surrounding the sprue. Use a coarse rubber disc (Craytex, White Flexie, Gold Lustre White) to smooth away the roughness left by the separating disc. Use light pressure and move the disc about quickly to avoid the formation of facets or flat spots. Use a finer Burlew or Gold Lustre Blue disc in a similar manner after the coarse disc (Fig 22-5, A). The entire external surface of the casting should now be smooth, with a satin finish. The axial surface should be finished to the margin. However, do not extend over the margin. To accomplish this, the disc should be rotated parallel with the margin, rather than perpendicular to it (Fig 22-5, B). Seat the restoration on the mounted working cast. If a separate die and working cast have been used, some of the stone replicating the gingiva may need to be removed to seat the restoration completely. Slowly adjust the gold in the interproximal areas until the restoration seats completely but still contacts the adjacent teeth. Coarse discs or stones should not be used for this purpose, as an open contact will result when the restoration is given its final polish. The casting must be completely seated before checking the occlusion on the articulator. Otherwise, it may be ground out of occlusion before it is even tried in the mouth. Adjust any excessive centric and eccentric contacts by using marking ribbon and green stones (Dura- Green, Shofu). Remove the restoration from the working cast and place it back on the die. Use a no. 0 "bud" finishing bur (Pfingst) to smooth out the grooves on the occlusal surface (Fig 22-6). Smooth the cusp ridges and blend them into the grooves on the occlusal surface with a small rubber sulci disc (Fig 22-7). External gold surfaces should have a satin-like finish produced by a Burlew rubber polishing wheel at try-in. For a novice, a highly polished surface is not desired at this time, because it will make detection of excessive occlusal and proximal contacts more difficult. The inner, or tooth-facing, surface should be air abraded or sandblasted in preparation for try-in. Try-in and Adjustment of Gold Restorations If you are careful and gentle, the try-in procedure can be accomplished on many patients without administering an anesthetic. The patient's unimpaired tactile sense can be valuable during the adjustment of the occlusion, and the annoyance of lingering anesthesia is avoided. If the patient is made uncomfortable by the procedure, however, an anesthetic most certainly should be given. Try-in and Adjustment of Gold Restorations Fig 22-5 Axial surfaces ate smoothed with a Burl. being smoothed, the wheel should be turned para Fig 22-7 Cusp ridges ai Cementation should be postponed if the patient reports that the tooth has been hypersensitive under the provisional crown. The tooth would be subjected to even greater chemical and thermal trauma by placement of a metal crown. In these cases, make sure the provisional restoration is not in hyperocclusion and that it covers all prepared tooth surfaces. Recement it for several days. If pulpitis persists, endodontic therapy will be necessary before the permanent restoration can be cemented. Never cement a crown permanently over a symptomatic tooth. Try-in Armamentarium 1. 2 x 2-inch gauze squares 2. Mallet 3. No. 15 straight chisel 4. Backhaus towel forceps 5. Miller forceps 6. Cotton pliers 7. Cotton pellets 8. Dental floss 9. Plastic bite wafer 10. Articulating paper 11. Silver plastic shim stock (13 mm thick) 12. Straight handpiece 13. 5/8-inch Burlew wheel on mandrel 14. Green stones 15. No. 2 round bur 16. Spratley knife 17. Contra-angle handpiece 18. Tapered white polishing stone 19. Petrolatum 20. 3/8-inch cuttle disc on mandrel Finishing and Cementatior nt of Gold Restorations Fig 22-14 A Richwil Crown Removt es or the softened cube (B). The pat is soaked in hot tap water for 1 n it opens quickly and forcefully t< Precautions must be taken during try-in to minimize the risk of the restoration being swallowed or aspirated. This is especially important with patients whose reflexes are diminished, such as those who are elderly or sedated. A small safety ring can be provided on metal crowns by cutting a thin slice from a hollow sprue (Fig 22-8). Attach it to the wax pattern where it will not interfere with the occlusion (Fig 22-9).14 Thread floss through the ring before trying the casting in the mouth (Fig 22-10). Leave the floss hanging out of the mouth during try-in and adjustments (Fig 22-11). This also makes removal of tightly fitting castings easier. If a safety line is not used, a gauze square should be placed on the floor of the mouth. Remove the provisional restoration by grasping the buccal and lingual surfaces with the tips of a Backhaus towel forceps and rocking it to the facial and lingual (Fig 22-12). An alternate technique utilizes a small mallet and a straight enamel chisel with a 1.5-mm-wide blade. The tip of the chisel is pointed in an ocdusal direction and engaged under a bulge on the buccal surface of the restoration near one of the proximal embrasures (Fig 22- 13). The chisel is tapped lightly to loosen the restoration. Most of the temporary cement will adhere to the inside of the provisional restoration. Carefully pick off any cement left on the surface of the preparation. A dry cotton pellet held in cotton pliers is run over the preparation surface to wipe off small clinging particles Wash with lukewarm water. Cold water will make the unanesthetized patient uncomfortable. Evaluation of a restoration should be carried out in the following sequence: 1. Proxima! contacts 2. Margins (completeness of seating) 3. Occlusion 4. Contours 5. Esthetics Adjustment of Proximal Contacts The proximal contacts of a restoration must be neither too tight nor too light. If they are too tight, they wiil interfere with correct seating of the restoration, produce discomfort, and make it difficult for the patient to floss. A proximal contact that is too light will allow impaction of strands of food, which is deleterious to the gingiva and annoying to the patient. Place the restoration on the tooth and seat it with firm finger pressure. Do not mallet or have the patient exert occlusal pressure. Jamming the restoration onto the tooth at this time may make it extremely difficult to remove. You should be able to remove a crown by grasping it with a dry gauze sponge and rocking it slightly. A crown that cannot be removed with the fingers may be removed by using a Richwii Crown Remover (Almore International, Portland, OR), which is a green, sticky cube. The cube is softened in hot water and placed over the crown (Fig 22- 14, A). The patient is instructed to bite into the cube and hold for a few seconds (Fig 22-14, B). Then a quick opening movement should remove the crown from the tooth preparation (Fig 22-14, C). Obviously, this requires Ihe presence of firm, natural opposing teeth with no cemented restorations on them. Finishing and Cem&nlatia Using the straight chisel and mallet as described for provisional crown removal may be necessary. Often a crown will be easier to remove after being worn for 24 hours without cement. If all else fails, the restoration must be removed by cutting it off. A frequent cause for failure of a restoration to seat completely is an overcontoured proximal surface. Hold the restoration firmly in place and test both proximal contacts with waxed floss (Fig 22-15). If you do not hold the crown firmly enough, it may become slightly elevated or tipped, allowing the floss to pass through even though the contact is actually too tight. Each contact should be as tight as the others in the mouth. If floss will not pass through the contact, remove the restoration and examine the proximal surfaces. At this point, the desirability of leaving a satin finish on a gold restoration becomes apparent, because there will be a shiny burnished area where the tight contact occurred. Use a Burlew or Craytex wheel to remove the shiny mark and try the casting back on the tooth. Repeat until floss can pass through with the same amount of resistance offered by the other contacts. If both proximal contacts feel too tight, adjust only the tighter contact first. Sometimes this will relieve the pressure on the second contact without it needing adjustment. Care must be taken not to remove too much material from the contact area. If the proximal contact is open or too light, this must be corrected by adding solder before • cementation. acceptable margin is not overextended, underextended, too thick, or open (Fig 22-16). A margin is generally considered to be open if the gap is greater than 50 |im, which means the tip of a sharp explorer can be inserted between restoration and tooth. A restoration that rocks perceptibly on the tooth cannot have closed margins on both sides at once. Subgingival marginal discrepancies are the most difficult to detect and the most detrimental to gingival health. The most common cause of poorly adapted margins is failure of the restoration to seat completely. If the proximal contacts are not too tight and the margins are still short or open, there may be some minute undercut, unseen defect, or distortion preventing seating. A convenient technique for improving the seating of castings of softer gold alloys is to produce a matte surface on the inner surface with a sandblaster or air brush, seat the restoration firmly on the tooth, remove it, and relieve any shiny areas with a no. 330 bur. Be careful not to destroy the metal projections that fit into grooves or boxes. There are a number of materials that can be used for locating internal discrepancies. The inside of the crown may be painted with chloroform and rouge or thinned typewriter correction fluid, or sprayed with a thin layer of a dry aerosol indicator (Occlude, Pascal Co, Bellevue, WA) (Fig 22-17). Disclosing wax (Kerr Manufacturing Co, Romulus, Ml) indicates not only points of interference, but the thickness and configuration of the future cement film, which in turn reveals the completeness of seating and the closeness of adaptation of subgingival margins.15 Fill the restoration half full of disclosing wax and heat it in a flame just enough to make the wax flow and adhere to the inner surface. The tooth must be wet with saliva to keep the wax from sticking to it. When the wax has resolidified, seat the restoration, hold it in place for approximately 10 seconds, and remove it. Areas of metal-tooth contact will appear inside a crown as shiny spots devoid of wax. Ideally, the margins (where no cement spacer was used on the die) should show intimate contact, and the remainder of the restoration should have a thin coating of wax representing the cement space. Relief of impinging areas with a no. 330 bur will usually allow the restoration to seat farther. Impression-type materials, such as Fit-Checker (GC Dental Industrial Corp, Tokyo) or alginate can also be used, but they are more time consuming. All disclosing materials must be completely removed from inside the restoration by swabbing with chloroform and sandblasting prior to cementation so that retention will not be diminished. The tooth may be cleaned with Cavilax (ESPE-Premier, Norristown, PA). Marginal Adaptation (Completeness of Seating) After the proximal contacts have been corrected, seat the restoration and examine the margins closely. An Cold Margin Finishing Type III and softer golds differ from other materials in that they can be burnished against the tooth to some extent This must not be attempted until you are certain the casting is seated as far as it will go. Try-in and Adjustment of Gold Restorations m Fig 22-16 Typos of defec verextended (A), underextended (B), thick {C), and open (D) Two types of margins need to be considered. Those margins that will be subgingivalcan be burnished on the die with a beavertail burnisher or fine stone. No intraoral finishing procedure is indicated for subgingival margins because of the risk of damage to the tooth and periodontal structures. Supragingiva! margins of inlays, onlays, and partial veneer crowns can be finished on the tooth. With proper finishing procedures, margins can be adapted to reduce the opening between the margin and tooth to less than the film thickness of the cement.16 Place the casting on the prepared tooth and have the patient seat it firmly by closing on a plastic bite wafer or a wooden stick. Verify that the restoration is completely seated and that the margins iit adequately. No attempt should be made to close gross marginal openings, because gold that has been moved or "dragged" by a coarse abrasive forms a soft, granular lip that can be easily broken or deformed during subsequent manipulation.17 A burnisher, such as a dull Spratley knife, can be used to press the margins against the tooth surface (Fig 22- 18). The restoration must be held in place with another instrument or by having the patient close on a bite wafer during burnishing. The use of a Spratley knife has been shown to improve marginal adaptation by as much as 30 urn.'8 If a white polishing stone, lubricated with petrolatum, is also used and followed by a cuttle disc, the adaptation of the margin can be improved by nearly 60 jim. Therefore, a white polishing stone and petrolatum are used for finishing after the burnishing. The white stone should always rotate from casting to tooth surface, under heavy pressure and at low speed (Fig 22-19). Cut slight amounts of gold and tooth structure. Check for open margins with an explorer. If slight defects exist, the procedure should be continued until the margin is smooth. Green stones are not recommended, as they may abrade too much tooth >ated with an indica s that prevent compleie seating. structure and gold. A final precemenlation smoothing can be achieved with a 3/8-inch cuttle disc Care should be exercised in removing the casting to prevent damage to the margins. A dull chisel can be placed under a proximal area, and several light taps with a mallet will remove the casting. The Backhaus towel forceps can also be used, taking care not to damage the margins. If there are sound opposing teeth, the Richwil Crown Remover can be used as described previously (page 391). A safety ring made as an integral part of the restoration to prevent aspiration (see Fig 22-8) can also be used as an aid in removing a crown following try-in, When the casting has been removed for the last time, the ring is removed and the area polished. If a restoration persists in not seating completely, you must recognize that inordinate amounts of time can be Finishing and Cemeritatioi spent in attempting to make a poor restoration fit. The end result of this expenditure of time will be a mediocre restoration at best. If a restoration will not fit and the cause cannot be quickly determined and corrected, the restoration should be remade. If the discrepancy in fit appears to be similar on the die and on the tooth, a new restoration can be fabricated on the same die, provided the die has not been damaged. Occlusal Adjustment Only after you are satisfied that the restoration is seated completely should any occlusal adjustments be performed. To provide a basis for comparison, instruct the patient to close into the customary position of maximum intercuspation with the restoration removed. Note the position of the teeth and the completeness of closure and contact. Locate a pair of teeth near the prepared tooth where the patient can hold a strip of 13-fim (.0005 inch) shim stock (Artus Corp, Englewood, NJ). Then insert the restoration and see if the patient can still hold the shim between the same pair of nearby teeth. If not, the crown is high in the intercuspal position (Fig 22-20). Place a thumb on the patient's chin and arc the mandible open and closed until the mandible is slowly guided into its most retruded position; have the patient close until the first tooth contact occurs. Ask the patient to point to the tooth touching. If the restoration is indicated, it is high and needs occlusal ad|ustment. Ask the patient to close together forcefully and try to make all teeth touch. If the mandible shifts to the side where the restoration is located, the buccal incline of the maxillary lingual cusp or the lingual incline of the mandibular buccal cusp needs adjustment (Fig 22-21). If the mandible shifts to the side away from the restoration, one of two deflective contacts requires correction. There is a possibility of a heavy contact between the lingual incline of the maxillary buccal cusp and the buccal incline of the mandibular buccal cusp (Fig 22-22). There may also be excessive contact between the lingual incline of the maxillary lingual cusp and the buccal incline of the mandibular lingual cusp that needs correction (Fig 22-23). Cut a piece of thin articulating paper the width of the restoration and place it in a Miller forceps. Hold it between the restoration and the opposing tooth, and have the patient close. Remove the restoration from the mouth and remove only the carbon marks on the appropriate surfaces Ignore other markings on the restoration at this time. This procedure should be continued until no mandibular shift is evident and shim stock can be held between adjacent pairs of teeth. Due to the resiliency of the bones and joints, the patient's ability to hold shim stock on the opposite side of the arch is not a sure indication that the restoration is adequately adjusted. Care must be taken not to overcorrect the occlusion. This can be monitored by placing a narrow strip of plastic shim stock over the restoration and having the patient close on it. The shim stock should offer the same amount of resistance when tugged from the side as do the adjacent teeth (Fig 22-24). If the shim stock holds on the adjacent teeth and not on the restoration, the restoration has been overadjusted and must be either added to or remade. Ideally, the anterior teeth should not touch in the centric position; they should miss by the thickness of the 13 fim (0,0005 inch) shim stock. Adjustment of the restoration in excursive movements is essential. This can be tested by again using the narrow strip of plastic shim stock. Place it between the restoration and opposing tooth, and ask the patient to close firmly, then have the patient move into a working relationship on the side of the mouth opposite the restoration. The shim stock should be held tightly in the intercuspal position, Try-in and Adjustment of Gold Restorations Fig 22-20 If the patient can hold shim stock on adjacent teeth with the crown out, but not with it in, the g 22-21 A premature contact on the buc il incline of the maxillary lingual cus oduces a buccal shift of the mandible. Fig 22-22 A premature contact on the lingua] slope of the maxillary buccal cusp produces a lingual shift of the mandible. Fig 22-23 A premature contact on the gual incline of the maxillary lingual i produces a lingual shift of the mandiblt but as soon as the nonworking movement starts, it should be able to be removed easily from between the restoration and opposing teeth. If not, replace the shim stock with articulating paper and locate the area of contact. For adjustment of the nonworking movement, the marks that are found on the buccal inclines of the maxillary lingual cusps and the lingual inclines of the mandibular buccal cusps must be eliminated (Fig 22-25). Working-side interferences on the restoration may be adjusted by having the patient move into a working relationship on the side of the mouth where the restoration is located. For the adjustment of working-side interferences, remove contacts on lingual inclines of maxillary lingual cusps and buccal inclines of mandibular lingual cusps (Fig 22-26) Contacts between the lingual inclines of the maxillary buccal cusps and buccal inclines of mandibular buccal cusps may or may not be removed depending on the occlusai scheme that is being established. If the goal is a canine-guided or mutually protected occlusion, these contacts should be removed. However, if group function is desired, these contacts are desirable and should be reduced only to the level at which they no longer cause disocclusion of the canine teeth. Teeth that are mobile may move during excursions, giving a false indication on the articulating ribbon. To detect movement, hold a fingernail against the facial surface of the restored tooth and its neighbor during excursions. Finally, protrusive interferences are identified and reFinishing and Cementatioi Precemenlation Polishing of Gold Restoratioi moved Again the patient closes on plastic shim stock in a retruded position and then moves the mandible forward. The distal inclines of the maxillary teeth and the mesial inclines of the mandibular teeth will be adjusted lo relieve protrusive interferences (Fig 22-27). Contacts should appear on anterior teeth during excursive movements. Since anterior teeth help to disengage posterior teeth during excursive movements, these are considered desirable contacts. Whenever possible, anterior guidance should be shared by two or more pairs of occluding teeth. Premature contacts on smooth surfaces can be located with great accuracy by adapting a strip of Occlusal Indicator Wax (Kerr) to the teeth of the restored quadrant with the shiny, adhesive side toward the restoration. Have the patient moisten the wax with saliva to prevent it from sticking to the opposing teeth and then tap the jaws in the maximum intercuspal position several times, The wax over the restoration should appear perforated to the same degree as the wax on the neighboring teeth. Excessive contacts will appear as bright spots uncovered by wax. Relieve these directly through the wax using a large highspeed round bur on metals and a diamond stone on ceramics. After these contacts have been equilibrated, apply more wax and have the patient execute several chewing strokes. Interferences will appear as wax-free areas not present in maximum intercuspation. Contours Improper contours may impair gingival health and detract from a natural appearance, as described in Chapter 19. They must be corrected before cementation. Excessive convexity near the gingival margin promotes accumulation of plaque. Surfaces directly occlusal to furcations are usually concave, and the concavity should extend occlusally on the axial surface of the restoration to improve access for a toothbrush. Esthetics Step back and view the restoration from a conversational distance to see if its contours harmonize with the rest of the patient's dentition. Let the patient look in a mirror so that any objections to the appearance can be dealt with before the restoration is cemented, Precementation Polishing Cold Restorations of \fter the occlusion has been adjusted and accessible nargins have been finished in the mouth, the restoration s polished to a high shine Fig 22-28 Casting is polished with soft Robinson brushes using firs tripoii and ihen gold rouge. Armamentarium 1. Straight handpiece 2. 5/8-inch Burlew wheel on mandrel 3 Sulci disc on small-head mandrel 4. No. 0 finishing bur 5. Mounted Robinson brushes (soft) 6. Tripoli 7. Gold rouge 8. 1-inch masking tape 9. Sandblaster Remove any rough spots on the axial surfaces with a 5/8-inch Burlew wheel. Stay 1 0 mm away from any margins that have already been finished in the mouth, as they are fragile and may be bent or polished away with this abrasive wheel. Then polish all the axial surfaces with tripoli on a soft-bristle brush (Fig 22-28). Run the handpiece in reverse to minimize the material thrown 
برچسب ها: 547. . Schnell RJ، Mumford GM، Phillips RW: An evaluation of phosphate bonded investments used with a high fusing alloy. J Prosthet DenM963; 13:324-336. i. Saas FA، Eames WB: Fit of unit-cast fixed partial dentures relating to casting ring size and shape. J Prosthet Dent 1980;43:163-167. !. Dental Technology Reference for Fixed Restorations، ed 7. Armonk، NY، JF Jelenko،  

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those done in molds made by vacuum investing were free of bubbles.44 Experienced technicians probably can obtain smooth castings with either vacuum pouring or open pouring.46 Although the open pour technique is more popular with experienced technicians because of the unimpeded view of the pattern as it is covered with investment, it is easier for the novice to obtain good results with vacuum pouring The procedure for investing a pattern for a single-tooth restoration to be cast in type II or III gold with the vacuum mix, vacuum pour technique is as follows: Place the assembled ring and crucible former into the hole at the top of the Vac-U-Spat investor (Fig 21-5). Hold the lid by the spindle with the paddle toward you and the inlay ring to the bottom. Look into the aperture through which the investment will flow into the ring, and make sure that the internal portion of the wax pattern is visible. Connect one end of the clear plastic vacuum tubing to the vacuum outlet on the Vac-U-Vestor. Insert the metal connector on the other end of the tubing into the hole in the lid of the Vac-U-Spat (Fig 21-6). Turn on the Vac-UVestor briefly. If the gauge shows a vacuum when the lid has not been set on the bowl, the tube is blocked. Turn off the machine and clear the tubing before proceeding. The lumen in the metal nozzle at the end of the tubing and the gauze filter just beyond the nozzle are the most common sites of blockage. Pour the recommended amount of room-temperature water into the bowl This must be carefully measured. T Gypsum-Bonded Investments Fig 21-5 The ring is seated on the crucibl placed in the Vac-U-Spat lid (B). then is Fig 21-6 Tubing is connected for investing. since the water-powder ratio has a critical effect on expansion (more water results in less expansion). Add a package of investment to the water and mix it with a hand-held spatula until all of the investment has become wet (Fig 21-7). Place the lid on the bowl and make sure it is firmly sealed. Turn on the Vac-U-Vestor and insert the spindle of ihe lid of the Vac-U-Spat into the smaller of the two drive chucks on the bottom of the unit (Fig 21-8). The gauge should register a vacuum. If it does not, there is probably leakage between the bowl and lid or between the lid and hose. Power-spatulate for 15 seconds. Since the length of spatulation can affect expansion of the investment, measure the time of spatulation precisely. Overspatulation will increase thermal expansion.35 Do not introduce another variable into the technique- Remove the spindle from the drive chuck. Do not turn off the Vac-U-Vestor, and do not disconnect the vacuum at this point. Place the drive nut of the Vac-U-Spat spindle on the vibrator knob. Make sure that the shaft is horizontal and the casting ring is in the lowest position on the circumference of the lid. Hold the Vac-U-Spat in this posiInvesting and Casting Fig 21-9 Starting tion for a few seconds until the investment has run to the lower side of the bowl (Fig 21-9). Slowly invert the Vac-U-Spat until the shaft points straight down, keeping the drive nut in contact with the vibrator (Fig 21-10). It should take slightly less than 30 seconds to traverse the 90-degree arc from the horizontal to the vertical position. Remove the drive nut from the vibrator knob, keeping the Vac-U-Spat inverted. While it is still in this position, turn off the vacuum pump and disconnect the vacuum hose (Fig 21-11). Then remove the casting ring and crucible former from the Vac-U-Spat lid. Place the crucible former on the vibrator knob for a few seconds to settle any investment that might have spilled during separation of the ring from the lid. Do not overvibrate; this may cause air to slip around the seal between the ring and the crucible former, rising up and lodging on the underside of the pattern. If a high-temperature (1.200°F, 650°C) burnout technique will be used, place the casting ring and crucible Gypsum-Banded Investments former into a humidor (a covered plastic container or sealed plastic bag with wet paper towels in the bottom) and let set at room temperature. If a low-temperature (900°F, 480°C) burnout technique is to be used, immediately immerse the ring in a 100°F (38CC) water bath to produce expansion of the wax pattern Allow the investment to set for a minimum of 30 minutes. Leave the ring in the humidor until you are ready for burnout and casting. To prevent clogging the drains with accumulated investment, empty the unused portion of investment remaining in the Vac-U-Spat bowl into the investment envelope (Fig 21-12). Fold over the top of the package so the waste can be disposed of neatly. Use a brush and running water to clean the bowl, lid, and paddle before the investment hardens on them. Casting Armamentarium for Types II and III Gold Alloys 1. Casting ring with invested wax pattern 2. Furnace 3. Centrifugal casting machine with crucible 4. Gas-air blowpipe 5. Matches 6. Casting alloy 7. Casting flux 8. Casting tongs 9. Toothbrush 10. Explorer 1. Jel-Pac 2. Porcelain casserole dish 3. Plastic-coated forceps 4. Bunsen burner Burnout Burnout prepares the mold for the molten alloy and allows thermsl expansion to occur. If thermal expansion alone is to provide the compensation expansion, a hightemperature technique (1,200°F, 650°C) is employed. If a 100° water bath (hygroscopic technique) was used to expand the wax pattern, a lower temperature (900°F, 480°C) can be utilized. Heating must be gradual to allow steam to escape without cracking the mold. Carefully separate the crucible former from the ring. Check the crater and bottom of the ring for any small chips of investment, and remove any that are found, for they could contaminate the casting later. Place the casting ring, with the crater down, into a 600°F <315°C) oven and leave it for 30 minutes. By burning out in an inverted position, much of the wax will run out of the mold as it is melted, carrying any loose chips of investment with it. With casting tongs, transfer the ring to a hotter furnace (either 900°F [482°C] or 1,200°F [650°C] depending on the technique used) for 1 hour. As an alternative, the ring can be placed in a cold oven and heated slowly to the casting temperature. The ring should be set crater up about 10 minutes before the casting is made. This allows oxygen to contact the internal area of the mold to insure complete wax residue elimination A black appearance of the investment surrounding the sprue hole is an indication that there are still carbon particles from the wax permeating the investment. These can impede the escape of gases through the investment as the casting alloy enters the mold and prevent the margins from being completely cast. A bright, clean appearance of the casting is the result of the reducing action of residual carbon and may indicate that it was cast too soon. Casting for Types II and III Gold Alloys No more than 30 seconds should be allowed to elapse between the time the ring is removed from the oven and the molten alloy is centrifuged into the mold. Any undue delay will cause heat loss and resultant mold contraction. Therefore, it is imperative that all materials and equipment used in casting be ready ahead of time. It is also helpful to enlist an assistant to transfer the hot ring from oven to cradle until more experience is gained. Place the crucible in its bracket on the arm of the casting machine (Fig 21-13). Do not melt gold in a crucible that has been used with a base metal alloy. Grasping the counterweight of the casting machine in the right hand, wind it clockwise three times. Raise the pin from the base of the machine in front of the crucible assembly. Slowly release the right hand until the pin rests against the arm, preventing it from unwinding. Place the casting alloy in the crucible, Enough bulk of metal must be used in casting to fill the mold, the sprue, and part of the crucible former to insure sharp, complete detail in the casting. Four pennyweights (dwt) of gold will usually suffice for most premolar restorations, while six are needed for molar castings. Buttons from previous castings can be reused provided they are well cleaned. Traces of sulfur from investment materials left on used buttons will reduce the alloy's ductility and increase pitting."6 Light the gas-air blowpipe and adjust the red gas and green air knobs to produce a conical flame (Fig 21-14, A). The first cone, the mixing zone, is a cool, colorless one. Around this area is a greenish-blue combustion zone in which partial combustion takes place; this is an oxidizing zone (Fig 21-14, B). Next is a dim blue tip, the reducing zone. This is the hottest area in the flame and is the only part of the flame used to heat the casting alloy. Beyond this is another oxidizing zone in which final combustion between the gas and surrounding air occurs. Neither of the oxidizing zones should be used for heating. They are not as hot as the reducing zone, and if the alloy comes in contact with them, copper and other nonnoble metals will be oxidized, changing the properties of the alloy. This can result in reduced strength and altered solidification shrinkage. The oxides also may become M| Investing and Casting A g ^ ^ A,t (Green) Gas (Rpdi ^ ~ " - Ret Oxidizing ucing zon " I ^ B Fig 21-14 The gas-air blowpipe </ of the (lame used tor melting gold (6). incorporated in the casting as impurities. Practice locating the reducing zone by directing the flame against the crucible to form a glowing hot area. Slowly move the flame closer. When it is too close, a central dark spot will be formed by the cooler combustion zone. Withdraw the torch until the dark spot just disappears. This is the ideal distance the torch should be from the gold. A small amount of flux should be sprinkled onto the warmed metal (Fig 21-15). Borax, used by itself as a flux, will help to exclude oxygen from the surface of the alloy and dissolve any oxides that are formed. Reducing flux, which contains carbon in addition to borax, will also reduce back to clean metal any oxides that happen to form. This helps to maintain the original composition of the alloy." Continue heating the gold until it balls up. As it approaches the casting temperature, the gold will become straw yellow in color. It will wiggle easily in the crucible when it is tapped and will follow the flame if it is moved slightly. If the reducing zone has been used properly, the molten gold will appear mirror-like and shiny. Keeping the flame on the gold, remove the casting ring from the oven with casting tongs and carefully place the Gypsum-Bonded In ring in the cradle (Fig 21-16). Gently slide the platform on which the crucible rests against the ring and cradle. Make sure it fits snugly so that the ring will not roll when the arm is released. Hold the blowpipe in one hand and apply gentle clockwise pressure on the counterweight with the other hand until the pin drops (Fig 21-17). Jiggle the weight slightly to see that the gold moves freely. Release the weight, allowing the machine to spin. To insure maximum fluidity of the gold, do not lift the torch out of position until ihe arm of the casting machine has been released. Allow the centrifuge to slow to a stop by itself. Cleaning the Casting After the gold button has lost its glow, remove the casting ring with the tongs and thrust it into a pan of cold water For a casting of Firmilay in a small ring, this quenching should occur about 5 minutes after casting to achieve the best grain structure. If it is quenched while it is too hot, the gold will be softer and weaker. If it is allowed to bench cool completely, the grain structure will be too large.48 An additional benefit of quenching is the disintegration of the hot investment when it contacts the cold water. Remove the ring from the water and push the investment and casting out of the ring, if they have not already fallen out Break off as much of the investment as possible by hand or with an old instrument and then scrub the casting and button with a stiff brush. The casting should appear smooth, with a dull, dark oxide layer. Remove the oxide layer and any remaining particles of investment by lightly sandblasting all surfaces with a 50-[im abrasive, taking care not to abrade thin margins (Fig 21-18) A process called pickling also has been widely used prepared for release. for cleaning gold castings. This involves soaking the casting in a hot acid solution for several minutes Jel Pak fJF Jelenko, Armonk, NY) is a much safer and less corrosive pickling agent than the formerly used sulfuric or hydrochloric acid. Still, contact with the skin and inhalation of vapors must be avoided. A porcelain casserole dish is used to contain the pickling solution, and plasticcovered pliers are used to introduce and remove the casting from the solution (Fig 21-19). Metal instruments must not come into contact with gold in strong solution, as electrodeposition may occur on the surface of the casting. Only gold castings may be cleaned by pickling. Because of the health and environmental hazards associated with pickling solutions, air abrasion with small-particle-size abrasives is the preferable means of cleaning castings Investing and Casting 1 Fig 21-19 Casting is placed in a porcelain casserole dish for pickling. The casting should be examined closely for casting defects. Figure 21-20 shows some common problems and their causes. A mistake is a failure only if we fail to learn from it. Investment of Inlay and Dowel-Core Patterns Less mold expansion is required for dowel cores and inlays than for crowns. If the casting is the least bit larger than the pattern, it will not fit into the tooth. Omitting the ring liner or increasing the investment water-powder ratio by 1.0 ml_ will result in a slightly undersized casting that will fit more easily into the cavity prepared in the tooth. The following technique is recommended for investing and casting a dowel-core pattern in a silver-palladium alloy (Albacast, JF Jelenko, Armonk, NY): Invest the pattern in Beautycast (Whip Mix Corp, Louisville, KY) using the standard water-powder ratio, without a ring liner. Burn out at 1,200°F (650°C). Because the casting temperature of Albacast is 2,150°F (1,177°C), a gas-oxygen torch or electric induction casting machine must be used to melt trie alloy. It is possible for an experienced operator to cast and cement gold inlays and dowel cores on the same day that the teeth are prepared by using the following accelerated technique for investment and burnout: Gypsum-Bonded Investments |3s i Multiple random nodules- Inadequate vacuum during IT Short, rounded margins with rounded or lumpy button— Alloy not hot enough or insufficient casting force Shrink Spue Sprue Buttor ;-spot porosity— attachment tuo bu 1 too small. Iky Random porosity- Dirt in wax pattern. Loose particles o( in from sharp edges (a vestment \rrow). Dropped ring, rapid heating of wet or unhardened mold, liner flush > excessive with end of ring, casting force.1 Short, rounded margins with sharp button— Pattern too far from end of ring or, if casting is shiny, incomplete burnout of wax. 1. Invest the pattern in a phosphate-bonded investment (Ceramigold, Whip Mix Corp, Louisville, KY) using a ring liner and standard special liquid dilution of 50/50. 2. Allow the investment to harden for 12 to 15 minutes. It should feel firm and warm. 3. Place the invested pattern directly into a 1,300°F (705°C) oven and allow 12 to 15 minutes for burnout. 4. Cast in gold alloy (type II or III for inlays, type III or IV for dowel cores). In this way, investment, burnout, and casting can be completed in 1 hour, saving the patient an additional appointment."9 Phosphate-Bonded Investments Phosphate-bonded investments are much stronger and withstand much higher temperatures than do gypsumbonded investments. They are used for investing and casting alloys with higher melting temperatures, eg, silver- palladium, gold-platinum, and nickel-chromium. To obtain sufficient expansion for crowns of these alloys, the mold must be heated to 1,400°F (760"C) or higher, temperatures that would cause decomposition of the calcium sulfate in a gypsum binder with the resultant release of contaminating sulfur into the mold.» In general, any alloy with a casting temperature in excess of 2,100°F (1,150°C), as differentiated from the fusion temperature, which is 100 to 150T lower, should be cast into an investment with a binder other than gypsum. (Because dowel cores do not require as much expansion of the mold as do crowns, they can be cast with a Ag-Pd alloy into a gypsum-bonded mold heated to only 1,200°F [650°C], as described earlier.) The powder contains phosphates of magnesium and ammonium, graphite (carbon), and large silica particles, while the special liquid provided with these investments contains an aqueous suspension of colloidal silica. Carbon-free phosphate investments (Hi-Temp, Whip Mix Corp, Louisville, KY) are available for use with base alloys that are made brittle in the presence of carbon. Magnesium phosphate reacts with primary ammonium phosphate to produce magnesium ammonium phosphate, which gives the investment its strength at room temperature 51 At higher temperatures, silicophosphates are formed; they give the investment its great strength. Expansion can be varied by the proportions of silica sol and water: . More silica sol and less . Less silica sol and more ater = more expansion. ater = le expa The usual proportion is three parts silica sol liquid to one part distilled water. The overall liquid-powder ratio for Ceramigold investment should remain constant: 9.5 cc liquid to 60 g of powder Investing Armamentarium for Phosphate-Bonded Investments 1. 200-cc Vac-U-Spat bowl and lid 2. Vacuum tubing 3. Vac-U-Vestor 4. Rubber crucible former 5. Casting ring 6. Plastic water measure 7. Spatula 8. PKT (Thomas) waxing instruments (no 1 and no 9. Cotton pliers 10. Bunsen burner and matches 11. Sticky wax 12. Sprue formers (hollow plastic or wax) 13. One package (60 g) of Ceramigold investment 14. Special liquid 15 Strip of liner 9.5 cm long 16. Small camel's hair brush Investing With Phosphate-Bonded Materials Attach a 10-gauge (2.6 mm) plastic sprue former to the tip of the incisal portion of a single crown wax pattern with sticky wax, using a PKT no. 1 instrument to melt and blend the junction. If there is a broad expanse of paperthin wax between the sprue and the margin, bridge it with a narrow (0.5 mm thick) strip of wax (Fig 21-21 ) that will serve as an internal sprue. This will provide a channel through which the molten alloy can flow more readily to reproduce the margin. The resulting ridge can be easily trimmed back to the desired thickness after the casting is made. Carefully remove the pattern from the die and grasp the sprue former with cotton pliers. Seat the sprue former into the soft wax in the center of the crucible former (Fig 21-22). The sprue former's length should be adjusted so that the pattern will be 6.0 mm from the end of the ring when it is in place. Build up the crucible former with wax, if necessary, so that no more than 6 0 mm of the sprue former will be exposed. Posterior patterns are sprued on the tip of the cusp with the greatest bulk. An 18-gauge wax sprue former (0.8-mm diameter) should connect the other cusp tip (in the veneering area) with the base of the crucible former (attach to the pattern while it is still on the die). The tip of this cusp should be lower than the point of entry of the main sprue (Fig 21-23). Adapt a layer of dry cellulose liner to the inside of the ring. Immerse the ring briefly in a bowl of water to moisten the liner. Assemble the ring, crucible former, and Vac- U-Spat lid. Place 9.5 cc of the liquid in the Vac-U- Spat bowl and add the contents of a 60-g package of Ceramigold investment. Connect the vacuum tubing and mechanically spatulate under a vacuum for approximately 15 seconds. Disconnect the vacuum and remove the Phosphate-Bonded Investments Sgi mproved by the addition of ai This type of investment possesses poor surface-wetting characteristics. Because of this, the problem of trapping bubbles during investing is even greater than with gypsum investments. Either vacuum or open investing can be used. Allowing the investment to set in a pressure pot will further reduce the size and number of bubbles." If there are small, restricted areas in the interior of a wax pattern (eg, long, thin crowns on incisors), gently brush the investment into the pattern with a small brush (Fig 21 - 24). Then place the ring over the crucible former and slowly pour the investment down one side of the ring with vibration. You should see a small stream of investment flow over the margin on one side of the pattern, down into the deepest recess, and gradually fill the pattern from the bottom up. Once the pattern is covered, the ring can be filled the rest of the way with a minimum of vibration. There should be an excess of investment above the end of the ring so the hardened glaze can be easily ground away on a model trimmer. If it is needed, an additional 0.7% expansion can be obtained by placing the investment-filled ring into a 100°F (38°C) water bath before it has hardened. 51 If this is done, the surface of the investment should be protected from the softening effect of water by a thin sheet of rubber or plastic wrap held in place by a rubber band. Wax patterns for metal-ceramic fixed partial dentures are invested and cast as one unit whenever possible because of the difficulty encountered in soldering the alloys used for this type of restoration. In these situations, the wax pattern should be fabricated on a one-piece die on which the dies of the individual abutment preparations have not been separated The wax pattern for a fixed partial denture should be invested in a large ring (round Fig 21-24 It may be necessary to paint phosphate-bonded inve merit into the wax pattern with a small brush. or oval, with a diameter of approximately 6.3 cm) to produce the most accurate casting.52 For lower-fusing gold alloy castings, sprue formers run directly from crucible former to wax pattern to provide rapid, turbulence-free access of the metal to the mold during casting. Patterns for metal-ceramic fixed partial dentures, however, must be sprued by an indirect method because the alloys used fuse and solidify at much higher temperatures.53 Because the ambient air is much colder than the molten metal, the exposed button is likely to solidify while the metal at the center of the ring is still liquid. This means that the button cannot serve as a reservoir to prevent shrink-spot porosity. Instead, a Investing and Castint A 10 gauge Fig 21-25 Pattern for a metal-ceramic fixed partial dent sprued indirectly. The feeder sprues and the horizontal runn 8 gauge, and the manifold sprues are 10 gauge. Fig 21-26 Molten alloy swirls through the manifold system, raisil the temperature of the surrounding investment (shaded area). Fig 21-27 As the alloy begins to solidify, the h ifold (dark shading] keeps it molten longer, pr the bridge. Fig 21 -28 Relationship of the dots o bulky horizontal runner bar is placed between crucible former and pattern. Place a piece of 8-gauge (3.4-mm diameter) hollow plastic sprue former material horizontally into the sprue former network to form a manifold between the crucible former and the wax pattern (Fig 21-25). Be sure to plug both ends of the hollow sprue former with wax to avoid the formation of thin projections of investment that might break off in the mold. As the alloy makes its way through the feeder sprues, runner, and manifold sprues, the temperature of the surrounding investment is elevated (Fig 21-26). The metal farthest from the manifold—the margins, and the surface of the button exposed to ambient room temperature—will cool lirst while the feeder bar is still fluid and can serve as a reservoir for solidification contraction in the fixed partial denture (Fig 21-27). The runner bar also helps to stabilize the pattern against distortion during investing, and it equalizes the flow of metal so that all parts of the mold will be filled evenly and simultaneously during casting.5'1 Orientation of invested fixed partial dentures in the casting machine can affect the flow of metal into the mold. The pattern is placed in a vertical position on the horizontal centrifugal casting machine to insure that all parts of the mold will fill simultaneously. To facilitate proper orientation, a wax dot can be placed on the crucible Phosphate-Bonded ln\ former. This will leave an imprint on the surface of the investment which can be seen when the ring is placed in the casting machine (see Fig 21-25). As an alternative, two dots can be scribed on the outside of the ring, one directly opposite the other (Fig 21-28). These dots should be aligned with the axis of the pattern before investing x pattern with quartz crucible Casting Armamentarium for Gold-Palladium Alloys 1. Casting ring with inv 2. Furnace 3. Centrifugal casting m 4. Colored safety glass 5. Gas-oxygen torch 6. Matches 7. Metal-ceramic alloy 8. Casting tongs 9. Laboratory knife 10. Toothbrush 11. Explorer Casting Gold-Palladium Alloys Special gold-palladium alloys are used for metal-ceramic restorations and where greater strength than that provided by type II! gold is required. After the investment has set for 1 hour on the benchtop, grind or scrape away some of the excess investment beyond the end of the ring. This will remove the smooth, dense surface layer and allow gases to escape more readily from the mold during casting. Remove the crucible former and place the ring in a 600°F (315°C) oven. After 30 minutes in the low-heat oven, place the ring in a 1,300°F (704°C) oven for 1 hour. If the ring is left at this temperature any longer, the investment will start to break down. Because of the higher melting temperature of the metal-ceramic alloy, the gas-air blowpipe is inadequate. A single-orifice, gas-oxygen torch should be used. To prevent accidents, exercise caution in the use of this torch. Oxygen always should be added to a gas flame, and the gas flame always should remain on until the oxygen has been turned off. If the gas is turned off first, there will be a small explosion inside the torch when the gasoxygen ratio reaches a critical level. To start the torch1 1. Turn on gas and ignite 2. Slowly add oxygen. To turn off the torch: 1. Turn off the oxygen. 2. Turn off the gas. A quartz crucible is preferred to a clay crucible. Use no flux with metal-ceramic alloys; it may upset the balance of the alloy and interfere with bonding later. Turn on Fig 21-29 Correct positioning of the ring ir wrth one dot facing upward. the torch and adjust the flame to make the inner cone 0.25 to 0.5 inch (6.0 to 12 mm) long. Wear light blue or other colored protective goggles to protect your eyes from the intense light. Preheat the crucible with the torch and then place the alloy in the crucible. Heat the alloy until it liquefies. It will go through four 2. Orange 3. White (dull) 4. White (mirror-like) When the gold is orange, transfer the ring from the furnace to the cradle of the casting machine. In casting a fixed partial denture, make sure that one of the dots on the ring is in an up position, indicating that the mold of the framework is vertical (Fig 21-29). Keep heating the gold. As it becomes white, a light fog or scum forms on the surface. As soon as that scum disappears and the metal is shiny, release the machine and cast. Bench cool the ring to room temperature. Metalceramic alloys should not be quenched. When it has cooled, remove the casting and pick off the remnants of the investment. Then wash the casting in water and lightly sandblast it. Do not pickle metal-ceramic alloys. Casting Base Metal Alloys These high-fusing alloys experience a high degree of shrinkage on cooling. To achieve the necessary mold expansion, the invested pattern should be placed in a water bath at 100°F (38°C) for 1 hour. Best results are obtained if the investment is allowed to cure overnight before proceeding with burnout. Place the ring in a cold oven and bring it up to 1,500°F (815°C) in approximately 1 hour. Allow it to heat soak at this temperature for approximately 2 hours to eliminate all traces of carbon. The recommended temperature may vary slightly for different alloys. Preheat the quartz crucible in the oven. Wind the casting machine, giving it one or two extra winds to compensate for the much lighter density of the base metal alloy. Remove the quartz crucible from the oven with casting tongs and place it in the bracket on the casting machine. Place the metal ingots in the crucible. Wear dark protective goggles for casting. As with goldpalladium alloys, a gas-oxygen torch must be used, but the higher casting temperatures of the base metal alloys require the use of a multiorifice tip. Turn on the gas first, adding oxygen to the gas flame. Adjust the flame to make the inner cones approximately 0.5 inch (12 mm) long. Heat the alloy evenly by moving the torch around to cover all ingots. They will not liquefy. The ingots, glowing a uniform color, will slump, and their edges will round over, but tough oxide skins will prevent them from coalescing. Technicians who are used to melting alloys that form into a shiny pool may overheat the base metal alloys. This common error can burn off lower melting constituents and create bonding problems when the porcelain is later applied.M If the alloy is overheated or "burned," throw it out. Cast immediately to avoid overheating. Bench cool the ring to room temperature. Remove the casting and pick off the remnants of investment. Clean the metal with an air abrasion unit using 50-u.m alumina. Do not pickle base metal castings. References 1. Hollenback GM. Science and Technic of the Cast Restoration. St Louis, CV Mosby Co, 1964, p 21. I Taggart WH: A new and accurate method of making gold inlays. Dent Cosmos 1907; 49:1117-1121. 3. O'Brien WJ: Evolution of dental casting. In Valega TM (eel): Alternatives to Gold Alloys in Dentistry. DHEW Publ No. (NIH) 77-1227. Washington DC, US Department of Health, Education and Welfare, 1977, pp 2-9. %. Dental Technology Reference for Fixed Restorations, ed 7. 1983. Armonk, NY, JF Jelenko & Co, 1983, p VII—2. 3. Duncanson MG: Nonprecious metal alloys for fixed restorative dentistry. Dent Clin North Am 1976; 20:423-433. 3. Current Dental Terminology, ed 1. Chicago, American Dental Association, 1991. 7. Council on Dental Materials, Instruments and Equipment: Status report on low-gold-content alloys for fixed prostheses. J Am Dent Assoc 1980; 100:237-240. i. Gouriey JM: Current status of semi-precious and conventional gold alloys in restorative dentistry. J Can Dent Assoc 1975, 41: 453-455. i. Kuschner ML: The carcinogenicity of beryllium. Environ Health PerepeeM981; 40:101-105. 3. Moffa JP, Guckes AD, Okawa MT, Lilly GT: An evaluation of nonprecious alloys for use with porcelain veneers. Part II. Industrial safety and biocompatibiiity J Prosthet Dent 1973; 30:432-441. 1. Covington JS, McBride MA, Slagle WF, Disney AL: metal casting alloys. J Pmsthet Dent 1985; 54:127-136. 2. Tai Y, De Long R, Goodkind RJ, Douglas WH: Leaching of nickel, chromium, and beryllium ions from base metal alloy in an artificial oral environment J Prosthet Dent 1992; 68:692-697. 3. Fisher AA; Contact Dermatitis, ed 3 Philadelphia, Lea and Febiger, 1986, p 745. X Peltonen L: Nickel sensitivity in the general population. Contact Dermatitis 1979; 5:27-32. >. Mjor IA, Christensen GJ: Assessment of local side effects ot casting alloys. Quintessence Int 1993; 24:343-351. >. Wirz J: Was ist dran am Palladium-streit? 1st das Material besser als sem Ruf? [What is the controversy about palladium— Is it better than its reputation?] Phillip J 1993- 9:407-408. '. Moffa JP. Physical and mechanical properties of gold and base metal alloys. In Valega TM fed): Alternatives to Gold Alloys in Dentistry. DHEW Publ No. (NIH) 77-1227 Washington DC, US Department of Health, Education and Welfare, 1977, pp 81-93. !. Jendersen MD: Non-precious metals and the ceramo-metal restoration. J Indiana Dent Assoc 1975; 54:6-10. ). Preston JD, Berger R: Some laboratory variables affecting ceramo-metal alloys. Dent Clin North Am 1977; 21.717-728. I. Lorey RE, Edge MJ, Lang BR, Lorey HS1 The potential for bonding titanium restorations. J Prosthod 1993; 2:151-155. . Akagi K, Okamoto Y, Matsuura T, Horibe T Properties of test metal ceramic titanium alloys. J Prosthet Dent 1992; 68:462-167. >. Rekow ED: Dental CAD-CAM systems—What is the state of the art? J Am Dent Assoc 1991; 122:42-48. 1. Revised American National Standard/American Dental Association Specification No. 5 for Dental Casting Alloys. New York, American National Standards Institute, 1988. k Hollenback GM, Skinner EW: Shrinkage during casting of gold and gold alloys. J Am Dent Assoc 1946; 33: J91-1 )99. >. Phillips RW. Skinner's Science ot Dental Materials, ed 9. Philadelphia, WB Saunders Co, 1991, pp 393-412. i. Scheu O+ A new precision casting technic. J Am Dent Assoc 1932; 19630-633. '. Mahler DB, Ady AB: An explanation for the hygroscopic expansion of dental gypsum products. J Dent Res 1960; 39:578-589. i. Hollenback GM: Simple technic for accurate castings: New and original method of vacuum investing. J Am Dent Assoc 1948, 36:391-397 i Asgar K, Mahler DB, Peyton FA: Hygroscopic technic for inlay casting using controlled water additions. J Prosthet Dent 1955; 5:711-724 Phosphate-Bonded Inv ) Mahler DB, Ady AB: The effect of the water bath in hygroscopic casting techniques J Prosthet Dent 1965; 15:1115-1121. . Craig RG: Restorative Dental Materials, ed 8. St Louis. CV MosbyCo, 1989, p 360. I. Davis DR, Nguyen JH, Grey BL: Ring volume/ring liner ratio and effective setting expansion in! J Prosthodont 1992' 5:403-408. !. Verrett RG. Duke ES: The effect of sprue attachment design on castability and porosity. J Prosthet Dent 1989; 61:418-424. I. Mumford GM, Phillips RW: Measurement of thermal expansion of cristobalite type investments in the inlay ring— Preliminary report. J Prosthet Dent 1958; 8:860-864. i. Mahler DB, Ady AB' The influence of various factors on the Prosthet Dent-\963\ 13:365-373. i. Priest G, Homer JA: Fibrous ceramic aluminum silicate as ,. J Prosthet Dent 1980: • ring lining i. Naylor WP, Moore BK, Phillips RW: A topographical assessmicroscopy. Quint Dent Technol1987, 11.413-420. I. Earnshaw R, Morey EF: The fit of gold-alloy full-crown castings made with ceramic casting ring liners. J Dent Res 1992; 71:1865-1870. i. Morey EF, Earnshaw R: The fit of gold-alloy full-crown castings made with pre-wetted casting ring liners. J Dent Res 1992; 71:1858-1864. . Craig RG: Restorative Dental Materials, ed 8 St Louis' CV MosbyCo, 1989, p 465. !. Earnshaw R: The effect of casting ring liners on the potential expansion of a gypsum-bonded investment. J Dent Res 1988:67:1366-1370. !. Johnson A: The effect of five investing techniques on air bubbie entrapment and casting nodules. Int J Prosthodont 1992; 5:424-433. I. Lyon HW, Dickson G, Schoonover IC: Effectiveness of vacuum investing in the elimination of surface defects in gold castings. J Am Dent Assoc 1953; 46:197-198. i. Phillips RW: Relative merits of vacuum investing of small castings as compared to conventional methods. J Dent Ras 1947; 26:343-352. r. NeyBridge and Inlay Book. Hartford, CT, JM Ney Co, 1955, p67. !. Du Bois LM, Ritnour KL, Weins WN, Rinne VW. The effect of the temperature at quenching on the mechanical properties of casting alloys. J Prosthet Dent 1987; 57:566-571. i. Campagni WV, Majchrowicz M: An accelerated technique for casting post and core restorations. J Prosthet Dent 1991; 66:155-156. ). O'Brien WJ, Nielson JP: Decomposition of gypsum investments in the presence of carbon. J Dent Res 1959; 38 541-
برچسب ها: those done in molds made by vacuum investing were free of bubbles.44 Experienced technicians probably can obtain smooth castings with either vacuum pouring or open pouring.46 Although the open pour technique is more popular with experienced technicians because of the unimpeded view of the pattern as it is covered with investment، it is easier for the novice to obtain good results with vacuum pouring The procedure for investing a pattern for a single-tooth restoration to be cast in type II or III gold with the vacuum mix، vacuum pour technique is as follows: Place the assembled ring and crucible former into the hole at the top of the Vac-U-Spat investor (Fig 21-5). Hold the lid by the spindle with the paddle toward you and the inlay ring to the bottom. Look into the aperture through which the investment will flow into the ring، and make sure that the internal portion of the wax pattern is visible. Connect one end of the clear plastic vacuum tubing to the vacuum outlet on the Vac-U-Vestor. Insert the metal connector on the other end of the tubing into the hole in the lid of the Vac-U-Spat (Fig 21-6). Turn on the Vac-UVestor briefly. If the gauge shows a vacuum when the lid has not been set on the bowl، the tube is blocked. Turn off the machine and clear the tubing before proceeding. The lumen in the metal nozzle at the end of the tubing and the gauze filter just beyond the nozzle are the most common sites of blockage. Pour the recommended amount of room-temperature water into the bowl This must be carefully measured. T Gypsum-Bonded Investments Fig 21-5 The ring is seated on the crucibl placed in the Vac-U-Spat lid (B). then is Fig 21-6 Tubing is connected for investing. since the water-powder ratio has a critical effect on expansion (more water results in less expansion). Add a package of investment to the water and mix it with a hand-held spatula until all of the investment has become wet (Fig 21-7). Place the lid on the bowl and make sure it is firmly sealed. Turn on the Vac-U-Vestor and insert the spindle of ihe lid of the Vac-U-Spat into the smaller of the two drive chucks on the bottom of the unit (Fig 21-8). The gauge should register a vacuum. If it does not، there is probably leakage between the bowl and lid or between the lid and hose. Power-spatulate for 15 seconds. Since the length of spatulation can affect expansion of the investment، measure the time of spatulation precisely. Overspatulation will increase thermal expansion.35 Do not introduce another variable into the technique- Remove the spindle from the drive chuck. Do not turn off the Vac-U-Vestor،  

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