FPROSD 211 (2) PDF - Fixed Prosthodontics

Fixed prosthodontics Crown & bridge department Faculty of dentistry, MTI university FPROSD 211 Course director DR. ESRAA ODEH  ‫‪Page |2‬‬...

Fixed prosthodontics Crown & bridge department Faculty of dentistry, MTI university FPROSD 211 Course director DR. ESRAA ODEH  ‫‪Page |2‬‬ ‫الرؤية‪:‬‬ ‫الرؤية‬ ‫تسعى الجامعة الحديثة للتكنولوجيا والمعلومات ان تكون احدى الجامعات الخاصة المتميزة‬ ‫والمؤثرة على المستوى المحلى وااللليمى‬ ‫الرسالة‬ ‫تعمل الجامعة الحديثة للتكنولوجيا والمعلومات على االرتماء بالمستوى العلمى والجودة للخريج من‬ ‫خالل تمديم برامج تعليمية متطورة من اجل تلبية احتياجات سوق العمل الحالى والمستمبلى وتمديم‬ ‫خدمات للمجتمع واستشارات وابحاث اكاديمية وتطبيمية متميزة ومن خالل شراكة مع جامعات‬ ‫محلية واجنبية‪.‬‬ ‫رؤية و رسالة الكلية‬ ‫الرؤية‬ ‫تتطلع كلية طب الفم و األسنان – الجامعة الحديثة للتكنولوجيا و المعلومات إلى أن تكون من‬ ‫أكثر الكليات تميزا على المستوى المحلي و اإللليمي في مجال طب األسنان‬ ‫الرسالة‬ ‫تلتزم الكلية بإعداد أطباء أسنان يتميزون بالجدارة المهنية لادرين على التوافك مع متطلبات‬ ‫سوق العمل و مواكبة التطور العلمي و اإلسهام فيه باألنشطة البحثية مع تلبية إحتياجات‬ ‫المجتمع في إطار ليم أخاللية‬  Page |3 Vision The College of Oral and Dental Medicine - Modern University for Technology and Information aspires to be one of the most distinguished colleges at the local and regional levels in the field of dentistry. Mission The college is committed to prepare dentists who are distinguished by professional merit, able to comply with the requirements of the labor market and keep pace with scientific development and contribute to it through research activities while meeting the needs of the surrounding community within the framework of ethical values.  ‫‪Page |4‬‬ ‫ز ز‬ ‫متمية ف تعليم طب األسنان‬ ‫الغاية األوىل‪ :‬تحقيق قدرة تنافسية‬ ‫الهدف األول‪:‬‬ ‫إستاتيجيات التدريس والتعلم بما يتفق مع اتجاه الدولة المرصية لتطوير التعليم الجامع‪.‬‬‫تطوير ر‬ ‫ز‬ ‫الثان‪:‬‬ ‫ي‬ ‫الهدف‬ ‫للتنامج ونظم التقويم والكتاب الجامع واألنشطة الطلبية لتنمية مهارات طلب‬‫تطوير المحتوى العلم ر‬ ‫متغتات سوق العمل‪.‬‬‫وخريج الكلية بما يتفق مع ر‬ ‫ر‬ ‫الهدف الثالث‪:‬‬ ‫استيفاء أعداد أعضاء هيئة التدريس والهيئة المعاونة بما يتناسب مع أعداد الطلب‪.‬‬ ‫الهدف الرابع‪:‬‬ ‫استخدام تكنولوجيا المعلومات وأساليب التعلم الحديثة‪.‬‬ ‫ز‬ ‫ز‬ ‫الغاية الثانية ‪:‬‬ ‫العلم‬ ‫ي‬ ‫التمي واإلبداع يف مجال البحث‬ ‫الهدف األول‪:‬‬ ‫تلب حاجة المجتمع‬ ‫تحفت منظومة البحث العلم بما يدعم تقديم خدمات بحثية ذات تطبيقات علجية ر‬ ‫رز‬ ‫المحل والدول‪.‬‬ ‫ز‬ ‫الثان‪:‬‬ ‫ي‬ ‫الهدف‬ ‫توسيع مجاالت التعاون ر‬ ‫والشاكة البحثية محليا واقليميا وعالميا‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫تطوير البنية البحثية والتكنولوجية للكلية‪.‬‬ ‫الهدف الرابع‪:‬‬ ‫االلتام بأخلقيات البحث العلم وضمان حقوق الملكية الفكرية‬ ‫رز‬ ‫الهدف الخامس‪:‬‬ ‫نش األبحاث العلمية المحلية والدولية والحث عل‬ ‫تشجيع أعضاء هيئة التدريس والهيئة المعاونة عل ر‬ ‫ز‬ ‫المشاركة العلمية ف المؤتمرات‪.‬‬ ‫الهدف السادس‪:‬‬ ‫ز ز‬ ‫الخريجي ف سوق العمل‪.‬‬ ‫ر‬ ‫تلب احتياجات‬ ‫إنشاء برامج تعليمية لمرحلة الدراسات العليا ر‬ ‫ز‬ ‫ز‬ ‫المدن لتقديم خدمات عالجية ف طب األسنان‬ ‫ي‬ ‫الغاية الثالثة ‪ :‬التكامل مع المجتمع‬ ‫الهدف األول‪:‬‬ ‫ز‬ ‫ز‬ ‫المدن المحيط لتلبية احتياجات المجتمع‪.‬‬ ‫التوسع ف التعاون مع مؤسسات المجتمع‬  ‫‪Page |5‬‬ ‫الهدف الثا ز ين‪:‬‬ ‫التوعية التثقيفية المستمرة داخليا وخارجيا لتلبية احتياجات المجتمع المحيط بالرعاية الصحية لألسنان‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫التطوير المستمر للخدمات العلجية بالعيادات الخارجية للكلية‪.‬‬ ‫الهدف الرابع‪:‬‬ ‫رز‬ ‫الخريجي‪.‬‬ ‫دعم برامج التواصل مع‬ ‫ُ ز‬ ‫الغايــة ال ـرابعة‪ :‬التــمي واإلبــداع الـمؤسـ ي‬ ‫ـس‬ ‫الهدف األول‪:‬‬ ‫تطوير البنية التحتية والتكنولوجية للكلية‪.‬‬ ‫ز‬ ‫الثان‪:‬‬ ‫ي‬ ‫الهدف‬ ‫تنمية قدرات القيادات االكاديمية واالدارية الحالية والمستقبلية‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫تنمية قدرات اعضاء هيئة التدريس والهيئة المعاونة والجهاز اإلداري‪.‬‬  Page |6 Strategic goals and objectives The first aim: achieving distinct competitiveness in dental education First goal: Developing teaching and learning strategies in line with the Egyptian state’s direction to develop university education. Second goal: Developing the program’s scientific content, evaluation systems, university book, and student activities to develop the skills of college students and graduates in accordance with labor market variables. Third goal: Fulfilling the numbers of faculty members and supporting staff in proportion to the numbers of students. Fourth goal: Using information technology and modern learning methods. The second aim: excellence and creativity in the field of scientific research First goal: Stimulating the scientific research system to support the provision of research services with therapeutic applications that meet the needs of the local and international community. Second goal: Expanding areas of cooperation and research partnerships locally, regionally and globally. Third goal: Developing the college’s research and technological infrastructure. Fourth goal: Commitment to scientific research ethics and ensuring intellectual property rights. Fifth goal: Encouraging faculty members and supporting staff to publish local and international scientific research and encouraging scientific participation in conferences. sixth goal: Establishing postgraduate educational programs that meet the needs of graduates in the labor market.  Page |7 The third aim: Integration with civil society to provide therapeutic services in dentistry First goal: Expanding cooperation with surrounding civil society institutions to meet community needs. Second goal: Continuous educational awareness, internally and externally, to meet the needs of the community surrounding dental health care Third goal: Supporting alumni communication programs. Fourth goal: Commitment to scientific research ethics and ensuring intellectual property rights.. The fourth aim: Institutional excellence and creativity First goal: Developing the college’s infrastructure and technology. Second goal: Developing the capabilities of current and future academic and administrative leaders. Third goal: Developing the capabilities of faculty members, supporting staff, and the administrative staff.  Page |8 1 Terminology and classification 4 2 Dental instruments 18 3 Principles of tooth preparation 35 4 Finish line 45 5 Complete cast metal crowns 57  Page |9 f C hapter 1 Introduction to Fixed Prosthodontics: Fixed prosthodontics is the art and science of restoring damaged teeth with cast metal, metal-ceramic, or all-ceramic restorations, and of replacing missing teeth with fixed prosthesis. The scope of fixed prosthodontic treatment can range from the restoration of a single to rehabilitation of the entire occlusion. Single teeth can be restored to full function, and improvement in cosmetic effect can be achieved. Missing teeth can be replaced with fixed prostheses that will improve patient comfort and masticatory ability, maintain the health and integrity of the dental arches and in many instances elevate the patient's self-image. Terminology: A Prosthesis: is any artificial replacement of a missing body part. Prosthodontics: Prosthodontics is that discipline of dentistry pertaining to the restoration of oral function, comfort, appearance and health by restoring natural teeth and replacing missing teeth and contiguous oral and maxillofacial tissue with artificial substitutes. Fixed Prosthodontics: Pertains to the restoration or replacement of teeth with artificial substitutes that are attached to natural teeth, roots, or implants and that are not readily removable.  P a g e | 10 Removable Prosthodontics: Pertains to the replacement of missing teeth and contiguous oral structures with artificial substitutes that are readily removable. Fixed prosthodontics A. Crown: is an artificial replacement that restores missing tooth structure by surrounding most or all of the remaining structure with a material such as cast metal, porcelain or a combination materials such as metal and porcelain. It is intended to reproduce both the form and function of the tooth and in some instance, to restore or enhance the appearance.  P a g e | 11 Types of crowns A. Complete Veneer Crowns: Restore all surfaces of the clinical crown. Therestoration material may be all metal e.g. "complete metal cast crown", all porcelain (ceramic) e.g. "porcelain jacket crown". A metal-ceramic combination e.g. "veneered and full veneered crown" or a metal with processed resin e.g. "veneered crown". B. Partial Veneer Crowns: Restore only a portion of the clinical crown. o Three-Quarter Crowns: restore the occlusal surface and three of the four axial surfaces (not including the facial surface). 0 o Reverse Three-Quarter Crowns: Restore all surface except the lingual surface. o Seven-Eighths Crowns: Are extensions of the three-quarter crown to include a major portion of the facial surface, usually the mesio-buccal cusp of maxillary molars.  P a g e | 12 o One-half crown veneers: Restore the occlusal and mesial surfaces, as well as portions of the facial and lingual surfaces. It is a modified form of three-quarter crown. o o MacBoyle retainer: Is a modified three-quarter crown, with its retention derived from grooves at the labio-proximal line angles usually used for mandibular anterior teeth. o Pinledge Retainer: Refers to the modification of an anterior three-quarter crown preparation to obtain primary retention and resistance from long parallel pins in the lingual or palatal surface of the clinical crown.  P a g e | 13 o Laminates: Are veneer restorations that restore the facial surface of a tooth for esthetic purposes. They are fabricated from resin or dental porcelain. They bond to etched enamel with a composite resin luting agent. o Resin-bonded Restorations: Are cast metal partial veneers that are bonded to etched enamel. Resin-bonded restorations are used most often as retainers for a fixed partial dentures (FPD). This type of prosthesis is commonly referred to as a Maryland bridge. o Inlay Retainer: It is a classic intracoronal cast restoration that restores the proximal and occlusal surfaces but does not protect or cover the cusps entirely. o Onlay Retainer: Is a modification of the inlay with cusp overlays on the occlusal surface to protect the integrity of the remaining tooth structure.  P a g e | 14 C. Radicular Retained Restorations: Radicular retained restorations consist of a post or dowel with an attached core that obtains its retention and resistance to displacement from the prepared root portion of an endodontically treated tooth. P a g e | 15  P a g e | 16 D. Temporary Crown: Is a crown made and used temporarily for the protection of the prepared tooth till the crown or bridge is completed and ready for cementation. B. Bridge: It is a fixed dental prosthesis which replaces and restores the function and esthetic of one or more missing natural teeth and can't be removed from the mouth by the patient. It is primarily supported by natural teeth or root. The tooth that gives support to the bridge is called "abutment tooth" COMPONENTS OF BRIDGE 1. Abutment Tooth: Is the natural tooth which supports and retains the bridge at one or both terminals. Pier (Intermediate Abutment tooth) Is an isolated abutment tooth where the anterior and posterior adjacent teeth to it are missing. 2. Retainer (Attachment), (Abutment Piece): Is a restoration rebuilding the prepared tooth and by means of which the pontics are anchored to the abutment teeth. 3. Pontic: (Dummy) is that part of the bridge which acts as the actual substitute for the lost tooth and is suspended between the retainers replacing the lost natural tooth functionally and esthetically. 4. Connector Joint: Is that part of the bridge uniting the pontic (s) with retainer (s) joining the component parts of the bridge. I. Rigid: Soldered, welded or cast type joint. II. Non rigid connector, dovetailed, occlusal rest or sub occlusal rest.  P a g e | 17 TYPES OF BRIDGE I. According to retention. 1. Simple bridges: Is a one single type bridge which may be fixed, or fixed free or Removable or Cantilever or Spring Cantilever Bridge. o Fixed Fixed Bridge: (Fixed Bridge), (Rigid Bridge), (Fixed Rigid Bridge), (Stationary-Fixed Bridge). Is a bridge where the abutment pieces and pontics are all soldered together and the bridge is cemented at both ends to the abutment teeth. o Fixed Supported Bridge:(Fixed-Movable), (Limited Stationary), (Broken Stress Bridge), (Semi- Rigid),(Fixed-Semirigid Bridge). Is a bridge which is not actually joined to one of the terminal abutment teeth but Is connected to it by means of a non-rigid connector allowing some individual movement of the abutment tooth.  P a g e | 18 o Cantilever Bridge:(Swing on Bridge), (Free End Bridge) is a bridge where the pontic is fixed to and derives its support from one or double retainers at one end only while the other end is supported. o Spring Cantilever Bridge: Is a cantilever bridge where the pontic is at the end of slightly resilient curved arm deriving its support from an abutment remote from the edentulous spaces. 2. Compound Bridge: Is a combination of bridges composed of two or more of the simple types.  P a g e | 19 II. According to site 1. Complex Bridge: Is a bridge that extends at one of its terminals beyond the canine. 2. Anterior bidge a. Unilateral Bridge: Is the two or three teeth anterior bridge which does not cross the median line. b. Bilateral Bridge: Is the three or four teeth bridge which involves teeth on both sides of the median line 3. Posterior bridge III. According to material Temporary Bridge: Is a bridge made and used temporarily for the protection of the prepared teeth and maintenance of the space till completion and cementation of the bridge.  P a g e | 20 SUMMARY A. Crown: 1- Full Coverage: Retained mainly by: A. Encircling the Preparation. 1) Metallic: a. One Piece: b. Two Piece: 2) Combined: a. Veneered with acrylic or porcelain b. Full Veneered with acrylic or porcelain. 3) Non-metallic: a. Porcelain Jacket Crown. b. Acrylic Jacket Crown B. Post in the root canal: 1) Retained by: a. Post only. b. Post and collar. 2) Posterior posts: a. Attached. b. Detached. 3) Material: a. All-metallic. b. Combined. c. Retained by both Methods: Post - Jacket Crown.  P a g e | 21 II. Partial coverage: Retained mainly by: 1) Grooves: a. Three Quarter Crown 3/4. b. Half Veneer Crown 1/2. c. Mac Boyle Crown "Retainer" d. Seven eights Crowns 7/8 2) Pins: Pin-Ledge Retainer. 3) Enclasping the preparation: Reverse Retention Retainer. 4) Combined means of retention: Modified types including both grooves and pins. B. Bridge: I. According to retention: A. Simple Bridge:. a. Fixed-Fixed. b. Fixed-Supported c. Cantilever. d. Spring Cantilever. e. Removable. B. Compound Bridge: Employing more than one of the above types. II. According to Material: A. Metallic: a. Precious alloy: Au, Pt. b. Semi-Precious Alloy: Ag, Pd. c. Non-precious Alloy: Cr. Ni. Co. Cu. Ti. Fe.  P a g e | 22 B. Combined: a. metallic with labial or buccal veneers. "Porcelain or acrylic b. Metallic with full porcelain veneer. c. Non Metallic with metal reinforcement or framework. C. Non-Metallic: a. All-Acrylic. b. All-Ceramic. III According to site: a.Anterior a. unilateral b. Bilateral b. Posterior c. complex : anterior and posterior segments involving the canine eminence.  P a g e | 23 c hapter 2 Introduction Dental instruments are classified according to their uses into: a. Diagnostic instruments. b. Cutting instruments. c. Restoring instruments. Cutting instruments are classified into: a. Hand cutting instruments. b. Powered (Rotary) cutting instruments. c. Laser equipment. d. Other equipment. (I) Hand Cutting Instruments This group includes a large number of instruments that are powered and held when used. They are usually of light weight and manufactured from a single piece of either: a) Carbon steel → increases hardness, and decreases corrosion resistance. b) Stainless steel remains bright under most conditions. c) Carbide inserts -to provide more durable cutting edges. d) Other alloys of: - Nickel –Cobalt- chromium P a g e | 24  P a g e | 25 The designs are extremely numerous and their purposes are various. Examples of this group are: 1) Chisels 2) Hatchets 3) Hoes excavators 4) Excavators 5) Angle former 6) gingival margin trimmer 7) Files II) Powered (Rotary) Cutting Equipment The use of abrasive or bladed instruments held in rotary hand piece is usually powered by compressed air. Power source for dental units: 1. Electric motor (driven). 2.Air driven (air or water turbine hand piece) (pneumatic) and either direct or belt driven. Air driven hand pieces continue to be the most popular type of hand piece equipment because of: 1. The overall simplicity of design. 2. Ease of control. 3. Versatility and patient acceptance. Hand piece: A hand piece is a device for holding rotary instruments transmitting power and for positioning them intraorally. According to the shape there are two types: 1) Straight hand piece. 2) Contra angle hand piece  P a g e | 26 Rotary speed ranges: The rotational speed of an instrument is measured in revolutions per minute (rpm).these ranges are generally recognized:  Low or slow speeds below 12,000 rpm.  Medium or intermediate speeds 12,000 to 200.000 rpm.  High or ultrahigh speeds above 200,000 rpm. (a) Low speed cutting is: A. Ineffective B. Requires a relatively heavy force application. C. Time consuming This results in: 1) Heat production at the operating site. 2) Produces vibrations of low frequency and high amplitude. The low speed range is used for: 1) Initial preparation of grooves and pinholes for crown and bridge construction. 2) Cleaning teeth. 3) Occasional caries excavation. 4) Finishing and polishing procedures. (b) High speed: At high speed, the surface speed needed for efficient cutting can be attained with smaller and more versatile cutting instrument.  P a g e | 27 Advantages: 1. This speed is used for tooth preparation and removing old restorations. 2. Diamond and carbide cutting instruments remove tooth structures faster with less 3. The number of rotary cutting instruments needed is reduced because smaller sizes pressure, vibration and heat generation.are more universal in application. 4. Operator has better control and greater ease of operation. 5. Patients are generally less apprehensive because annoying vibration and operating ime decreased. 6. Instrument lasts longer. 7. Several teeth in the same arch can and should be treated at the same appointment. Cutting Tools: These are smaller tools, which are held in hand piece of various types. This variation in the shape is a result of the need for specialized designs for particular clinical applications or to fit particular hand piece. Are divided into two major subdivisions: 1) Dental rotary burs. 2) Dental rotary abrasives: a. Stone. b. Disc. Common design characteristics: Rotary cutting instruments have certain design features; each instrument consists of three parts: 1) Shank. 2) Neck. 3) Head. (1) Shank: The shank is the part that fits into the hand piece, and accepts the rotary motion from the hand piece. The shank design and dimension vary with the hand piece for which it is intended. They may have: a) Long shanks for use in straight hand piece. (Straight hand piece shank). b) Short latch shanks for use in a latch contra angle (latch type angle hand piece shank).  P a g e | 28 c) Friction grip shanks design for use in an ultrahigh speed hand piece (friction type angle hand piece shank). (2) Neck: The neck is the intermediate portion of an instrument that connects the head to the shank. The main function of the shank is to transmit rotational and translational force to the head. (3) Head: The head is the working part of the instrument, the cutting edge or points of which perform the desired shaping of tooth structure. The head of the instrument shows greater variation in design and construction, for this reason the characteristics of the head form the basis on which rotary instruments are usually classified. a) Type of cutting: a. Bladed (bur). b. Diamond abrasive. A B b) Material of construction: o Carbon steel. o Tungsten carbide. o Diamond ships.  P a g e | 29 o Sand. c) Head size. d) Head shape.  Dental Bur The term dental bur is applied to all rotary instruments that have bladed cutting heads manufactured in various shapes and sizes. - Classification according to their shape: 1. Round. 2. Inverted cone. 3. Fissure: o Tapered. o Straight (cylindrical). 4. Pear 5. Wheel. 6. End and side cutting. 7. End cutting. 8. Finishing o Pointed. o Round  P a g e | 30 According to its flute design into: 1) Plain. 2) Cross-cut.  Diamond abrasive instruments: The second major category of rotary dental cutting instruments involves abrasive rather than blade cutting. Advantages: 1) Diamond instruments have long life. 2) Great effectiveness in cutting enamel and dentine because of their high hardness. Classification: These instruments defy rigid classification because of the endless variety of shapes and sizes manufactured. A. Classification according to diamond particles: o Coarse(125 to 150 μm) o Medium(88 to 125 μm) o Fine (60 to 74) μm o Very fine (38 to 44 μm)  P a g e | 31 B. Classification of abrasive diamond stones according to head shape: The wheel stone:  They are shaped like wheels of different sizes.  They are supplied in the mounted or demounted form.  The wheel stone is used for: a. Reduction of incisal surface of anterior teeth for jacket crown preparation. b. Reduction of lingual or palatal fossa of anterior teeth for jacket crown preparation. c. Reduction of occlusal surface of molars and premolars for all types of crowns.  P a g e | 32 They are classified according to their edge type into: a. Square of flat edge wheel stone. b. Rounded edge wheel stone. c. Pointed edge wheel stone. d. Grooved edge wheel stone. e. Beveled edge wheel stone. f. Unusual shaped wheel stone. 2] Tapered stone: These are mounted stones applied in different sizes. They are conical in shape with: a. Flat end: used for achieving shoulder finishing line. b. Round end: used for achieving chamfer-finishing line.  P a g e | 33 Cylindrical stone: They are available in the mounted form only and shaped like cylinders, supplied in different sizes, used for achieving shoulder-finishing line. 4] Round and oval shaped stones: Supplied in mounted form only. Inverted cone stones: They are mounted stones supplied in different sizes. Cup shaped stones: Could be supplied in the mounted and demounted type. Barrel shaped stones: Mounted only. Pear shaped stones: Mounted only. Bud shaped stones: Mounted only. Root facer stone: Mounted only. Used for preparation of the root face in case of post crown with collar preparation.  P a g e | 34  DISCS Abrasive rotary instruments used for proximal slicing, or reduction of all types of preparation. Supplied either in the mounted or demounted form. They are used with conventional and standard speeds. Classification of discs: According to the abrasive material used: a) Carborundum b) Diamond Used for proximal slicing c) Metal d) Sand paper → used for smoothening and finishing preparation. a b c d  P a g e | 35 According to the size: a) Small disc (3/8 inch in diameter.) b) Medium disc (5/8 inch in diameter.) c) Large disc (7/8 inch in diameter). According to the shape: a. Flat shaped disc. b. Cup shaped disc➜ used for reduction of distal surface of lower posterior teeth 6/6 due to curve of Spee. According to the side of abrasive material: a) Safe sided: abrasive material on one side to prevent injury of adjacent teeth. b) double sided: abrasive material on both sides for economic purpose, and used when adjacent teeth are missing.  Finishing instruments: Rotary instruments used to finish and polish restorations includes: 1. Finishing burs 2. Mounted stones 3. Abrasive discs 4. Rubber cups 5. Impregnated abrasive rubber discs.  P a g e | 36 Laser Equipment  Lasers are devices, which produce beams of very high intensity light.  Uses of lasers in dentistry have been identified that involve the treatment of soft tissues and the modification of hard tooth structure.  The effect of the laser depends the beam and the extent to which the beam is absorbed.  There are several types available based on the wave length  The laser range from long wave length (infrared) through visible wave length to short wave length (ultraviolet). Excimer is special ultraviolet laser. At the present time carbon dioxide CO₂, and ND: YAG laser has shown the promise for any application. Infection may be transmitted in dental operation through: 1. Direct contact with: a) Blood. b) Oral fluids. c) Other secretions. 2. Indirect contact with contaminated instruments.  P a g e | 37 Sterilization equipment  Use and Care of Sharp Instruments and Needles o Sharp instruments and needles contaminated with patient's blood and saliva should be considered potentially infective and handled with care to prevent injuries. o Used needles should never be capped o Used disposable syringes and needles and sharp items should be placed in an appropriate puncture- resistance containers Methods of Sterilization and Disinfection of Dental Instruments 1. Instruments should be cleaned thoroughly by scrubbing with soap and water detergent solution or with mechanical device as ultrasonic cleaner which increase the efficiency of cleaning the reduce handling of sharp instruments to remove debris. 2. During cleaning instruments, special gloves that protect the skin from possible punctures or wounds are recommended. 3. All critical and semi-critical dental instruments that are heat stable should be sterilized routinely between uses by steam under pressure (autoclaving), dry he or chemical vapor, following the instructions of the manufacturers of the instruments. 4. Critical and semi-critical instruments that will not be used immediately should be packaged before sterilization. P a g e | 38 P a g e | 39  P a g e | 40 C hapter 3 Introduction The design and preparation of a tooth for a cast metal or porcelain restoration are governed by five principles: 1. Preservation of tooth structure 2. Retention and resistance form 3. Structural durability of the restoration 4. Marginal integrity 5. Preservation of the periodontium At times it may be necessary to compromise one or more for the sake of another. For example, sound tooth structure may have to be sacrificed in order to produce a more retentive form, to create space for the bulk of restorative material necessary for structural durability or an esthetic veneer, and to allow the restoration to seat with closefitting margins. The specific reduced form given to the coronal portion of the tooth in order to receive an extra- coronal restoration varies according to: 1. Tooth size and form. 2. Tooth position and alignment in the dental arch. 3. Type of restoration indicated. The principles of tooth preparation can be divided into three broad categories: 1. Biologic consideration: which affect the health of the oral tissues. 2. Mechanical considerations: which affect the retention and the resistance form and resistance to deformation. 3. Esthetic considerations: which affect the appearance of the patient.  P a g e | 41 A. Biologic consideration 1. Conservation of tooth structure: One of the basic tenets of restorative dentistry is to conserve as much tooth structure as possible because the excessive cutting leads to: a) Thermal hypersensitivity, pulpal inflammation and may be lead to necrosis. b)The tooth might be over tapered or shortened and thus affecting the mechanical properties (retention and resistance) of the prepared tooth. 2.Prevention of damage during tooth preparation to: a) The adjacent tooth. b) Soft tissue. c) The pulp. a) The adjacent tooth : Iatrogenic damage to the proximal contact area of adjacent tooth makes it more susceptible to dental caries. Therefore, a metal matrix band put around the adjacent tooth for protection may be helpful but the preferred method is to use a fine, tapered fissure diamond bur to pass through the interproximal contact area leaving a slight lip of enamel without causing excessive tooth reduction. Fig. (2) Damage to adjacent teeth is prevented by making a thin "lip" of enamel as the bur passes through a proximal contact. b) Soft tissues: Tongue and cheeks can be preserved by careful retraction with an aspirator tip, mouth mirror. Using gingival retraction cord to reflect the gingiva in case of subgingival finishing line. c) The pulp: Tooth preparations must take into consideration the morphology and size of the dental pulp chamber. Causes of pulpal damage: 1. Extreme temperature: This is generated by friction between a rotary instrument and the surface being prepared, and this depends on:-  P a g e | 42 This heat can be minimized by the use of water coolant high speed with light touches. Water coolant is useful because it cools the tooth and the bur, and removes the tooth debris from the cutting blades because clogging reduces the cutting efficiency and generates more frictional heat. 2. Chemical irritation. Certain dental materials (bases, restorative resins, solvents, and luting agents) can cause pulpal damage when applied to freshly cut dentin. cavity varnish or dentin bonding agents will form an effective barrier in most instances but their effect on the retention of a cemented restoration is controversial. 3. Bacteria irritation. Bacteria that either left behind or gained access to the dentin because of microleakage lead to pulpal damage. Because the vital pulp resist infection, the common use of antimicrobial agent such as consepsis after tooth preparation has not been documented in clinical trial. 4. Preservation of periodontal tissue: which is the most important considerations for the future dental health: a) The restoration should have proper contact, embrasure form, occlusion and a healthy occluso-gingival contour otherwise a persistent gingival inflammation occur. (Difficult to maintain plaque control by the patient). b) Whenever possible the margin of the preparation (finishing line) should be placed supragingivally. B. Mechanical considerations The design of tooth preparations must adhere to certain mechanical principles; otherwise, the restoration may become dislodged or may distort or fracture during service. Mechanical considerations can be divided into three categories: 1. Providing retention form. 2. Providing resistance form. 3. Preventing deformation of the restoration. 1. Providing retention form: Retention: is the ability of the preparation to resist the removal of the crown restoration along its path of insertion. Path of insertion: An imaginary line along which the restoration can be inserted an removed without causing lateral forces on the abutment. The crown restoration should have a single path of insertion to be retentive. Which is mostly parallel to the long axis of the tooth as shown in fig.(4) sometimes not parallel for example: in 3/4 crown for anterior teeth the path of insertion should be parallel to the incisal 2/3 of the tooth crown(not to the long axis)as shown in fig.(5)  P a g e | 43 - Therefore, it is the direction through which the restoration could be precisely seated on the prepared tooth or teeth. - With the present casting techniques and equipment a casting which fits snugly and accurately on the prepared tooth could be obtained. - However, failure in establishing a path of insertion for a single restoration may result in either: a. Distortion of the wax pattern, b. Failure in seating the restoration. The path of insertion could be classified into: 1. For single restoration: a. Line of insertion It is single direction through which the restoration could be precisely seated on the prepared tooth. Any deviation from this line will make the seating of the restoration impossible. Therefore, parallelism between the opposing axial surfaces is indicated b Range of insertion: It denotes the converging angle of 2 opposing surfaces within its limits, the restoration could be precisely seated on the prepared tooth 2. For a bridge "2 or more retainers": a. Common line of insertion - It is the single direction through which all the retainers of a fixed-fixed bridge could be precisely seated on the corresponding abutment teeth.  P a g e | 44 - Any deviation from the common line of insertion will make the seating of the bridge impossible. Therefore, parallelism between all the opposing axial surfaces of all abutment teeth is indicated. b. Common range of insertion - It denoted the sum of the smallest converging angles - of the mesial plus of the distal surfaces of the abutment teeth, within its limit, all retainers of a fixed-fixed bridge could be precisely seated on the corresponding abutment teeth.. Factors Affecting the Path of Insertion: 1. Reduction of axial surfaces. 2. rounding of axial line angles. 3. Proximal grooves. 4. Ledges and/or indentations. 5. Pinholes. P a g e | 45  P a g e | 46 2. Providing resistance form. Resistance: is the ability of the preparation to resist the dislodgment of the restoration by forces directed obliquely or horizontally to the restoration. Factors affecting retention and resistance: 1- Taperness of the preparation. 2. Surface area of the preparation. 3. Length and height of the preparation. 4. Diameter of the tooth (tooth width). 5. Texture of the preparation. 6. Accessary means. 1- Taperness of the preparation: The more nearly parallel the opposing walls of preparation the greater retention will be, but parallel wall is difficult to be obtained in the patient mouth without undercuts, also parallel walls might lead to difficulty in seating of the crown restoration, thus (6) degree convergence angle is mostly used to provide the needed retention. To produce an optimal 6ₒtaper or convergence angle, each opposing axial wall should have an inclination of three degree to the path o insertion.(fig.6,fig.7). Taper and Resistance: The parallel axial walls the more will be the resistant crown restoration (fig.8). 2- Surface area of the Preparation: Increasing the surface area will increase the retention of the restoration.  P a g e | 47 Factors that influence surface area are: a) Size of the tooth: The larger the size of the tooth the more will be the surface area of the preparation, the more will be the retention thus full metal crown on molar tooth definitely more retentive than that on premolar tooth. b) Extend of coverage by restoration The more the area that will be covered by the crown restoration the moreretention and resistance will be, thus full coverage crown is more retentive & resistant than 3/4 crown restoration on the same tooth. c) Accessory feature: such as boxes grooves and pin hole. 3- Length (height) of the preparation: Increasing the length increase retention and resistance and vice versa. 4-Diameter of the tooth (tooth width): Wider tooth is more retentive than narrower one (increasing tooth width will increase the retention of crown restoration. Under some circumstances crown on narrow tooth can have greater resistance to tipping than one on the wider tooth, this occur because the crown on the narrower tooth has shorter radius for rotation resulting in a lower tangent line and a larger resisting area. Ex.: The walls of a short wide preparation must be kept nearly parallel to achieve adequate resistance  P a g e | 48 from. 5-Texture of the Preparation. Texture of the preparation might affect on the retention of cast crown. Smooth surfaces less retentive than rough (mechanical interlocking). 6- Extra retention means: The retention of a preparation can be greatly enhanced by the additionof:  grooves,  pin holes  boxes. 3. Resistance to deformation: A restoration must have sufficient strength to prevent permanent deformation during function, so the restoration must has structural durability and marginal integrity. a).Structural durability The restoration must be rigid enough not to flex, perforate (metal) or even fracture(plastic) during occlusal forces. Sufficient tooth structure should be removed to create enough thickness to the ideal occlusion. Preparation features related to Structural durability: 1. Occlusal reduction: Occlusal reduction must reflect the geometric inclined planes of occlusal surface with bevelling of the functional cusps (palatal cusps of the upper posterior teeth and the buccal of lower posterior) Fig. (12). Notes e enough space will destruct the tooth structure. Occlusal clearance: is the space between occlusal surface of prepared tooth and that of the opposing tooth. It should evaluate in centric and eccentric relation.  P a g e | 49 2. Axial reduction: it must be sufficient to provide enough space to the restoration to duplicate the normal contour of the tooth without flexure during occlusal forces. b).Marginal integrity: The configuration of the finishing line determines the shape and bulk of the restoration margins. The requirements of the restoration margins: c. Esthetic consideration: Patients prefer their dental restorations to look as natural as possible. This can be achieved by: 1. Minimal displaying of metal collar. 2. Maximum thickness of porcelain material will enhance the shade (colour) of the restoration. 3. Correct shade selection. 4. Porcelain occlusal surfaces, aesthetically no metal appearance is more preferable by the patient. 5. Subgingival margin.  P a g e | 50 C hapter 4 P a g e | 51 P a g e | 52 P a g e | 53 P a g e | 54 P a g e | 55 P a g e | 56 P a g e | 57 P a g e | 58 P a g e | 59 P a g e | 60 P a g e | 61  P a g e | 62 C hapter 5 Introduction Metal crown is a full crown covering all axial surfaces of the tooth as well as the occlusal surface and made of metal. It is one of the most commonly indicated,crown restorations for posterior teeth. Because it made of metal, it should be used when the patient doesn’t mind the appearance of metal or when esthetic is not a factor. It can be used as a single unit or as a retainer for a F.P.D, especially when,we have a small abutment tooth with long span edentulous area to overcome the occlusal forces and prevent bridge displacement. Since it is a full crown, it has better retention and resistance than other crown restorations such as 3/4 Crown and 7/8crown because all the axial walls are included as well as the occlusal surface. Requirements of an adequate full metal crown: The following criteria should be assessed carefully: 1. Removal of adequate amount of tooth structure. 2. Preservation of remaining tooth structure. 3. Reduction should produce a crown of acceptable strength. Types of metal alloys used for full metal crown 1. High noble alloys (gold alloys). 2. Low noble alloys (silver-palladium and gold-palladium alloys). 3. Non-noble alloys (Nickle-chromium alloy).  P a g e | 63 Indications of full metal crown 1. A tooth with extensive destruction due to caries or trauma in order to protect the remaining tooth structure from fracture. 2. A tooth with large amalgam restoration in order to protect the remaining tooth structure and amalgam from fracture. 3. Endodontically treated teeth. 4. When maximum retention and resistance needed as in a tooth with short crown. 5. Recontouring of the tooth as in a tooth receiving a clasp for removable partial denture. 6. As a bridge retainer. 7. Correction of minor inclination. 8. A patient with high caries index. 9. Correction of the occlusal plane. Contra-indications of full metal crown 1. If high esthetic need is demanded. 2. When less than maximum retention and resistance necessary. 3. When a more conservative crown could be used such as 3/4 crown as in a tooth with intact buccal surface and very short span bridge. 4. When caries index is low. Advantages of full metal crown 1. Greater retention and strength. 2. High resistance to deformation. 3. Modification of axial tooth contour is possible 4. More conservative than other types of full crown such as porcelain fused metal and all ceramic crowns. Disadvantages of full metal crown 1. Extensive tooth structure removal as compared with partial crown such as 3/4crown. 2. Difficulty to test the vitality of the tooth especially by electrical pulp tester. 3. May interfere with taste. 4. Display of metal. Preparation steps: 1. Occlusal surface preparation. 2. Buccal surface preparation. 3. Lingual surface preparation. 4. Proximal surfaces preparation. Depth Orientation grooves (D.O.G) are grooves prepared in the surface of the tooth to act as a guide or reference to determine the amount of tooth structure removed by preparation. If the preparation is done without these grooves, under and over preparation is possible, and more time will be spent by repeated checking of the preparation.  P a g e | 64 The type of finishing line recommended for full metal crown is chamfer finishing line; therefore, a round end tapered fissure bur is used in the preparation. Knife edge finishing line may also be used. The recommended tooth reduction for full metal crown is shown in the figure below: Occlusal surface preparation - The aim of the occlusal surface preparation is to create 1.5mm occlusal clearance over the functional cusps and 1 mm over the non-functional cusps. - Planar occlusal reduction (anatomical reduction) following the geometric inclined planes of the occlusal surface should be done for the following objectives:  -To provide a restoration with uniform thickness.  -To preserve the tooth structure (axial wall length).  -To improve the retention- resistance features of the preparation. The sequence of the occlusal surface preparation is as follows: 1. Depth orientation grooves (D.O.G) are prepared in the occlusal surface by a fissure bur to follow the inclines of the cusps. A D.O.G is prepared in each cuspextending from the cusp tip to the central groove, which represents the deepest part of the occlusal surface. 2. The depth of each groove corresponds to the diameter of the fissure bur used. i.e. a fissure bur with 1.5 mm diameter is used to prepare D.O.G on the functional cusps, while a fissure bur with 1 mm diameter is used to prepare D.O.G on the non-functional cusps. 3. Any tooth structure between D.O.G should be removed following the normal contour of the cusps 4. A wide bevel is placed on the functional cusps. 5. The occlusal clearance is then checked in centric & eccentric occlucal relations.  P a g e | 65 Buccal surface preparation 1. Three D.O.G with 1 mm depth are prepared in the buccal surface of the tooth, one placed in the center of the wall and one in each medial and distal transitional line angles. These grooves are prepared parallel to the long axis of the tooth or to the proposed path of insertion of the restoration. 2. Move the bur mesially and distally following the inclination of this surface to remove any islands of tooth structure between D.O.G. 3. The gingival extent of the preparation will determine the position of the margin (whether to be placed supragingivally, which is preferable, or there is a need to extend the finishing line subgingivally. 4. A round-end tapered fissure bur is used during axial reduction to obtain chamfer finishing line.  P a g e | 66 Lingual surface preparation The preparation of the lingual surface is the same as that of the buccal surface. Proximal surfaces preparation - Using a very thin long pointed tapered diamond bur (long needle), the contact is removed carefully with the bur rested on the prepared tooth (to prevent any damageto the adjacent tooth), moving the bur up & down, the contact will be opened bucco-lingually.  P a g e | 67 - Once the contact is opened, a round-end tapered fissure bur is used to plane the wall while forming a chamfer finishing line. - Safe-sided disc can also be used during the proximal reduction in order to prevent any damage to theadjacent tooth. - Placing a matrix band on the adjacent tooth can also help. Finishing o After completing the preparation of the occlusal and axial surfaces, smoothening of all surfaces is done to remove sharp line and point angles because they act as stress concentration areas. o Smooth preparation surfaces will aid all fabrication phases as impression making, waxing, investing and casting i.e. remove sharp line angles by low speed. - A seating groove is finally placed in the buccal surface of the lower molar and the palatal surface of the upper molar.  P a g e | 68 The advantages of placing a seating groove are: 1. It acts as a guide during the placement of the crown. 2. It prevents the rotation of the crown (by increasing the resistance). 3. It improves the retention.  Whenever possible, the finish line (F.L.) should be placed where the margins can be finished by the dentist and cleaned by the patient.  In the past, the concept has been to place margins as far subgingivally as possible.Later, this was seen to lead to periodontitis. Advantages of supragingival F.L.: Easy finishing, cleaning, impression making and evaluating on recall visits. Causes of subgingival F.L. placement: 1. Caries, erosion or restoration. 2. Proximal contact area extending to gingival crest. 3. Short preparation. 4. Esthetic requirement. 5. Root sensitivity..  P a g e | 69 ESRA’A ODEH  P a g e | 70 ESRA’A ODEH  P a g e | 71  Fundamentals of fixed prosthodontics, 4th edition  Art and science of fixed prosthodontics, Cairo University  Book of fixed prosthodontics by Prof Dr Atef f Fathy