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Chandra Dept. of Cons & Endo Contents : 2 Contents Introduction Historical Perspective Indications & Contraindications Advantages & Disadvantages Tooth preparation for Cast Restorations General Principles Bevels, Margins & Flares Preparation for Metal Inlays & Onlays Preparation for Ceramic Inlays & Onlays Slide 3: 3 Tooth Preparation for Posterior Crowns Full Metal Crown Metal Ceramic Crown All Ceramic Crown Tooth Preparation for Anterior Crowns All Ceramic Crown Metal Ceramic Crown Introduction : 4 Introduction Slide 5: 5 Tooth Preparation “Tooth preparation is defined as the mechanical alteration of a defective, injured, or diseased tooth to best receive a restorative material that will reestablish a healthy state for the tooth, including esthetic corrections where indicated along with normal form and function” Slide 6: 6 Restoration “Restoration is defined as any material or prosthesis that restores or replaces lost tooth structure, teeth or oral tissues” (Glossary of Prosthodontic Terms - 8) Slide 7: 7 Cast: “Life size likeness of some desired form” “To produce a shape by thrusting a molten liquid or plastic material into a mold possessing the desired shape” Casting: “Something that has been cast in a mold; an object formed by the solidification of a fluid that has been poured or injected in a mold” (Glossary of Prosthodontic Terms - 8) Historical Background : 8 Historical Background 1835 – John Murphy First Inlay Fabricated Porcelain inlays 1880 – Ames & Swasery Used burnished foil technique for fabricating Inlays 1897- D. Philbrook First CAST INLAY is attributed to him Introduced the concept of forming an investment around a wax pattern Eliminating the wax and filling the mold with a “Gold alloy” 1907 – W.M. Taggart “Lost wax technique” Reported the development of “Pneumatic Pressure Casting” Introduced the technique for Cast Gold Dental restorations Popularized the Gold Inlay as a Dental restoration Indications : 9 Indications Replace lost tooth structure (In extensively involved teeth) Restoration of endodontically treated teeth Correction of Occlusion & Diastema closure Support for partial or complete dentures Retainers for fixed prosthesis Slide 10: 10 Partially sub-gingival restorations Cracked teeth (Vertically, horizontally or diagonally) As an adjunct to successful PDL therapy by correction of tooth anomalies which predispose to PDL problems Esthetics Dissimilar metals Contraindications : 11 Contraindications Developing or deciduous teeth High Plaque or Caries indices Occlusal disharmony Dissimilar metals Small restorations Advantages : 12 Advantages Higher strength (Compressive, Tensile, Shear & Yield) Ability to reproduce precise form and minute details Control of contours and contacts Biocompatibility of materials (Noble or passivated alloys) Slide 13: 13 Not affected by tarnish & corrosion Increased longevity of cast restorations Fewer voids, less internal stresses, no layering effect when compared to amalgam Cast restorations can be better finished, polished or glazed, thus better Esthetics & no harm to P-D organ Disadvantages : 14 Disadvantages Technique sensitive No. of appointments & higher chair time High Cost Splitting forces Mouth preparation prior to Cast Restorations : 15 Mouth preparation prior to Cast Restorations Every measure is to be taken to ensure longevity & success of a cast restoration Control of Plaque Control of Caries Control of periodontal problems Control of pulpal health of tooth Proper foundation Occlusal equilibration Diagnostic wax-ups and temporary restorations Features of Tooth Preparation For CastRestoration : 16 Features of Tooth Preparation For CastRestoration Slide 17: 17 Cast Restorations Intracoronal Extracoronal (Mortise Shaped) Definite walls & floors joined at Line & Point Angles Created by occlusal & axial surface reduction May end gingivally with no definite flat floor General Principles : 18 General Principles Greater surface extension in outline form than amalgam This facilitates support & efficient marginal manipulation More extensive surface involvement to compensate for the cariogenically weak joints of cast/cement/tooth interface Slide 19: 19 The design for a cast restoration are governed by 5 principles: Preservation of the Tooth Structure Retention & Resistance Structural Durability Marginal Integrity Preservation of the Periodontium Preservation of Tooth Structure : 20 Preservation of Tooth Structure In addition to replacing lost tooth structure, the cast restoration must preserve the remaining structure Preservation of tooth structure may involve limited amounts of tooth being prepared Retention & Resistance : 21 Retention & Resistance Retention prevents removal of the restoration along the path of insertion or long axis of the tooth preparation Resistance prevents the dislodgement of the restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces Retention & Resistance : 22 Besides applying the general principles of tooth and cavity preparation, cast restoration preparations should have the following features: A). Preparation Path: Prep should have a “Single Insertion path” Path is parallel to long axis of tooth crown Helps in retention & decreases the micro-movements of restoration during function Retention & Resistance Slide 23: 23 Single path of Insertion opposite to direction of Occlusal Loading All reductions in tooth structure should be oriented towards ONE path (Withdrawal & Insertion path of future wax pattern) Slide 24: 24 B). Apico-Occlusal Taper: For max retention, opposing walls & axial surfaces should be perfectly parallel to each other Slight divergence of opposing walls in Intracoronal Slight convergence of axial walls in Extracoronal Taper should be 2-5° from path of prep Uses opposing internal surfaces Uses external opposing surfaces Slide 25: 25 Taper can be altered according to following features: Length of prep and/or axial wall: Greater the length, more the taper (not more than 10°) Less the length, less taper (approaching 0°) Dimensions of surface involvement: Greater surf involvement, more detailed the internal anatomy, thus greater FRICTION To diminish friction; Taper is Increased Need for Retention: Greater the need of retention, more will be the need to achieve parallelism (thus less taper) Slide 26: 26 C). Circumferential Tie: The peripheral marginal anatomy of the preparation is called as the “Circumferential Tie” Should fulfill the requirements advocated by Noy: If the prep ends on enamel, the enamel must be supported by sound dentin Enamel rods forming the cavosurface margin should be continuous with sound dentin Enamel rods forming the cavosurface margin should be covered with a restorative material Angular cavosurface angles should be trimmed Structural Durability : 27 Structural Durability Occlusal reduction Functional Cusp Bevel Axial Reduction Marginal Integrity (Bevels) : 28 Marginal Integrity (Bevels) Bevels are defined as “flexible extensions” of a cavity preparation, allowing the inclusion of surface defects, supplementary grooves and other areas on the tooth surface Two types of Bevels: Occlusal Bevels Gingival Bevels Types & Design Features of Occlusal and Gingival bevels : 29 Types & Design Features of Occlusal and Gingival bevels Partial Bevel: Involves part of the enamel only Not used in cast restorations Short Bevel: Includes entire enamel wall but no dentin Class I alloys (Type 1 & 2) Slide 30: 30 Long Bevel: Includes all of the enamel wall and up to one half of the dentinal wall Most frequently used bevel for cast materials Full Bevel: Includes all of the dentinal and enamel wall Well reproduced by all 4 classes of cast alloys Deprives prep of internal resistance & retention Slide 31: 31 Counterbevel: When capping cusps this protects & supports them Given opposite to an axial wall on the facial and lingual surfaces Hollow Ground (Concave) Bevel: Allows more space for the cast material bulk Used to improve retention and resistance to stresses Slide 32: 32 Function of Occlusal & Gingival Bevels: Bevels create an obtuse angled marginal tooth structure (Strong tooth anatomy) Produce an acute angled marginal cast alloy (most amenable to finishing & burnishing) Makes it possible to decrease the cement line by bringing the cast alloy closer to the tooth They are also a part of one of the major retention form for cast restorations Types & Design Features of Facial and Lingual Flares : 33 Types & Design Features of Facial and Lingual Flares Primary Flare: Conventional & basic part of circumferential tie facially & lingually for an Intra-coronal prep. Similar to a Long bevel (enamel & part of dentin) Specific angulation - 45° to the Inner Dentinal wall proper May be hollow ground if part of the circumferential tie and the prep is for Non noble alloys Slide 34: 34 Function & Indications of Primary Flare: Perform the same function as bevels Brings the facial and lingual margins of the cavity prep to cleansable – finishable areas Indicated for the facial and lingual proximal walls of an intra-coronal prep Flares : 35 Flares Slide 36: 36 Secondary Flare: Is always a flat plane superimposed peripherally to a primary flare Is prepared in a “Hollow Ground Form” to accommodate the materials with low castability Prepared solely in Enamel (may contain dentin) Has various angulations depending on the involvement, extent and function Slide 37: 37 Functions & Indications of Secondary Flare: Performs same functions as bevels In wide bucco-lingual lesions, where both walls are thinned down; the 1° flare ends with an acute angled marginal tooth structure (Unsupported enamel) 2° flare at the correct angulation creates an obtuse angle of marginal tooth structure (No sacrifice to retention & resistance) Slide 38: 38 In broad contact areas or malposed contact area, the 1° flare does not bring the facial/lingual walls to cleansable or finishable areas A 2° flare placed peripherally to 1° flare will accomplish this without changing the 45° angulation Surface defects or calcifications facial or lingual to the 1° flare’s facial or lingual margin can be involved in the prep by a 2° flare Retention Features : 39 Retention Features Principal/Primary Retention forms: Parallelism Dovetails Surface area frictional retention Masticatory loads directed to seat the restoration Slide 40: 40 Secondary/Auxiliary Retention forms Luting Cements: Their action is primarily mechanical, locking the cast to tooth structure by filling the space between them, wetting the details of both the casting and tooth preparation and filling in these vacancies or irregularities Luting cements used: Type I GIC, Zinc Polycarboxylate Grooves: : 41 Located completely in dentin Can be located at the mesial & distal wall/the gingival floor of the facial or lingual portion of a cavity preparation Should be located as internally as possible, adjacent to the axial wall Prevent lateral displacement of the mesial, distal, facial & lingual parts of restoration Grooves: Slide 42: 42 Can also be located externally in extra coronal preparation, they can be placed anywhere where there is sufficient dentin bulk without impinging on the pulp chamber, root canal system or other anatomy Slide 43: 43 Reverse Bevel Placed at expense of the gingival floor, creating an internal dentinal plane including gingivally-axially, locking the restoration & preventing proximal displacement Slide 44: 44 Internal box Most efficient immobilizing retention, resistance means Prepared in dentin with four vertical surrounding walls joining a floor at definite line & point angles Can be located next to marginal ridge with intact proximal wall Should have a minimum size of 2mm in three dimensions, but should not have equal length, width & depth Slide 45: 45 External box A preparation opening to the axial tooth surface with three, four or five surrounding walls & floors They can be proximal, facial or lingual Slide 46: 46 Slot Slot is a internal cavity within a floor of preparation having a continuous surrounding walls & floors Junction between the floor & surrounding walls is rounded Less locking than an internal box Slot should have a 2 to 3 mm depth Slide 47: 47 Pins Can be cemented & threaded, parallel & non parallel, vertical & horizontal, cast & wrought Collar Is a surface extension completely surrounding a cusp or a surface of a tooth Skirt Is a specific extension involving a part of the axial angle of a tooth Finish Line Configurations (Margins) : 48 Finish Line Configurations (Margins) Finish line refers to the border of the preparation where the prepared tooth structure meets the unprepared surface of the tooth A smooth, well defined finish line is beneficial, regardless of the design used, to facilitate the laboratory procedures and finishing of the restoration Various Margins… : 49 Various Margins… A – Knife Edge B - Chamfer C – Shoulder D – Bevelled Chamfer E – Bevelled Shoulder Slide 50: 50 Chamfer: Finish line for Cast metal crowns Width is 0.5 mm Exhibits least stress Is made with a Round end diamond (Torpedo) Heavy Chamfer is used to provide a 90°cavosurface angle Slide 51: 51 Shoulder: Given in All ceramic crowns and Metal Ceramic Crowns Wide ledge provides resistance to occlusal forces & minimizes stress Flat end tapered diamond bur is used Types: Radial Shoulder Beveled Shoulder Slide 52: 52 Knife Edge (Feather edge): Least tooth structure involvement Used when tooth is Bell Shaped Used for a very castable – burnishable alloy (Gold) Is very thin in cross section and chances of restoration fracture are more Chamfer or Shoulder with a bevel: Used by some who believe that a bevelled margin is easier to detect in an impression It makes the margins of the casting more burnishable Slide 53: 53 Instrumentation for Tooth Preparation : 54 Preliminary Shaping: Tapered fissure burs or diamond stones with or without rounded ends Cutting strokes should be pre-planned Rotary tools should be carefully selected and dimensions measured Gross Removal of Tooth Structure: Cylindrical diamonds (#555) or Tapered Carbides (No.271) Proximal Reduction: 169L or 699 Carbide burs used in bucco-lingual direction Instrumentation for Tooth Preparation Slide 55: 55 Removal of undermined enamel & gaining access: Removed with hand cutting inst like Enamel hatchets, Chisels These are self limiting in cutting undermined enamel only Rotary burs are seldom used Removal of Carious Dentin & Placing of Bases: Spoon Shaped Excavators Round burs (No.2 & 4) Boxing Up: Tapered fissure bur Slide 56: 56 Formulation of Cap and Shoe Anatomy: Cylindrical diamond stones or tapered fissure burs Bevels and counter-bevels given with Round carbides or ball shaped diamond stones Merging Walls & Bevels: Round or Hour Glass Shaped Diamond Final Shaping: Mainly done with Hand Instrumentation Chisels, Hatchets, GMT’s, Angle formers Finishing burs Designs of Cavity & Tooth Preparation : 57 Designs of Cavity & Tooth Preparation The general designs of tooth preparation to accommodate cast restorations: Inlays Onlays Inlays : 58 Inlays An Inlay is an intra-coronal cast restoration which involves the occlusal and proximal surfaces of a posterior tooth Tooth Preparation for Inlays : 59 Tooth Preparation for Inlays Indications: Cavity width not to exceed 1/3 of inter-cuspal distance Strong, self-resistant cusps Indicated teeth have minimum or no occlusal facets Tooth is not to be used as an abutment in FPD or RPD Occlusion or occluding surfaces are not to be changed by the restorative procedure Armamentarium : 60 Carbide burs are used Side & end surfaces of the bur must be straight - to form uniformly tapered walls Through out the prep for cast inlay, cutting instruments used to develop the vertical walls are oriented to a single “draw” path (long axis of tooth) Armamentarium Burs : 61 Burs Burs used are No. 271, 169L & No. 8862 Sides & end surface of 271 bur meet in a rounded manner to prevent sharp internal angles Burs are “plane cut” so that vertical walls are smooth General Shape : 62 General Shape The outline of the occlusal portion of this preparation is dovetailed internally Proximal portion is usually boxed in shape Slide 63: 63 Proximal View of Class II Inlay Occlusal View of Class II Inlay Location of Margins : 64 Location of Margins In occlusal portion the facial, lingual, and sometimes proximal margins are located on the inclined planes of the corresponding cusps, triangular ridges or marginal ridges Bucco-lingual width of the cavity does not exceed 1/3rd intercuspal distance Facial and lingual margins of the proximal portion is in the corresponding embrasures Gingival margins should extend to include surface defect and concavities and to eradicate marginal undercuts Slide 65: 65 Tooth Preparation Initial Preparation External & Internal Outline Form Occlusal Step Proximal Box Final Preparation Removal of Carious Dentin Pulp Protection Prep of Bevels & Flares Occlusal Step : 66 Occlusal Step No. 271 bur is held parallel to long axis of tooth – enter pit/fossa closest to marginal ridge Punch cut of 1.5 mm Maintaining 1.5 mm extend the outline to involve the central groove/fissure Outline is extended to a Dovetail (retention form) Slide 67: 67 The correct pulpal depth for an inlay is established with a tapered fissure bur. Used to create flat floors and well defined internal angles The tapered sides of the bur are used to help establish the desired divergence of the walls. Average taper should be 2-5° Slide 68: 68 Widen the preparation to desired facio-lingual width in anticipation for proximal box preparation Facial & lingual walls of occlusal step should go around the cusps in curves Isthmus should be only slightly wider than bur; conserving dentin for pulpal protection Proximal Box : 69 Proximal Box No. 271 used to cut a proximal ditch Mesio-distal width of ditch should be 0.8 mm (0.3 mm in enamel & 0.5 mm in dentin) A thin layer of enamel is left on the proximal surface to protect the adjacent tooth while the proximal box is being prepared Extend proximal ditch facially & lingually as well Slide 70: 70 Box should be slightly divergent (5-10°) towards pulpal floor in gingivo-occlusal direction Gingival extent to be checked with length of bur (Extent of caries determines the depth) Flat gingival floor with a slightly converging axial wall is created A hand instrument, such as an enamel hatchet, is helpful in smoothening walls of the preparation Slide 71: 71 Over cutting the facial or lingual walls may result in: Over extension of margins in the completed preparation A weakened tooth structure Possible injury to the soft tissue Variations in Proximal Margin Design : 72 Variations in Proximal Margin Design Design of proximal margins will vary with: Extent of tooth tissue loss Location of that loss Tooth form Positional relationship with adjacent tooth Need for retention form Convenience (Ref: Operative Dentistry 3rd Ed – G. Charbeneau) Slide 73: 73 The axial wall is made to an even depth into the tooth from the facial to the lingual wall Should be flat or slightly rounded (Bucco-lingually) Should meet pulpal floor in an extremely rounded junction (Prevents stress concentration in tooth & casting) Depth axially is 1-1.5 mm from DEJ (depends on the cariogenic lesion proximally) Axial Wall: Final Preparation : 74 Final Preparation Removal of infected dentin & Pulp protection After initial prep, evaluate for any carious dentin If present, excavate using a spoon excavator or a No. 2 or 4 round bur Pulp Protection may be done using: Light cured GIC Ca(OH)2 Pulp Exposure : 75 Pulp Exposure If pulp is advertently exposed, a clinical evaluation must be made Direct Pulp Capping v/s Endodontic treatment Criteria for Pulp capping: Exposure is less than 0.5 mm Tooth is asymptomatic with no signs of pulpitis Hemorrhage is easily controlled Invasion of pulp chamber was relatively atraumatic Clean, uncontaminated operating field Bevels & Flares : 76 Bevels & Flares Slender, flame shaped, fine grit diamond (8862) bur is used Occlusal, Gingival Bevels are given Secondary flare is given to facial and lingual wall Occlusal Bevel : 77 Occlusal Bevel Long bevel (almost 1/3rd of facial & lingual walls) Angulation of 30-45° to the long axis of crown A tapered diamond or finishing bur is used to create a short but distinct bevel at the occlusal finish lines Angulation should increase with increase in cavity width; to accommodate the bulk of the cast metal & resist the stresses near the cusps Gingival Bevel : 78 Gingival Bevel Bevel the gingival margin by moving the instrument facially along the gingival margin Instrument may be tilted mesialy to form a bevel with correct steepness Bevel should be 0.5 – 1.0 mm wide and blend with the lingual secondary flare Function of Gingival Bevel: Weak enamel is removed Results is 30° metal that is burnishable Lap sliding fit is produced at gingival margin Secondary Flare : 79 Secondary Flare Flaring of the proximal walls to extend the margins into embrasures Makes them more self cleansing and accessible to finishing procedures A blunted and stronger enamel margin is produced Direction of flare results in 40° marginal metal which is more burnishable Slide 80: 80 The proximal bevel or flare should be established slightly beyond the contact area and is blended with the gingival bevel A rotary disk , placed at an angle of 45º, can provide a smooth, flat bevel without undercuts The tapered fissure bur (No. 169L) is positioned at an angle to give an occlusal divergence for the retentive grooves. The grooves should be at a depth of 0.3 mm Clinical Tips for Inlays : 81 Clinical Tips for Inlays Avoid sharp internal line angles and undercuts Smooth prep walls and trim excess lining material with finishing diamond or bur Do not include undercuts Create a 5º to 10º divergence in the proximal walls from the floor to the occlusal margin of the preparation Features of a Class II Inlay : 82 Features of a Class II Inlay Marginal Integrity: Gingival & Occlusal Bevel Proximal Flare Retention & Resistance: Dovetails Isthmus Proximal Box Slide 83: 83 Variation in Inlay Preparation : 84 Variation in Inlay Preparation Removal of Undermined approximal enamel Access made within the marginal ridge Slide 85: 85 Flattening of Gingival Floor Extending the occlusal outline for a Dovetail Class I Inlay Preparation : 86 Class I Inlay Preparation Initial Punch Cut – 1.5 mm Extension of cavity; Flat Floor Occlusal View of Outline form showing extensions into facial and lingual grooves Slide 87: 87 Occlusal Bevel given with Flame shaped Bur & Diamond Occlusal outline made with No. 271 Bur Slide 88: 88 Onlays : 89 An Onlay caps one or more than one of the cusps of a posterior tooth and is designed to help strengthen a tooth that has been weakened by caries or previous restorative experience Onlays “It is essentially an inlay which covers one or more than one cusp” General Principles : 90 General Principles All finish lines are “Bevelled” The bevel creates second plane for close adaptation of the gold to the tooth Bevelled Shoulder – Centric Cusp Nonbevel or Chamfer – Non-centric Cusp Gingival margin, facial & lingual walls of proximal box are like an Inlay General Shape : 91 General Shape Capping of the functional cusps and shoeing of the non functional cusp The outline of the occlusal portion of this preparation is dovetailed internally and follow the cups externally Proximal portion is usually boxed or cone shape Location of Margins : 92 Location of Margins Facial and lingual margins on the functional side are located on the facial and lingual margins, gingivally to be away from the contact Involves 1/4th to 1/3rd of the facial or lingual surfaces Should include all facial and lingual grooves and be parallel to the contour of the cusp tips and crest of ridges On non functional side the facial and lingual margins are just gingival to the tip and ridge crests of the involved cusps and away from occlusal contact In proximal portion secondary flares are always used Tooth Preparation for Onlay : 93 Tooth Preparation for Onlay Tapered fissure bur is used for preparing the outline (6-10 degree taper) Occlusal Prep: Initial entry made into central fossa to depth of 1.0 mm into dentin (total depth = 2.5 mm) Occlusal outline should be as conservative as carious lesion permits Bur is kept in long axis of intended path so that the internal taper is approx 3-5° divergence for each internal wall Slide 94: 94 Proximal Boxes: Facial & lingual walls should exhibit a combined divergence of 6-10° from each other Facio-lingual dimension is determined by extent of caries, old restoration and adjacent tooth Bevels extend the preparation beyond the proximal contact area Slide 95: 95 After the bevels are placed, there is an access for completing the preparation’s finish lines and the margins of the restoration The proximal box is extended to/ slightly beyond the contact area. Bevels will provide the desired proximal clearance Slide 96: 96 A bur of known diameter is used to establish depth cuts (1.5 – 2.0 mm for centric cusps & 1.0 – 1.5 mm for non centric) to guide the correct reduction of the cusps Cusps are reduced in accordance with the occlusal anatomy Non centric cusps require less reduction Cuspal Reduction: Slide 97: 97 Shoulder is prepared on the centric cups and should have precise line angles Barrel shaped bur- to create chamfer on non-centric cusps Shoulder & Chamfer Preparation Bur is held parallel to tooth and shoulder Of 1.0 mm height & 1.0 mm in axial depth is cut Bur is positioned 45° to the axial surface Slide 98: 98 Gingival Bevel: Flame shaped Diamond (8862) Distinct bevel given on gingival margins 0.5 mm width & 45° to external surface of tooth Proximal Bevel: Flame shaped Diamond (8862) Proximal bevel should blend smoothly with gingival bevel and buccal & lingual bevels Retention Grooves: No.169L Bur is used Grooves placed at linguoaxial and facioaxial line angles Slide 99: 99 Finished Onlay with Precise internal angles, Occlusal line angles are rounded, correct taper and grooves placed Retention grooves are placed at linguoaxial and Facioaxial line angles Slide 100: 100 Slide 101: 101 Ceramic Inlays & Onlays : 102 Ceramic Inlays & Onlays Ceramics : 103 Ceramics Properties of newer ceramics are closer to tooth enamel than cast metals or composites Etching the ceramic (Glass Ceramic) surface , exposes the crystalline structures Similar to enamel etching Etched ceramic can be adhesively bonded to enamel (high bond strength) Indications : 104 Indications Small to moderate carious lesions Large carious or traumatic lesions with undermined enamel to the extent that a cast metal restoration or full crown is mandatory Endo treated tooth, where access cavity has compromised the strength and prognosis of tooth In metal allergy In an arch opposed by already present porcelain restorations Contraindications : 105 Contraindications Greatest contraindication to etched porcelain inlays is the evidence of para-functional habits and aggressive wear of dentition Although technique sensitivity is not a contraindication, the inability to maintain dry field can be a problem ! Advantages of Ceramic Inlays : 106 Advantages of Ceramic Inlays Superior esthetics & highly conservative Good adhesion Restorations show good micro/ morphologic margins Less plaque accumulation – Good PDL health Resistance to abrasion Cusp fractures can be avoided in larger restorations (MOD) due to adhesion Cerinlay Prep Set (Intensiv) : 107 Cerinlay Prep Set (Intensiv) Diamond Burs ( 80 –μm grit) Finishing Burs (20 –μm grit) Principles of Preparation : 108 Principles of Preparation Slightly conical diamond burs are used Prep should have conical walls (6° convergence angle) Rounded line & Point angles Angle made by internal & external surfaces of inlay must be as close to 90° (Butt joint) Bevels are contraindicated Occlusal clearance must be at least 1.5 – 2.0 mm Ceramic Inlay should be at least 1.5 mm thick : 109 Ceramic Inlay should be at least 1.5 mm thick Slide 110: 110 Hollow ground chamfer confined to the marginal enamel will aid in developing an effective seal Slide 111: 111 Diag of hollow ground chamfer used to expose the enamel rods for an increased bond strength, increased marginal seal and a transition for better esthetic blend To summarize… : 112 To summarize… Optimum isolation is a must Flat pulpal floor Rounded internal line angles 6-10° taper of axial walls Well defined smooth Butt joint Hollow ground chamfer & No Conventional Bevels Pinlays : 113 Pinlays Different from pin retained amalgams In Pinlays, pins adhere to the cast material with no evident interface These contain pins as an auxiliary source of retention Indications : 114 Indications Shallow & wide teeth Short teeth (Attrition, fracture etc) Incompatibility in length in 2 axial walls in same tooth In teeth with completely lost cusp(s) In cavities where a dovetail can’t be made In teeth where axial walls are absent or very short, pins are placed in the gingival floor In thin delicate teeth (anteriors) where extensive cavity prep can’t be done Slide 115: 115 Pins for Cast Restorations Pins for Cast Restorations According to their relationship to the long axis of the tooth According to the modes of incorporating them into the casting Slide 116: 116 Wrought pins for Cast restorations are made of Iridio-Platinum or Rhodium gold alloys for Cast Gold alloys For Ni-Cr or Castable Ceramic, same pins can be used; But Stainless Steel or Chromium based pins can be used too Wrought metal pins are pre-fabricated, cold worked pins of various shapes and diameters Slide 117: 117 Cast Pins are fabricated as a part of the restoration in an evaporating wax casting machine Their advantage is structural continuity between the restoration proper and the pin Tooth Preparation forCrowns : 118 Tooth Preparation forCrowns Posterior Crowns : 119 Posterior Crowns Full Metal or Cast Metal Metal Ceramic Crown All Ceramic Cast Metal Crown : 120 Cast Metal Crown Armamentarium: No. 170L Bur Round end tapered diamond Short Needle Diamond Torpedo diamond Torpedo bur Utility Wax Occlusal Reduction : 121 Occlusal Reduction 1.5 mm clearance on functional cusps & 1.0 mm on non-functional Depth orientation grooves are placed for reference Round end tapered diamond is used for groove placement Wide bevel is placed on functional cusp Buccal, Lingual & Proximal Reduction : 122 Buccal, Lingual & Proximal Reduction Buccal & Lingual walls are reduced with Torpedo diamond It produces desired axial reduction & a chamfer finish line Initial cuts are made with Short needle diamond “Sawing motion” – avoiding adjacent teeth Once room is obtained, Torpedo diamond is used to plane walls & form the chamfer Slide 123: 123 Metal Ceramic Crown (PFM) : 124 Metal Ceramic Crown (PFM) Armamentarium: Flat end tapered diamond H158-012 radial fissure bur RS-1 binangle chisel Silicone Putty and accelerator (For Putty index) Silicon Putty (Index) : 125 Silicon Putty (Index) Slide 126: 126 2.0 mm in Functional cusp and 1.5 mm in Non functional Overall reduction of 1.5 mm Flat end tapered diamond is used to form a Shoulder Chamfer is given where porcelain is not given Those parts which are veneered with ceramic are smoothened with H158-012 radial fissure bur All Ceramic Crown : 127 All Ceramic Crown Preparation of the posterior all-ceramic crown requires at least 0.8 mm to 1.5 mm of reduction on the buccal and lingual aspects Best Esthetics Shoulder with uniform width of 1 mm is given Dicor, IPS Empress, In-Ceram Slide 128: 128 Anterior Crowns : 129 Anterior Crowns All Ceramic PFM Crowns All Ceramic Crown : 130 All Ceramic Crown Armamentarium: Flat end tapered diamond Small wheel diamond H158-012 Radial fissure bur RS-1 binangle chisel Slide 131: 131 Depth orientation grooves given on labial & incisal surfaces 1.2 – 1.4 mm on labial & 2.0 mm on Incisal edges Incisal & labial reduction done with Flat end tapered diamond, so that shoulder is formed Lingual reduction done with Small wheel diamond Slide 132: 132 Slide 133: 133 Metal Ceramic Crown : 134 Metal Ceramic Crown Armamentarium: Flat end tapered diamond Small wheel diamond Long needle diamond Torpedo diamond Torpedo Bur H158-012 Bur RS-1 binangle chisel Slide 135: 135 Uniform reduction of 1.2 mm on facial surface Facial surface is prepared in 2 planes Labial grooves are cut in 2 planes One set parallel with gingival half & one set parallel to incisal half Incisal reduction should be 2 mm Slide 136: 136 Lingual reduction is done with Small wheel shaped diamond Lingual axial reduction is done with a Torpedo diamond & carbide finishing bur Obtain a minimum of 0.7 mm clearance from opposing tooth Slide 137: 137 In Conclusion… : 138 In Conclusion… Technique Sensitive Lengthy & time consuming Expensive A boon to the patient Superior Esthetics Ability to produce a better Morphology Longevity & Biocompatible Slide 139: 139 References : 140 References Sturdevant’s Art & Science of Operative Dentistry Operative Dentistry – M.A. Marzouk Fundamentals of Operative Dentistry – J.B. Summit Fundamentals of Tooth Preparation – H.T. Schillinburg Bonded Ceramic Inlays – J.F. Roulet & S. Herder Fundamentals of Fixed Prosthodontics – H.T. Schillinburg Handbook of Inlays, Crowns & Bridges – G.F. Kantorowicz Dental clinics of North America GPT - 8 Internet Sources You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.