3. TOOTH PREPRATION.ppt
- 1. Good Morning
- 2. Tooth Preparation for Full Veneer Crowns
- 3. CONTENTS Introduction and history of full veneer crowns Terminologies Rotary Instruments used for tooth preparation Preparation for full veneer crowns a. Complete cast metal crown b. Anterior metal ceramic crown c. Posterior metal ceramic crown d. Porcelain jacket crown e. Cast ceramic crown Conclusion
- 4. Tooth preparation is a far more important phase of fixed partial denture prosthesis treatment although some practitioners never realize this. It must be done with skill and meticulous attention to detail, for everything that follows – pulpal vitality, periodontal health, a good esthetic result, proper occlusion, protection of remaining tooth structure, and the longevity of the restoration itself – will depend on it. INTRODUCTION
- 5. Although fixed prosthodontic crown and bridge work dates to as back as 300 to 400 BC where in one of the oldest tombs of Sidon, a Phoenician specimen was found consisting of gold wire fastened around six anterior teeth, two of them being pontics. But crown and bridge fixed partial prosthesis was indeed in a crude state of development till as late as 1850. The early crown were not fabricated by casting. It was made by flowing solder over gold foil that had been adapted to the tooth preparation, with wrought wire staples in the preparation grooves. Inlays were made in a similar fashion by flowing solder into a foil matrix adapted to the cavity preparation. HISTORY
- 6. A major step in this direction was the development of the porcelain jacket crown by Land in 1886 when low-fusing porcelain fused in a gold matrix made its appearance. In 1907 William H. Taggart announced his method of making gold castings, using a disappearing wax pattern. Lost Wax technique This application of an old method revolutionized the technical aspect of restorative dentistry. It made possible exceptional refinements in the construction of fixed partial prosthetic appliances.
- 7. BIOLOGIC Conservation of tooth structure Avoidance of over contouring Supra gingival margins Harmonious occlusion Protection against tooth fracture MECHANICAL Retention form Resistance form Deformation ESTHETIC Minimum display of metal Maximum thickness of porcelain Porcelain occlusal surfaces Subgingival margins PRINCIPLES OF TOOTH PREPARATION (According to Rosenstiel) Optimal restoration
- 8. PRINCIPLES OF TOOTH PREPARATION According to Shillingburg, the design of a preparation for a cast restorations and the execution of that design are governed by five principles: 1. Preservation of tooth structure 2. Retention and resistance 3. Structural durability 4. Marginal integrity 5. Preservation of the periodontium.
- 9. TERMINOLOGIES Tooth preparation: is defined as the mechanical treatment of dental disease or injury to hard tissues that restores a tooth to original form. (Tylman) The process of of removal of diseased and / or healthy enamel and dentin and cementum to shape a tooth to receive a restoration. GPT- 8 Crown / artificial crown: a metal, plastic, or ceramic restoration that covers three or more axial surfaces and the occlusal surface or incisal edge of a tooth (GPT) Full veneer crown / Complete crown: A restoration that covers all the coronal tooth surfaces ( mesial, distal, facial, lingual and occlusal ) Chamfer Finish line: A finish line design for tooth preparation in which the gingival aspect meets the external axial surface at an obtuse angle Shoulder finish line : A finish line design for tooth preparation in which the gingival floor meets the external axial surfaces at approximately a right angle(GPT)
- 10. Retention form : The feature of a tooth preparation that resists dislodgement of crown in a vertical direction or along the path of placement (GPT) Resistance form : The features of a tooth preparation that enhance the stability of a restoration and resist dislodgement along an axis other than the path of placement Bevel : The process of slanting the finish line and curve of a tooth preparation (GPT)
- 11. ROTARY INSTRUMENTS USED FOR FULL VENEER PREPARATIONS Shape Use Round end tapered diamond 1.Depth orientation grooves 2.Occlusal reduction 3.Functional cusp Torpedo diamond 1.Axial reduction 2.Chamfer finish line Short needle 1.Initial interproximal axial reduction in posterior teeth Long needle 1.Initial proximal axial reduction in anterior teeth
- 12. Small wheel diamond 1. Lingual reduction in anterior teeth Tapered fissure bur (171L) 1.Seating groove 2.Proximal groove (posterior teeth 3.Smoothing and finishing 4.Occlusal and incisal bevels
- 13. End cutting bur Conventional shoulder finishing Torpedo bur 1.Axial wall finishing 2.Chamfer finishing Flame bur 1. Flare and bevel finishing Tapered fissure burs (169L & 170L) 1.Initial groove alignment 2.Angles of proximal boxes 3.Smoothing and finishing 4.Occlusal and incisal bevels
- 14. FULL VENEER CROWNS COMPLETE CAST CROWN ALL CERAMIC CROWN METAL CERAMIC
- 15. COMPLETE CAST METAL CROWNS Complete cast metal crowns can be used where the break down of tooth structure is severe, to the extent that is has been described in operative dentistry as “the final attempt to preserve the tooth”. The terms “full crown”, “full cast crown” and “complete crown” can be used interchangeably with full veneer crown to describe a restoration entirely made of cast metal.
- 16. Indications Extensive destruction from caries or trauma. Endodontically treated teeth. Existing restoration that needs the use of a more conservative restoration Necessity for maximum retention and strength. To provide contours to receive a removable appliance. Other re-contouring of axial surfaces (minor corrections of malinclinations). Correction of occlusal plane. Contraindications Should not be used in mouths with uncontrolled caries Less than maximum retention necessary. Esthetics.
- 17. Advantages Strong. High retentive qualities. Usually easy to obtain adequate resistance form. Option to modify form and occlusion. Contact areas can be conveniently developed. Embrasure areas can be enhanced for periodontally compromised dentition. Disadvantages Removal of large amount of tooth structure. Adverse effects on tissue. Vitality testing not readily feasible. Display of metal.
- 18. Planar occlusal reduction is done using round end tapered diamond and no: 171 bur. Depth orientation grooves are made on the triangular ridges and primary developmental grooves. The depth orientation grooves should be 1.5mm deep on functional cusps and 1mm deep on non-functional cusps. The tooth structures between the orientation grooves are removed following cuspal contours. TOOTH PREPARATION FOR COMPLETE CAST CROWN
- 19. Functional cusp bevel is done using round end tapered diamond and no: 171 bur. Depth orientation grooves are placed across the facial occlusal line angle of the mandibular molar. The bevel should parallel the inward facing inclines of the cusps of the opposing tooth, at a depth of 1.5 mm usually forming a 45 angle with the axial wall.
- 20. Facial and lingual axial reduction is done with a torpedo diamond producing a definite chamfer finish line at the same time. The facial and lingual reduction are carried as far as possible into the interproximal embrasures without nicking the adjacent teeth.
- 21. Mesial and distal axial reduction. A short thin tapered diamond is placed against the facial surface of the remaining interproximal tooth structure. It is held upright and moved up and down, directing it lingually with light pressure. Once sufficient space has been produced, sweep the short thin diamond back and forth planning the surface to smoothness.
- 22. Chamfer finishing. Torpedo bur is used to produce a distinct finish line and to round of the angles of the preparation.
- 23. Seating groove is made on the axial surface using no: 171 bur. The groove should be cut to the full diameter and it should extend gingivally to a point 0.5 mm above the chamfer.
- 24. Features of full veneer crown preparation and the function served by each
- 26. The use of porcelain fused to metal restorations has grown from the development of the first commercially successful porcelain/ gold alloy restoration by Weinstein et al in 1950’s. While a porcelain-fused to metal crown can serve as a strong and esthetic restorations, patients too often receive this type of restoration for minor irregularities that could have been better handled by conservative treatment or none at all.
- 27. Indications • Esthetics • Need to incorporate occlusal or cingulum rests • If porcelain jacket crown is contraindicated. Contraindications • Large pulp chamber. • Intact buccal wall. • When more conservative retainer is technically feasible. ANTERIOR METAL-CERAMIC CROWN
- 28. Advantages • Superior esthetics as compared to cast gold restoration. • Retentive qualities are excellent Disadvantages • Removal of substantial tooth structure. • Subject to fracture because porcelain is brittle. • Difficult to obtain accurate occlusion in glazed porcelain. • Shade selection can be difficult • Inferior esthetics compared to porcelain jacket crown. • Expensive.
- 29. Depth orientation grooves: A flat end tapered diamond is first aligned with the incisal portion of the facial surface and two vertical cuts are made to the full diameter of the diamond fading out at the “break” where the curvature of the facial is the greatest. Three similar grooves are made maintaining the same instrument parallel to the gingival segment of the facial surface. Two incisal orientation grooves 2.0 mm deep are made. ANTERIOR PORCELAIN FUSED TO METAL CROWN PREPARATION
- 30. Incisal reduction: A flat end tapered diamond is used to reduce the incisal edge by 2.0 mm keeping the plane of the reduced surface parallel to the former incisal edge. A round wheel diamond may also be used for incisal reduction.
- 31. Facial reduction, incisal half: A flat end tapered diamond is used to remove the tooth structure remaining between the orientation groove in the incisal portion of the facial surface.
- 32. Facial reduction, gingival half: A flat end tapered diamond is used to reduce the gingival segment and extend well into the proximal surface. 1.2 mm to 1.4 mm is the accepted reduction for a porcelain fused to metal restoration. If there is sound tooth structure interproximaly a vertical wall or “wing” of it, is left standing in each interproximal area lingual to the proximal contact.
- 33. Lingual reduction: A small round diamond with a head 1.4 mm in diameter is used to make four depth orientation cuts. A small round wheel diamond is used create a concave surface over the lingual surface of the tooth incisal to the cingulum.
- 34. Lingual axial reduction is done with a torpedo diamond producing a definite chamfer finish line at the same time. If there is limited space between the facio proximal angle of the wing and the proximal surface of the adjacent tooth, use a long needle diamond to reduce the axial wall lingual to the wing. The lingual axial wall should be parallel with the cervical one third of the facial surface.
- 35. Facial axial finishing: No: 171 bur is used to smooth the entire facial surface and round over any sharp angles on the incisal angle or along the edges.
- 36. Shoulder finishing: No: 957 bur or end cutting bur is used to finish the shoulder.
- 37. The features of an anterior porcelain fused to metal crowns preparation on an anterior tooth
- 38. POSTERIOR PORCELAIN FUSED TO METAL CROWN PREPARATION
- 39. Appearance zone Maxillary - premolars - first molars Mandibular – first premolar
- 40. POSTERIOR PORCELAIN FUSED TO METAL CROWN PREPARATION Planar occlusal reduction is done using round and tapered diamond and no: 171 bur. Depth orientation grooves are made on the triangular ridges and primary developmental grooves. The depth orientation grooves should be 1.5 to 2.0 mm in occlusal areas where porcelain coverage is required. The tooth structures between the orientation grooves are removed following cuspal contours.
- 41. Functional cusp bevel is done using round end tapered diamond and no: 171 bur. Depth orientation grooves are placed across the lingual incline of the maxillary lingual cusp. The bevel should parallel the inward facing inclines of the cusps of the opposing tooth, at a depth of 1.5 mm usually forming a 45 angle with the axial wall.
- 42. Depth orientation grooves A flat end tapered diamond is first aligned with the occlusal portion of the facial surface and three vertical cuts are made to the full diameter of the diamond, fading out at the “break” where the curvature of the facial surface is the greatest. Two similar grooves are made maintaining the same instrument parallel to the gingival segment of the facial surface. A single depth orientation groove may also be used.
- 43. Facial reduction, occlusal half: A flat end tapered diamond is used to remove the tooth structure remaining between the orientation groove in the occlusal portion of the facial surface.
- 44. Facial reduction, gingival half: A flat end tapered diamond is used to reduce the gingival segment and extend well into the proximal surface. 1.2 mm to 1.4 mm is the accepted reduction for a porcelain fused to metal restoration.
- 45. Proximal axial reduction: Short needle diamond facilities interproximal reduction with out nicking the adjacent tooth. Once separation between the teeth is achieved the needle diamond is used to plane the proximal axial wall.
- 46. Lingual axial reduction: A torpedo diamond is used for lingual axial reduction and to round over the corner created at the line angle with the proximal surfaces.
- 47. Axial finishing: All axial surfaces to be veneered with metal are finished using a torpedo finishing bur producing the chamfer finish line. The facial surface and those areas of the proximal surfaces to be veneered with porcelain are smoothened with the no: 171 bur. Lingual to the proximal contact, the transition from the deeper facial reduction to the relatively shallower lingual axial reduction result in a vertical wall or “wing” of tooth structure.
- 48. Shoulder finishing: No: 957 bur is used to finish the shoulder and is planed with a sharp 1.0 m wide chisel. Gingival bevel: Flame diamond and finishing bur are used to produce a narrow bevel, no wider than 0.3 mm.
- 49. The features of a posterior porcelain fused to metal crown preparations for a porcelain fused to metal crown on an posterior tooth and the function served by each.
- 51. The all ceramic crown differs from other ceramic veneer restorations because it’s not cast in gold or some other metal It is capable of producing the best cosmetic effect of all dental restoration. However since it is entirely made of ceramic, a brittle substance, it is more susceptible to fracture. For many years the only type of all ceramic crown was the porcelain jacket crown, which was built up in increments over a matrix or shell formed by thin platinum foil adapted to a cast or die of the prepared tooth. A lot of recent advances have improved the properties of dental porcelain. However more than any other restoration all ceramic crown depends for its very survival on the tooth preparation beneath. Tooth support is more critical for fracture resistance of the restoration than is the bulk of porcelain.
- 52. Indications • High esthetic requirement. • Considerable proximal caries. • Incisal edge reasonably intact. • Endodontically treated teeth with post-and –cores. • Favourable distribution of occlusal load. Contraindications • When superior strength is warranted and metal-ceramic crown is more appropriate. • Significant caries with insufficient coronal tooth structure for support. • Thin teeth faciolingually. • Unfavourable distribution of occlusal load.
- 53. Advantages • Excellent esthetics • Good tissue response even for subgingival margins. • Slightly more conservative of facial wall than metal ceramic • Brittle nature of material. • Can be used as single restoration only. Disadvantages: • Reduced strength compared to metal ceramic crown. • Proper preparation extremely critical • Among least conservative preparations • Brittle nature of material • Can be used as single restoration only
- 54. PORCELAIN JACKET CROWN PREPARATION Depth orientation grooves: A flat end tapered diamond is first aligned with the incisal portion of the facial surface and two vertical cuts are made to the full diameter of the diamond, fading out at the “break” where the curvature of the facial surface is the greatest. Three similar grooves are made maintaining the same instrument parallel to the gingival segment of the facial surface. Two incisal orientation grooves 2.0 mm deep are made.
- 55. Incisal reduction: A flat end tapered diamond is used to reduce the incisal edge by 2.0 mm keeping the plane of the reduced surface parallel to the former incisal edge. A round wheel diamond may also be used for incisal reduction.
- 56. Facial reduction, incisal half: A flat end tapered diamond is used to remove the tooth structure remaining between the orientation groove in the incisal portion of the facial surface.
- 57. Facial reduction, gingival half: A flat end tapered diamond is used to reduce the gingival segment and extend well into the proximal surface. Extend the facial reduction through the proximal surfaces with the flat end tapered diamond producing a shoulder in the process.
- 58. Lingual reduction: A small round diamond with a head 1.4 mm in diameter is used to make four depth orientation cuts. A small round wheel diamond is used to create a concave surface over the lingual surface of the tooth incisal to the cingulum.
- 59. Lingual axial reduction: A flat end tapered diamond is employed for axial reduction to prepare the vertical lingual wall. Blend the reduction of each axial surface with that on the adjacent axial surface.
- 60. Axial finishing: No: 171 bur is used to smooth the axial surfaces and to round all distinct positive angles on the preparation.
- 61. Shoulder finishing: No: 957 bur is used for preparing a smoothly cut shoulder perpendicular to the line of force or to the long axis of the tooth.
- 62. The features of all ceramic crowns preparation for a porcelain jacket crown on an anterior tooth and the function served by each.
- 63. POSTERIOR ALL CERAMIC CROWN PREPARATION Occlusal reduction: A large round end tapered diamond is used to place depth orientation grooves on triangular ridges and major grooves. The final occlusal reduction should be 1.5 mm to 2.0 mm deep. Remove the tooth structure remaining between the depth- orientation grooves with the large round- end tapered diamond.
- 64. Functional cusp bevel: The large round end tapered diamond is used to produce depth orientation grooves in the facial incline of the facial cusp. A minimum of 1.5 mm of clearance is necessary.
- 65. Facial and lingual axial reduction: The large round end tapered diamond is used to obtain axial reduction ranging from 1.0 to 1.5 mm by making depth orientation grooves and removing the tooth structure between them. The axial reductions are carried out as far as possible into the proximal embrasures.
- 66. Complete axial reduction: A short needle diamond is used to begin the proximal axial reduction without touching the adjacent tooth. The axial reduction interproximally is complete by running the round end tapered diamond.
- 67. Preparation finishing: round end tapered carbide bur is used to finish the axial surfaces and the functional cusp bevel.
- 68. The features of a cast ceramic crown preparation for an all ceramic crown on a posterior tooth and the function served by each.
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