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Tooth preparation for full veneer crowns /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in

continuing dental education , training dentists

in all aspects of dentistry and offering a wide

range of dental certified courses in different

formats.

Indian dental academy provides dental crown &

Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit

www.indiandentalacademy.com ,or call
0091-9248678078

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  • 1. TOOTH PREPARATION FOR FULL VENEER CROWNS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  • 2. CONTENTS OF THE SEMINAR 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 Review of literature Conclusion References www.indiandentalacademy.com
  • 3. INTRODUCTION 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 else 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. www.indiandentalacademy.com
  • 4. HISTORY 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. www.indiandentalacademy.com
  • 5. TOOTH PREPARATION FOR FULL VENEER CROWNS www.indiandentalacademy.com
  • 6. The significance of tooth preparation grew steadily as technology made possible an increasingly accurate fit of cast restorations. With improvement in the technology of fabricating restorations, there was a tremendous increase in the complexity of restoration designs and in the demands placed on retainers by more sophisticated prostheses. During the same time period that new types of all-metal restorations were evolving, efforts were being made to produce restorations that could restore the patient esthetically as well as functionally. www.indiandentalacademy.com
  • 7. 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. 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. www.indiandentalacademy.com
  • 8. From the beginning, restorative dental procedures have been limited far more by the technology available than by a lack of ingenuity on the art of dentists. These technological improvements have not decreased the need for skilled, knowledgeable restorative dentists. On the contrary, they have made knowledge and skill that much more critical. Technology in the hands of a skilled operator makes it possible to do more work of an even higher quality. www.indiandentalacademy.com
  • 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) 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-7; 1999) Full veneer crown / Complete crown: A restoration that covers all the coronal tooth surfaces ( mesial, distal, facial, lingual and occlusal ) (GPT-7; 1999) Chamfer Finish line: A finish line design for tooth preparation in which the gingival aspect meets the external axial surface at an obtuse angle (GPT-7; 1999) 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-7; 1999) www.indiandentalacademy.com
  • 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-7; 1999) 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 (GPT-7; 1999) Bevel : The process of slanting the finish line and curve of a tooth preparation (GPT-7; 1999) www.indiandentalacademy.com
  • 11. ROTARY INSTRUMENTS USED FOR FULL VENEER PREPARATIONS Shape Round end diamond Use tapered 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 www.indiandentalacademy.com
  • 12. Small wheel diamond Tapered (171L) fissure 1. Lingual reduction in anterior teeth bur 1.Seating groove 2.Proximal groove (posterior teeth 3.Smoothing and finishing 4.Occlusal and incisal bevels www.indiandentalacademy.com
  • 13. Tapered fissure (169L & 170L) burs 1.Initial groove alignment 2.Angles of proximal boxes 3.Smoothing and finishing 4.Occlusal and incisal bevels End cutting bur Conventional shoulder finishing Torpedo bur 1.Axial wall finishing 2.Chamfer finishing Flame bur 1. Flare and bevel finishing www.indiandentalacademy.com
  • 14. TOOTH PREPARATION FOR FULL VENEER CROWNS www.indiandentalacademy.com
  • 15. CONTENTS OF THE SEMINAR 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 Review of literature Conclusion References www.indiandentalacademy.com
  • 16. INTRODUCTION 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 else 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. www.indiandentalacademy.com
  • 17. HISTORY 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. www.indiandentalacademy.com
  • 18. The significance of tooth preparation grew steadily as technology made possible an increasingly accurate fit of cast restorations. With improvement in the technology of fabricating restorations, there was a tremendous increase in the complexity of restoration designs and in the demands placed on retainers by more sophisticated prostheses. During the same time period that new types of all-metal restorations were evolving, efforts were being made to produce restorations that could restore the patient esthetically as well as functionally. www.indiandentalacademy.com
  • 19. 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. 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. www.indiandentalacademy.com
  • 20. From the beginning, restorative dental procedures have been limited far more by the technology available than by a lack of ingenuity on the art of dentists. These technological improvements have not decreased the need for skilled, knowledgeable restorative dentists. On the contrary, they have made knowledge and skill that much more critical. Technology in the hands of a skilled operator makes it possible to do more work of an even higher quality. www.indiandentalacademy.com
  • 21. 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) 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-7; 1999) Full veneer crown / Complete crown: A restoration that covers all the coronal tooth surfaces ( mesial, distal, facial, lingual and occlusal ) (GPT-7; 1999) Chamfer Finish line: A finish line design for tooth preparation in which the gingival aspect meets the external axial surface at an obtuse angle (GPT-7; 1999) 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-7; 1999) www.indiandentalacademy.com
  • 22. Retention form : The feature of a tooth preparation that resists dislodgement of crown in a vertical direction or along the path of placement (GPT-7; 1999) 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 (GPT-7; 1999) Bevel : The process of slanting the finish line and curve of a tooth preparation (GPT-7; 1999) www.indiandentalacademy.com
  • 23. ROTARY INSTRUMENTS USED FOR FULL VENEER PREPARATIONS Shape Round end diamond Use tapered 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 www.indiandentalacademy.com
  • 24. Small wheel diamond Tapered (171L) fissure 1. Lingual reduction in anterior teeth bur 1.Seating groove 2.Proximal groove (posterior teeth 3.Smoothing and finishing 4.Occlusal and incisal bevels www.indiandentalacademy.com
  • 25. Tapered fissure (169L & 170L) burs 1.Initial groove alignment 2.Angles of proximal boxes 3.Smoothing and finishing 4.Occlusal and incisal bevels End cutting bur Conventional shoulder finishing Torpedo bur 1.Axial wall finishing 2.Chamfer finishing Flame bur 1. Flare and bevel finishing www.indiandentalacademy.com
  • 26. FULL VENEER CROWNS COMPLETE CAST CROWN METAL CERAMIC ALL CERAMIC CROWN www.indiandentalacademy.com
  • 27. 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. www.indiandentalacademy.com
  • 28. Clinicians have long considered full veneer crowns to be the most retentive of veneer preparations Controlled laboratory studies have shown that when compared with partial veneer designs, the full veneer crown exhibits superior retention and resistance It does not mean that it must be used in every case Instead should be used on those teeth whose restoration demands maximum retention. Selection of full veneer retainer becomes mandatory when the abutment tooth is small or when the edentulous space is long. www.indiandentalacademy.com
  • 29. 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. www.indiandentalacademy.com Esthetics.
  • 30. 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. www.indiandentalacademy.com
  • 31. TOOTH PREPARATION FOR COMPLETE CAST CROWN 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 nonfunctional cusps. The tooth structures between the orientation grooves are removed following cuspal contours. www.indiandentalacademy.com
  • 32. 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. www.indiandentalacademy.com
  • 33. 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. www.indiandentalacademy.com
  • 34. TOOTH PREPARATION FOR FULL VENEER CROWNS www.indiandentalacademy.com
  • 35. CONTENTS OF THE SEMINAR 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 Review of literature Conclusion References www.indiandentalacademy.com
  • 36. 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 planing the surface to smoothness. www.indiandentalacademy.com
  • 37. Chamfer finishing. Torpedo bur is used to produce a distinct finish line and to round of the angles of the preparation. www.indiandentalacademy.com
  • 38. 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. www.indiandentalacademy.com
  • 39. Features of full veneer crown preparation and the function served by each www.indiandentalacademy.com
  • 40. METAL CERAMIC RESTORATION www.indiandentalacademy.com
  • 41. 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. www.indiandentalacademy.com
  • 42. ANTERIOR METAL-CERAMIC CROWN 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 technically feasible. www.indiandentalacademy.com is
  • 43. 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. www.indiandentalacademy.com
  • 44. ANTERIOR PORCELAIN FUSED TO METAL 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 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. www.indiandentalacademy.com
  • 45. 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. www.indiandentalacademy.com
  • 46. 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. www.indiandentalacademy.com
  • 47. 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. www.indiandentalacademy.com
  • 48. 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. www.indiandentalacademy.com
  • 49. 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. www.indiandentalacademy.com
  • 50. 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. www.indiandentalacademy.com
  • 51. Shoulder finishing: No: 957 bur is used to finish the shoulder. www.indiandentalacademy.com
  • 52. The features of an anterior porcelain fused to metal crowns preparation on an anterior tooth www.indiandentalacademy.com
  • 53. POSTERIOR PORCELAIN FUSED TO METAL CROWN PREPARATION www.indiandentalacademy.com
  • 54. Appearance zone Maxillary - premolars - first molars Mandibular – first premolar www.indiandentalacademy.com
  • 55. 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 www.indiandentalacademy.com contours.
  • 56. 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. www.indiandentalacademy.com
  • 57. 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 www.indiandentalacademy.com be used.
  • 58. 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. www.indiandentalacademy.com
  • 59. 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. www.indiandentalacademy.com
  • 60. 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. www.indiandentalacademy.com
  • 61. 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. www.indiandentalacademy.com
  • 62. 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. www.indiandentalacademy.com
  • 63. 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. www.indiandentalacademy.com
  • 64. 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. www.indiandentalacademy.com
  • 65. ALL-CERAMIC CROWNS www.indiandentalacademy.com
  • 66. 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. www.indiandentalacademy.com
  • 67. • • • • • • • • • 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 www.indiandentalacademy.com distribution of occlusal load.
  • 68. • • • • • • • • • • 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 www.indiandentalacademy.com
  • 69. 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. www.indiandentalacademy.com
  • 70. 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. www.indiandentalacademy.com
  • 71. 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. www.indiandentalacademy.com
  • 72. 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. www.indiandentalacademy.com
  • 73. 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. www.indiandentalacademy.com
  • 74. 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. www.indiandentalacademy.com
  • 75. Axial finishing: No: 171 bur is used to smooth the axial surfaces and to round all distinct positive angles on the preparation. www.indiandentalacademy.com
  • 76. 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. www.indiandentalacademy.com
  • 77. The features of all ceramic crowns preparation for a porcelain jacket crown on an anterior tooth and the function served by each. www.indiandentalacademy.com
  • 78. CAST 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 depthorientation grooves with the large round-end tapered diamond. www.indiandentalacademy.com
  • 79. 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. www.indiandentalacademy.com
  • 80. 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. www.indiandentalacademy.com
  • 81. 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. www.indiandentalacademy.com
  • 82. Preparation finishing: round end tapered carbide bur is used to finish the axial surfaces and the functional cusp bevel. www.indiandentalacademy.com
  • 83. The features of a cast ceramic crown preparation for an all ceramic crown on a posterior tooth and the function served by each. www.indiandentalacademy.com
  • 84. REVIEW OF LITERATURE www.indiandentalacademy.com
  • 85. Dennis et al (1974) – while describing the fundamentals of tooth preparation, stated thatAll preparations require the incorporation of factors to prevent the dislodgement of the restoration by functional stresses. Retention form counteracts the tensile stresses, and resistance form counteracts the shearing stresses. A preparation with resistance form will be retentive; the opposite is not necessarily true. The same method is often used when incorporating the factors of both retention and resistance form. www.indiandentalacademy.com
  • 86. Thus, for practical purposes, these factors can be considered together as:I. Principles1. Parallelism 2. Length 3. Surface area II. Factors- and c 1. Primary factors- axial surfaces 2. Secondary factors: a. Groove b. Box c. Pinholes d. combinations of a, b, www.indiandentalacademy.com
  • 87. David A. Felton et al (1987) found that teeth prepared for full crowns by using diamond burs will have 31% greater retention than preparations made with carbide bur. Alternative retentive features should be considered in preparation design if carbide burs are used. www.indiandentalacademy.com
  • 88. Shillingburg HT et al (1987) - stated that theoretically, the most retentive preparation would be with parallel walls. However in order to avoid undercuts and allow complete seating of the restorations during cementation, the walls must have some taper. One which lies within the range of 2 to 6.5 degrees has been considered to be optimal www.indiandentalacademy.com
  • 89. Jeffrey Nordlander et al (1988) studied the convergence angles of full coverage preparations performed in a clinical environment and concluded that the ideal convergence of 4 to 10 degrees is seldom achieved. The mean convergence angle of mandibular preparations were greater than mean maxillary convergence angle and premolar convergence angle tended to be smaller than anterior convergence angles. www.indiandentalacademy.com
  • 90. Gerard Byrne (1992) compared shoulder, shoulder bevel and chamfer finish configurations and studied their effect on fit of cemented complete crowns. He observed that Incisor cast crowns did not seat completely regardless of finish line design Finish line form did not affect the fit of incisor cast crowns (cemented or not ) www.indiandentalacademy.com
  • 91. El Mowafy OM et al (1996) - investigated the effect of varying crown preparation taper and height on the retention in metal ceramic crowns cemented with zinc phosphate cement and resin cements. They reported significantly higher retention in both Standard (24 degree TOC and a constant height of 4.0±0.25mm) and Conical preparation (with same height but TOC 70 degree) cemented with resin cement than the zinc phosphate cement. They also reported significantly higher retentive force for the crowns of Conical preparations cemented with resin cements than that of the crowns of Standard preparation cemented with zinc phosphate cement. Also short crowns cemented with resin cement had significantly higher retention force than long crowns cemented with zinc phosphate www.indiandentalacademy.com
  • 92. Mohammed F. Ayad et al (1997) studied the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of restorative cemented restorations. Greatest retention value was for tooth preparations refined with carbide burs and cemented with Panavia-EX, an adhesive resin cement. Least retention values was for teeth preparations completed with finishing bur and luted with zinc phosphate cement. www.indiandentalacademy.com
  • 93. Charles J. Godacre et al (2001) – Reviewed literature covering 250 years of clinical practice with emphasis on scientific data acquired during last 50 years. On the basis of the current scientific studies, they proposed certain guidelines for preparing teeth for complete crowns www.indiandentalacademy.com
  • 94. Omar Zidan et al (2003) - studied the relation between the preparations’ taper and retentive capacities of conventional zinc phosphate cement, glass ionomer cement and adhesive resin cements. They concluded that: The retentive values of adhesive resin cements at 24 degree taper is 20% higher than the retentive values of the conventional zinc phosphate and glass ionomer cements at 6 degree taper Increasing taper of the preparations from 6 to 12 degrees did not affect the retention of the crowns within the different cement groups. The choice of the cement for crown prepared within this ideal range of taper might be of limited clinical value Increasing the taper to 24 degrees decreases the retention of crowns significantly. www.indiandentalacademy.com
  • 95. CONCLUSION 1. The total occlusal convergence (TOC), formed between two opposing axial surfaces, ideally ranges from 10 to 20 degree. 2. 3 mm should be the minimal occluso-cervical / incisocervical dimension of the incisors and premolars prepared with recommended 10 to 20 degree total convergence 3. The minimal occlusal cervical dimension of molars should be 4 mm when prepared with 10 to 20 degrees TOC. 4. The ratio of the occluso-cervical/inciso-cervical dimension of a prepared tooth to the facio-lingual dimension should be at least 0.4 or higher for all teeth 5. Facio proximal and linguo proximal line angles should be preserved wherever possible. www.indiandentalacademy.com
  • 96. 6. When the above features are missing the teeth should be modified with auxiliary resistance features such as axial grooves or boxes, preferably on proximal surfaces. 7. Many molars need auxiliary grooves or boxes to enhance resistance form because of their short occluso- cervical dimensions and the unfavorable ratio of the occluso- cervical dimension to the faciolingual dimensions 8. The type of finish line selected for use with metalceramic crowns should not be based on marginal fit but on the type of crown/ retainer, esthetic requirements, ease of formation and personal preference. 9. Expectations of enhanced marginal fit with certain finish lines could not be validated by recent research. www.indiandentalacademy.com
  • 97. 10.Esthetic requirements and tooth conditions determine finish line locations relative to the gingiva with a supra gingival location being more acceptable. 11.When sub gingival finish lines are required, they should not be extended to the epithelial attachment 12.Line angle should be rounded, and reasonable degree of surface smoothness is desired. 13.Both shoulder and chamfer finish lines can be used with all-ceramic crowns if the crowns are bonded to the prepared teeth. Depths greater than 1 mm are not required when a semi translucent type of allceramic crown is used. 14.Chamfer finish lines approximately 0.3 mm deep www.indiandentalacademy.com are well suited for all-metal crowns
  • 98. 15.Axial and occlusal reductions for all-metal crowns should be at least 0.5 mm deep and 1,0 mm deep, respectively. For metal-ceramic crowns, facial/axial reductions in excess of 1 mm can compromise the remaining tooth structure external to the pulp, whereas 2.0 mm of occlusal reduction is commonly achievable even on a young tooth. Two millimeters incisal/occlusal reduction is recommended for allceramic crowns. 16.Line angle should be rounded on all-ceramic tooth preparation to reduce stress in the definitive restoration. With crowns that use metal, the primary purpose of line angle rounding is to facilitate pouring impressions and investing wax patterns without trapping air bubbles and to facilitate removing casting nodules www.indiandentalacademy.com
  • 99. 17.Smooth tooth preparation appears to enhance the fit of restorations. Surface roughness generally increases retention with zinc phosphate cement, but its effect with adhesive cements ( polycarboxylate, glass ionomer, resin) has not been as definitely determined. A reasonably smooth preparation is therefore recommended. www.indiandentalacademy.com
  • 100. REFERENCES www.indiandentalacademy.com
  • 101. El Salam Shakal MA, Pfeiffer P, and Hilgers RD. Effects of tooth preparation design on bond strengths of resin bonded prostheses; a pilot study. J Prosthet Dent. 1997; 77: 243249. Felton DA, Ed Kanoy B and White JT. The effect of surface roughness of crown preparations on retention of cemented castings. J Prosthet Dent. 1987; 58: 292-296. Nordlander J Weir D, Stoffer W and Ochi S. The taper of clinical preparations for fixed prosthodontics. J Prosthet Dent. 1988; 60: 148-151. Byrne G. Influence of finish-line form on crown cementation. Int. J Prosthet Dent. 1992; 5: 137-144. Rouse JF. Full veneer versus traditional veneer preparation. A discussion of interproximal extension. J Prosthet Dent. 1997; 78: 545-549. Charles Goodacre, Wayne V. Campagni, and Steven A. Aquilino, -Tooth preparation of complete crown: An art form based on scientific principle.JProsthet.Dent2001; 85:363-76 El-Mowafy O.M., Fenton A.H.,Forester N., Milenkovice M.Retention of metal ceramic crowns cemented with resin cement :effects of preparation taper ,,and height – www.indiandentalacademy.com J.Prosthet.Dent 1996;76:524-29.
  • 102. Omar Zidan and Gerry C. Ferguson – The retention of complete crowns prepared with three different tapers and luted with four different cements, J. Prosthet.Dent. 2003;89:565-71 Ayad MF, Rosenteil SF and Salama M. Influence of tooth surface roughness and type of cement on retention of complete cast crowns. J Prosthet Dent. 1997; 77: 116-121. Fundamentals of tooth preparations for cast metal and porcelain restorations. Shillinburg HT Jr. Quintessence Publishing Co. Inc. 1987 Contemproary Fixed Prosthodontics. Rosenstiel Tylman’s Theory and Practice of fixed prosthodontics. 8th edition. All India Publishers and Distributors www.indiandentalacademy.com
  • 103. THANK YOU www.indiandentalacademy.com
  • 104. THANK YOU www.indiandentalacademy.com
  • 105. www.indiandentalacademy.com
  • 106. www.indiandentalacademy.com
  • 107. www.indiandentalacademy.com
  • 108. www.indiandentalacademy.com
  • 109. Samuel E. Guyer. (1970) discussed the types and modifications of the four elements of tooth preparation 1. Occlusal reduction, 2. Axial reduction, 3. Margins, 4. Means of retention and resistance form. He has applied these 4 principles on multiple tooth preparation which involves three steps: 1. Occlusal reduction, 2. Axial reduction, 3. Retention of resistance form placement. He has introduced guidelines for grouping of teeth for multiple preparations. www.indiandentalacademy.com
  • 110. J.R. Gavelis et al (1980) discussed the influence of marginal design of a full crown on the occlusal seat and marginal seal of a cemented full crown restorations. Feather edge and parallel bevel demonstrated the best marginal seal, followed by full shoulder, 45 degree shoulder, and finally 90 degree shoulder with 30 degree and 45 degree bevels. The 90 degree shoulder demonstrated best seating followed by 45 degree shoulder, 90 degree shoulder with 45 degree bevel, feather edge, 90 degree shoulder with 30 degree bevel, chamfer with parallel bevel and degree shoulder with parallel bevel. www.indiandentalacademy.com
  • 111. H. W. Anslem Wiskott et al (1997) investigated the relationship between tooth preparation height and diameter and the resistance of cemented crowns to dynamic loading. The relationship between abutment height and resistance to dynamic lateral loading was found approximately linear and crowns luted using resin composite cement were the most resistant. www.indiandentalacademy.com
  • 112. Julia Fischer et al (1997) described a new restoration method the edge up technique that enables the correction of defects in the anterior teeth with maximum preservation of tooth substance. The special preparation method involves a circular extended shoulder preparation in the enamel or an angle preparation using a special preparation kit. www.indiandentalacademy.com
  • 113. Jung-Zen Syu et al (1993) Evaluated axial and marginal fit of crowns made for three tooth preparations that had different labial finish lie configurations: shoulder, shoulder-bevel and chamfer. No significant differences were found among the group for marginal or axial gaps crown fit was not influenced by any of the three finish lines and castings with well fitting margins exhibited measurable axial wall space. www.indiandentalacademy.com
  • 114. THANK YOU www.indiandentalacademy.com