7.CLASS II INLAY CAVITY PREPARATION.pptx

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1. CAST METAL RESTORATIONS (CLASS II INLAY CAVITY PREPARATION) PRESENTED BY:- DR. ADITEE AGRAWAL PG 2 nd YEAR DEPT. OF CONSERVATIVE DENTISTRY AND ENDODONTICS.

2. CONTENTS:- INTRODUCTION DEFINITIONS CAST METAL RESTORATION:- INDICATIONS AND CONTRAINDICATIONS ADVANTAGES AND DISADVANTAGES PREOPERATIVE CONSIDERATIONS PRINCIPALS OF CAVITY PREPARATION FOR CAST RESTORATIONS TYPES AND DESIGN FEATURES OF OCCLUSAL AND GINGIVAL BEVELS FUNCTIONS OF OCCLUSAL AND GINGIVAL BEVELS

3. TYPES AND DESIGN FEATURES OF FACIAL AND LINGUAL FLARES PREPARATION FEATURES OF CIRCUMFERENTIAL TIE TOOTH PREPARATION FOR CLASS II CAST METAL INLAYS MODIFICATIONS IN INLAY TOOTH PREPARATION MODIFICATIONS OF PROXIMAL CAVITY DESIGN TOOTH PREPARATION WITH SURFACE EXTENSION

4. INTRODUCTION Dr. PHILL BROOK in 1897, was the first to introduce inlay in dentistry who gave the concept of forming an investment around wax pattern, eliminating the wax and filling the resultant mold with a gold alloy. In 1907 Taggart changed the practice of restorative dentistry by introducing his technique for cast gold restorations. It was most certainly Taggart who recognized the significance of cast gold restorations.

5. MATERIALS FOR CAST METAL RESTORATIONS Until recently gold based alloys have been the only ones used for cast dental restorations. The ADA sp # 5 still requires 75% of gold- plus-platinum group metals to be present in alloys for cast restorations. According to Sturdevant’s there are four distinct groups of alloys: The traditional high gold alloys Low gold alloys Palladium- silver alloys Base metal alloys

6. According to Marzouk : Class I: gold and platinum group based alloys Class II : low gold alloys Class III: non- gold palladium based alloys Class IV: nicklel chromium based alloys Castable moldable ceramics.

7. DEFINTION Inlay:- A fixed intracoronal restoration,a dental restoration made outside of tooth to correspond to the form of the prepared cavity , which is then luted into the tooth.

8. Onlay :- A restoration that restores one or more cusps and adjoining occlusal surfaces or the entire occlusal surface and is retained by mechnical or adhesive means.

9. INDICATIONS Large restorations: Better strength Control of contours and contacts Better alternative to a crown to teeth that have been greatly weakened by caries or by a large failing restoration, but facial and lingual surfaces are unaffected by disease/injury. For such a weakened teeth , the superior physical properties of the casting alloys are desirable to withstand occlusal loads placed on the restorations.

10. Endodontically treated teeth: Molars and premolars with endodontic treatment can be restored with cast metal onlay . Teeth at risk for frature :- Teeth with extensive restoration, fracture line in enamel and dentin must be recognized as cleavage planes for future tooth fracture.

11. Dental rehabilitation with cast metal alloy: When cast metal restorations have already been used to restore adjacent or opposite teeth, the continue use of same metal to avoid electrical or corrosive activity that may occur if the dissimilar metals are used. Removable prosthodontic abutment: Teeth that are to serve as abutment for a removable partial denture can be restored with cast metal restoration.

12. CONTRAINDICATION:- High caries rate: Facial and lingual tooth surface must be free of caries or previous restorations. If present, the tooth must be restored with full crown. Young patients:- Amalgam or composite are the restorative materials for Class I and Class II restorations unless the tooth is severely broken down or endodontically restored.

13. Esthetics:- Their use restricted to the tooth surfaces that are not visible at conversational distance. Small restorations:- Amalgam and composite serves as a better option.

14. ADVANTAGES Strength Biocompatibilty Low wear Control of contacts and contours.

15. DISADVANTAGES Number of appointments and more chair time. Extensive tooth preparation Cost and temporary restoration requirement Technique sensitive Spliting forces

16. Preoperative considerations Occlusion :- Occlusion contacts must be evaluated It must be decided that occlusal relationships can be improved with a cast metal restoration. The pattern of occlusal contacts influences the preparation design, the selection of interocclusal records, and the type of articulator.

17. Anaesthesia :- Eliminates pain, reduces salivation. Considerations for temporary restorations:- An index can be fabricated preoperatively using elastomeric impression or alginate.

18. TECHINQUES Direct technique Indirect technique

19. DIRECT TECHIQUE:- Where inlay wax is inserted into the prepared cavity , carved, contacts made and taken out of the cavity. The lab procedure than follow.

20. Indirect technique: When an impression of the prepared cavity is taken and all the procedures are followed in the model in the lab.

21. GENERAL PRINCIPLES Greater surface extension in outline form than amalgam. This facilitates support and efficient marginal manipulation. More extensive surface involvement to compensate for the cariogenically weak joints of cast/cement/tooth interface.

22. The design for a cast restoration is governed by 5 principles:- Preservation of the tooth structure Retention and resistance Structure durability Marginal integrity Preservation of the periodontium .

23. Preservation of tooth structure:- In addition to replacing the lost tooth structure, the cast restoration must preserve the remaining structure. Preservation of tooth structure may involve limited amounts of the tooth being prepared.

24. Retention and resistance :- Retention prevents removal of the restoration along the path of insertion or long axis of the tooth preparation. Resistance prevents dislodgment of the restorations by forces in an apical or oblique direction and prevents any movement of the restoration under occlusal forces.

25. Besides applying the general principles of tooth and cavity preparation, cast restoration preparations should have the following features:- Preparation path:- Preparation should have a “ Single Insertion Path ” Path is parallel to the long axis of tooth crown. Helps in retention and decreases the micro movements of restoration during function.

26. B) Apico - occlusal taper:- For maximum retention, opposing walls and axial surfaces should be perfectly parallel to each other. Slight divergence of opposing walls in Intracoraonal . Slight convergence of axial walls in Extracoronal . Taper should be 2-5° from path of preparation.

27. 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 preparation ends on enamel, enamel must supported by sound dentin. Enamel rods forming the cavosurface margin should be continous with sound dentin. Enamel rods forming the cavosurface margin should be covered by restorative material. Angular cavosurface angle should be trimmed.

28. Structural durability:- Occlusal reduction Functional cusp bevel Axial reduction

29. Marginal integrity( Bevels):- Bevels are defined as “ flexible extensions ” of cavity preparation, allowing the inclusion of surface defects, supplementary grooves and other areas on the tooth surface. Two types of bevels:- Occlusal bevel Gingival bevel

30. Types and design features of occlusal and gingival bevels Partial bevel: Involves part of the enamel only, Not exceeding 2/3 rd its Dimension. Not used in cast restoration, except to trim weak enamel rods.

31. Short bevel :- Includes entire enamel wall but not dentin, it is used with Class I alloys specially for type 1 & 2 ( Gold platinum based alloys).

32. Long bevel:- Includes all enamel and upto ½ of the dentinal wall, its major advantage is that it preserves the internal boxed up resistance Most frequently used bevel for cast materials.

33. Full bevel:- Includes all of the enamel and dentinal walls of the cavity wall and floor. Its use should be avoided except in cases where it is impossible to use any other form of bevel.

34. Counter bevel:- When capping cusps these protect and support them. Given opposite to an axial wall on the facial and lingual surface.

35. Hollow ground (concave bevel):- Allows more space for cast material bulk. Used to improve retention and resistance to stresses.

36. Functions of occlusal and gingival bevel:- Bevels create an obtuse angles marginal tooth structure (strong tooth anatomy) Produce an acute angled marginal cast alloy( most amenable finishing and burnishing). Makes it possible to decrease the cement line by bringing cast alloy closer to the tooth. They are also part of one of the major retention form of cast restorations.

37. PRINCIPLES OF CAVITY DESIGN FOR CAST INLAY RESTORATIONS:- The class II inlay involves the occlusal and proximal surfaces of a posterior tooth and may cap one cusps but not all of the cusps.

38. Indications:- Cavity width not to exceed 1/3 of intercuspal distance. Strong, self resistant cusps. Indicated teeth have minimal or no occlusal facets. Tooth is not be used as an abutment in FPD or RPD. Occlusion or occluding surface are not be changed by restorative procedure.

39. Steps for class II cast metal inlays:- initial preparation Occlusal step Proximal box Resistance and retention form Final preparation Removal of infected caries and pulpal protection Preparation of bevels and flares Modification

40. Initial preparation :- ARMANTERIUM:- BURS:- Burs used are no. 271, 169L & no. 8862 Sides and the end surface of the bur meet in a rounded manner to prevent sharp internal angles. Burs are “ plane cut ” so that vertical walls are smooth.

41. Outline form Occlusal part consist of an dovetail form and a proximal box.

42. Occlusal step:- Initial entry is made in the central fossa / pit with a tapered fissure bur no. 271 to establish the pulpal floor (punch out ) to a depth of 1.5 mm The depth is determined by extent of existing carious lesions or restorations or the need for additional retention.

43. The occlusal outline is extended mesiodistally along the central groove and stopped just short of the marginal ridge. The is kept in vertical position in the long axis of the tooth through out the preparation so that its taper provides the 3-5°divergence to the facial and lingual walls (total divergence of 6- 10° )

44. Primary resistance form:- Use of box shape Preservation of cusps and marginal ridges Slight rounding of internal line angles Capping weakened cusps Adequate thickness of restorative material.

45. Preserving dentin support

46. Shallow enamel fault less than 1/3 rd the thickness of enamel can be removed by enameloplasty

47. Final extension in the facial and lingual triangular grooves with 169L bur forming the dovetail

48. Dovetail aids in additional retention as it fits in the preparation only in occlusal to gingival direction

49. Extending the margin distally into distal marginal ridge to expose the proximal dentino -enamel junction

50. Cutting the proximal ditch with no. 271 bur

51. Extension of proximal ditch facially and lingually beyond the caries and which should clear the adjacent tooth by 0.2-0.5 mm

52. Penetration of enamel by side of bur at its gingival end, followed by breaking of the isolated enamel

53. Planning the walls

54. Removing caries on the axial wall

55. Removing the remaining infected dentin with no. 2 or 4 round bur

56. Insertion of suitable base and completed base

57. Preparation of the bevels and flares:- The slender flame shaped fine grit diamond is used to bevel the occlusal and gingival margins and to apply the secondary flare on the proximal facial and lingual walls. It will result in 30-40° marginal metal and 140-150° cavosurface margin.

58. For the facial and lingual proximal walls in an inlay cavity preparation for castings flares are used, which are the flat or concave pheripheral portions of the facial and lingual walls. There are two types of flares:- Primary flare Secondary flare

59. The Primary Flare: Is the conventional and basic part of the cavity facially and lingually for an intracoronal preparation. It is very similar to a long bevel formed of enamel and part of the dentin on the facial or lingual wall. Primary flare also have a specific angualation i.e 45° to the inner dentinal wall proper.

60. Functions and indications:- These design fearures perform the same function as bevels. They can bring the facial and lingual margins of the cavity preparation to cleansable finishable areas. They are indicated for any facial or lingual proximal wall of an intracoronal cavity preparation.

61. Secondary flare:- It is almost always a flat plane superimposed peripherally to a primary flare. It is usually prepared solely in enamel. unlike primary flares, secondary flares have different angulations, involvement and extent depending on their function. Functions and indication of secondary flare:- lesions with wide bucco -lingual extension. Contact areas too broad.

62. Bevelling gingival margin

63. After completion of the gingival bevel facial secondary flare is made

64. Bevelling axio-pulpal line angle and mesial marginal ridge

65. Completed preparation

66. Modifications of class II inlay cavity preparation:- For esthetics: Absence of secondary flare on facial proximal surface

67. Facial and lingual groove extension

68. Extension gingivally to extend root surface lesion

69. Capping cusps:- When the occlusal outline is extended up the cusp slopes more than half the distance from primary groove, capping the cusp should be considered. If it is extended two thirds or more, capping is necessary.

70. MODIFICATIONS OF PROXIMAL CAVITY DESIGN:- Box preparation Slice preparation Auxillary slice preparation Modified flare

71. Box preparation:- Introduced by Dr. G. V Black in which the proximal cavities are prepared box shaped with and buccal and lingual walls and a definite gingival floor. Advantages:- it has its own retention and resistance form . Direct wax pattern can be made. The outline form of proximal surfaces can be made on all types of teeth.

72. Slice preparation:- A slice is referred to the placement of extra coronal taper using a disk of adequate diameter to contact nearly the entire proximal surface. This form of cavity is modified so that the proximal surface is flat without definite side walls. These slices are generally placed on the buccal and lingual proximal surfaces independently. The slice may extend to the cervical floor, or more frequently will terminate at some point occlusal floor.

73. Slice preparation involves conservative disking of the proximal surface to establish the buccal and lingual extent of finish lines and provide a lap joint for finishing .

74. Auxillary slice preparation:- Wraps partially around the proximal line angles, thus providing additional tooth support. Resistance form is enhanced. Provide external retention form.

75. Modified flare:- The modified flare preparation is a hybrid between the box and slice preparations. Buccal and lingual proximal walls initially formed with minimal extension, then disked in a plane that only slightly reduces the proximal wall dimension.

76. Tooth preparation for cast restoration with surface extension:- Reverse Secondary Flare:- This is a surface extension of the basic intracoronal inlay or onlay cavity preparation. The reverse secondary flare is in the form of partial bevel. It involves only enamel, with its maximum depth at its junction with the main cavity preparation.

77. It ends on the facial or lingual surface with a knife edge finishing line, and its extent should not exceed the height of contour of the facial or lingual surface in the mesio -distal direction, nor should include the tip of the cusp.

78. Indications:- Surface extensions are required to include facial and lingual defects beyond the axial angle of the tooth. A surface extension is needed to eradicate severe peripheral marginal undercuts. A surface extension is needed to add to the retentive capability of the restoration proximally. Contraindications:- This type of surface extension is contraindicated for Class IV and Class V cast materials.

79. REFERNCES Art and Science of Operative Dentistry- Sturdevant’s . fifth edition. Fundamentals of Operative Dentistry- Marzouk . Operative dentistry- Summit Principles and Practice Operative Dentistry. Third edition. Gerald T. Charbeneau .

80. THANK U