CLASS II CAVITY PREPARATION for amalgam

dentistry, class 2 cavity preparation

1. See image below at: www.columbia.edu/ itc/hs/dental/ operative/ matrixband.html

2. Proximal 3 main sites where caries occur: Occlusal Cervical

3. PROXIMAL CONTACT AREA It is the area of proximal height of contour of the mesial or distal surface of a tooth that touches its adjacent tooth in the same arch.

4. When teeth erupt to make contact with previously erupted teeth, there is initially a CONTACT POINT .

5. This becomes a CONTACT AREA because of wear of 1 proximal surface against another during physiologic tooth movement.

6. IN AN ADULT MOUTH WITH ALL TEETH PRESENT, THERE ARE ______PROXIMAL CONTACT AREAS. 60

7. Knowing proximal contacts - facio/buccolingually -inciso/occlusogingivally

8. IMPORTANCE OF PROXIMAL CONTACTS

9. 1. They prevent food impaction. Food impaction can result in periodontal disease, carious lesions and possible movement of teeth.

10. 2. Proximal contacts along with the interdigitation of teeth through occlusal contacts stabilizes & maintains the integrity of the dental arches.

11. Embrasures They are V- shaped spaces that originate at the proximal contact areas between adjacent teeth and are named for the direction toward which they radiate.

12. 1. Facial/ Buccal 2. Lingual/ Palatal 3. Incisal/ Occlusal 4. Gingival

13. The proximal enamel surfaces immediately gingival of the contact area are highly susceptible to caries because

14. these areas are relatively free from the effects of mastication of food, tongue movement and salivary flow.

15. Caries start just below the contact area.

16. Class II lesions Carious lesions present on the proximal surfaces of posterior teeth are called as

17. How do we approach this leison?

18. OCCLUSAL approach.

19. Composite Which material can we use? Amalgam

20. CLASS II CAVITY PREPARATION FOR AMALGAM

21. 3 IMPORTANT STEPS: OCCLUSION LOCAL ANESTHESIA ISOLATION

22. CLASS II CAVITY PREPARATION OCCLUSALSTEP PROXIMALBOX

23. INITIAL CAVITY PREPARATION OCCLUSAL STEP BUR USED: 245 PLACE THE BUR PARALLEL TO THE LONG AXIS OF THE TOOTH

24. DEPTH OF OCCLUSAL STEP: 1.5- 2mm (0.1 to 0.2mm into dentin) WIDTH OF OCCLUSAL STEP: 1/4 th the intercuspal distance / width of 245 bur.

25. WALLS: BUCCAL LINGUAL MESIAL DISTAL PULPAL FLOOR CONVERGENT SLIGHTLY DIVERGENT

26. EXTEND PREPARATION MESIALLY STOPPING 0.8mm SHORT OF THE MARGINAL RIDGE. How do we know that we are 0.8mm short of the ridge?

27. demo- 1

28. PROXIMAL BOX PREPARATION PROXIMAL DITCH CUT REMOVING PROXIMAL ENAMEL WALL REMOVING WEAKENED ENAMEL

29. PROXIMAL DITCH CUT: Bur should cut 2/3 rd at expense of dentin and 1/3 rd at expense of enamel. 0.5 to 0.6mm into dentin 0.2 to 0.3mm into enamel

30. DIRECTION TO BE USED WHILE PREPARING THE PROXIMAL DITCH CUT: BUCCOLINGUAL

31. DEPTH OF PROXIMAL DITCH CUT: just below contact area or just beyond the depth of caries. How do we confirm the depth clinically ?

32. WIDTH OF PROXIMAL DITCH CUT: Wider faciolingually than class I. (Margins should clear adjacent tooth by 0.2 to 0.3 mm.)

33. Demo-2

34. IMPORTANCE OF KEEPING THE MESIAL WALL WHILE PREPARING DITCH CUT: Acts as a guide for the bur. Axial wall will follow the contour of external tooth surface. Protects the adjacent tooth from damage.

35. II. REMOVING PROXIMAL ENAMEL Make two proximal extensions, one facially and other lingually.

36. Matrix band may be used to protect the adjacent tooth. Remaining enamel is fractured out with a spoon excavator.

37. Demo- 3

38. III. REMOVING WEAKENED ENAMEL Use an enamel hatchet or a binangle chisel.

39. Demo- 4

40. AXIAL WALL GINGIVAL SEAT

41. PROXIMAL BOX OCCLUSAL STEP …Go hand in hand.

42. DEPTH OF PROXIMAL BOX: just below contact area or just beyond the depth of caries.

43. WIDTH OF PROXIMAL BOX: Such that margins clear the adjacent tooth by 0.2 to 0.3 mm.

44. AXIAL DEPTH OF GINGIVAL SEAT:

45. WHY DO WE BREAK CONTACTS IN A CLASS II CAVITY PREPARATION? To place cavity margins in self cleansing areas. To facilitate finishing of margins.

46. To facilitate placement of the matrix band. Evaluation of margins for recurrent caries at the time of recall.

47. WHICH CONTACTS DO WE BREAK IN A CLASS II CAVITY PREPARATION? BUCCAL LINGUAL/ PALATAL GINGIVAL

48. BY HOW MUCH DO WE BREAK CONTACTS IN A CLASS II CAVITY PREPARATION? BUCCAL: 0.2-0.3mm LINGUAL/ PALATAL: 0.2-0.3mm GINGIVAL: 0.5mm

49. PRIMARY RESISTANCE AND RETENTION FORM

50. Flat pulpal and gingival walls. Restricting extension of walls. PRIMARY RESISTANCE FORM

51. Restricting occlusal outline form to areas receiving minimal occlusal contact. Rounding off the internal line angles. Providing enough thickness of amalgam to prevent its fracture under mastication.

52. Occlusal convergence of facial and lingual walls. Dovetail design of occlusal step. PRIMARY RETENTION FORM

53. REVERSE CURVE

54. Reverse curve is a curve that permits a 90- degree amalgam marginal angle. It also conserves tooth structure.

55. Mostly given in maxillary molars, where contact area is more buccal. But it can also be given in mandibular posterior teeth where contact area is more pronounced on one side.

56. FINAL CAVITY PREPARATION REMOVAL OF REMAINING CARIOUS DENTIN.

57. 2. PULP PROTECTION

58. 3. SECONDARY RESISTANCE AND RETENTION FORM

59. Round off axiopulpal line angle. This decreases stress concentration and increases the bulk of amalgam. SECONDARY RESISTANCE FORM

60. Round off axiopulpal line angle with gingival marginal trimmer.

61. Demo-5

62. 1. PROXIMAL LOCKS Burs used: 169L or 33 ½ or ¼ bur. Location: axiofacial and axiolingual line angles. SECONDARY RETENTION FORM

63. Depth : 0.5mm

64. 2. SLOTS Burs used: ¼ or ½ bur. Location: gingival floor Depth: 0.5-1mm Width (faciolingual): 2-3mm

65. 4. FINISHING OF EXTERNAL WALLS

66. 5. CLEANING, INSPECTING AND VARNISHING

67. MESIOOCCLUSAL MESIOOCCLUSODISTAL BLACK’S SPECIAL CAVITY AND CONVENTIONAL CAVITY TUNNEL PREPARATION SANDWICH TECHNIQUE