The document discusses modifications that can be made to class II cavity preparations in primary molars to decrease stresses. This includes using concave pulpal floors and rounded internal line angles. It also recommends a relatively wider isthmus width that is one-third the intercuspal distance, and conservative proximal extensions that cannot pass an explorer tip. The document provides details on techniques for class II cavity preparations, such as using a #330 bur then switching to a #245 bur for extensions. Matrices, bases, condensation, and carving of amalgam restorations are also outlined.

1. Modifications
 Concave pulpal floor
and gingival seat
 Rounded internal
line angles
both decrease stress
in the restoration
View from distal surface
of primary 1st molar
B L

2. Modifications
 Relatively wider isthmus width
one-third the inter cuspal distance
 Conservative proximal extensions
light, but cannot pass an explorer tip through

3. Modifications
No proximal grooves
No reverse curves

4. Class II

5. Class II cavity preparation in
Primary molars
• Complete class 1 using #330 bur
• Extend occlusal outline to marginal ridge
• Switch to #245 Bur - 3 mm length
• Sweep bur buccolingually in a pendulum motion
and in a gingival direction.
• Break contacts and check with explorer
• Axial wall should follow external contour
• Width of isthmus 1/3 of occlusal table
• Proximal box widest at gingival margin
• Rounded axiopulpal line angle
• No bevel at the gingival margins

6. Class II Cavity Preparation
Mandibular

7. Class II Cavity Preparations
No MOD’s on first primary molars !!

8. Class II Cavity Preparations

9. Protect adjacent proximal surface

10. Class II cavity preparation in
Primary molars

11. Cross-sectional View of Class II
 Gingival floor position
 Box is perpendicular to long axis
 Rounded angles

12. Correct Incorrect
Class II cavity preparation in
Primary molars

13. Correct Incorrect
Class II cavity preparation in
Primary molars

14. Class II cavity preparation in
Primary molars
Correct Incorrect Incorrect

15. Common Errors - Class II’s

16. Failures of Amalgam Restorations
Fracture of the isthmus of a Class II
due to insufficient bulk of amalgam
Marginal failure in proximal box area
due to excessive flare of the cavo-surface margin
Recurrent caries
failure to extend preparation adequately

17. w T-band
w Tofflemire
• does not fit contour of primary tooth well
• difficult to fit multiple matrices
w Spot welded
• allows for multiple matrix placement
• requires a spot welder chair side
w Auto-matrix
• costly
Types of Matrices

18. Spot Welded Matrix
 Cut matrix and spot weld ends
3/16 “ wide and thin (..002”) matrix
 Form a loop
 Hold ends in spot welder
 Weld at low setting

19. Adapting Matrix Band
Place band over tooth with welded on
buccal
Seat band extends 0.5-1 mm gingival to the
cavo-surface margin
Band extend occlusally .5-1mm beyond the
marginal ridge
Stabilize band with finger

20. Adapt Matrix Band to Tooth

21. Matrix
Grasp welded ends with flat-nose, serrated
pliers (#110) at center of buccal surface of
tooth tightly
Spot weld band at crease and trim ends
Return to tooth and wedge properly
Remove matrix by inserting flat blade
instrument between tooth and matrix at
crease

22. Cavity Bases and Liners
– Purpose of base prior to
condensation is to prevent thermal
insulation for the pulp.
– Use of calcium hydroxide influences
formation of secondary dentin.
• Initiates local inflammatory response
at site of contact between pulp and
calcium hydroxide

23. Condensation and Carving
 “Back to back” condensation of Class II’s
 Carving described as “hill and valley”
 Polishing procedure

24. Condensing & Carving of
Amalgam
• Using an amalgam carrier, add increments &
condense using positive finger rest.
• Overfill prep, begin to carve and burnish the
occlusal portion with a lateral condenser
• After initial set, create the marginal ridge using an
explorer
• Carve restoration & remove excess from margins
using a cleoid-discoid or hollenback carver
• Carefully remove band and burnish restoration
using a ball burnisher.
• Apply moist cotton pellet or pumice paste for
final smoothening
• Remove rubber dam and check occlusion

25. Finishing of Amalgam Restorations
• Reduce tarnish and corrosion
• Improve marginal integrity
Polishing should be delayed for 24
hours

26. Interproximal Box
• Buccal and lingual walls should go straight
out into the interproximal box in Class II
cavity preparations
• Buccal & lingual walls convergent towards
occlusal
• Gingival floor just past contact or height of
contour, flat & well defined
• Axial wall convex to follow the surface
anatomy
• Axial depth should be 1 mm
• Buccal and lingual cusps adjacent to box
should have plenty of sound tooth structure
left ie. They shouldn't be too thin.

27. “slot” preparation
• Modified class II cavity design for the
• placement of RMGIs.

28. CLASS II PREPARATION
COMPARISON
• AMALGAM
- 0.5 mm into dentin
- no cavo-surface bevel
- 0.5 mm prox.clearance
- isthmus 1.0+
- no gingival bevel
- occlusal dovetail
• COMPOSITE
- 0.5 mm into dentin
- cavo-surface bevel
- 0.5 mm prox. clearance
- isthmus 1.0+
- gingival bevel
- no dovetail needed

29. Lack of buccal clearance / unsupported enamel
CLASS II COMPOSITE
RESIN RESTORATION

30. Outline form includes all carious defects

34. Bevel gingival margin

35. Gingival bevel

36. Clearance ( convenience form )

37. Clearance ( convenience form )
Clearance
Place explorer tip on
gingival floor and pull
through buccal/lingual
space

38. AE – enamel 15 seconds

39. Rinse thoroughly

40. Well wedged Tofflemire band

41. Palodent band - bitine ring

42. Application of bond resin to moist dentin

43. Air thin bond resin

44. Light-cure bond resin 20 seconds

45. Apply thin layer of flowable C.R.

46. Apply thin layer of flowable C.R.Light-cure flowable C.R.for 30 seconds

47. Express a small amount of C.R. before using

48. Place C.R. with a condenser

49. 1st. application of C.R.

50. 1st. application of C.R.
Light-cure 1st. layer of C.R. 30 seconds

51. 2nd. application of C.R.

52. Use of contact instrument

54. Light curing 2nd. C.R. application 30 seconds

55. Hole left after removal of contact instrument

56. 3rd. application of C.R.

57. Developing occlusal anatomy before curing

58. 40 second cure of final increment of C.R.

60. Use of round bur to develop anatomy

61. Use an explorer to check for flash/ditching

62. Use of Soflex disk to shape marginal ridge

63. Check occlusion / adjust

64. Finishing diamond
Finishing bur
White stone
Round bur
C.R. polishing system

65. C.R. polishing system

66. Acid etching prior to placing surface sealant

67. Application of a surface sealant