1. Class III Cavity Preparation
Alaa Sabrah, BDS, MSD, PhD
11 Dec, 2014

2. Goals and Objectives What is the definition of class III cavity?
Identify the different types of class III cavity Preparation?
Compare and contrast different approaches to caries for class III ?
Compare the design and retention form for the different types of class III cavity Preparation?
Describe the clinical technique for treating class III carious lesion?

3. Definition
Class III- Smooth surface, involves proximal surface of anterior tooth
H. Devlin Operative Dentistry, Springer-Verlag Berlin Heidelberg 2006

4. Type of Approach
Lingual Approach
Facial Approach
Depends or caries location, extent of caries, access to carious lesion
Facial approach: caries location, alignment of teeth, replacement restoration
Lingual approach preferred: more esthetic, conserves facial enamel
use unless it would remove excessive amount of tooth structure
staining less visible if it occurs

5. Clinical Technique Anesthesia (Pt comfort, decrease salivary flow).
Occlusal assessment (determine design, adjust the restoration function).
Shade selection (before dehydration).
Isolation (visibility, effective bonding).
Tooth preparation.
Pulp Protection.
Restoration.

6. Modified Conventional
Tooth Preparation
Class III
Conventional
Beveled Conventional
Modified Conventional

7. Tooth Preparation Indication: restoration of root surface.
Why? No enamel margin
Design: Butt Joint margins.
Walls = walls for amalgam
Cavosurface margin=90˚
External walls ┴ root surface.
Uniform depth.
0.75 mm
Root surface
Axial wall
External wall

8. Tooth Preparation steps
Outline form: No. ½, 1, or 2 round carbide bur or diamond bur. Initial depth 0.75 mm.
Remove caries: pulpal depth dictated by carious lesion or existing restoration.
0.75 mm
Root surface
External wall
Caries removal

9. Tooth Preparation steps
Retention:
Retention grooves can
increase retention,
decrease effect of polymerization shrinkage,
increase marginal seal by resisting tooth flexural forces.

10. Tooth Preparation steps
Retention:
Retention grooves placement:
No. ¼ round bur
Internal portion or the external wall.
0.25mm from root surface.
0.25mm depth.
0.25mm from root surface
0.25mm depth

11. Tooth Preparation steps
Retention:
Retention grooves location:
The bisector of the angle formed by the junction between axial wall and external wall.

12. Modified Conventional
Tooth Preparation
Class III
Conventional
Beveled Conventional
Modified Conventional

13. Tooth Preparation steps
Indication: restoration of large carious lesion or replacing defective restoration in the crown.
Why? More retention/resistance are needed
Design: some beveled enamel margins with conventional wall design.
Cavosurface margin=45˚ on beveled, 90˚ on non beveled margins.
External walls ┴ enamel surface

14. Tooth Preparation steps
Outline form: No. ½, 1, or 2 round carbide bur or diamond bur.
Point of entry:
Within inciso-gingival dimension of carious lesion or defective restoration.
Instrument ┴ enamel surface.
Neck of the bur as far into the embrasure as possible.

15. Tooth Preparation steps
Outline form: No. ½, 1, or 2 round carbide bur or diamond bur.
Point of entry:
Incorrect entry: overextend the lingual outline into potential stress areas (marginal ridges) and unnecessarily weakens the tooth.

16. Tooth Preparation steps
Outline form: No. ½, 1, or 2 round carbide bur or diamond bur.
Axial wall:
Initial depth 0.2 mm into dentin.
Outwardly convex: following normal external tooth contour and DEJ inciso-ginigivally and facio-lingual.

17. Tooth Preparation steps
Enamel surface
External wall
Axial wall
Remove caries: undermined enamel can be left in non-stress area.
Retention:
Enamel bevel or flare
Retention groves

18. Tooth Preparation steps
Retention:
Bevel
Increase surface area.
Flame shaped or round diamond bur.
45˚ to the external tooth surface.
mm width.
All accessible enamel margin except gingival margin.
Avoid on lingual margin if the margin is subjected to occlusion.
Enamel surface
45˚

20. Tooth Preparation steps
Retention:
Retention grooves
Not necessary unless the cavity is too large.
Along incio-axial and gingivo-axial line angle.
No. ¼ round bur.

21. Tooth Preparation steps
Retention:
Retention grooves
0.2mm inside DEJ.
0.25 mm depth.
Bisect the angle formed by the junction of axial wall and external wall.

22. Modified Conventional
Tooth Preparation
Class III
Conventional
Beveled Conventional
Modified Conventional

23. Tooth Preparation
Indications: small and moderate lesions or faults designed to be as conservative as possible in the crown.
Why? All enamel margins
Design: scooped or concaved
Cavosurface margin ≥ 90˚
External walls = no shape.
Only include caries or defective restoration.

24. Tooth Preparation steps
Outline form: No. ½, 1, or 2 round carbide bur or diamond bur.
Point of entry:
Within inciso-gingival dimension of carious lesion or defective restoration.
Instrument ┴ enamel surface.
Neck of the bur as far into the embrasure as possible.
Axial wall not uniform in depth.

25. Tooth Preparation steps
Enamel surface
External wall
Axial wall
Remove caries: undermined enamel can be left in non-stress area.
Retention:
Enamel bevel or flare

26. Combined cavity preparation design
What if the caries extends on both crown and root surface?

28. Place calcium hydroxide in deep caries on the axial wall.
Pulp Protection
Place calcium hydroxide in deep caries on the axial wall.
Add RMGIC linear to protect the calcium hydroxide from being dissolved by Acid etch application.

29. Restorative Procedure.
Anterior teeth: Aesthetic restoration (composite) is almost always indicated.
Composite contraindicated for restoration extended on root surfaces.

30. Restorative Procedure.
Add RMGIC linear to.
Decrease microleakage on root surface
Decrease gap formation.
Decrease recurrent caries formation.

31. Class III Resin Restoration

32. Class III Resin Restoration
Use clear Mylar strip to provide “proximal wall” to restore against
Place wedge between the teeth gingivally to seal the cervical margin, and protect the adjacent teeth.

33. Class III Resin Restoration
Etching:
Manufacture instruction.
Placed 0.5mm beyond the prepared margins.
15-30 s.
Wash and dry.
Dentin should remain moist (NO over drying or polling of excess water I allowed).

34. Class III Resin Restoration
Place bonding agent according to manufacturer instructions.
Air dry to remove any solvent.
Light cure for s.

35. Class III Resin Restoration
Restore with resin composite.
Contour with resin placement instrument
Adapt and hold mylar strip and cure

36. Class III Resin Restoration
Finish and Polish Restoration
Finishing burs, strips for interproximal, discs to contour and polish, #12 scalpel blade for gingival flash

37. Class III Resin Restoration
Maintain Proximal Contact
Wedge slightly separates teeth, aids in creating proximal contact with resin
Use finishing burs, stones or scalpel for contouring

38. Class III Resin Restoration
Finishing discs Finishing Strips

39. Class III Resin Restoration
Proximal finishing strips and discs
Finishing and polishing
Use strips in “S” motion, do not remove proximal contact

40. Class III Resin Restoration
#12 scalpel works well to finish flash at cervical
margin, use with care
Polish surface with Soflex discs

41. Class III Resin Restoration