The Correct Answer is a) Shallow preparation <1.5mm
Class I Amalgam tooth preparation
Elimination of caries, preservation of tooth structure, remove enamel that is undermined by caries.
Routine extension in non carious fissures and pits is no longer justified.
Occlusal cavosurface bevel is contraindicated in these preparations.
Outline should include only faulty and defective occlusal pits and fissures.
Avoid sharp angles in marginal outline.
Need 90-100 degree cavosurface angle.
Opposing walls need to be parallel or converge slightly to the occlusal table for retention form.
Keep facial and lingual margin extensions as minimal as possible between the central groove and the cusp tips.
Sufficient depth (>1.5mm) to give adequate thickness of the restoration.
Parallelism or slight occlusal convergence of external walls.
Preparations (faciolingually) exceeding the intercuspal distance should have remaining cusps evaluated for restoration.
Conservative Class I Composite tooth (adhesive) preparation
Limit removal of tooth structure to amount needed to remove caries and severely thinned enamel.
Preparation tends to be shallower than in amalgam preparations.
Retention is provided by bonding, no need to penetrate enamel if caries does not.
Preserve as much enamel as possible to improve bonding, preparation can be shallower.
Preparation should be narrower to limit occlusal wear and reduce polymerization shrinkage.
Rounded internal line angles which enhances resin adaptation.
No extension for prevention. Occlusal pits only include if there is caries, they can be treated with sealants.
An axial and/or pulpal wall of varying depth (not uniform) is allowed.
Enamel does not have to be fully supported by dentin.
Ref:
Sturdevant, C.M., Sturdevant’s Art and Science of Operative Dentistry 4th Ed. 2002
Mosby. Page 539, Page 671.
Summit, Robbins, & Schwartz, 2nd Ed, Fundamentals of Operative Dentistry 2001 Ch 10,11.
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