principles of cavity preparation... pptx

Principles of cavity preparation

1. PRINCIPLES OF CAVITY PREPARATION Presented By: Dr. Asawer Ahmed Fayyad Fallujah Specialized Dental Center

2. INTRODUCTION It's the mechanical alteration of a defective, injured or diseased tooth structure in order to best receive a restorative material to reestablish a healthy state of the tooth including esthetic corrections when indicated, along with normal form and function.

3. CAVITY CLASSIFICATIONS A. According to the number of surfaces involved: Simple cavity: One surface involved. Compound cavity: Two surfaces involved. Complex cavity: Three surfaces (or more) involved.

4. B. According to the site involved with carious lesion on enamel pits and fissures, on enamel smooth surfaces, or on root surfaces (Senile caries).

5. C. G.V Black classification; According to anatomical areas involved and associated type of treatment which was presented by G.V Black:

6. PRINCIPLES OF CAVITY PREPARATION Proper cavity preparation is accomplished through systematic procedures based on definite phvsical and mechanical principles. These are: Establishing outline form

7. Obtaining resistance form Obtaining retention form Obtaining convenience form Removing remaining caries Finishing cavity walls and margins Cleaning of the cavity

8. CL I CAVITY PREPARATION The outline form mesially and distally should be parallel to external tooth surface Retention is obtained by: Flat pulpal floor Dove tail Convergence of buccal and lingual walls occlusally about 5

9. Resistance is obtained by: Width of the cavity 1/4 ofJCD Depth of the cavity l.5-2m Medial and distal walls should be parallel or slightly diverged occlusaly. Cavosurface line angle should be between (90°-110°) Internal line angles should be rounded

10. CLASS I CAVITY OF THE BUCCAL PIT OF LOWER FIRST MOLARS The outline form should be a triangle in shape, with a depth of 1.5 mm, the base of the triangle should be towards the gingival and the tip of the triangle should be towards the occlusal surface.

11. Retention form: the mesial and distal walls of the cavity should be slightly converged to the outside; the gingival seat should be perpendicular to the outer surface. The axial wall should be flat. Resistance form: Depth of the cavity is 1.5-2mm. Rounded internal line angles. Gingival seat is perpendicular to the outer surface Cavosurface line angle (90-110").

12. CLASS I CAVITY OF UPPER MOLARS The Oblique ridge is smooth, has a good bulk of enamel, so it is highly resistance to dental caries, and should be preserved by doing two separate class I cavities one mesially and other distally.

13. Distally there is a groove that extends from the occlusal surface to the palatal surface and ends by a non-coalesced pit, so caries almost extend along this groove, and our cavity preparation should be extend palatally. We end our preparation in the palatal surface by what we called (Step). This step is necessary otherwise if we deepening the all occlusal surface to include all caries palatally this make a danger of hitting the pulp.

14. CL II CAVITY PREPARATION Retention is obtained by: Convergence of the buccal and lingual walls of the box occlusally Dovtail Flat gingival wall (seat) Retentive grooves

15. Resistance is obtained by: Width of the cavity 1/4 ofintercuspal distance ([CD) Cavosurface line angle (90°-110°). Axiopulpal line angle is beveled Gingival cavosurface line angle is beveled Rounded internal line angles and removal of the unsupported enamel

16. CL III CAVITY PREPARATION Resistance form: The gingival wall (seat) should be perpendicular to the long axis of the tooth. The axial wall should be parallel to the long axis of the tooth.

17. Retention form: Flat gingival wall (seat). Retention grooves axioincisally and axiogingivally. Dovetail on the lingual surface.

18. CL IV CAVITY PREPARATION Resistance form: Proximal facial and lingual preparation walls that form 90-degree cavosurface angles, which are subsequently beveled.

19. Retention form: Etched enamel margin, which may be with wider bevels. Groove-shaped or other forms of undercuts Dovetail extensions Combination of undercut and dovetail

20. CL V CAVITY PREPARATION FOR AMALGAM The shape of class V cavity is trapezoidal in shape or could be kidney shaped to be more conservative Resistance Form Depth of the cavity is 1.5mm The axial wall of the cavity Should Not Be Flat, the axial wall should be slightly convex Mesial and distal walls should be slightly diverged. Occlusal and gingival walls should be perpendicular to the long axis of the tooth and parallel to each other

21. Retention Form Retention means in class V cavity is Made By making retention grooves or retention holes. This depends on the size of cavity, in small conservative cavity, retention holes are made, while in large class V cavity. retention grooves are necessary. In case of more extensive class V cavity we may need to (pins) as extra retention. Position of the retentive means: best position is Axioocclusal and Axiogingival line angles.

22. CL V CAVITY PREPARATION FOR COMPOSITE Retention form: Bevel the enamel margins acid etch to the enamel surface

23. Resistance form: Proximal facial and lingual preparation walls that form 90-degree cavosurface angles, which are subsequently beveled. Gingival and occlusal floors prepared perpendicular to the long axis of the tooth. Internal line angles should be slightly curved (rounded).

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