FUNDATINMENTALS OF CAVITY PREPARATION.pptx

fundamentals of cavity preparation

1. FUNDAMENTALS OF CAVITY PREPARATION Presented by- Dr. SONAL BANSAL

2. Tooth preparation is the mechanical alteration of a defective, injured, or diseased tooth such that placement of restorative material reestablishes normal form (and therefore function) including esthetic corrections, where indicated. INTRODUCTION

3. (1) conserve as much healthy tooth structure as possible (2) remove all defects while simultaneously providing protection of the pulp–dentin complex, (3) form the tooth preparation so that, under the forces of mastication, the tooth or the restoration (or both) will not fracture and the restoration will not be displaced, (4) allow for the esthetic placement of a restorative material where indicated. objectives of tooth preparation

4. G.V. Black presented a classification of tooth preparations according to diseased anatomic areas involved and by the associated type of treatment. Class I Class II Class III Class IV Class V Class VI

5. All preparations required to treat pit-and- issure caries are termed Class I preparations. these include preparations on (1) occlusal surfaces of premolars and molars, (2) occlusal two thirds of the facial and lingual surfaces of molars, and (3) the lingual surfaces of maxillary incisors. Class I Cavity

6. Preparations required to correct caries lesions that develop in the proximal surfaces of posterior teeth are termed Class II preparations Class II cavity

7. Preparations required to correct caries lesions that develop in the proximal surfaces of anterior teeth that do not include the incisal edge are termed Class III preparations. CLASS III CAVITY

8. Preparations required to correct caries lesions or other defects that develop in the proximal surfaces of anterior teeth that include the incisal edge are termed Class IV preparations. CLASS IV CAVITY

9. Preparations required to correct caries lesions or other defects that develop in the gingival third of the facial or lingual surfaces of all teeth are termed Class V preparations. CLASS V CAVITY

10. Preparations required to correct caries lesions or other defects that develop in the incisal edges of anterior teeth or the occlusal cusp tips of posterior teeth are termed Class VI preparations. CLASS VI CAVITY

11. A tooth preparation is termed simple if only one tooth surface is involved, compound if two or three surfaces are involved, Complex if a preparation involves four or more surfaces. Mesioocclusal ( MO) the tooth preparation involving the mesial and occlusal surfaces is termed mesioocclusal preparation. Mesioocclusodistal (MOD) the preparation involving the mesial , occlusal , and distal surfaces is a mesioocclusodistal preparation. Tooth Preparation: Terminology

12. a complex preparation involving the mesial , occlusal , distal, and lingual surfaces is an “MODL.” The process of creating a preparation in a tooth results in the formation of preparation walls or Floors, An internal wall is a prepared surface that does not extend to the external tooth surface. External wall : An external wall is prepared surface that extends to the external tooth surface. Axial wall : An axial wall is an internal wall parellel to tooth surface Pulpal Wall : A pulpal wall is wall perpendicular to long axis of the tooth and occlusal of the pulp

13. Floor or Seat : A seat or floor is prepared wall that is reasonably flat and perpendicular to the occlusal force that are directed occlusogingivally Enamel wall :The enamel wall is that portion of prepared external wall consisting of enamel. Dentinal wall : The Dentinal wall is that portion of prepared wall consisting of dentin, in which mechanical retention features may be located.

14. the junction of two or more prepared surfaces is referred to as the angle. his transition area from one surface to another is designed to be smooth and rounded, rather than abrupt or sharp, to limit stress concentration. A line angle is the junction of two planar surfaces of diferent orientation along a line. An internal line angle is the line angle whose apex points into the tooth. the external line angle is the line angle whose apex points away from the tooth. the point angle is the junction of three planar surfaces of diferent orientation.

15. the cavosurface angle is the angle of tooth structure formed by the junction of a prepared wall and the external surface of the tooth. the actual junction is referred to as cavosurface margin

16. Tooth Preparation: Stage and Procedural Step

17. Definition: placing the cavity margins in the positions they will occupy in the final preparation except for finishing enamel walls & margins. preparing an initial depth of 0.2~0.8 mm pulpally of the dentinoenamel junction position or normal root surface position. Outline Form and Initial Depth

18. the outline form is designed, regardless of the type of tooth preparation, such that (1) all unsupported or weakened (friable) enamel is usually removed, (2) all faults are included, and (3) all preparation margins are usually placed in a position that allows inspection and finishing of the subsequent restoration margins.

19. Extent of carious lesion, defect or faulty old restoration. Esthetic considerations. Occlusal requirements. Adjacent tooth contour. Cavosurface marginal configuration which varies with type of restorative material used. FACTORS DETERMING OUTLINE FORM

20. Primary resistance form may be defined as the shape and placement of the preparation walls (floors) that best enable the remaining tooth structure, as well as the anticipated restoration, to withstand masticatory forces primarily oriented parallel to the long axis of the tooth. Step 2: Primary Resistance Form

21. To use the box shape with a relatively flat floor, which helps the tooth resist occlusal loading by virtue of being at right angles to the forces of mastication that are directed in the long axis of the tooth To restrict the extension of the external walls to allow strong cusp and ridge areas to remain with sufficient dentin support To have a slight rounding of internal line angles to reduce stress concentrations in tooth structure PRINCIPLES

22. To cap weak cusps and envelope or include enough of the weakened tooth structure within the restoration in extensive tooth preparations to prevent or resist fracture of the tooth by forces in the long axis and obliquely directed forces To provide enough thickness to restorative material to prevent its fracture under load To bond the material to tooth structure when appropriate

23. Assessment of the occlusal contact on the restoration and remaining tooth structure. Amount of remaining tooth structure ( eg . In class IV restorations , the cavity is kept narrow faciolingually to obtain resistance form) All weakened , friable tooth structure should always be removed. FACTORS AFFECTING RESISTANCE FORM

24. Enhancement of the resistance form by bonding the restoration to the remaining tooth. Type of restorative material- The minimum thickness of restorative material required for restoration with :- amalgam 1.5 mm, cast restoration 1 mm ,ceramics 2 mm; to resist fracture. Occlusal stresses on the tooth ( Greater the occlusal force , the greater is the potential for future fracture)

25. 1. Relatively flat floor 2. Box shape 3. Inclusion of weakened tooth structure 4. Preservation of cusps and marginal ridges 5. Rounded internal line angles 6. Adequate thickness of restorative material 7. Reduction of cusps for capping when indicated FEATURES

26. DEFINITION ( Sturdevant ) Primary retention form is the shape or form of the conventional preparation that resists displacement or removal of the restoration by tipping or lifting forces.. Step 3: Primary Retention Form

27. For Amalgam restorations :- In most class I and all class II preparations, the amalgam is retained in the tooth by developing external tooth walls that converge occlusally Occlusal convergence of the proximal portion helps in conserving the marginal ridges The cavosurface angle where the proximal facial and lingual surfaces meet the marginal ridge is a desirable 90 degrees because of the occlusal convergence of the preparation Adhesive systems provide some retention by micromechanically bonding amalgam to tooth structure and reducing or eliminating microleakage . PRINCIPLES

28. For Composite restorations :- Composite restorations are retained in the tooth by a micromechanical bond that develops between the material and the etched and primed prepared tooth surface. The enamel and dentin are etched by an acid ,and the dentin is primed with a dentin bonding agent before placement of the composite. Other conventional- type composite restorations may require a separate enamel bevelling procedure that would be done in final tooth preparation.

29. Close parallelism of the opposing walls, with small angle of divergence (2-5 degrees) from the line of draw , helps in enhancing retention. The degree of divergence needed primarily depends on the length of the prepared walls: the greater the vertical height of the walls , the more divergence is permitted , but within the range mentioned. In class II preparations , an occlusal dovetail may aid in preventing the tipping of the restoration by occlusal forces For Cast Metal restoration

30. DEFINITION ( Sturdevant ) - Convenience form is the shape or form of the preparation that provides for adequate observation, accessibility, and ease of operation in preparing and restoring the tooth. Principles- Allow access for caries removal Allow access for restoration placement Allow access to margins for finishing, evaluation and cleaning CONVIENIENCE FORM

31. Step 5 Removal of any remaining infected dentin if indicated Step 6 Pulp protection Step 7 Secondary resistance & retention form Step 8 Procedure for finishing external walls Step 9 Final procedures Final steps

32. Definition: The elimination of any infected carious tooth structure or faulty restorative material left in the tooth after initial cavity preparation. Removal of any remaining infected dentin if indicated

33. Removal of dentinal caries using round burs and spoon excavators

34. Using liners or bases to protect the pulp or to aid pulpal recovery or both. Pulp protection

35. Most compound and complex cavity preparations require additional resistance and retention form. The exception being those preparations that are very conservative. Secondary resistance and retention forms

36. It is made by- 1. Mechnical form:  Proximal locks  Proximal slots

37. Proximal locks

38. Slot on gingival wall

39. Definition: is the further development of a specific cavosurface design and degree of smoothness that produces the maximum effectiveness of the restorative material being used. Objectives:  To create the best marginal seal possible between the restorative material and tooth structure;  To afford a smooth marginal junction;  To provide maximum strength of both the tooth and the restorative material at and near the margin. Finishing the external walls

40. The strongest enamel margin is that margin which is composed of full-length enamel rods that are supported on the cavity side by shorter enamel rods, all of which extend to sound dentin

41. It is done by- The design of the cavosurface angle The degree of smoothness of the wall The design of the cavosurface angle: depending on the material  amalgam: 90°  composite: beveling 30°~ 40°

42. Bevelling done by GMT

43.  cleaning  inspecting  varnishing  conditioning Final procedures

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