Class I cavity preparation for Amalgam.pptx

amalgam cavity preparation,
conservative amalgam class I cavity
amalgam cavity preparation
steps in cavity preparation

1. Class I cavity preparation for Amalgam DR BEVERLEY THEMUDO

2. Class I Caries Restoration on Occlusal Surface of Premolars & Molars . Restorations on Occlusal Two Thirds of the Facial and lingual surfaces of Molars. Restoration on lingual Surface of Maxillary Incisor

3. How do pits and fissures get carious? union failure of tooth lobes  organic debris collects  acid formation/ incubator effect  area not self cleansing • susceptible tooth + bacteria+ food + time = caries

4. WHY AMALGAM? Strength Longevity Ease of use Clinically proven success In addition, amalgam is the only restorative material with an interfacial seal that improves over time.

5. Indications: Moderate-to-large restorations Restorations that are not in highly esthetic areas of the mouth Restorations that have heavy occlusal contacts Restorations that cannot be well isolated Restorations that extend onto the root surface Abutment teeth for a removable partial denture

6. CONTRAINDICATIONS Esthetically prominent areas of posterior teeth Small-to-moderate Classes I and II restorations that can be well isolated Small Class VI restoration

7. The objectives of treatment

8. STAGES OF TOOTH PREPARATION

9. OUTLINE FORM (1) carious tooth structure should be eliminated. (2) margins should be placed on sound tooth structure.

10. a bur (no 245 or 330) is used to cut through the enamel to gain access to the carious dentin. The preparation is widened to give access to all carious dentin and to remove any unsupported enamel. No sharp angles Smooth Conservative Don’t overextend prep into mesial or distal marginal ridges

11. A No. 245 bur with a head length of 3 mm and a tip diameter of 0.8 mm or a smaller No. 330 bur is recommended The silhouette of the No. 245 inverted cone bur reveals sides slightly convergent toward the shank (this produces an occlusal convergence of the facial and lingual preparation walls, providing adequate retention form for the tooth preparation). The slightly rounded corners of the end of the No. 245 bur produce slightly rounded internal line angles that render the tooth more resistant to fracture from occlusal force. The No. 330 bur is a smaller and pear-shaped version of the No. 245 bur. It is indicated for the most conservative amalgam preparations

12. When replacing a defective restoration (recurrent caries lesion), the outline form will be determined by 1. The outline form of the old restoration. 2. Additional carious lesion. 3. The resistance form required

13. Outline form of class I on different teeth

14. RESISTANCE FORM

15. Resistance of tooth Keeping the facial and lingual margin extensions as minimal as possible between the central groove and the cusp tips Extending the outline to include fissures , thereby placing the margins on relatively smooth, sound tooth structure Minimally extending into the marginal ridges (only enough to include the defect) without removing dentinal support Eliminating a weak wall of enamel by joining two outlines that come close together (i.e., less than 0.5 mm apart) Extending the outline form to include enamel undermined by caries .

16. Resistance of restorative Adequate thickness for the restorative material Margins should be approximately 90 degrees. Flat pulpal floor (resist forces directed in the long axis of the tooth Rounding of internal line angles

17. RETENTION FORM Opposing walls of Class 1 occlusal restorations should should converge slightly occlusally Grooves: bucco -pulpal or lingo-pulpal

18. CONVENIENCE FORM Creating sufficient access to the carious lesion to facilitate: Visibility Instrumentation during cavity preparation and restoration.

19. REMOVAL OF REMAINING CARIES Extension of the cavity should ensure that all caries has been removed from the peripheral DEJ. Best removed using spoon excavator or slow speed round bur

20. FINISHING OF THE EXTERNAL WALLS AND FLARES

21. Pulp Protection ! Cavity sealers ! Varnish ! Adhesive Sealers ! Cavity liners ! Cavity bases

22. Amalgam Placement Set-up Assemble instruments Triturator Amalgam capsules and dappen dish Amalgam carrier, condensers, carvers, burnishers, explorer, and mirror

23. The initial condenser should be small enough to condense into the line angles but large enough not to "poke holes" in the amalgam mass. Usually a smaller condenser is used while filling the preparation and a larger one for overpacking Each condensing stroke should overlap the previous condensing stroke to ensure that the entire mass is well condensed.  STEPPING OF CONDENSOR The preparation should be overpacked 1 mm or more using heavy pressure

24. Precarve burnishing is a form of condensation. As stated previously, tooth preparations should be overfilled with amalgam. To ensure that the marginal amalgam is well condensed before carving, the overpacked amalgam should be burnished immediately with a large burnisher Precarve burnishing produces denser amalgam at the mar gins of occlusal preparations

25. Part of the edge of the carving blade should rest on the unprepared tooth surface adjacent to the preparation margin Using this surface as a guide helps to prevent overcarving the amalgam at the margins and to produce a continuity of surface contour across the margins. Deep occlusal grooves should not be carved into the restoration, because these may thin the amalgam at the margins, invite chipping, and weaken the restoration The thin portion of amalgam extending beyond the margin is referred to as flash.

26. CLASS I OCCLUSOLINGUAL AMALGAM RESTORATIONS

27. the mesiodistal width of the lingual extension should not exceed 1 mm, except for extension necessary to remove carious or undermined enamel or to include unusual fissuring When indicated, the tooth preparation should be cut more at the expense of the oblique ridge rather than centering over the fissure (weakening the small distolingual cusp). Especially on smaller teeth, the occlusal portion may have a slight distal tilt to conserve the dentin support of the distal marginal ridge.

28. the lingual surface is prepared with the bur's long axis parallel with the lingual surface The tip of the bur should be located at the gingival extent of the lingual fissure . AVOID "roll out" onto the lingual surface, because this could "round over" or damage the cavosurface margin. The facial inclination of the bur must be altered as the cutting progresses to establish the axial wall of the lingual portion at a uniform depth. The axial wall should follow the contour of the lingual surface of the tooth. An axial depth of 0.5 mm inside the DEJ is indicated if retentive locks are required; an axial depth of 0.2 inside the DEJ is permissible if retentive locks are not required.

29. The No. 245 bur may be used with its long axis perpendicular to the axial wall to accentuate (i.e., refine) the mesioaxial and distoaxial line angles. This will also result in the mesial and distal walls converging lingually because of the shape of the bur.

30. A matrix is helpful to prevent "land-sliding" during condensation and to ensure marginal adaptation and strength of the restoration.

31. QUESTIONS?