1. Class II Amalgam Cavity Preparartion
Date: 6/11/2014
Asalaam Alekum
Class II Amalgam Cavity Preparartion
Dr. Gaurav garg ( M.D.S.)
Lecturer, College of Dentistry
Al Zulfi, M.U.

2. Contents Outline form Retention form Secondary retention
Resistance form
Reverse curve
References

3. Outline form
Occlusaly similar to that for the Class I tooth preparation
Proximally there is a box shape extension ( Occlusal Step)

4. No. 245 or no. 330 bur can be used for preparation
Enter tooth with punch cut and extend distally along central fissure at uniform depth of 1.5 mm ( 0.5 mm inside DEJ)
Bur position for entry- slight lingual tilt

5. 1 2 3 5 4

7. B
Wedging. A, Round toothpick wedge placed in gingival embrasure protects gingiva and rubber dam during preparation of proximal box. B, Triangular wedge is indicated when deep gingival extension of proximal box is anticipated, because wedge's greatest cross-sectional dimension is at its base. Consequently, it will more readily engage the remaining clinical tooth surface

8. DEJ

9. Proximal box:
Buccolingual extension: there should be mm clearance from adjacent tooth buccaly & lingually
Gingivally there should be a clearance of 0.5 mm from adjacent tooth
Axial wall should follow the external tooth contour

10. Removeremaining undermined proximal enamel with enamel hatchet on facial proximal wall (A), lingual proximal wall (B), and gingival wall (C).

11. Beveling axiopulpal line angle

12. A, Bevel of enamel portion of gingival wall is established with gingival margin trimmer to ensure full-length enamel rods forming gingival margin.
B and C, Sharp angles at linguogingival and faciogingival corners are rounded by rotational sweep with gingival marginal trimmer ( GMT).

13. Retention form Occlusal convergence of buccal & lingual walls
Proximal Dovetail

14. Secondary Retention
Retention Locks ( No. 169L or ¼ round bur can be used)
169L
¼ round

15. Resistance form
Minimal extension, Ideal Isthmus width- 1/4th of Intercuspal distance
Smooth outline and smooth walls
90 degree cavosurface angle
Flat pulpal & gingival floor
Gingival floor should be bevelled
( degree), to remove unsupported enamel rods
Rounded all internal line angle
Bevelled axiopulpal line angle

16. Final finished cavities
¼ th of ICD
Buccal wall
Pulpal floor
Palatal/ Lingual wall
Axiopulpal line angle
Axio- buccal line angle
Axio-lingual line angle
Axial wall
Axiogingival line angle
Gingival floor

17. Reverse Curve
In case of maxillary teeth, mostly the molars, the contact area is more buccally, i.e.; the lingual embrasures are more than the buccal embrasures
In such cases, extending the bucco- proximal wall into the embrasure lead to excessive cutting of the buccal cusps
To avoid this, a reverse curve ( S- shaped) is made in the buccal proximal wall so as to have sufficient amount of dentin in that area & also to achieve butt joint with the cavosurface margins
Such a curve, though mostly given in maxillary molars, can be given in any tooth where the contact area is deviated or more pronounced on one side.

18. Advantages of reverse curve
Conservation of tooth structure ( preserve cuspal inclines)
Creation of 90 degree cavosurface angle
Less display of restorative material ( enhance esthetics)

20. References & Suggested reading
Sturdevant's art & science of operative dentistry Theodore M. Roberson, Harald O. Heymann, Edward J. Swift, Jr.
Principles of operative dentistry (2005)- A.J.E. Qualtrough, J.D. Satterthwaite, L.A. Morrow and P.A. Brunton.
Fundamentals of Operative Dentistry- 2nd Edition- Summitt & Robbins

21. THANK YOU!