Class II Amalgam Cavity PreprationMentorship : Dr. Elham Zajkani Designed by : Fateme Omidi & Mohammad Hosein Nosrati

A. The tooth is entered with a punch cut, and extension is done distally along central fissure at a uniform depth of 1.5 to 2 mm (1.5 mm at fissure; because of the inclination of the unprepared tooth surface, the corresponding measurement on the prepared wall is greater).

B. Bur position to begin the proximal ditch cut. The proximal ditch is extended gingivally to the desired level of the gingival wall (i.e., floor).

C. Variance in the pulpal depth of the axiogingival line angle as the extension of the gingival wall varies: a, at minimal gingival extension; b, at moderate extension; c, at extension that places gingival margin in cementum, whereupon the pulpal depth is 0.75 to 0.8 mm and the bur may shave the side of wedge.

D. The position of the proximal walls (i.e., facial, lingual, gingival) should not be overextended with the No. 245 bur, considering additional extension will occur when the remaining spurs of enamel are removed.

E. When a small lesion is prepared, the gingival margin should clear the adjacent tooth by only 0.5 mm. This clearance may be measured with the side of the explorer. The diameter of the tine of a No. 23 explorer is 0.5 mm, 4 1 inch (6.3 mm) from its tip.

F. The faciolingual dimension of the proximal ditch is greater at the gingival level than at the occlusal level.

G. A round toothpick wedge placed in the gingival embrasure protects the gingiva and the rubber dam during preparation of the proximal box. A triangular wedge is indicated when a deep gingival extension of the proximal box is anticipated because the wedge’s greatest cross-sectional dimension is at its base. Consequently, it more readily engages the remaining clinical tooth surface.

H. Management of small- to moderate-sized carious lesion on the pulpal wall. a, Infected carious dentin extending beyond the ideal pulpal wall position. b, Incorrect lowering of the pulpal wall to include infected carious dentin. c, Correct extension facially and lingually beyond the infected carious dentin. Note the excavation below the ideal pulpal wall level and the facial and lingual seats at the ideal pulpal wall level.

I. Occlusal view of the mesio-occlusal preparation before placement of the retention grooves.

J. Proximal view of the mesio-occlusal preparation.

K. Retentive grooves position, translation, and depth.

L. Occlusogingival orientation.

M. The bevel of the enamel portion of the gingival wall is established with a gingival margin trimmer to ensure full-length enamel rods forming the gingival margin. The sharp angles at the linguogingival and faciogingival corners are rounded by rotational sweeping with a gingival margin trimmer.

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