The influence of modified cavity design and finishing techniques on the margin region of amalgam restorations: a simulated clinical study.

The use of high copper amalgams has substantially reduced the marginal fracture around amalgam restorations. Modified cavity designs and finishing techniques have been proposed for occlusal amalgam restorations in order to reduce further the long-term marginal fracture around these restorations. Clinical and laboratory studies are required before these techniques can be recommended to clinicians and taught to dental students with confidence. Using eighty extracted third molar teeth, this in vitro study examines four combinations of cavity design and finishing technique. After finishing, the restorations were photographed for evaluation of the initial marginal fracture attributable to the finishing technique, and sectioned twice to enable examination of the margin regions to determine the cavo-surface angles, amalgam margin angles and the occurrence of amalgam excess at and beyond the cavo-surface angle. Although careful application of the modified cavity design provided a mean cavo-surface angle of 100-110 degrees and assisted in achieving a mean amalgam margin angle of at least 70 degrees, long-term clinical and further laboratory studies are required before the cavity design modification can be recommended for routine use.