An SEM study of overhang removal methods.

The sonic scaler, the curet, and the reciprocating motor-driven diamond tip were evaluated by comparing the number of rough root surfaces produced by each device in recontouring overhanging root-surface margins of amalgam and composite resin restorations. Ninety extracted human teeth were restored with amalgam or composite resin so that overhangs were created. Each instrument was used to remove 30 overhangs. The root surfaces apical to the overhangs were photographed under the scanning electron microscope at a magnification of x 140 and compared by five dentists, in a single-blind manner, with two control photomicrographs of surfaces classified as rough (treated with a coarse diamond bur) or not rough (treated with a greenstone). The number of rough responses for each instrument were compared statistically. For both restorative materials, the sonic scaler produced a significantly greater number of rough responses than did the other two instruments. Similar comparisons between the curets and the diamond-tip system showed no significant differences. No differences in the number of gaps produced between restoration and tooth were noted among the instruments. Clinical ease of overhang removal was greatest for the reciprocating motor-driven diamond tip and least for the curet. The approximate time to remove an overhang from a tooth was 3 minutes for the motor-driven diamond tip, 7 minutes for the sonic scaler and 15 minutes for the curet.