Removal of amalgam overhangs. A profilometric and scanning electron microscopic evaluation

Forty recently extracted teeth with Class II amalgam restorations with overhangs were divided into four groups of 10 teeth each. The overhangs were removed using one of the following instruments in each group: trimmer, chisel, surgical blade and reciprocating motordriven diamond tip. Instrumentation was performed until no irregularity could be detected clinically with a No. 3 explorer. The tooth-amalgam interfaces were examined by combined use of a surface measuring instrument and a scanning electron microscope. Four tracings from each specimen were recorded and the discrepancy at the tooth-restoration interface was measured. The mean score for each tooth was determined, and the results were analyzed statistically. The tooth-restoration interfaces were photographed at 140 magnification with the SEM. The results indicated that all instruments tested were effective in removing overhangs, since none of the mean discrepancies registered after instrumentation exceed 4 micron. The surgical blade, and especially the reciprocating motor-driven diamond tip eliminated overhangs better than the chisel. Both SEM photographs and the profilometric tracings revealed gaps or voids at the toothamalgam interface, ranging from 10 to 50 micron.