Relationship between gap width and recurrent dental caries beneath occlusal margins of amalgam restorations

This study examines the relationship between gap width and the presence of recurrent dental caries subjacent to occlusal margins of amalgam restorations. The study population consisted of 35 adult patients of the university's dental clinic who were having occlusal amalgam restorations removed solely because of defective margins. In this group, an impression was made recording the width of a clinically detected gap between the amalgam restoration and the adjacent enamel cavosurface. Of this study population, 20 teeth with recurrent caries were identified from 18 subjects after restoration removal. Upon removal of the restoration, the presence and location of recurrent dental caries associated with a margin was noted. The mean gap widths of recurrent carious sites and non-carious sites were compared in the same tooth. A difference of 187 microns was found between the mean gap width of the recurrent caries sites and the non-carious sites, with the recurrent caries gaps being wider. A paired t-test based on the differences was calculated (P < 0.0001). The results suggest that there is a direct association between gap width and recurrent caries in occlusal margins of amalgam restorations.