Marginal Ditching and Staining as a Predictor of Secondary Caries Around Amalgam Restorations: A Clinical and Microbiological Study

Abstract

Caries at the margins of restorations is difficult to diagnose. In particular, the relevance of both marginal ditching and staining around amalgam restorations is unclear. This clinical study questions the relevance of marginal ditching and color change to the level of infection of the dentin beneath the margins of amalgam restorations. Clinically visible sites (330) on the tooth/restoration margin were selected on 175 teeth. The enamel adjacent to each site was noted as stained (a grey discoloration) or stain-free. One hundred and seventy-eight sites were clinically intact, 83 sites had narrow ditches (< 0.4 mm), and at 49 sites, wide ditches were present (> 0.4 mm). Twenty sites with frankly carious lesions were also included. Plaque was sampled at the tooth-restoration margin, and the dentin was sampled at the enamel-dentin junction below each site. Samples were vortexed, diluted, and cultured for total anaerobic counts, mutans streptococci, lactobacilli, and yeasts. Plaque samples showed that margins with wide ditches (> 0.4 mm) harbored significantly more bacteria, mutans streptococci, and lactobacilli than did clinically intact margins and margins with narrow ditches. There were no significant differences in the degree of infection of the dentin beneath clinically intact restorations and those with narrow ditches, but samples associated with wide ditches and carious lesions yielded significantly more bacteria, mutans streptococci, and lactobacilli. The color of the enamel adjacent to the sample site was irrelevant to the level of infection of the dentin beneath the filling margin, provided a frankly carious lesion was not present. The results suggest that amalgam fillings where margins show wide ditches or carious lesions should be replaced. Narrow ditches and color change alone should not trigger the replacement of a filling.