Validity of bite-wings for diagnosis of secondary caries in teeth with occlusal amalgam restorations in vitro

This investigation was carried out to establish the validity of bite-wing radiographs for the diagnosis of secondary caries in teeth with occlusal amalgam restorations. One hundred and fifty-nine extracted molars with occlusal amalgam fillings and characteristics that might be indicative of the presence of secondary caries were selected. The characteristics were a blueish-gray discolouration of enamel, a brownish discolouration of the amalgam-enamel margin, marginal breakdown of the restoration, and/or deep fissures at the margin of the restoration. The teeth were radiographed in a bucco-lingual direction to obtain images comparable to bite-wings. Subsequently, the crowns were sectioned (700 microns) and glued on plastic sheets. The sections were recorded radiographically and then examined by independent examiners. Radiolucencies as well as radiopacities adjacent to the restoration were considered to be caries. The validation of the bite-wing radiographic diagnosis was achieved by comparison with the radiographs of the sections. A sensitivity of 64% and a specificity of 98% were calculated. Large lesions were always visible on the bite-wing radiograph (100%), the majority of medium-sized lesions (89%) and 40% of small lesions. Small radiopacities were detected more often than small radiolucencies.