Validity of radiographs for diagnosis of secondary caries in teeth with class II amalgam restorations in vitro.

In the present in vitro study, the validity was determined of bite-wing radiographs for the diagnosis of secondary caries in approximal parts of teeth with class II amalgam restorations in vitro. The study was performed on 47 molars and 49 premolars providing 68 and 69 filled approximal surfaces, respectively. The teeth were radiographed in a buccolingual direction to obtain images comparable to bite-wings. Radiolucencies and radio-opacities were scored as caries. Subsequently the teeth were sectioned (700 microns) in transverse or sagittal direction and then the sections were radiographed. Validation was performed against these radiographs of sections, on which also radiolucencies and radio-opacities were scored. Statistical analysis of the results revealed significant differences between the validity parameters for molars and premolars, being for sensitivity 73 and 80%, respectively, for specificity 90 and 95%, for positive predictive value 95 and 92%, and for negative predictive value 58 and 86%. For molars, the results did not differ significantly from the results of our previous study on caries diagnosis in teeth with occlusal fillings. The present experiment showed that bite-wing radiographs are useful for the diagnosis of secondary caries under approximal parts of class II amalgam restorations, just as for secondary caries diagnosis adjacent to class I restorations.