Evaluation of an indirect method for assessing the quality of amalgam restorations in epidemiological studies.

The purpose of the present study was to compare an indirect method with direct clinical observations for its ability to assess the clinical quality of amalgam restorations. Two evaluators examined independently the quality of 290 amalgam restorations in 25 patients. All restorations were examined directly as well as indirectly using seven well-defined characteristics. Direct assessment consisted of visual examination utilizing mirror and explorer. Indirect observations were made with the aid of color transparencies and bite-wing radiographs. The results showed a high interexaminer agreement for the indirect method which was even higher than for the direct method. No statistically significant differences existed between the two examiners in both methods. When using color transparencies for the indirect method, there is a high degree of agreement between both methods. Only one characteristic, the "anatomic form", showed significant differences in the sense that an unsatisfactory "anatomic form" is diagnosed more often by direct evaluation. Therefore, the indirect method, using color transparencies, is reliable in assessing quality of amalgam restorations except for "anatomic form". When using bite-wing radiographs for the indirect method, unsatisfactory characteristics were diagnosed more frequently indirectly than directly. On the basis of the results, it was concluded that bite-wing radiographs are indispensable in examining amalgam restorations.