Diagnosis of secondary caries and crevices adjacent to amalgam.

Teeth with Class II amalgam fillings (n = 77) were mounted in blocks in approximal contact and radiographed. Fifteen dentists examined radiographically the gingival area of the fillings/teeth and 2 weeks later they examined the teeth visually and by probing. The diagnoses were then validated by the authors using stereomicroscopic examination of the fillings/tooth surfaces and longitudinal sections of the teeth. The teeth were divided into three groups: fillings without failure (controls), fillings with secondary caries and fillings with crevices. The rate of false positive diagnoses (secondary caries) was reduced from 12 to 3 per cent when the radiographical examination was supplemented with 'clinical' findings; similarly, the rate of secondary caries detection and detection of crevices increased from 47 to 64 per cent and 8 to 47 per cent, respectively. Clinical examination in addition to radiographical interpretation improves the quality of secondary caries diagnosis. The results indicate that the diagnosis of small, secondary, caries lesions is uncertain, and that many crevices are wrongly diagnosed as secondary caries.