Class II amalgams: interobserver variations in replacement decisions and diagnosis of caries and crevices

Teeth with Class II amalgam fillings (n = 77) were mounted in blocks in approximal contact and radiographed. Fifteen dentists examined the teeth radiographically, visually and by probing and were asked to decide whether or not replacement fillings were required. The diagnoses were validated by the authors using stereomicroscopic examination of the fillings/tooth surfaces and longitudinal sections of the teeth. During validation the teeth were divided into three groups: fillings without failure (controls), fillings with secondary caries (S1-S3) and fillings with crevices (C1-C2). The number of replacement decisions varied from 27 to 49. On average, 5.3 per cent of the controls were suggested as requiring replacement but the variation between dentists was great. For the small secondary carious lesions, S1, there was a consistency between the number of positive diagnoses and replacement decisions for all but four dentists. Of these fillings, 36 per cent were suggested as requiring replacement on average, while the values for S2, S3, C1 and C2 surfaces were 68.9, 92.1, 20.8 and 52.2 per cent, respectively. The variations in diagnoses and replacement decisions between the dentists were greater for the S2 lesions than the S3 lesions. The dentist who was most eager to re-restore fillings suggested that 75 per cent of the fillings with the small crevices (C1) and 100 per cent with the large crevices (C2) should be replaced. Conversely, one dentist would not replace any of the fillings with small crevices (C1) and only 17 per cent of those with large crevices. The dental profession needs guidelines for the standardisation of clinical decisions based on treatment philosophy.