Evaluation of Cavitation in Approximal Caries Lesions

Objectives: The decision to treat initial approximal carious lesions is based mainly on interpretation of bitewing radiographs and, moreover, on cavitation of approximal surfaces. The aim of this study was to compare cavitation and radiographic status of approximal lesions. Methods: 285 extracted teeth were used in this study. Standardized radiographs were taken, and approximal caries was evaluated according to the generally accepted criteria R0 (no radiolucency), R1 (radiolucency confined to the outer half of enamel), R2 (inner half of enamel), and R3 (outer half of dentin). Approximal surfaces with deep radiolucencies (R4) were excluded. A total of 165 approximal surfaces revealed R1-R3 lesions, and these were examined by 1) clinical observation with the naked eye (NE), 2) observation with magnifying eyeglasses (ME, 4.3x), 3) using a stereomicroscope (SM, 10x), and using SEM (up to 500x). Results: The results showed that in surfaces with R3 caries, cavitation was visible in 56 of 59 cases with the naked eye. When using SEM, all surfaces revealed cavitation (100 %). Regarding the surfaces with R2 lesions, 36 of 46 cases showed cavitation (NE); the corresponding values were 39/46 (ME), 41/46 (SM), and 46/46 (SEM). With regard to R1 lesions, 36/60 (NE), 43/60 (ME), 45/60 (SM), and 58/60 cases revealed cavitation. Cavitation of sound surfaces (R0) was present in some 10 % of the examined surfaces (24/261, NE; 33/261, SEM). Conclusions: From this study, it can be concluded that cavitation (defined as breakdown of the surface) is present in significantly more cases than previously thought, even in cases with R1 caries. This might be an explanation why even small radiolucencies are likely to progress, albeit slowly. Thus, close follow-ups should strongly be recommended when considering a preventive treatment regimen with small radiolucencies.