Progression of proximal caries in the mixed dentition: a 4-year prospective study.

PURPOSE The purpose of this study was to investigate the survival rate and median survival time of different stages of proximal caries in 196 children aged 6 to 8 years at baseline examination. METHODS Proximal caries and its progression were diagnosed from bitewing radiographs taken at 1-year intervals over a period of 4 years. The mesial surface of the first permanent molars, the mesial and distal surfaces of the first and second primary molars, and the distal surface of the primary canine were examined. Sound surfaces, caries lesions in the external- and internal-half of the enamel and external-, middle-, and internal-third of the dentin, as well as filled, extracted, and exfoliated teeth were recorded. A life table analysis was performed to estimate the annual and cumulative survival rates and the median survival time of each state of proximal lesions. RESULTS For the sound mesial surfaces of the first permanent molars, the cumulative survival rate was 76% and the median survival time was over 48 months. The corresponding values for the external-half of the enamel lesions were 41% and 45 months. Regarding the sound mesial and distal surfaces of the primary teeth, the cumulative survival rate was 92% and the median survival time was over 48 months. The corresponding values for the external and internal-half of the enamel lesions were 40% and 31 months, and 29% and 22 months, respectively. The value of the cumulative survival rate for the external-third of dentin lesions was 42%, with a median survival time of 34 months, and the value for the middle-third of the dentin was 38% with a median survival time of 17 months. CONCLUSIONS The risk of developing carious lesions in the sound proximal surfaces of both primary teeth and first permanent molars is low during the mixed dentition period; the progression of the external-half of enamel lesions of the first permanent molars is low for the first 3 years and becomes faster thereafter; and as the time period that the tooth exposed to cariogenic factors increases, the progression of the proximal caries is faster for all stages of the lesion in the primary teeth.