Caries rates for the mesial surface of the first permanent molar and the distal surface of the second primary molar from 6 to 12 years of age in Sweden.

The aim was to analyse the pattern of caries rates in enamel and dentin of the mesial surface of the first permanent molar (mesial 16, 26,36,46; here called 6m) and the distal surface of the second primary molar (distal 55,65,75,85; here called 05d) from 6 to 12 years of age. The material consisted of retrospectively collected bite-wing radiographs of a cohort of 374 children aged 5-7 years at baseline and followed to 11-12 years of age. The following scoring system was used: score 0 = no visible radiolucency, 1-2 = radiolucency in the outer (1) or inner (2) half of the enamel up to the enamel-dentin border, 4 = radiolucency with obvious spread in the outer half of the dentin, and 5 = radiolucency in the inner half of the dentin. Two transitions were used: state 0-2 = the time lapse from state 0 until the lesion had reached state 2, and state 2-4 = the time lapse from state 2 until the lesion had reached state 4 or 5. At the age of 9, the mean defs (decayed, extracted and filled surfaces) of 05d was 0.70 and the mean DFS of 6m was 0.19. The enamel caries rates (state 0-2) were 4.6 new lesions/100 tooth surface-years for 6m and 11.3 for 05d. The dentin caries rates (state 2-4) were 20.5 new lesions/100 tooth surface-years for 6m and 32.6 for 05d. In conclusion, the enamel caries rate for 05d was more than twice that for 6m. Both surfaces had relatively high dentin caries rates, indicating that for these surfaces between 6 and 12 years of age, the rate of progression into the dentin is generally relatively high once the lesion has reached the inner half of the enamel as judged radiographically.