Influence of approximal caries in primary molars on caries rate for the mesial surface of the first permanent molar in swedish children from 6 to 12 years of age.

The objective was to assess the influence on the caries rate for the mesial surface of the first permanent molar (6m) of the caries status of the distal surface of the second primary molar (05d) in children from 6 to 12 years of age. The study design was retrospective and included 374 children with an average of 5 sets of bite-wing radiographs. The mean age of the children was 6.7 years when the first bite-wing radiographs were taken and 11.5 years at the time of the latest radiographs included in the study. The approximal surfaces were classified according to a scoring system: 0 = no visible radiolucency, 1= radiolucency in the outer half of the enamel, 2 = radiolucency in the inner half up to the enamel-dentin border, 3 = radiolucency with a broken enamel-dentin border but with no obvious involvement of the dentin, 4 = radiolucency with obvious spread in the outer half of the dentin, and score 5 = radiolucency in the inner half of the dentin. The influence of the status of 05d on the caries rate for 6m (state > or =2) was assessed by using a model for dependence between the two neighbouring surfaces. Presence or absence of approximal caries in the distal surface of the first primary molars (04d) and/or the mesial surface of the second primary molars (05m) at the time of eruption of 6m was also related to the caries rate for 6m. The caries rate for 6m was 15 times higher if 05d had developed enamel/enamel-dentin border caries (state 2 or 3) compared to a radiographically sound 05d (state 0 or 1). No significant increase in the caries rate for 6m was found when 05d had deeper unrestored dentin caries than when 05d had superficial caries (state 2 or 3). Furthermore, for preventing caries in 6m, no benefit could be found from restoring an 05d with dentin caries with amalgam as opposed to leaving the carious lesion unrestored until exfoliation. The caries rates for 6m and 05d were 3.4 and 2.7 times higher, respectively, in the presence of dentin caries/restoration in 04d/05m compared to absence of dentin caries in these molar surfaces at the time of eruption of 6m. In conclusion, the caries rate for 6m depended on the status of 05d and increased 15 times if 05d had enamel/enamel-dentin border caries compared to a sound 05d. Deeper unrestored or restored dentin lesions in 05d did not result in a higher caries rate for 6m compared with more shallow carious lesions in 05d.