OBJECTIVEThis study aims to investigate the caries status of the first permanent molar and primary tooth among 7- to 9-year-old children in Tangshan city and the correlation between caries of primary tooth and the first permanent molar.

METHODSA stratified cluster sampling method was used on the basis of the Basic Approach of Oral Health Survey of WHO and the Guideline of the Third National Oral Health Survey. A total of 10 primary schools were randomly sampled in clusters that included 51 primary school sampling spots in Tangshan. The caries status of 1 794 children aged 7 years to 9 years was examined.

RESULTSThe prevalence rate of the first permanent molar caries was 47.49% (852/1 794), the mean number of DMFT was 1.30 ± 1.59, the mean number of DMFS was 1.96 ± 3.40, and the filling rate was only 2.35% (20/852). The preva- lence rate and mean DMFT of the first permanent molar caries showed significant difference between different ages and genders (P < 0.05). However, the mean DMFS of the first permanent molar caries only showed significant difference between the various ages (P < 0.05). The prevalence rate of the primary tooth caries was 83.11% (1 491/1 794), the mean number of dmft was 4.82 ± 3.55, the mean number of dmfs was 6.51 ± 5.61, and the filling rate was 12.41% (185/1 491). Caries of primary tooth was the first permanent molar caries risk factor [r = 0.277, OR = 5.736, P = 0.00, 95% CI (4.175, 7.881)]. Significant correlation was found between the caries of primary tooth and first permanent molar (r = 0.274, P < 0.001).

CONCLUSIONCaries status of the first permanent molar among 7- to 9-year-old children in Tangshan city is serious. Caries status of primary tooth may play an important role in predicting the first permanent molar caries in clinic and prevention.