Objective This study aims to determine the fissure morphology, prevalence, and severity of caries in the first permanent molars of 7-year-old to 9-year-old children in the Dalian development area. The study also aims to investigate the relationship between fissure morphology and noncavitated lesions.Methods A multi-stage, cluster sampling method was used. Three schools were randomly selected from 20 elementary schools in the Dalian development area. All of the children in the selected schools completed clinical oral examinations. A diagnosis criterion of the International Caries Detection and Assessment System was used to assess the cavitated and noncavitated dental caries in the first permanent molars. Fissure depth and fissure stain were also assessed.Results The total size of the study sample was 1 160. The prevalence of cavitated caries was 19.1%, and the mean D3-6FT score was 0.31. No significant differences were found between urban and rural sub-jects, between men and women, and among different age groups. The prevalence and D1-2FT score of noncavitated caries were 42.1% and 0.86, respectively. The D1-2FT score for rural children was significantly higher than that for urban children, and the D1-2FT score for girls were higher than that for boys. No statistical differences were found among different age groups. The prevalence of deep fissures in the first permanent molars was 44.7%. The prevalence of noncavitated caries increased with increasing fissure depth.Conclusion The prevalences of noncavitated caries and deep fissure in the first permanent molars of 7-year-old to 9-year-old children in Dalian were high. Fissure morphology was found to be related to noncavitated caries.
