Contributions of social context to inequality in dental caries: a multilevel analysis of Japanese 3-year-old children

Background: Community context as well as individual health behavior affects oral health status. However, the contribution of social context to dental caries among people in various regions remains unclear when individual health behavior is taken into account. Objectives: To determine the influence of community context on dmft among 3-year-old children. Methods: After all Japanese municipalities (n = 2522) had been stratified into nine regions with three caries levels, 44 municipalities were randomly selected. Community health service workers were asked to collect information on sociodemographic characteristics, oral health-related behavior, and dental condition for 3-year-old children during community dental health check-ups. Community-related variables, including socioeconomic status, social support, and social cohesion, were obtained from census data. Multilevel analysis was used to determine the effects of social context and individual behavior on dental caries. Results: A total of 3301 parents (79.9%) of 3-year-old children from 39 municipalities participated in our survey, and complete information was obtained from 3086 of them. Results of the analysis showed that 90.8% (P < 0.001) of variance in dmft occurred at the individual level and that 9.2% (P < 0.001) of the variance occurred at the community level. Individual-level variables explained only 6.6% of the individual level variance in dmft. Community-level variables explained 47.2% of the community level variance. Conclusions: There are statistically significant effects of social context on dmft in municipalities in Japan.