Community-level factors as well as individual-level factors affect individual health. To date, no studies have examined the association between community-level social gradient and edentulousness. The aim of this study was to investigate individual- and community-level social inequalities in edentulousness and to determine any explanatory factors in this association. We analyzed the data from the Japan Gerontological Evaluation Study (JAGES). In 2010-2012, 112,123 subjects aged 65 or older responded to the questionnaire survey (response rate = 66.3%). Multilevel logistic regression analysis was applied to determine the association between community-level income and edentulousness after accounting for individual-level income and demographic covariates. Then, we estimated the probability of edentulousness by individual- and community-level incomes after adjusted for covariates. Of 79,563 valid participants, the prevalence of edentulousness among 39,550 men (49.7%) and 40,013 women (50.3%) were both 13.8%. Living in communities with higher mean incomes and having higher individual-level incomes were significantly associated with a lower risk of edentulousness (odds ratios [ORs] by 10,000 USD increments were 0.37 (95% confidence interval [CI] [0.22-0.63]) for community-level and 0.85 (95% CI [0.84-0.86]) for individual-level income). Individual- and community-level social factors, including density of dental clinics, partially explained the social gradients. However, in the fully adjusted model, both community- and individual-level social gradients of edentulousness remained significant (ORs = 0.43 (95% CI [0.27-0.67]) and 0.90 (95% CI [0.88-0.91]), respectively). One standard deviation changes in community- and individual-level incomes were associated with 0.78 and 0.84 times lower odds of edentulousness, respectively. In addition, compared to men, women living in communities with higher average incomes had a significantly lower risk of edentulousness (p-value for interaction < 0.001). Individual- and community-level social inequalities in dental health were observed. Public health policies should account for social determinants of oral health when reducing oral health inequalities.

Background: Dental caries is still serious problem among Japanese children. Previous studies suggested that higher consumption of vegetables prevent dental caries. Eating order habit, such as eating vegetables at start of meal, called “Vege-first”, may increase the amount of vegetable consumption, and in turn, prevent dental caries. However, no published studies have examined the impact of “Vege-first” habit on dental caries. The aim of this study to investigate the association between “Vege-first” and dental caries among Japanese children. Methods: We used the 2015 cross-sectional data from the Adachi Child Health Impact of Living Difficulty (A-CHILD) study, a population-based study of all first-grade students in Adachi City, Tokyo, Japan. The number of DMFT (decayed, missed due to decay, and filled teeth) was used as an outcome. Poisson regression analyses were applied to determine the independent association between “Vege-first” habit and the number of DMFT after controlling for the effects from child’s sex, parents’ marital status, socioeconomic status, and frequency of tooth brushing, drinking sweet beverages, and snacking. Results: Of 3,689 valid Japanese children participants, 38.2% had DMFT and 11.6% were having the “Vege-first” habit. The number of DMFT decreased linearly with “Vege-first” habit (p < 0.001). After controlled for covariates, the number of DMFT was still significantly and independently decreased with “Vege-first” habit (prevalence ratio=0.89 (95% confidential interval [0.81-0.98])). Conclusions: This study showed that having the “Vege-first” habit was associated with dental caries even accounting for socioeconomic status, dental health behavior, and dietary habits. Health policy introducing “Vege-first” habit may be effective to prevent pediatric dental caries. Key messages: Eating habit which vegetables at start of meal called “Vege-first” may increase the amount of vegetable consumption and possibly reduce dental caries. The habituation of Vege-first was likely to reduce child’s dental caries even accounting for socioeconomic status, dental health behavior and dietary habits.