Trajectory of social inequalities in the treatment of dental caries among preschool children in Japan.

OBJECTIVES: The longitudinal trend of dental health inequalities among preschool children has not been described. In this study, we aimed to measure the trajectory of both relative and absolute inequalities in caries treatment among preschool children in Japan. METHODS: We used data from the Longitudinal Survey of Babies in the 21st Century (LSB21), which is an ongoing national representative longitudinal study. The target population was families residing in Japan with newborn baby/babies born between 10 January and 17 January or 10 July and 17 July 2001. Data regarding caries treatment history and socioeconomic status (SES) were collected using a self-reported questionnaire. SES was assessed on the basis of the parents' educational attainment. In total, 35 260 children were followed from 2.5 to 5.5 years through annual surveys. To evaluate absolute and relative inequalities, we calculated the slope index of inequality (SII) and relative index of inequality (RII), respectively. RESULTS: The rate of caries treatment at the age of 2.5 years was <10% for all SES groups; this increased to more than 30% at 5.5 years of age. Children with lower SES received more frequent caries treatment, and both absolute and relative social inequalities were statistically significant. SII showed a significant increase throughout the follow-up period, with values of 4.13% (95% confidence interval [CI], 3.16; 5.09) and 15.50% (95% CI, 13.68; 17.32) at 2.5 and 5.5 years of age, respectively. In contrast, RII decreased with an increase in the treatment rate for all groups, with values of 1.83 (95% CI, 1.59; 2.11) and 1.53 (95% CI, 1.46; 1.61) at 2.5 and 5.5 years of age, respectively. CONCLUSION: Our results suggest that the rate of caries treatment is higher for preschool children with lower SES in Japan, with significant widening of absolute inequalities along with the growth of the children.

Association between maternal education and malocclusion in Mongolian adolescents: a cross-sectional study.

OBJECTIVE: Malocclusion is a highly prevalent condition, affecting 20-60% of adolescents worldwide. Although its treatment is often expensive and unaffordable for disadvantaged individuals, few studies have examined the relationship between malocclusion and socioeconomic status. We investigated the prevalence of malocclusion among Mongolian adolescents and its association with maternal education in a community-based sample in Mongolia. DESIGN: Cross-sectional study. SETTINGS: 2 large secondary schools with different backgrounds in Ulaanbaatar, Mongolia. PARTICIPANTS: Complete dental casts of 557 randomly recruited Mongolian schoolchildren aged 11-16 years were evaluated using the Dental Health Component of the Index of Orthodontic Treatment Need to dichotomise orthodontic treatment requirements. Exclusion criteria were the presence of orthodontic treatment history and absence of maternal educational status. Questionnaires were administered to caregivers to assess socioeconomic status. Poisson regression analysis was performed to examine the association between malocclusion and maternal educational status. RESULTS: The prevalence of malocclusion requiring orthodontic treatment among all adolescents was 35.2% (95% CI 31.2 to 39.2). In the unadjusted analysis, the prevalence ratio (PR) for malocclusion was higher (PR=1.46; 95% CI 0.96 to 2.20) among adolescents of mothers with a high educational background than among those of mothers with a low educational background. After adjusting for covariates, the PR remained significantly higher (PR=1.72; 95% CI 1.06 to 2.82) among adolescents of mothers with a high educational background. Other socioeconomic status variables, including family income and the educational level of the father, showed no association with malocclusion. CONCLUSIONS: These findings suggest that malocclusion requiring orthodontic treatment in adolescents is more prevalent among children of mothers with high levels of education. Further studies are needed to clarify the behavioural factors and environmental circumstance that contribute to this.

Association between malocclusion and headache among 12- to 15-year-old adolescents: a population-based study.

OBJECTIVES: Headaches are a common problem among adolescents, and malocclusion is a possible risk factor. The purpose of this study was to investigate the association between malocclusion and headache among Japanese adolescents aged 12-15 years using a population-based sample. METHODS: A total of 938 adolescents (94.7% of the target population in Koshu City) participated. A modified version of the Index of Orthodontic Treatment Need (IOTN) was used by orthodontists to evaluate occlusal characteristics, and the frequency of headaches (none, rarely, sometimes) was assessed via questionnaire (N = 938). Ordered logistic regression analyses were used to analyze the association between malocclusion and headache. RESULTS: The prevalence of malocclusion diagnosed using the modified version of the IOTN was 44.9%. Multiple ordered logistic regression analyses showed that the odds ratio (OR) of having malocclusion for headache was 1.38 (95% confidence interval [CI]: 1.06-1.80), after adjustment for demographics, lifestyle, and dental status including orthodontic treatment history and tooth size. Moreover, among occlusal traits, lower crowding was independently associated with headache (OR: 1.64, 95% CI: 1.07-2.51). CONCLUSIONS: We found that malocclusion, especially lower crowding, was associated with headache in a population-based sample of adolescents aged 12-15 years in Japan. Further study is needed to elucidate the mechanisms by which malocclusion affects headache.