"Ethnic disparities in the prevalence of Molar-Incisor-Hypomineralisation (MIH) and caries among 6-12-year-old children in Catalonia, Spain"

Background In recent years, there has been uneven improvement in school children’s oral health, highlighting inequalities in access to dental care and health outcomes, particularly among ethnic minorities. The most prevalent oral disease in childhood, caries, is preventable, as its risk factors are well known. However, MIH, a common condition affecting the enamel of permanent incisors and/or molars, has no established aetiology or preventive measures. Aim To study the prevalence of MIH and caries in 6- and 12-year-old schoolchildren and their association with ethnic disparities and other relevant factors. Methods A cross-sectional study among schoolchildren was conducted in 725 children from Masnou (Barcelona, 2013) and in 577 children from Sant Andreu de Llavaneres (Barcelona, 2018-2020). Data collection was carried out by means of clinical examination and a selfreferenced questionnaire. Oral health outcomes included: presence of dental caries, presence of MIH, hypomineralised second primary molars (HSPM). All variables were analysed according to ethnic disparities and other variables such as socioeconomics, diet, hygiene habits, plaque and access to dental services. We performed multivariate Poisson regression models with robust variance to examine ethnic disparities in MIH and caries. Results The overall prevalence of MIH and caries was 12.2% and 30.5%, respectively. The prevalence of MIH was lower in immigrants than in native children, although not statistically significant (10% vs. 12.8%, p=0.24). The prevalence of caries was higher among immigrant than native children (40.8% vs 28.5%, p<0.001). The multivariate analysis demonstrated that ethnicity, child’s age, and plaque accumulation were associated with the prevalence of caries. No significant associations were observed for MIH. Children with HSPM were more likely to develop MIH (PR=2.6). Conclusions This cross-sectional study based in Catalonia, Spain showed that there are ethnic disparities in caries as observed with other child’s diseases; however, they do not seem to follow the same pattern for MIH. More studies are needed (i) to explore how MIH behaves among populations in terms of inequality; (ii) to study the aetiological factors of MIH; and (iii) to identify potential factors associated with MIH and caries that have not been studied and that may contribute to the observed ethnic disparities.