[Molar-incisor hypomineralization among 12-years old children in Arkhangelsk region].

Aim: To estimate the prevalence of molar incisor hypomineralisation (MIH) across genders and place of residence as well as its association with dental caries among 12-years-old children in Northwest Russia.

Method: A cross-sectional study included 1233 (653 girls) randomly selected 12-years-old children from 7 urban and 5 rural areas of Arkhangelsk region. MIH and its severity were diagnosed using Weerheijm et al (2003) and Mathu-Muju & Wright (2006) criteria. Dental caries was studied at the D3 level following WHO (2013) recommendations. Prevalence of MIH and caries and means for Decayed-Missing-Filled (DMFT) scores are presented with 95% confidence intervals (CI). Pearson's chi-squared tests and Mann-Whitney tests were used for dichotomous and numerical data, respectively. The study was approved by the Ethical Committee of the Northern State Medical University, Arkhangelsk, Russia.

Results: The overall prevalence of MIH was 2.1% (95% CI: 1.44-3.07). The prevalence of mild MIH was 46.2% (95% CI: 28.8-64.5). Average and severe MIH were diagnosed in 26.9% (95% CI: 13.7-46.1) of children each. The prevalence of caries among those with and without MIH was 100% (95% CI: 87.1-100.0) and 74.8% (95% CI: 72.3-77.2), respectively (p=0.003). DMFT values for children with and without MIH were 4.46 (95% CI: 3.20-5.72) and 2.41 (95% CI: 2.28-2.53), respectively (p<0.001).

Conclusion: Although the prevalence of MIH in Northwest Russia is lower than in most other countries our findings suggest that hypomineralised molars are much more prone to caries.