An inverse relationship between dental fluorosis and Molar Incisor Hypomineralization in Mexican schoolchildren in an area with a high concentration of fluoride in drinking water: A cross-sectional study

To evaluate the association between the frequency and severity of dental fluorosis and Molar Incisor Hypomineralization (MIH) in 8-12-year-old schoolchildren living in an area with a high concentration of fluoride in the drinking water. The present cross‑sectional study was conducted on Mexican children (n = 573) selected from one community presenting a drinking water fluoride concentration of 1.39 ppm/F. The prevalence of dental fluorosis was ascertained using the Thylstrup and Fejerskov Index (TFI). The presence and severity of MIH was evaluated using the European Academy of Pediatric Dentistry (EAPD) criteria. A multinomial regression model was used to estimate the odds ratio (OR) and the 95% confidence intervals (CI), using the severity of MIH as the result. The prevalence of MIH was 37.7% and, by severity, was 16.1% mild, 14.3% moderate, and 7.3% severe. The prevalence of dental fluorosis in permanent dentition was 70.9% (TFI ≥1) and, by severity, was 29.2% (TFI = 0), 45.6% (TFI 1-3) and 25.3% (TFI ≥4), while 54.5% of subjects were found to have poor oral hygiene. Schoolchildren with fluorosis (TFI ≥4) were 49% less likely [OR = 0.51; p = 0.025] to present mild MIH than children with fluorosis (TFI