Community water fluoridation and dental caries in early childhood: A multilevel analysis of the 2023 Brazilian National Oral Health Survey

Community water fluoridation is widely recognised as an effective and equitable population-level strategy for preventing dental caries. However, its relevance has been questioned in recent international debates, particularly in settings with widespread access to other fluoride sources. This study examined the association between municipal community water fluoridation coverage and dental caries outcomes among 5-year-old children residing in 313 Brazilian municipalities. This cross-sectional study used individual-level data from the Brazilian National Oral Health Survey (SB Brasil 2023) and municipal-level data on community water fluoridation coverage from the Water Quality Surveillance Information System (Sisagua). The analytical sample comprised 6128 5-year-old children. Caries experience was assessed using the dmft index, and untreated caries were measured as the number of decayed primary teeth. Multilevel negative binomial regression models with random intercepts for municipality were fitted, incorporating rescaled sampling weights and adjusting for sex, race/ethnicity, maternal education, and household income. The findings revealed that higher municipal community water fluoridation coverage was associated with lower caries experience. In fully adjusted models, each unit increase in fluoridation coverage (0-1) was associated with a reduction in mean dmft (RR = 0.74; 95% CI: 0.63-0.86) and untreated caries (RR = 0.73; 95% CI: 0.64-0.84). Persistent socioeconomic and racial inequalities were observed, with higher caries levels among Black, Mixed-race, and Indigenous children. In conclusion, community water fluoridation remains an effective and equitable public health intervention for preventing early childhood caries in Brazil, particularly in contexts of social inequality and heterogeneous municipal implementation.