Municipality-level characteristics associated with very good quality water fluoridation in Brazil in 2018

The aim of this study was to analyze factors associated with the quality of fluoridation in water supply systems in Brazil in 2018. An ecological study was conducted using official data sources on fluoridation provision and fluoride concentration surveillance in 2018. Inclusion criteria were municipalities with a water supply system and accurate data. Municipalities meeting the quality standard, defined as having 80% or more of water samples within the optimal level for caries prevention were classified as "very good" fluoridation quality. Independent variables encompassed structural aspects, socioeconomic factors, and indicators of managerial and technical capabilities in water surveillance. Prevalence ratios were estimated using Poisson regression with robust variance. A total of 58.9% of municipalities with water supply systems had fluoride-adjusted water, with 65.3% adequately contributing to the surveillance data system. Among these, 42.2% exhibited "very good" fluoridation quality. Quality was higher in larger municipalities with elevated socioeconomic indexes and per capita expenditure on sanitary surveillance above the median. Additionally, municipalities with a conformity rate of free residual chlorine concentration of 75% or higher had better fluoridation quality. After adjusting for all variables, fluoridation quality was lower in municipalities with above-median per capita gross domestic product, higher socioeconomic inequality, and below-median monthly household per capita income. Fluoridation quality was linked to municipality-level characteristics concerning structural aspects, socioeconomic factors, and managerial and technical factors in water surveillance. The information generated regarding the coverage features of surveillance and fluoridation strategies can be highly valuable for redirecting inter-sectoral public policy management.