Water fluoridation, functional dentition and tooth loss in Brazilian adults: a multilevel analysis of SB Brasil 2023.

OBJECTIVE: To evaluate the association between water fluoridation and the maintenance of functional dentition (≥20 teeth) and tooth loss in Brazilian adults aged 35 to 44, considering individual and contextual factors. METHODS: This study employed a cross-sectional design using data from SB Brasil 2023 (n=9,019). The main exposure was the availability of fluoridated water in municipalities, obtained from national sanitation information systems. The outcomes analyzed were (i) functional dentition (binary) and (ii) number of missing teeth (count). To reduce confounding bias, inverse probability weighting was used to balance individual (age, sex, education, and income) and contextual (municipal development index and dental service coverage) covariates. The analysis was performed using multilevel Poisson models for functional dentition and multilevel negative binomial models for missing teeth. The robustness of the results was assessed using E-values, estimating sensitivity to potential unmeasured confounders. RESULTS: After adjustment, fluoridation showed no significant association with functional dentition (PR 1.24; 95%CI 0.91-1.68). However, it was significantly associated with a lower rate of missing teeth (RR 1.30; 95%CI 1.01-1.67). Sensitivity analysis (E-value) indicated high susceptibility to unmeasured confounders for the count outcome. CONCLUSION: In the context of widespread use of fluoridated dentifrice, water fluoridation demonstrated a significant protective effect against tooth loss in adults, although it was totally or partially confounded by socioeconomic variables. These findings reinforce the importance of universal fluoridation policies, which should be combined with strategies targeting vulnerable groups, aiming to reduce inequalities and promote oral health in the adult population.