Relationship between fluoride levels in the public water supply and dental fluorosis

Objective: To assess the prevalence of dental flourosis among schoolchildren subjected to different fluoride concentrations in the public water supply of their cities. Methods: The sample comprised 386 seven-year-old schoolchildren living in two municipalities in the State of São Paulo that practiced external control over the fluoridation of the water from 1998 to 2002: one with homogenous fluoride concentration and the other with oscillating concentration. Dental fluorosis was determined by dry examination of the upper permanent incisors using Dean's index. Scores classified as questionable were considered to represent fluorosis. Sociodemographic variables and questions regarding oral health were assessed using a structured questionnaire sent to the children's parents or the adults responsible for these children. Correlates of fluorosis were assessed using multivariate logistic regression (p<0.05). Results: Both municipalities presented a mild degree of fluorosis. The prevalence of fluorosis in the municipality with oscillating fluoride content in the water was 31.4%, and it was 79.9% in the municipality with homogenous fluoride content. The prevalence of fluorosis was associated with the municipality with homogeneous fluoride levels in the water (OR=8.33, 95% CI: 5.15; 13.45) and with not owning a car (OR=2.10, 95% CI: 1.27;3.49). Conclusions: The prevalence of dental fluorosis was higher in the city with better control of fluoride levels in the water supply, however, this higher prevalence was not related with children's satisfaction with the appearance of their teeth.