Urinary fluoride levels and prevalence of dental fluorosis in three Brazilian cities with different fluoride concentrations in the drinking water

Urine samples from three daytime periods were collected from 545 5-50-year-old residents of three different Brazilian cities: Garca had fluoridated drinking water since 1973, Bauru since 1975 and Itapolis was not fluoridated. Dental fluorosis was examined in 985 5-24-year-olds using the Thylstrup-Fejerskov index (TF). The subjects were asked to estimate their daily intake of liquids and frequency of beverage consumption. The analysis of 94 water samples showed high variations in the fluoride content of the drinking water. The mean fluoride concentration of the water samples in Garca was 0.9 mg/L (range 0.75-1.2), in Bauru 0.64 mg/L (range 0.01-1.3), and in Itapolis 0.02 mg/L. Mean urinary fluoride concentration was 1.31 mg/L (s 0.61) in Garca, 0.88 mg/L (s 0.49) in Bauru, and 0.39 mg/L (s 0.21) in Itapolis. Self-reported daily liquid intake was not related to urinary fluoride concentration. The mean prevalence of fluorosis was 13.3% in Garca, 6.8% in Bauu, and 1.7% in Itapolis, with mainly categories TF 1 and TF 2 being recorded. Subjects with dental fluorosis tended to show a higher mean urinary fluoride concentration but the difference was not statistically significant. The study showed that fluoride exposure measured by urinary fluoride excretion was within the range expected for the level of fluoride concentration in the drinking water. However, enamel fluorosis tended to be markedly lower than expected. This study revealed that fluoride levels in the two cities with fluoridated drinking water were variable. To optimise anticaries benefits and minimise the risk of fluorosis greater control of the fluoride dosing of the drinking water is required.