Introduction Water fluoridation and fluoride dentifrice contribute effectively in caries prevention. Both resources have nearly universal coverage in Sao Paulo, Brazil, since the 1980s. However, multiple exposures to fluoride demand the surveillance of dental fluorosis. This study aimed to assess fluorosis prevalence from 1998 to 2008.

Methods Epidemiological surveys of oral health conducted in 1998 (n=244), 2002 (n=253) and in 2008 (n=4249) informed fluorosis prevalence among 12-year-old school children. Although using different sample sizes, all surveys were considered representative for the city. Dental examinations were performed at schools, under natural illumination. The assessment of dental fluorosis used the index proposed by Dean in 1942, and recommended by the WHO for oral health surveys in 1997. Data analysis used the comparison of proportions included in the Epi-Info software.

Results Fluorosis prevalence was 43.9% (95% CI 37.7% to 50.1%) in 1998, 33.2% (27.7% to 39.2%) in 2002, and 39.1% (37.6% to 40.6%) in 2008. Mild and very mild fluorosis accounted for 88% of cases observed in 1998, 95% in 2002, and 94% in 2008. Less than 1% of examined children had severe fluorosis in 1998 and 2008; no cases were observed in 2002. No statistically significant difference was observed for the overall prevalence and for rates that specifically assessed differential levels of fluorosis during the period.

Conclusion The prevalence of dental fluorosis among children in Sao Paulo was stationary in the period 1998 to 2008. Most of the prevalence refers to mild and very mild levels of fluorosis, with no impact in function and aesthetics.