457 schoolchildren living in two rural areas of Mexico were assessed for water fluoride levels, fluorosis and tooth decay. Childjren living in communities with 1.5 ppm of fluoride had a rate of fluorosis of 60.5%. Children living in homes with fluoride levels of 0.70 ppm (the level used in fluoridated US communities) was still high at 39.4%. Of great interest, researchers found a higher rate of tooth decay and cavities in children with moderate to high fluorosis. This has not been reported previously and is of greater concern as teh percent of children with moderate to high fluorosis has increased dramatically the past 20 years in the US.
Objective: To explore the association between fluoride in drinking water and the prevalence and severity of fluorosis and dental caries in children living in communities receiving fluoridated salt.
Material and methods: Participants were schoolchildren (n = 457) living in two rural areas of the State of Morelos, Mexico, where the water fluoride concentration was 0.70 or 1.50 ppm. Dental caries status was assessed using Pitts' criteria. Lesions that were classified as D3 (decayed) were identified to determine the decayed, missing, and filled teeth index (D3MFT). Fluorosis was assessed using the Thylstrup-Fejerskov Index (TFI). Information regarding drinking water source and oral hygiene practices (tooth brushing frequency, dentifrice use, and oral hygiene index) was obtained.
Results: The prevalence of fluorosis (TFI ≥1) in communities with 0.70 and 1.50 ppm water fluoride was 39.4 and 60.5% (p = 0.014), respectively, while the prevalence of more severe forms (TFI ≥4) was 7.9 and 25.5% (p < 0.001), respectively. The mean D3MFT was 0.49 (±1.01) in the 0.70 ppm community and 0.61 (±1.47) in the 1.50 ppm community (p = 0.349). A logistic regression model for caries (D3 >1) showed that higher fluorosis categories (TFI 5-6 OR = 6.81, p = 0.001) were associated with higher caries experience, adjusted by age, number of teeth present, tooth brushing frequency, bottled water use, and natural water fluoride concentration.
Conclusions: The prevalence of fluorosis was associated with the water fluoride concentration. Fluorosis at moderate and severe levels was associated with a higher prevalence of dental caries, compared with lesser degrees of fluorosis. The impact of dental fluorosis should be considered in dental public health programs.