Objective: To determine the sources of fluoride exposure and the prevalence and severity of fluorosis and dental caries and sources of fluoride exposure in the permanent dentition of 11-year-old children.

Material and methods: A cross-sectional study of 111 children attending elementary schools in the State of Mexico, where the concentration of fluoride in drinking water is < 0.3 ppm, was performed using a self-administered questionnaire was directed towards the children' mothers. The level of fluorosis was determined using both the Dean's Modified Index (ID) and the Community Fluorosis Index (CFI). The decayed, missing, filled teeth (DMFT) was recorded using methods recommended by the World Health Organization (WHO). Statistical analysis was conducted using bivariate analysis with a chi2 test; odds ratios (OR) and 95% confidence intervals (CI). Logistic regression models were used in the final model.

Results: Children had a fluorosis prevalence of 52.73% (95% CI: 48.2-55.4) with CFI = 0.75 +/- 0.91 (95% CI: 0.58-0.92). The caries prevalence was 53.2% (95% CI: 50.1-56.3) with DMFT = 1.27 +/- 1.67 (D = 0.85 and F = 0.42). Children who had no fluorosis showed more caries (p = 0.001). Dental fluorosis was associated with the initial age of brushing (before age four), OR = 0.511 (0.338-0.772); frequency of brushing (three times a day), OR = 0.681 (0.483-0.958), brushing before sleeping (yes), OR = 0.664 (0.473-0.932), and applications of fluoride (yes), OR = 0.756 (0.576-0.994). Dental caries was associated with several variables, such as initial age of brushing, OR = 11.28 (4.6-27.7), frequency of brushing, OR = 0.245 (0.109-0.553), brushing before sleeping, OR = 8.03 (3.295-19.59), and applications of fluoride, OR = 14.2 (4.54-44.53). In the final regression model, the level of caries and fluorosis was significantly associated (p = 0.000) with the amount of fluoride exposure. The multivariate shows this relationship.

Conclusions: Fluorosis prevalence was high for low levels and low for more severe levels. According to the CFI in the studied example, dental fluorosis represents a public health problem in the studied sample. Dental caries was low with a predominance of tooth decay. Exposure to different sources of fluoride, was a risk factor for the development of fluorosis and a benefit with regard to dental caries.