Timing of fluoride intake in relation to development of fluorosis on maxillary central incisors

Objectives: Several studies have focused on the timing of fluoride intake relative to the development of dental fluorosis. This study reports the relationships of fluoride intake during the first 48 months of life with fluorosis on early-erupting permanent teeth. Methods: Subjects were followed from birth to 48 months with questionnaires every 3-4 months. Questionnaires gathered data on intakes from water, diet, supplements, and dentifrice to estimate total fluoride intake. Early-erupting permanent teeth of 579 subjects were assessed for fluorosis using the Fluorosis Risk Index (FRI) at approximately age 9. Fluorosis cases were defined as having FRI definitive or severe fluorosis on both maxillary central incisors. Individuals with FRI questionable fluorosis were excluded. The importance of fluoride intake during different time periods was assessed using t-tests and logistic regression. Results: One hundred and thirty-nine (24%) subjects had fluorosis on both maxillary central incisors. Mean fluoride intake per unit body weight (bw) ranged from 0.040 to 0.057 mg/kg bw, with higher intake during earlier time periods and relative stability after 16 months. In bivariate analyses, fluoride intakes during each of the first 4 years were individually significantly related to fluorosis on maxillary central incisors, with the first year most important (P < 0.01), followed by the second (P < 0.01), third (P < 0.01), and fourth year (P = 0.03). Multivariable logistic regression analyses showed that, after controlling only for the first year, the later years individually were still statistically significant. When all four time periods were in the model, the first (P < 0.01) and second years (P = 0.04) were still significant, but the third (P = 0.32) and fourth (P = 0.82) were not. Conclusions: The first two years of life were most important to fluorosis development in permanent maxillary central incisors; however, this study also suggests the importance of other individual years.