Risk factors for dental fluorosis in a fluoridated community

We conducted a case-control study to determine the sources of fluoride which are particular risk factors to dental fluorosis. Cases and non-cases were identified by the screening of 8-, 9-, and 10-year-old schoolchildren in the fluoridated community of East York, Ontario. Parents were interviewed about the child's first five years of residence and about diet and preventive caries practices. The Mantel-Haenszel odds ratio and associated chi-square tests were used to assess the association of fluorosis with several potential sources, controlling for other sources of fluoride and mother's education. The prevalence of mild fluorosis [1-4 on the Thylstrup and Fejerskov (1978) Index] was 13%. Those who brushed their teeth before the age of 25 months had 11 times the odds of fluorosis compared with those beginning toothbrushing later; prolonged use of infant formula (greater than or equal to 13 months) was associated with 3.5 times the risk of fluorosis, compared with no, or shorter duration of, formula use. We estimate that these factors were responsible for 72% and 22%, respectively, of the cases in our population. Dental fluorosis is not a public health problem in East York, but parents should be advised to supervise toothbrushing by children under 2 years of age.