The effects of a break in water fluoridation on the development of dental caries and fluorosis

Durham, NC, fluoridated since 1962, had an 11-month cessation of fluoridati on between September, 1990, and August, 1991. The purpose of this study was to assess the effects of this break on the development of caries and fluor osis in children. Study participants were continuously-resident children in Kindergarten through Grade 5 in Durham's elementary schools. There were 16 96 children, 81.4% of those eligible, for whom a questionnaire was complete d and clinical data recorded. Age cohorts were defined by a child's age at the time that fluoridation ceased. Caries was recorded in children in the B irth Cohort through Cohort 3, and fluorosis for children in Cohorts 1 throu gh 5. Caries was assessed in the primary first and second molars according to the decayed-filled index; fluorosis on the labial surfaces of the upper permanent central and lateral incisors was assessed by the Thylstrup-Fejers kov (TF) index. Mother's education was associated with caries; higher educa tion of the mother had an odds ratio of 0.53 (95% Cl 0.40, 0.76) for caries in the child. No cohort effects could be discerned for caries. Overall pre valence of fluorosis was 44%. Prevalence in Cohorts 1, 2, 3, 4, and 5 was 3 9.8%, 32.3%, 33.0%, 62.3%, and 57.1%, respectively. These cohort difference s remained statistically significant in regression analysis. It was conclud ed that while the break had little effect on caries, dental fluorosis is se nsitive to even small changes in fluoride exposure from drinking water, and this sensitivity is greater at 1 to 3 years of age than at 4 or 5 years.