September 2011

Objective: The main aim of the study was to investigate the association between water fluoride concentration and caries as well as fluorosis occurrence in adolescents in Iran. As a secondary aim we studied the relationship between caries and fluorosis occurrence. Basic research design: We examined 12-16 year-olds (n=373) in Orumiyeh [0.3 mgF-/l, low-fluoride (LF)] and Pol Dasht [3.2 mgF-/l, high-fluoride (HF)] for caries-status [D3-Level, Pitts & Fyffe (DMFS)] and fluorosis prevalence [Thylstrup & Fejerskov index (TF)]. Children completed questionnaires about several sociodemographic and oral health related factors of the previous years. To adjust for confounding, we used log risk regression and estimated relative risks (RR) and 95% confidence intervals (CI). Results: For 12-13 year-olds mean DMFS were 1.9 (sd 2.5) and 1.1 (2.2) in the LF and the HF-areas, respectively. Prevalence of aesthetically relevant fluorosis (TF>2) was 1% (LF) and 87% (HF). Water fluoride concentration (adjusted for age and SES) was inversely associated with caries-status [RR: 0.7, (CI 0.6-0.8)]. RR for fluorosis was 17 (CI 8-33). In HF-area, caries scores were significantly higher for children with TF≥5 on upper central incisors compared with TF≤4 (p<0.05 Mann-Whitney test). Conclusions: Caries prevalence in the examined areas in Iran is quite low. Aboveoptimal water fluoride concentration seems to be effective in reducing caries experience, but increases the occurrence of fluorosis. Severe fluorosis seems to be associated with higher caries occurrence in a high-fluoride area. Key words: caries, fluorosis, water fluoridation, fluoride, Iran