Correlation between urinary fluoride level and prevalence of dental caries-the effects of defluoridation for 10 years

Objective To study the relationship between the level of fluoride in urine and the prevalence of dental caries in children before and after the defluoridation, and to provide a basis for assessment of the effects of defluoridation projects and for control of dental caries. Methods Wamiao Village, in Jiangsu Province, a formerly severe endemic fluorosis area, was selected to carry out the study. All children aged 8 - 13 years old before the defuoridation were investigated from September to November in 2002, and children 8 - 10 years old who were born after the defluoridation were investigated from September to November in 2013. Urinary fluoride level of the children and the prevalence of dental caries were determined, and their relationships were analyzed. The urina sanguinis samples of children were collected in the morning, and the urine fluoride level was tested using the fluoride ion selective electrode. Dental caries diagnoses was referenced to "Dental Caries". Results Totally children's urine samples were 236 and 68 respectively before and after defluoridation. Urinary fluoride level of the children was significantly decreased from (3.53 ± 1.81)mg/L (before defluoridation) to (1.39 ± 0.66)mg/L (after defluoridation,t = 9.506,P 0.05). The DMFT increased from 1.18 (before defluoridation) to 1.68 (after defluoridation), and the epidemic levels of dental caries were all at lower levels. The relationship between urine fluoride level and the prevalence of dental caries as well as the DMFT before defluoridation was a U-shape dose-response curve; which was gone after defluoridation. Conclusions The urinary fluoride level is significantly decreased after defluoridation for 10 years, the prevalence of dental caries is increased but not significantly. The results of this study indicate that the measure of fluoridation to prevent dental caries needs to be further validated. Key words: Fluorine; Water; Urine; Dental caries