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Introduction: Dental fluorosis is a kind of hypoplasia, hypomineralization or dentin and enamel deficiency ,occurring during formation, due to fluoride overuse. Considering the importance of epidemiological studies in identifying diseases and designing necessary prevention plans, the present study was fulfilled to assess dental fluorosis in 8-27 years old population of Dehloran, Mousian and Dasht Abbas areas during 2006. Materials & Methods: Throughout this analytical descriptive study, 573 cases of 8-27 years old population were selected using a cluster sampling method and examined in respect of different fluorosis rates (Dean index: normal, questionable, very mild, mild, moderate and severe) and DMFT rate (WHO index) using observations and questionnaires. The gained data were analyzed using t - student and chi – square tests. Findings: Generally commenting, 86.6% of the studied populations showed degrees of fluorosis and only 13.4% of them proved free from the disease. Dasht Abbas district showed the highest prevalence of fluorosis. The maximum rate of fluoride in Dehloran town's water was 0.67,while it was 0.78 in Dasht Abbas meanwhile, the rate in Mousian district was 0.37 ppm. Totally, 82.9% of the samples with 12 and less records of residential experience and 91.6% with more than 12 years of residential experience indicated fluorosis. The uninfected people showed a mean DMFT of 2.84, while the fluorosis–free cases showed a mean DMFT of 3.38 without any significant differences. Discussion & Conclusion: The research came to the conclusion that totally 86.6% of 8-27 years old population of Dehloran, Mousian and Dasht Abbas residential places indicated degrees of infection with dental fluorosis in 2006, a rate considered to bo too high for such a population.

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Introduction: If the fluoride concentration in drinking water is lower than the standard level, it causes dental caries and if it be more than standard level it causes dental fluorosis. The aim of this study was to determine whether a relationship exists between the groundwater fluoride(F) concentration and dental caries in children living in 7 areas of Nourabade Mamasani town in Iran. Materials & Methods: F level of the town drinking water was measured by the SPADNS method. All the children of the 4 age groups of 6, 9, 10, and 12 were sampled for a total of 3349 in seven districts of the town. All the 28 teeth of the children were subject to this test. The drinking water in the region is totally of groundwater supply. The residents have essentially the same socio-economic living standards and nutritional conditions. Findings: In these 7 areas, the F level in the drinking water was from 0.53 to 1 mg/L., While the number of decayed permanent(Dt) teeth per child ranged from 0.13and 0.34 to the number of decayed deciduous(dt) teeth ranged from 0.5 to 3.9 Although the F level in the drinking water was below the national level, the dental caries were below the national level. Over this narrow concentration range, there appeared to be a weak association between the F level in the drinking water and Dt and dt. Linear regression analyses showed very weak decreases of the Dt and dt scores with increasing water F level is not significant. Discussion & Conclusion: This study shows that in low concentrations of F ranging 0.1 to 0.53mg/L, there is a negligible effect on prevention of dental caries.