title: The effect of water fluoride concentration on dental caries and fluorosis in five Iran provinces: A multi-center two-phase study.
abstract: BACKGROUND
  Water fluoride level is unknown in many regions of Iran. Besides, only few non-controlled studies world-wide have assessed the effect of water fluoride on dental fluorosis and caries. We aimed to measure the fluoride level of 76 water supplies in 54 cities and evaluate the effect of fluoride on dental caries and fluorosis in a large multi-project study.
  
  
  METHODS
  In the first phase (cross-sectional), fluoride levels of 76 water tanks in 54 cities/villages in five provinces of Iran were randomly evaluated in five subprojects. In the second phase (retrospective cohort), 1127 middle school children (563 cohort and 564 control subjects) in the high and low ends of fluoride concentration in each subproject were visited. Their decayed, missing and filled teeth (DMFT) and fluorosis states were assessed. The data were analyzed using Chi-square, Mann-Whitney U and independent-samples t-test (α = 0.05).
  
  
  RESULTS
  Mean fluoride level was 0.298 ± 0.340 mg/L in 54 cities/villages. Only eight water tanks had fluoride levels within the normal range and only one was higher than normal and the rest (67 tanks) were all at low levels. Overall, a significant association was observed between fluoride level and fluorosis. However, this was not the case in all areas, as in 2 of 5 provinces, the effect of fluoride on fluorosis was not confirmed. In 4 of the 5 areas studied, there was a significant link between fluoride level and DMFT.
  
  
  CONCLUSIONS
  Extremely low fluoride levels in Iran cities are an alarming finding and need attention. Higher fluoride is likely to reduce dental caries while increasing fluorosis. This finding was not confirmed in all the areas studied.
authors.affiliation: Department of Pediatric Dentistry, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Gholamhossein
authors.initials: G
authors.lastname: Ramezani
authors.affiliation: Department of Statistics, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Nasser
authors.initials: N
authors.lastname: Valaie
authors.affiliation: Iranian Tissue Bank and Research Center, Tehran University of Medical Sciences, Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan
keywords: Community fluorosis index; Dean's fluorosis index; dental caries; dental fluorosis; water fluoride