Quality of the water fluoridation and municipal-level indicators in a Brazilian metropolitan region

Abstarct This study explored the relationship between water fluoridation quality and development indicators at municipal level. In addition, fluoride concentrations found were classified based on two criteria for interpreting the samples. A cross-sectional ecological exploratory study was carried out including all municipalities of the metropolitan region of Great Vitória, ES, Brazil. From May to October 2016, 648 samples of water were collected covering water treatment plants responsible for more than 80% of the population of each municipality. The fluoride concentration of each sample was determined using ion-specific electrode and the results were classified according to the federal act and the criterion proposed by the Collaborating Center of the Brazilian Ministry of Health for Oral Health Surveillance. The outcome was the rate of values included in the optimal concentration interval and the independent variables were municipal-level indicators related to demographics, economics, sanitation, health conditions and human development characteristics. The Spearman test and Kappa statistic were used in the analysis. The percentage of samples presenting optimal fluoride concentration ranged from 68.1 to 81.4%, considering the two criteria used. The Kappa statistic between the criteria was 0.671 (p-value = 0.001). Human development, average coverage of supervised toothbrushing, and total population showed a strong positive correlation with the quality of fluoridation while infant mortality and tooth-extraction/dental procedures ratio showed a strong negative correlation. The plausibility of observed correlations encourages further investigations of potential causes.