Heterocontrol of water fluoridation in a municipality in northeast of Brazil after the privatization of the public supply service

Aim: The aim of the present study was to analyze fluoride levels in the public water supply of Teresina, Piauí, Brazil, following the change of the public supply service. Methods: This is a prospective descriptive laboratory study. The water samples were collected from 13 random locations over a period of 13 months. Three neighborhoods were randomly selected from each of the four zones (north, south, east and southeast) of the municipality (n=12) and one location close to the Water Treatment Plant (WTP) (n=1). The samples collect followed the VIGIFLUOR guide. Fluoride concentration analyses were performed in duplicate using a specific ion electrode (Orion 96–06; Thermo Scientific Orion., Boston, MA, USA) coupled to a VersaStar potentiometer (Thermo Scientific Orion), and the results were expressed in mg F/L (ppm F). Descriptive analysis and classification of samples were carried out according to the criteria of the Ministry of Health Collaborating Center for Oral Health Surveillance. Results: Out of the 169 samples analyzed, 158 samples (93.5%) were classified as inappropriate (ranging from 0.00 to 0.34 ppm F), and 11 samples were classified as appropriate (6.5%) (ranging from 0.45 to 0.74 ppm F). Conclusions: The majority of the water samples from the public supply in Teresina, particularly from the southeast and east zones, exhibited fluoride concentrations below the range considered optimal for controlling dental caries and minimizing the risk of fluorosis. Implementing heterocontrol is essential to maintain the quality of water distributed to the population.