Dental fluorosis following downward adjustment of fluoride in drinking water

The drinking water fluoride concentration in Hong Kong was reduced by about 0.2 ppm in June 1978. This study was undertaken to determine whether the prevailing level of dental fluorosis was affected by such a minor change. Cohorts of children (N = 1,062) aged seven to 12 years, who were born both before and after the fluoride reduction, were examined clinically using Dean's fluorosis index. Based on upper right central incisors, dental fluorosis prevalence decreased from 64 to 47 percent and the community fluorosis index decreased from 1.01 to 0.75 (P less than .01). Thus, dental fluorosis was reduced, although the reduction in water fluoride concentration was not sufficient to achieve the minimal fluorosis level that Dean associated with a fluoride concentration optimal for caries prevention. Variation in dental fluorosis has been reported previously to result from marked sudden changes, during tooth formative years, to drinking water fluoride concentration. This study confirms preliminary findings that variation in dental fluorosis arising from minor changes to the fluoride level in drinking water is also measurable.