Abstract
The aim of this study was to determine the optimum fluoride levels in drinking water for minimizing dental caries with maximum safety in Kitatsugaru area (north latitude 41°), Japan. The fluoride concentrations of drinking water in this area ranged from 0.3 to 3.2 ppm and the mean annual temparature was 9.6°C (49.3°F). The fluoride concentrations of drinking water were divided into six groups related to wells in the districts, i. e., group I, 0.31-0.38 ppm; group II, 0.52-0.63 ppm; group III, 0.82-0.95 ppm; group IV, 1.01-1.56 ppm; group V, 1.74-1.96 ppm; and group VI, 2.90-3.18 ppm. Community fluorosis index (CFI) and caries incidence in relation to groups of water fluoride concentrations were evaluated. 387 school children aged 6 to 12 years were given an oral examination. Of these 358 had resided in the area from birth and had used community well water continuously.
In the Kitatsugaru area, dental fluorosis and nonfluoride enamel opacities were present in 39.1 per cent and 6.7 per cent of the children, respectively. The CFI of this area was 0.68, which is higher than borderline. When water fluoride concentrations and their CFI were compared, there was a marked distribution of CFI ranging from 0.02-1.95 from the lowest (0.31-0.38) to the highest group (2.90-3.18). Community fluorosis indices of the water groups were as follows: Group I, 0.02; Group II, 1.53; Group III, 0.14; Group IV, 0.47; Group V, 096; Group VI, 1.95. It is evident that frequency and degree of dental fluorosis increase with increase with increasing fluoride concentration of the water except in Group II. This indicates that the higher CFI values of Group II was due to the variation of fluoride concentration in the drinking water because of re-boring the well.
There was a statistically significant difference (P<0.01) in caries prevalence and incidence in each water group (Group I-VI) when compared with the control district (Matsuo: F<0.1 ppm). The results obtained in this study suggest that the optimal fluoride concentration for caries prevention in this area would be 0.8-0.9 ppm. Furthermore, epidemiological findings in this study suggests that the occurrence of dental fluorosis might be affected by the transient influence of fluoride at the time of the initial calcification of enamel rather than to continuous influence during enamel formation.
