Abstract:This study investigated the relative effects of fluoride concentration in drinking water and daily habits on the dental caries of 4-and 5-year-old children living in 8 regions in the Tohoku, Kanto, Ko-shin-Estu and Hokuriku districts, who has received differing water fluoride levels for at least 7 years.There were 20 water-supply systems in the 8 regions, and their fluoride concentration ranged from 0 to 1.4 ppm, which was confirmed by my own analysis.In 1983, dental examinations were carried out by three dentists who had been trained to obtain reproducibility and objectivity of diagnosis, adopting the' Blind Recording Method', whereby those three dentists had no information about the regions, such as the fluoride concentration in the drinking water. In addition, the information on the childrens' daily habits was obtained through a questionnaire to their parents.Subjects chosen for analysis were 1078 4-and 5-year-old children who had lived in the regions since birth.A significant negative correlation was found between mean dfs and the fluoride concentration in the drinking water.An analysis of the factors which have an influence on the dfs number was also made by means of the 'quantification theory (1)', that is a series of multivariate analyses, because caries is a disease with many causes.A relative measure of the influece of a factor was provided by the magnitude of the absolute value of the partial correlation coefficient,The partial correlation coefficient of the fluoride concentration in the drinking water was 0.259(4-year-olds) and -0.298 (5-year-olds), and this was the highest coefficient (p<0.01) of all. That of regional factor was second (p<0.05), and the coefficients of the other factors were not significant. 'Quantification theory (1)' made the inverse relationship between the caries prevalence of deciduous
