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[Epidemiological analysis of dental caries prevalence of the different types of permanent teeth in a fluoride and a non-fluoride community].

This study aimed at evaluating the effect of caries reduction with natural fluoride in the drinking water for the different types of permanent teeth. The study was conducted to survey of 370 schoolchildren in a fluoride area (Kitatsugaru, Aomori; F 0.3-3.2ppm) and of 528 children in a non-fluoride area (Matsuo. Iwate: F<0.1 ppm), aged 6-11 years. Both communities belong to a rural area of northern Japan. Social, economical, and environmental conditions are almost identical in these two communities. Furthermore, caries prevalence in the non-fluoride area is very close to the data obtained from the National Caries Survey (1975) of Japan for the age group studied in this report.Caries reduction of the upper incisor group (1, 2) was remarkably higher in the fluoride area, especially in the children of age 11. With regards to the percentage of the children with DMF in the upper incisor group, the fluoride area percentage was 4.6% vs 37.9% in the nonfluoride area. As a consequence, the caries reduction rate was 88%. On the other hand, the percentage of the children with DMF in the lower 1 st molar group (6) was 66.6% (caries reduction rate: 16.6%) in the 0.8ppm fluoride drinking water group and 64.9% (caries reduction rate: 18.8%) in the 0.90-1.06ppm fluoride drinking water group, and that of the non-fluoride area was 79.9%.With DMFT indices (Mean DMF) of whole erupted teeth examined in 0.8ppm and 0.90-1.06ppm fluoride drinking water groups, the value of the fluoride area was approximately 1/2 of the non-fluoride area through the ages of 6-11. At age 11, the DMFT index was 4.3 in the non-fluoride area, and 2.3 in the 0.8 ppm and 1.9 in the 0.90-1.06ppm fluoride area.No significant differences were observed between fluoride and non-fluoride areas concerning teeth eruption rates in different age groups or different types of permanent teeth. Delayed or accelerated eruption of teeth during the ages of 6-10 in a fluoride area, compared with a nonfluoride area has been reported, but delay of tooth eruption caused by fluoride was not found in our study.