エナメル質表層におけるフッ素濃度分布 (II)

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  • Distribution of Fluoride in Human Enamel Surfaces (II)
  • エナメルシツ ヒョウソウ ニ オケル フッソ ノウド ブンプ 2 エナメルシツ
  • エナメル質生検法による検討

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The purpose of this study was to assess the fluoride concentrations in surface enamel using a biopsy procedure, in relation to fluoride contens of drinking water in a fluoride area (Kitatsugaru, 0.3-3.2 F- ppm occuring naturally) and a fluoride-free area (Matsuo, 0.07 F- ppm in drinking water). Dental fluorosis was found in 12.9 percent (including moderate and severe cases) of 404 school children aged 6 to 11 years old (79 percent including questionable enamel mottling) in this fluoride area, which was reported in our previous paper (1975). This study also aims to investigate a parameter for distinguishing between dental fluorosis and nonfluoride opacities based on fluoride concentration in surface enamel in vivo. The subjects for biopsy samples were 39 school children aged 9 and 10 in the fluoride area and 11 subjects aged 9 and 10 from the fluoride-free area.<BR>A round filter paper disc (φ5mm) was put onto the labial surface of the maxillary central incisor. The disc was then impregnated with 10μl of 0.5 M perchloric acid using a micropipet. Exposure time of the tooth surface was 60 seconds. Fluoride was determined by means of a fluoride ion activity combination electrode (ORION, 69-09) and calcium by atomic absorption spectrophotometry.<BR>The results were as follows:<BR>The fluoride concentrations of the central incisors at the depth of approximate 4μm were 1490±549 ppm (Mean±S.D.) in the fluoride area and 939±432 ppm in the fluoride-free area. A significant difference of fluoride concentration in surface enamel was found between the fluoride ares and the fluoride-free area. Furthermore, a significant correlation was established between the fluoride concentration of surface enamel and both the actual concentrations of drinking water at present (r=+0.55, P<0.001) and the degree of dental fluorosis biopsyed (r=+0.35, p<0.05).<BR>These results suggest that a high concentration of fluoride in surface enamel seems to be mostly caused by the actual amount of fluoride in drinking water due to incorporation into surface enamel, rather than by an increase in the amount of fluoride ions present during enamel formation or pre-eruption. Regarding caries experience in these two areas, the DMFT Index was 1.34±1.69 in the fluoride area and 2.54±2.49 in the fluoride-free. area. It is suggested that the low caries incidence in the fluoride area resulted from an increase of fluoride content in surface enamel due to water-born fluoride after eruption.

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