低濃度フッ化アンモニウム歯面塗布溶液のエナメル質粉末に及ぼす影響について

Abstract

The purpose of this study was to evaluate the possibility of use for fluoride topical treatment of a dilute ammonium fluoride solution, in which the fluoride concentration was 1/5 times lower than that of APF solution.Human enamel powder (200 mesh passed) was treated with solutions of NH4F (1, 800ppmF-, pH 3.4) and APF (9, 000ppmF-, pH 3.4) for 5min. at 37°C. A part of the specimen was washed with 1M KOH solution for 72 hours.In experiment 1, fluoride uptake by enamel powder was determined by means of chemical analysis and identification of reaction products using X-ray diffractometry.In experiment 2, the relationship between CaF2 formation and release into synthetic saliva, the increase of permanently bound fluoride, and acid solubility in enamel were observed by means of chemical analysis and X-ray diffractometry. In order to identify fluorapatite formation, variance of line profile, peak shift and a-axis lattice parameter of enamel apatite were examined using X-ray diffractometry. Crystallite size and β-TCP formation during heating at 1, 000°C were determined to evaluate the crystallinity of enamel apatite. The acid solubility test was performed by messuring calcium released into 0.4M acetate buffer (pH 4.0) from enamel.In experiment 3, scanning electron microscopic observations were made and the infrared spectra of the enamel powder were studied.The following results were obtained.The fluoride uptake of NH4F treated enamel was higher than that of APF treated enamel. X-ray diffractometry showed that CaF2 was formed in the experimental groups, and a large amount of CaF2 with high crystallinity was formed in NH4F treated enamel (experiment 1).CaF2 formed in emanel was released into synthetic saliva and permanently bound fluoride increased with time. Hydroxyfluorapatite was indicated in the line profile of fluoride-treated enamel powder. Peak shift and decrease of the a-axis lattice parameter also showed the formation of hydroxyfluorapatite. The amount of β-TCP produced by heating in fluoride-treated enamel decreased in enamel immersed in synthetic saliva, and the crystallinity of enamel apatite was increased. The acid solubility test proved an acquisition of high acid resistance by the enamel powder treated with fluoride (experiment 2).Scanning electron microscopic observation of enamel powder treated with NH4F revealed larger deposits of crystalline materials than that treated with APF. Infrared spectra of enamel powder treated with fluoride revealed the formation of fluorapatite (experiment 3).I concluded that a dilute ammonium fluoride solution (1, 800ppmF-, pH 3.4), in which fluoride concentration was 1/5 times of APF solution, had the same effect on enamel powder as conventional APF solution. I suggest that a dilute ammonium fluoride solution is useful as safe agent for fluoride topical application in clinical use.