[Studies on fluoride mouth-rinsing solution for dental caries prevention. II. Fluoride uptake and acid solubility].

The effect of fluoride mouth-rinsing solution on human enamel was examined by means of electron probe microanalysis and X-ray diffraction. Experiments were made in vitro by applications of phosphoric acid-acidified NaF solution (500 ppm of F-; pH 5.0) to the intact enamel.The distribution of fluorine, calcium and phosphorus in enamel following the topical fluoride treatment (30 minutes every day for 8 weeks) were demonstrated by electron probe microanalysis.X-ray diffractometry was performed by the use of X-ray microfocus diffraction. Reaction roducts and crystallinity of the enamel were observed in the X-ray diffraction pattern obtained with a microphotometer. The variation of crystallinity was estimated from the half-maximum breadth values (310), (002) reflections of enamel apatite.Electron probe microanalysis shows that the fluorine concentration of surface enamel was increased not only on flat surfaces but also in fissure areas by the repeated use of fluoride mouthrinsing solution. Espeiaclly high concentration of fluorine was observed at the subsurface decalcified area of the enamel surface.In the X-ray diffraction experiments, no reaction product was detected. The crystallinity of enamel apatite of the surface layer was increased in both a- and c-axis directions by application of fluoride mouth-rinsing solution. In the inner layer it seemed that the crystallinity of enamel apatite in the a-axis was also increased by the use of fluoride mouth rinse.