Abstract
The present study was made to examine the effects of fluoride mouth rinsing solutions on the powdered enamel by chemical analysis and X-ray diffractometry. Experiments were done in vitro with the powdered enamel (200 mesh) as material. Phosphoric acid-acidified NaF solutions (100 ppm of F-; pH 5.0, 250 ppm of F-; pH 5.0) were used as the mouth rinsing solutions. Fluoride, calcium, and phosphor, us contents in enamel were determined by using an ORION ion meter (model 901), anatomic absorption spectrophotometer (HITACHI polarized zeeman 180-80), and Dryer's method, respectively.
X-ray diffractometry was performed with an automatic recording X-ray diffractometer to observe the crystallinity and identify the reaction products in enamel following the application of fluoride solutions. For the observations of crystallinity, the half-maximum breadth (β1/2) was measured, and the values calculated from Scherrer's equation were defined as the parameters of crystallinity. The reaction products were studied by identification with the ASTM indexes, observations of alterations in the diffraction line profiles and peak shifts at diffraction angles of 50-59 degrees (20). Determination of β-tricalcium phosphate produced by heating treatment (1000°C, 5 hours) was carried out using X-ray diffractometry.
In the experiments with fluoride mouth rinse, the fluoride content of enamel increased with time. The Ca/P mol ratio of fluoride treated enamel was similar to that of control enamel. Chemical analysis and X-ray diffractometry showed that no CaF2 was produced, while a large amount of hydroxyfluorapatite with considerably high crystallinity was pruduced. The amount of β-tricalcium phosphate produced by heating treatment decreased with time. Thus it appears that the imperfect apatite decreases following rinsing with fluoride solutions. Thus the effect of dilute fluoride mouth-rinsing solutions on powdered enamel is quite high in spite of the fact that the concentration of fluoride was lower than in conventional mouth-rinsing solutions.
In other words, the repeated application of fluoride mouth rinse with dilute fluoride solutions over a long period will produce hydroxyfluorapatite with high crystallinity without CaF2 formation. Therefore, the dilute fluoride solution for mouth rinse is an effective caries perventive.
