EPMA Analysis of Artificial Caries Lesions on Enamel Treated with Sodium Fluoride in Combination with Pyridoxine Hydrochloride Solution.

A cariostatic effect of soduim fluoride in combination with pyridoxine hydrochloride solution on artificial caries lesion formation was reported previously. The purpose of the present study was to examine the mode of action of this solution on enamel. Intact human enamel was immersed and stirred in three kinds of solution at 37°C for 1 hour. The three solutions were as followes: (1) sodium fluoride in combination with pyridoxine hydrochloride solution, 900ppm of fluoride (F-), pH 4.5-NaF +VB6 group; (2) hydrochloric acid-acidified sodium fluoride solution, 900ppm of fluoride (F-), pH 4.5-NaF group; and (3) de-ionized water-control group. Artificial caries lesions were formed with Moreno's demineralizing solution (1974), consisting of 50% hydroxyapatite in saturated lactate buffer (pH 4.5). Distribution of phosphorus, calcium, and fluoride in enamel were determined with line analysis by EPMA, and state analysis was performed to identify the reaction products in fluoride treated enamel.The enamel surface contained 30-33% F in the NaF+VB6 group, and 14-15% F in the NaF group. Only Ca and F were detected in fluoride-treated superficial enamel by magnified analysis. Ca and F were also detected in the crystal deposits, and a large amount of calcium fluoride was seen in the NaF+VB6 group. The state analysis with EPMA showed that the reaction products were calcium fluoride and fluorapatite, and the volume of reaction products was very large in the NaF+VB6 group.In EPMA analysis of caries lesions, the fluoride level was higher than in other sound enamel surfaces, and the NaF+VB6 group showed the highest level of fluoride. Calcium and phosphorus level in the NaF+VB6 group was the same as in the sound enamel layer, and the level was low in the NaF and control groups because of subsurface demineralization of the enamel. In state analysis with EPMA, fluorapatite was detected in the carie lesions, and the volume of fluorapatite was very high in the NaF+VB6 group.In conclusion, soduim fluoride in combination with pyridoxine hydrochloride solution acted by producing calcium fluoride and fluorapatite on the enamel surface. Then calcium fluoride was released slowly into the demineralizing solution, and reacted with calcium and phosphorus in solution to produce fluorapatite. The greater formation of calcium fluoride in the NaF+VB6 group had a higher cariostatic effect than NaF solution alone.