[Uptake of fluoride into enamel and its effect on acid resistance by application of fluoride-releasing sealant--Part 1. Comparison with acid phosphate fluoride].

The newly developed fluoride-releasing sealant (F + sealant) used in this experiment is expected to have the combined cariostatic effects of a sealant and fluoride. The purpose of this study was to investigate F + sealant's effects on the enamel in regard to the uptake of fluoride and resistance to acid. F + sealant's effect was compared to that of acid phosphate fluoride (APF) which has effect as topical fluoride applicant. Bovine teeth applied with F + sealant or APF were immersed for 4 weeks in a pH 7.0 phosphate buffer at 37 degrees C. After 4 weeks of immersion, each tooth was biopsied with pH 1.0 sodium acetate-hydrochloric acid buffer. The fluoride and calcium in the biopsy samples were analyzed by means of fluoride ion electrode and atomic absorption spectroscopy, respectively. The following results were obtained: (1) The fluoride in the enamel was significantly increased by the incorporation of fluoride from the F + sealant. Almost all fluoride in the surface enamel was found to be fluorapatite by the method of alkaline extraction. (2) The amount of fluoride increased by APF application was about 50% of that of F + sealant application. (3) The calcium released from the enamel treated with F + sealant or APF decreased by 13% and 9%, respectively, compared to that without treatment.