Abstract
Fluoride varnish (F-varnish) has been already used for treatment of hypersensitive dentin in clinic. In this study, F-varnish was examined in vitro the possibility of application for caries inhibition. Experiments were made in vitro of applications of F-varnish, containing 5% NaF or placebo-varnish with the intact enamel surface and fissure, for two weeks at 37°C twice a week, followed by 1, 2 or 3 weeks of washing with distilled water. Fluoride uptake and release, morphological observation, and acid solubility test on enamel blocks following treatment with F-varnish, or after washing were studied by means of electron probe microanalysis (EPMA), chemical analysis and sacanning electron microscopy (SEM).
The fluoride uptake of F-varnish-treated enamel surface and fissure were increased, especially a large amount of CaF2 deposited on the outer surface layer and fissure of enamel. Although, CaF2 was released after washing for three weeks, fluoride was taken up at the depth of approximately 40μm. The acid solubility test proved that the acquisition of acid resistance was greater in F-varnish-treated enamel than in the control even after washing for three weeks. SEM of enamel surface showed that CaF2 was formed in the F-varnish-treated enamel, and clearly showed that there was an acid-resistant picture after perchloric acid-etching.
Therefore, we suggest that F-varnish which applied to treat hypersensitive dentin may be effective in clinical use for caries inhibition, because the treatment time of enamel can be extended.
