A study on the promotion and suppression of demineralization of human dental hard tissues and hydroxyapatite

Demineralization of human dental enamel and dentine and their analogue comp ound, hydroxyapatite, was examined by using pH-metry to measure the time-co urses of neutralization of acetate, formate, lactate or propionate buffer s olution or of acidification of EDTA solution. The extent of neutralization by enamel, dentine and hydroxyapatite was different for each acid but incre ased in the same order: propionate, acetate, lactate and formate. This orde r was consistent with that of the K values of these acids. The pH-metry was used to determine the influences of sodium chloride and sucrose on deminer alization of enamel, dentine and hydroxyapatite by acetate, formate, lactat e and propionate and by EDTA. The demineralization by these bioorganic acid s was suppressed by sucrose but promoted by sodium chloride, except that th e demineralization of enamel by acetate and propionate was little affected. The demineralization of enamel, dentine and hydroxyapatite by EDTA was lit tle affected by sucrose but promoted by sodium chloride. The promotive effe ct of sodium chloride on demineralization may be due to the increasing of s olubility product by this salt and the suppressive effect of sucrose may be due to the formation of a calcium saccharate formed from the sucrose react ed with calcium on the surface of apatite crystal and/or the reduction of s olubility product by the sucrose. In this study, it was also ascertained th at the use of pH-metry made it possible to determine easily the demineraliz ation.