The Inhibitory Effect of Condensed Phosphates on the Formation and the Growth of Hydroxyapatite

Abstract

Dental calculus is a hard crystalline deposit of calcium phosphates such as hydroxyapatite and its precursor phases. In the present work, the effects of condensed phosphates on the calcification reaction and on the growth process of hydroxyapatite, which is considered to be the final product in calcification process, have been investigated. The results have shown that triphosphate inhibited conversion of the precursors into hydroxyapatite. This is due to the adsorption of triphosphate onto the precursor surface. Furthermore, it has been found that the marked inhibitory effects of triphosphate on hydroxyapatite crystal growth and dissolution can be interpreted in terms of a Lang muir-type adsorption model, assuming that the active sites are blocked by the adsorption on the surface. A similar effect has also been observed for cyclo-hexaphosphate with a higher degree of polymerization than that of triphosphate. In contrast to these linear phosphates, no adsorption of cyclic cyclo-triphosphate was detected