The mineralization and demineralization kinetics of synthetic hydroxyapatite and human dentin.

摘要

Dentin, a mineralized tissue within the tooth, consists of 70% inorganic mineral, mainly non-stoichiometric hydroxyapatite (HAP), and 20% organic matrix. Studies of dentin have become increasingly important due to population aging and periodontal diseases. In this work, the Constant Composition (CC) method was employed to compare the kinetics of dentin and HAP mineralization/demineralization in calcium phosphate solutions. Dentin mineralization required a minimum supersaturation {dollar}sigmasb{lcub}rm HAP{rcub}sim 5{dollar}. Significant dissolution of dentin took place in solutions even supersaturated with respect to HAP. The effective kinetic order n for dentin growth with respect to relative supersaturation ({dollar}sigmasb{lcub}rm HAP{rcub}{dollar}) was {dollar}sim{dollar}6, considerably greater than that for HAP (n = 2-3). Dentin demineralization exhibited a striking insensitivity to relative undersaturation. Mineralization/demineralization of dentin and HAP were influenced by ionic strength, pH and molar calcium/phosphate ratio in the reaction solutions. The calcium phosphate minerals were preferentially nucleated on intertubular dentin surfaces and the presence of the smear layer markedly influenced the mineral deposit. The kinetic data suggest a polynucleation mechanism for the mineralization on both dentin and HAP surfaces, but in the case of dentin, it is very important to take into account the role of organic matrix, especially the inhibiting influence of noncollagenous proteins. Macromolecule {dollar}beta{dollar}-lactoglobulin reduced the dissolution rate of HAP. Inorganic ions, zinc and strontium, were shown to adsorb on the dentin surface and decrease its dissolution rate significantly.