Magnesium stabilization of amorphous calcium phosphate: A kinetic study
Abstract
The kinetics of the conversion of amorphous calcium phosphate (ACP) to hydroxyapatite (HA) at pH 8 at 26.0°, 37.5 and 48.0 C, in the presence of Mg has been studied in two sets of experiments in which (a) Mg-free ACP was added to solutions containing different amounts of Mg, or, (b) ACP precipitated in the presence of Mg was left in contact with its mother liquor. If the Mg/Ca ratio in the system exceeded 0.2 no conversion was observed. In the range of Mg/Ca ratios found in bones and teeth (mole ratios from 0.004 to 0.04), the induction period of the transformation (time before first HA crystals observed) increased with increasing Mg concentration, but the rate of the first order transformation was independent of Mg content. It is shown that the Mg effects the transformation by reducing the ACP solubility.
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