Synergistic effects of magnesium and carbonate on properties of biological and synthetic apatites.

Magnesium (Mg) and carbonate (CO3) are minor elements associated with enamel, dentin and bone apatite. The purpose of this study was to determine the effect of Mg and CO3 on some properties of synthetic apatites to gain insights on their effects on biological apatites. Biological apatites from human enamel and dentin and from bovine bone and synthetic apatites with/without Mg or CO3 were characterized using x-ray diffraction, infrared absorption, thermogravimetry and chemical analyses. Dissolution in acidic buffer was also determined. Results from this study demonstrated: (1) the synergistic effects of Mg and CO3 on reducing the crystallinity and increasing the extent of dissolution of synthetic apatites; (2) dentin and bone, compared to enamel apatite contained higher levels of Mg and CO3; had lower crystallinity and higher extent of dissolution. The lower crystallinity and higher extent of dissolution of dentin and bone compared to enamel apatite may be partly attributed to their higher Mg and CO3 concentrations.