Fluoridated hydroxyapatites synthesized with organic phosphate ester.

Fluoridated hydroxyapatites with various fluoride contents were synthesized with organic phosphate ester monomer as a source of P at pH 9.5 and 80 degrees C. The a-axis dimensions of the fluoridated hydroxyapatites decreased with the increase of the fluoride content in the same way as the fluoridated hydroxyapatites synthesized with inorganic phosphate under the same conditions. However, for the same calculated degree of fluoridation in the feed solution, fluoridated hydroxyapatites synthesized with organic P had higher fluoride contents than those synthesized with inorganic P. The crystallinity of the former decreased initially, then increased with increasing fluoride content; but on the whole it was lower than that of the latter. The apparent solubility at pH 4.0 and 37 degrees C decreased dramatically and monotonically with increasing fluoride content and approached an almost constant value at a fluoride content above that of fluorapatite, at which value calcium fluoride was detected.