Physico-chemical and thermal properties of chlor-, fluor- and hydroxyapatites

Structural studies predict that the stability of chloride (ClAp)-, or fluoride (Fap)-substituted apatites compared to unsubstituted hydroxy (OHAp)-apatites will increase in the order: ClAp < ORAp < FAp. The purpose of this study is to determine the effect of chloride (CI) and fluoride (F) substitution on the thermochemical and dissolution properties of apatites. Synthetic apatites were prepared by hydrolysis method and characterized using x-ray diffraction, FTIR and thermogravimetric analyses. Substitution of Cl-for-OH caused an expansion in a- and contraction in c-axis dimensions; F-for-OH caused a contraction in a-axis and no significant change in the c-axis. The extent of dissolution, thermal stability and beta-TCP/HA ratio after sintering at 950degreesC, decrease in the order: ClAp much greater than OHAp much greater than Fap.