Synthesis and characterization of bioactive hydroxyapatite/fluoroapatite solid solutions using corals

Abstract

Hydroxyapatite/fluoropatite solid solutions were prepared by two different methods using Indian coast corals. In the ‘low temperature method’ a known volume (50%) of hydrofluoric acid was added to the coral and an exchange reaction with diammonium phosphate was carried out to form apatite at 250°C under hydrothermal conditions. The coralline derived hydroxyapatite by the above method was reacted with 50 mol% sodium fluoride at 900°C in the ‘high temperature method’. The X-ray powder diffraction, infrared spectroscopy and thermal analysis techniques were employed to characterize the fluorination of the hydroxyapatite.In vitro solubility study in phosphate buffer solution of pH 7·2 indicate the stability of the apatites. The low temperature method of fluorination seems to be advantageous due to betterin vitro stability and absence of impurity phases.