THE DEPENDENCE OF OSTEOBLASTIC RESPONSE ON VARIATIONS IN THE CHEMICAL-COMPOSITION AND PHYSICAL-PROPERTIES OF HYDROXYAPATITE

Two synthetic hydroxyapatite powders (A and B), supplied by different manufacturers, were physically and chemically characterized before bei ng die pressed and sintered at 1250 degrees C. The powders were charac terized using X-ray diffraction (XRD), infrared spectroscopy (IRS), X- ray fluorescence, surface area analysis (BET), particle size analysis and scanning electron microscopy (SEM). The materials were then presse d and sintered to produce hydroxyapatite discs of similar densities an d grain sizes for in vitro evaluation. The ceramics were seeded with o steoblastic cells and after 15 days in culture the cell morphology was assessed using scanning electron microscopy (SEM), the ultrastructure of the cells was studied using transmission electron microscopy (TEM) with EDAX, and the rate of cell growth was assessed using biochemical techniques. The results clearly showed that the rate of cell prolifer ation but not the rate of alkaline phosphatase production, was highly dependent on the composition of the hydroxyapatite powders that were u sed to make the ceramic discs. The ultrastructural studies confirmed t he relative viabilities of the cells and the nature of the ceramic int erface indicating visually the marked differences in the performance o f the two materials.