The dependence of osteoblastic response on variations in the chemical composition and physical properties of hydroxyapatite

Abstract

Two synthetic hydroxyapatite powders (A and B), supplied by differentmanufacturers, were physically and chemically characterized before being diepressed and sintered at 1250°C. The powders were characterized using X-raydiffraction (XRD), infrared spectroscopy (IRS), X-ray fluorescence, surface areaanalysis (BET), particle size analysis and scanning electron microscopy (SEM).The materials were then pressed and sintered to produce hydroxyapatite discs ofsimilar densities and grain sizes for in vitro evaluation. The ceramicswere seeded with osteoblastic cells and after 15 days in culture the cellmorphology was assessed using scanning electron microscopy (SEM), theultrastructure of the cells was studied using transmission electron microscopy(TEM) with EDAX, and the rate of cell growth was assessed using biochemicaltechniques. The results clearly showed that the rate of cell proliferation butnot the rate of alkaline phosphatase production, was highl!y dependent on the composition of the hydroxyapatite powders that were used to makethe ceramic discs. The ultrastructural studies confirmed the relativeviabilities of the cells and the nature of the ceramic interface indicatingvisually the marked differences in the performance of the two materials.