Evaluation of Homogeneity for Sintered Hydroxyapatite by CT-Values

Hydroxyapatite was prepared from calcium nitrate and disodium hydrogenphosphate solutions. Heating this at 1000°C for 1h yielded round-shaped hydroxyapatite particles with diameters of about 0.5μm. A green compact of the hydroxyapatite (green compact-I) was fromed by an uniaxial compression process (300kg/cm2), and then a green compact II was made by an isotropic compression (1000kg/cm2) of the green compact-I. A hydroxyapatite sintered body (porous structure) was obtained by heating the green compact-II at 1150°C for 2h. Internal homogeneities of these green compacts and sintered bodies were evaluated from CT-values measured with a CT-scanner. Depending on the method proposed in this study to indicate homogeneity using the ratio of the standard deviation of linear absorption coefficient to linear absorption coefficient, the green compact-I was most homogeneous, followed by the green compact-II. The sintered body was comparatively inhomogeneous.