BIOLOGICAL EVALUATION OF HYDROXYAPATITE BY HIGH-VELOCITY FLAME SPRAYING TECHNIQUE

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In 1988, we have developed a high-velocity flame-spraying technique for applying HA onto titanium alloys. From our results (comparative study ; HVFS-HA and Plasma-HA), we have understood as follows ;(1). From X-ray diffraction pattern analysis, the HA layr of both Plasma-HA and HVFS-HA showed a well maintained structual pattern characteristic of HA.However, the Plasma-HA on the plate was oriented to the C axis of HA.(2). In regard to surface microstructure, HVFS-HA was much more porous than plasma-HA and plasma-HA showed microbreakage due to the rapid reduction in temperature.(3). Solubility tests indicated the pH values of Plasma-HA and HVFS-HA to be comparable. The solubility of Ca was higher for Plasma-HA than HVFS-HA.(4). In vivo, the thickness of coated HA layr tended to decreased at 1 month, 3 months, 6 months and 1 year for both Plasma-HA and HVFS-HA.However, Plasma-HA showed a greater decrease in thickness than did HVFS-HA,although the difference was not significant.(5). From biological findings, in the first month, Plasma-HA was superior to HVFS-HA and prominent bone was noted on the surface of Plasma-HA and 3 months, 6 months and 1 year, there were no differences biologically.