|Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 1998 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1997 : ¥2,900,000 (Direct Cost : ¥2,900,000)
In order to develop the artificial bone exhibiting the ability to detect the extension of a fatigue crack and to impede it, two-phase composite system consisting of tetracalcium phosphate particles dispersed in hydroxyapatite polycrystals was designed. The mechanism of intelligent functions of the composites proposed was as follows. When a fatigue crack filled with saliva extends from the surface of the composites to tetracalcium phosphate particles , the tetracalcium phosphate particles dissolves in saliva, and then hydroxyapatite crystals have been precipitated in the crack. As a result of dissolution of tetracalcium phosphate and subsequent pricipitation of hydroxyapatite in the crack, the fatigue crack advance is restrained by lowering the effective crack driving force actually experienced at the crack tip, which based on the blunting of the crack tip and on the generation of wedging, bridging, or sliding force between the crack surfaces.
In this study, in order to estimate the dens
ification behavior of powder compacts compsed of hydroxyapatite and tetracalcium phosphate, the powder compacts containing 30 mol% tetracalcium phosphate were sintered at 1150ﾟC to 1350ﾟC for 3 hours both in air and in CaO powder. Bulk densities of sintred composites were determined by Archimedes immersion technique in toluene, and crystaline phases were identified using X-ray diffraction technique. Although the maximum density of 96% theoretical was obtained when the composites were heated at 1250ﾟC for 3 hours, it was revealed that the addition of tetracalcium phosphate blocked he sintering of hydroxyapatite. From the results of X-ray diffraction experiments, it was found that tetracalcium phosphate existed with hydroxyapatite within the range from the surface of the sintered composites to the depth of about 500 mu m for the composites sintered at 1350ﾟC for 3 hours both in air and in CaO powder.