Abstract
Hydroxyapatite (HAp) is one of the most effective biomaterials used in artificial bone and dental design implant. It is important to investigate in detail the mechanical characteristics of HAp for the improvement of mechanical reliability of those. HAp implant is usually made by sintering HAp powder. In general, it has been considered that the thermal stress caused by heating and cooling processes in sintering disappears and does not remain in the material, because such sintered material does not reach an actual density of 100% which is the perfectly solid state. However, if residual stress occurs in sintering, it will exert a profound influence on the mechanical strength and biocompatibility of HAp implant in vivo. Therefore, we present a method for measuring residual stress in sintered HAp using polychromatic X-rays, and investigate the effect of preforming pressure, sintering temperature and sintering pressure on the residual stress. As a result, large tensile residual stress on the surface of implant and steep stress gradient were confirmed by this method, and the relationship between the magnitude of residual stress and several conditions of HAp sintering was clarified.
