1. Field of the Invention
This invention relates to a sintered apatite body, and more specifically, to a sintered apatite body having increased mechanical strength, and a process for producing an apatite powder having improved sinterability.
2. Description of the Prior Art
In recent years, ceramic materials have been superseding polymeric or metallic materials for use as medical implant materials, because ceramics are more stable in the living body than synthetic resins and metals, and are non-toxic and non-irritating. These three properties, however, are insufficient for implant materials, and a problem of affinity with the living tissues is still to be solved.
The pore sizes of conventional implant materials composed mainly of Al.sub.2 O.sub.3 are controlled in order to improve their "affinity" with cells or tissues, but their chemical bondability to the living tissues is extremely poor. Accordingly, conventional implant materials should be strengthened in physical bonding by, for example, bonding more securely with a nut. Sometimes, this brings about the defect that the embedded implant is freed within the living body because of insufficient adhesion, or by a rejection of the living body.
Apatite [Ca.sub.5 (PO.sub.4).sub.3 OH], a main mineral constituent of bones and teeth, has attracted considerable attention as an implant material which remedies the defects of Al.sub.2 O.sub.3 -based implant materials. It has been made clear that a sintered body of apatite is an implant material having an affinity with the living body near that of living bones because of the composition and crystal structure of apatite, and it is less necessary to control the pore size of the apatite for improving its affinity with the cells or tissues.
Apatite, however, has the defect that it has poor sinterability, and a sintered body of apatite has low mechanical strength.