Abstract
Some ceramics able to bond to living bone are now widely used as bone-repairing material. Their applications are, however, limited to less loaded regions, because of their low fracture toughnesses and high elastic moduli. It has been revealed that the essential requirement for the material to be bonded to bone is the formation of a bonelike apatite layer on the surface of the material in the living body. For this, the material should have a functional groups effective for the apatite nucleation on its surface and increase in the ionic activity product of the apatite in the fluid near its surface. On the basis of these findings, bioactive metals with high fracture toughnesses have been developed by controlling their surface structure. Preparation of apatite-polymer composites with analogous structure to the natural bone is also being attempted.
