Hydroxyapatite (HAp) ceramics are attractive materials for bone and tooth implant, since they closely resemble bone and tooth mineral and have been reported to show superior biocompatibility and ability to bind directly to bone. Recently, several workers have attempted to develop HAp coated subperiosteal and endosseous subperiosteal implant materials, because it is practicaly difficult to make these implant materials with complicated shapes (for example, saddle type and frame-work structure) by sintered HAp ceramics alone, and furthermore, such implant materials are too weak to function after implantation even if it were possible. The purpose of this study is to estimate the effects of Li3PO4 on the sintering of HAp, especially lowering of sintering temperature of HAp, because the reduction of sintering temperature is considered to be effective to control the reaction between HAp and other materials. Li3PO4 was very effective; Addition of 1.1wt% Li3PO4 gave dense sintered HAp's by 920°C-100min and 940°C-30min firings. Under these conditions, the bulk density of sintered HAp ceramics was 3.10g/cm3. SEM photographs of etched surfaces of sintered bodies indicated that addition of Li3PO4 accelerates grain growth of HAp.
