Alumina Powder / PMMA Composite Cements: An Evaluation of Osteoconductivity

New composites consisting of high molecular weight polymethyl m ethacrylate (hPMMA) and δor α-alumina powder (designated δAPC and αAPC, respectively), which allow direct bone formation on their surfaces in vivo, have been developed. Especially, δAPC allowed much more bone formation on the surface. δ-Alumina powder was manufactured by fusing pulverized alumina powder and quenching it. It was composed mainly of δ-crystal phases of alumina. The purpose of the present study was to evaluate osteoconductiv ity of hese composites. The hPMMA itself was used as a reference material. These three typ es of composites were packed into the intramedullary canals of rat tibiae to evaluate osteoconduc tivity, as determined by an affinity index. Rats were sacrificed at 4 and 8 weeks after surgery. The affinity index, equal to the length of bone in direct contact with the composite surface expr ssed as a percentage of the total length of the composite surface, was calculated for each composit e at each interval. Histologically, new bone had formed along the surface of both δ APC and αAPC within 4 weeks. The affinity indices for both δAPC and αAPC increased significantly with time up to 8 weeks. At 8 weeks , the affinity index for δ APC was significantly higher than those for αAPC and hPMMA. This study revealed that the excellent osteoconductivity of δAPC was due to the alumina’s δ-crystal phases and the high molecular weight of hPMMA. δAPC shows promise as a basis for developing a highly osteoconductive biomaterial.