title: Composites consisting of poly(methyl methacrylate) and alumina powder: an evaluation of their mechanical and biological properties.
abstract: We developed new composites consisting of comparatively high molecular weight poly(methyl methacrylate) (hPMMA) and delta-alumina powder or alpha-alumina powder (designated delta-APC and alpha-APC, respectively) that allowed direct bone formation on their surfaces in vivo. delta-Alumina powder was manufactured by the fusing and quenching of pulverized alumina powder. It was composed mainly of delta-crystal phases of alumina. The purpose of this study was to evaluate the static mechanical properties and biological properties of these composites. The hPMMA itself was used as a reference material. The bending strength and Young's modulus of both delta-APC and alpha-APC were significantly higher than those of hPMMA, and the alumina composites are believed to be strong enough for use under weight-bearing conditions. The three types of composites were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index. Rats were sacrificed 4 and 8 weeks after surgery. The affinity index, equal to the length of bone in direct contact with the composite surface and expressed as a percentage of the total length of the composite surface, was calculated for each composite at each interval. Histologically, new bone had formed along the surfaces of both delta-APC and alpha-APC within 4 weeks. The affinity indices for both delta-APC and alpha-APC increased significantly with time up to 8 weeks. At 8 weeks, the affinity index for delta-APC was significantly higher than the indices for alpha-APC and hPMMA. This study revealed that the excellent osteoconductivity of delta-APC was due to the delta-crystal phases of alumina and the high molecular weight of hPMMA. delta-APC shows promise as a base for developing a highly osteoconductive and mechanically strong biomaterial.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Kawahara-cho 54, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan. shinzato@mbox.kyoto-inet.or.jp
authors.forename: Shuichi
authors.initials: S
authors.lastname: Shinzato
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kokubo
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Kitamura
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D001843:Bone Cements / Q000737:chemistry*; D001842:Bone and Bones / Q000648:ultrastructure; D008297:Male; D019563:Mechanics; D008970:Molecular Weight; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D013977:Tibia / Q000648:ultrastructure
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D019904:Polymethyl Methacrylate; D000537:Aluminum Oxide