T. Kokubo et al. Biomaterials 24(2003)2161-2175 旧mdmm NaOH- and heat-treated 亘 12 Time /week Time/ week Fig 12. Detaching fracture loads of the untreated and the NaoH- and heat-treated titanium metals implanted in a rabbit tibia(A), and the pull-out fracture loads of those implanted in a rabbit femur(B) for various periods BC A Screw: Ti-6A1-2Nb-Ta alloy B. Socket: Ti-6Al-2Nb-Ta alloy C Socket surface: macroporous Ti (NaOH and heat treatments) D. Cup: Ultra-high molecular weight polyethylene E Head: Y-TZP F Proximal NaoH and heat treatments) G Stem: Ti-6Al-2Nb-Ta alloy Fig. 13. Bioactive titanium metal in a clinical hip joint system(photograph courtesy of Kobe Steel Ltd, Japan) The Zr-OH groups in the tetragonal structure are also effective for apatite nucleation, as described above. A Metal Apatite Bone nano-composite of ceria-stabilized tetragonal zirconia (Ce-TZP)and alumina has been suggested to have excellent wear and fracture resistance as well as a low- temperature degradation in its strength [79]. When this Ta type of nano-composite was subjected to treatment in an aqueous solution of concentrated H, PO4, H2 SO4, HCI or Naoh at 95C for 4d, it formed many Zr-OH groups on its surface and, as a result, formed apatite in SBF [80]. By using this type of bioactive TZP, it is expected that bifunctional implants can be designed that have wear resistance and bone-bonding ability. These will be useful in the repair of joint systems 3. 2. Soft bioactive materials Fig 14. SEM-EDX profile of the interface between the NaoH-and heat-treated tantalum metal and a rabbit tibial bone(8 weeks after All the bioactive ceramics and metals described above ave higher elastic moduli than that of human corticalThe Zr–OH groups in the tetragonal structure are also effective for apatite nucleation, as described above. A nano-composite of ceria-stabilized tetragonal zirconia (Ce-TZP) and alumina has been suggested to have excellent wear and fracture resistance as well as a low￾temperature degradation in its strength [79]. When this type of nano-composite was subjected to treatment in an aqueous solution of concentrated H3PO4, H2SO4, HCl, or NaOH at 95C for 4 d, it formed many Zr–OH groups on its surface and, as a result, formed apatite in SBF [80]. By using this type of bioactive TZP, it is expected that bifunctional implants can be designed that have wear resistance and bone-bonding ability. These will be useful in the repair of joint systems. 3.2. Soft bioactive materials All the bioactive ceramics and metals described above have higher elastic moduli than that of human cortical Fig. 12. Detaching fracture loads of the untreated and the NaOH- and heat-treated titanium metals implanted in a rabbit tibia (A), and the pull-out fracture loads of those implanted in a rabbit femur (B) for various periods. Fig. 13. Bioactive titanium metal in a clinical hip joint system (photograph courtesy of Kobe Steel Ltd., Japan). Fig. 14. SEM-EDX profile of the interface between the NaOH- and heat-treated tantalum metal and a rabbit tibial bone (8 weeks after implantation). T. Kokubo et al. / Biomaterials 24 (2003) 2161–2175 2169