Preparation and Biomechanics of High-performance Artificial Bones Containing

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Novel biomaterials for application to artificial bone with modulus of elasticity close to that of natural bone were prepared using bioresorbable poly-L-lactic acid (PLA) and high strength β-Ca(POィイD23ィエD2)ィイD22ィエD2 fibers (CPF) treated with dilune NaOH solution. PLA dissolved by using methylene chloride was mixed with the fibers. After drying the mixture, it was hot-pressed uniaxially under a pressure of 40 MPa at 180℃, resulting in fabrication of a PLA-composite containing CPF. Almost no degradation in the bending strength was observed even when a large amount of the fibers (【approximately equal】50 wt%) was introduced, and the modulus of elasticity was increased effectively with increasing the fiber content. The PLA-composite with modulus of elasticity of >5 GPa similar to that of natural bone was found to be prepared when the fiber content was over 35 wt%. The bending test of the composites showed that very high energy is consumed for their fracture and that the fracture proceeds ste … More p by step, even beyond the maximum stress.After the PLA sample was soaked in simulated body fluid (SBF) for 90 days, the maximum stress was decreased extremely and the specimen showed typical brittle fracture similar to that of conventional ceramics. Hardening originated from hydrolysis of PLA is supported to suppress degradation of the materials in modulus of elasticity, although the maximum stresses are decreased. The PLA-composite containing 35% CPF showed the characteristic fracture pattern even after the soaking for 90 days in control to that PLA. Hydrolysis of PLA induces serious degradation in the composite would be also converted into a brittic material by the soaking in SBF as well as the PLA sample without CPF. However, since CPF in the composite can share an applied load successfully, the material shows non-catastrophic fracture even after the soaking. Hybridization of CPF into PLA as a matrix phase has great advantages that modulus of elasticity is improved to the value close to that of natural bone and that degradation of the material in toughness in a wet environment is relatively restricted. The mechanical properties of the PLA composites are expected to meet the biomechanical requirements of some applications such as bone plates or temporary internal fixation of bones broken damaged. Less