| Objective To fabricate the active biodegradable polymer cage of cervical intervertebral fusion, the poly-L-lactide with high molecular weight and the powders of hydroxyapatite will be firstly prepared by chemical codeposition and open-loop polymerization respectively. They will be commixed well-proportioned in the solution of chloroform in different ratio of weight, the composite will be hot-pressed and machined into cages which are in definite specs, the best one with well characteristics of physics and chemistry will be choosed.Methods1. The preparation and token of raw and processed materials.CD The preparation of poly-L-lactic with high molecular weight: L-lactic monomers made in China were dehydrated and polymerized into poly-L-lactics which were purified by filtration and deposition.(2) The preparation of powder of hydroxyapatite: The counteraction was taken between 0.3% H3PO4 and Ca (OH) 2 in solution, the productions were filtrated and sintered at 800 C,then they were comminuted into powder.(3) The token of raw and processed materials: The viscosity-average molecular weight, the rotation of the plane of polarization of polarized light, the 'H-NMR spectrum and the contents of tantalum of PLLA were measured. The characteristics (density and crystallization) of hydroxyapatite were analyzed.2. The fabrication and machining of HAp/PLLA cages.?The compounding of HAp/PLLA: The powder of hydroxyapatite and poly-L-lactic was mixed symmetrically together in the solution ofchloroform in different ratio of weight (50/50, 35/65, 15/85 and 0/100) .(D After the chloroform was vaporized completely, the dry composites were hot-pressed and founded in cylindrical mold, and then machined into cages which are hollow and whose surface is screw threaded.(3) The measuring of the characteristics of HAp/PLLA cage: The surficial structural character of HAp/PLLA composites were observed by scanning electron microscope (SEM). The viscosity-average molecular weight of HAp/PLLA composites pre-hot pressing and pro-hot pressing and the prime biomechanics of HAp/PLLA cage including terminal compressive stress and the module of elasticity were measured. The degradation characteristics of HAp/PLLA cage in different ratio of weight were also analyzed in vitro and in vivo.Result1. The PLLA with higher viscosity-average molecular weight 318.363KDa was achieved by using monomer/initiator mole ratio of 8000 and polymerization at 130C for 48h.The purification of PLLA can be increased by dissolution-precipitation treatment of the as-products.2. The HAp with higher purification and crystallization can be achieved by using the concentration of H3PO4and Ca (OH) 2 of 0.3% and 0.5mol/l respectively, and reaction at 60 癈 and pH value 9 for 7h.3. The HAp/PLLA composites of different ratio of weight can be gained using solution-ultrasonic decentralization. The HAp/PLLA cage can be founded at 170癈 and under the pressure of lOMPa for 15min.4. The study on HAp/PLLA cages on different ratio of weight indicated that the correlation is positive between the characteristics including viscosity-average molecular weight, prime biomechanical stress and module of elasticity and the content of PLLA in composites, but the velocity of degradation is reverse. The relation of velocity and times of degradation shows a similarity of inverse proportion curves, the change is larger pre 16 weeks, and smaller pro 24 weeks.5. The experiments of degradation of HAp/PLLA cages with 35/65weight ratio showed that the velocity of degradation in vivo is faster than in vitro, the biomechanics of that are all well.Conclusion The PLLA with higher viscosity-average molecular weight can be synthesized using L-lactic monomers made in China by open-loop polymerization. The powder of HAp with high purification and crystallization can be gained by chemical codeposition and sintered. The HAp/PLLA composites have symmetrical density by solution-ultrasonic deconcentration, the HAp/PLLA cage...
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