The Development Of Two Kinds Of Shapeable Recombined Artificial Bone And Related Experimental Studies In Vitro And In Vivo

Objective:To explore new kinds of bone substitute for bone grafting,two kinds of shapeable recombined artificial bone were prepared in this study,and their porosity rates,pore sizes and mechanical properties were determined.Related experiments were carried out here to investigate their biocompatibility,biOdegradatiofl and osteogenic abilities for the purpose of farther applications. Methods: 1. The preparation of the recombined artificial bone. Nacre,deminerialized bone and poly-DL-lactic acid were selected to prepare the two bone substitutes:nacre/pOlYlaCtiC acid recombined artificial bone (NPRB) and demineralized bone/polylactic acid recombined artificial bone (BPRB).Particles of NaCl was introduced into the mixture to produce pores by solute leaching technique. A new methods was performed to improve the properties of the composites and its effects on the porosity and the compressive strengths of the composites were compared to the solvent casting technique.Some properties of the composites such as porosity rate,pore size and mechanical strength were detected when the composites were performed with different constituent ratio,different NaCl mass and different size of NaC1 particles.Accroding to these datas,the optimum formulae of the recombined artificial bone were chose.The porosity rate,pore size,compressive and flexural strengths of the two kinds of artificial bone were investigated when they were performed with their optimum formulae. 2.In vitro study with the biocompatibility and degradation of the two bone substitutts. Human osteoblast cells were cultured with the artificial bone immersed in the medium,their morphological characters and proliferation were observed by optics microscope and scanning electron microscope.Degradation behaviour of NPRB and BPRB was followed over a 16 weeks period when they were immersed into saline at 37E~ in vitro. 3.In vivo study of NPRB and BPRB as bone defect grafts. A defect of 1.5cm in length was produced at both radii of 48 New Zealand r..bbits,the defects were filled with NPRB or BPRB or nothing randomly.The animals ocal and whole body response to the implants was observed post-operation,and their serum calcium level in different period was detected.New bone formation in the defects and degradation of the implants was evaluated by X-ray,BMC (Bone mineral content) and CPMR (Counts per-minute radioactivity) in the defects,and histomorphological analysis was done after the animals were sacrificed. Results: 1. The preparetion of the recombined artificial bone. The recombined artificial bone fabricated by the new perform method possessed lower porosity rate but heavily higher mechanical strength.The optimum formulae were acceped as follow:the mass radio of nacre (or deminera1ize bone) and PLA should be 1:1 ,the salt added to the mixture should take 50% mass of the total mixture,the salt particles size should be 1 5Otm-2OOj.tm.The average porosity rate of NPRJ3 is about 47.65%,its pore size is 218.83.tm,compressive strength is 16.1OMPa,flexural strength is 60.18MPa;to BPRB,the data is 55.2%,227,33tm,5.52MPa and 19.61MPa respectively. 2. In vitro study with the biocompatibility and biodegradation of the two bone substitutes. Neither NPRB nor BPRB have cytotoxicity,compared to the negative control group,both of them can facilitate the...