【作者】 陈跃军；

【导师】 冯波；

【作者基本信息】 西南交通大学 ， 材料学， 2009， 博士

【摘要】 钛和钛合金具有良好的力学性能和生物相容性,是主要的外科植入件优选的替代材料。目前医用钛在临床应用中主要存在着以下问题：一是生物力学相容性相对较差,其弹性模量与人体硬组织不匹配；二是生物活性较差,不能与人体硬组织形成化学骨性结合。因此,有必要降低弹性模量以提高其生物力学相容性以及表面改性以提高其生物活性。医用多孔钛是基于生物组织可以长入,提高机械固定作用而开发的,这就要求多孔钛具有足够的孔隙率及孔径大小,并且还须具备一定的力学性能。然而,孔隙的增加必然导致力学性能的下降,如何在具备较高孔隙率及良好孔隙结构的同时,使多孔钛达到与人体自有骨组织相匹配的力学性能,这一直是医用多孔钛研究及应用中存在的问题。另外,目前医用多孔钛还存在连通孔的闭塞率较高,孔径大小不合理等问题,而三维贯通的孔隙结构及合适的孔径大小对于骨组织的修复过程也有着重要影响。粉末浆料发泡法通常用于多孔陶瓷的制备,操作简便,成本低,不需要加压处理,本文选用此方法来制备多孔钛植入体。根据金属钛粉末的性质特点,本研究对传统浆料发泡法的工艺方法及参数(如粘结剂的选择,发泡剂用量及发泡时间,烧结温度和保温时间等)进行改进,制备出具有三维连通孔隙的多孔钛,并表征了其物理性能、孔隙特征以及力学性能,研究了发泡剂用量、烧结温度等对多孔钛表面形貌和力学性能的影响；随后,通过化学处理活化其表面,并构建了一种具有分级多孔结构的多孔钛种植体；分别通过体外仿生矿化和小牛血清蛋白吸附试验,考察了活化处理及多孔结构对诱导矿化和蛋白吸附的影响；通过体外细胞培养,评价了多孔钛的细胞相容性；通过动物体内实验,考察其对骨整合的影响；最后,对含钇的多孔钛种植体的性能进行了初步研究。本文首先对发泡剂、烧结温度等工艺参数对多孔钛孔隙率、显微组织以及表面形貌的影响进行了研究。结果表明,当发泡剂用量为10%、25%、40%时,多孔钛孔隙率分别为48%、64%及76%;烧结温度对多孔钛的物理性能和表面形貌有重要影响,当烧结温度升高时,烧结体线收缩率增大,孔的形状由不规则形状逐渐变成圆形,并且烧结颈变粗大,基体烧结成一个整体。研究中还发现,发泡法制备的多孔钛不但孔隙结构互相贯通,而且同时包含100-400μm的大孔以及20μm左右的微孔；孔隙率为48%、64%及76%多孔钛的压缩强度分别为246±10MPa、102±7.1MPa及23.6±3.4MPa,能够满足负重植入体的要求。另外,多孔钛具有一定的能量吸收能力和抗冲击性能,在植入时有望提高植入体的早期稳定性。通过化学方法对多孔钛进行活化处理,结果表明,经过酸碱处理后的多孔钛呈现出一种独特的三维分级多孔结构,其中包含三种不同孔径大小的孔隙,即100-400μm的大孔、20μm左右的微孔以及网络状几百纳米大小的孔隙。生物仿生矿化和蛋白吸附结果表明,这种多孔钛具有良好的生物活性和生物相容性,在模拟体液中浸泡3天即可快速沉积HA,且其复杂的多孔结构提供大的比表面积和表面能,大大促进了其对蛋白质的吸附能力。将其与成骨细胞联合培养,结果表明,分级多孔结构以及材料表面的化学状态对细胞的生长有明显影响,能够促进成骨细胞的黏附、增殖及分化；酸碱处理多孔钛表面成骨细胞生长行为良好,细胞完全铺展,伪足较多,且细胞向内部孔隙生长。通过动物体内植入实验进一步考察了其对骨整合的影响。结果表明,发泡法制备的多孔钛具备良好的生物相容性以及骨传导能力。HA涂层以及材料的多孔结构对骨组织的生长有明显影响,可以促进骨组织向材料内部孔隙长入,具有分级多孔结构的多孔钛种植体在动物体内植入4周和12周后,都具有最高的与骨剪切强度和新骨形成率,骨整合情况良好。最后,本研究通过在纯钛中添加氧化钇,考察了稀土钇对于多孔钛性能的影响。研究结果表明,添加0.2%和0.5% Y2O3均可以提高多孔钛种植体的强度,而添加量为1.0%时,压缩强度则明显下降；在钛基体表面以及颗粒间隙均有富Y颗粒存在,并且Y元素在基体分布较均匀；富钇颗粒中不仅含有稀土氧化物,还有Ti／Y金属间化合物的存在,有利于其力学性能的改善；含钇多孔钛种植体生物力学相容性良好,有望提高种植体的长期稳定性。更多还原

【Abstract】 Due to good mechanical properties and biocompatibility, titanium (Ti) and Ti alloys are the main pieces of the preferred alternative to surgical implant materials. For Ti in medical use, however, the following questions still exist in clinical applications currently:Firstly, it has relatively poor biomechanical compatibility and its elastic module does not match the human hard tissue. Secondly, with poor biological activity, it also can not form a chemical combination with human bone tissue. Therefore, it is necessary to reduce the elastic modulus to increase its bio-mechanical compatibility and treat the surface modification to enhance its biological activity. Medical porous Ti was developed for it can allow biological tissue to grow into pores to improve the mechanical fixation, which requires porous Ti to have sufficient porosity, pore size and necessary mechanical properties. However, the increase of porosity increase will inevitably lead to a decline in mechanical properties. It has been a problem for porous Ti in medical research and applications that how to obtain porous Ti with not only high porosity and good pore structure but also mechanical properties of a certain to match the autogenously bone tissue. Also, the connecting-hole occlusion rate of porous Ti was higher and the pore size is irrational at present, while the three-dimensional interconnected of the pore structure and appropriate pore size also have important impact on bone tissue repair process.The slurry foaming method was commonly used in the preparation of porous ceramics. As this method is simple, low cost and no pressure-treated, it was used to the preparation of porous Ti implants in this paper. According to the characteristics of Ti powder, the methods and parameters of traditional slurry foaming process (such as the choice of binders, foaming agents and time of foaming, sintering temperature and holding time, etc.) were modified and porous Ti with three-dimensional interconnected pore structure was prepared. Their physical properties, pore characteristics and mechanical properties were characterized, and the effect of the amount of vesicant and sintering temperature on the surface morphology and mechanical properties were also investigated. Then, chemical treatments were conducted to activate the surface, and a hierarchical porous structure was constructed. Biomimetic mineralization and BSA adsorption experiments were used respectively to study the effect of activation treatment and porous structure on the mine-induced and BSA adsorption. Through cell culture in vitro, the cell compatibility of porous Ti was evaluated and animal experiments were used to study the impact of osseointegration. Finally, the performance of porous Ti implant containing yttrium was investigated preliminary.Firstly, the impact of vesicant, sintering temperature and other process parameters on porosity, micro-texture and surface morphology of were studied in this paper. The results showed that the foaming method can prepare porous Ti with high porosity, and its porosity can be controlled by adjusting the amount of foaming agent. When the foaming agent dosage was 10%,25% and 40%, the porosity of porous Ti was 48%,64% and 76%, respectively. Sintering temperature has a major impact on the surface morphology and physical properties of porous Ti. When sintering temperature increased, the linear shrinkage rate of sintered body also increased and the holes became round from irregular shape gradually. Finally, as the sintering neck became thicker and large, the matrix sintered into a whole.The study also found that the porous Ti prepared by slurry foaming method had not only interconnected pore structure, but also included macropores size 100-400μm and micropores size 20μm. Porosity was the important factor to affect the mechanical properties of porous Ti. When the porosity was 48%,64% and 76%, the compressive strength of porous Ti was 246±10MPa,102±7.1MPa and 23.6±3.4MPa, respectively, which meet the requirements of implants. Moreover, due to the energy absorption capacity and impact resistance, the porous Ti is expected to improve the early stability of the implants.Porous Ti was activated by chemical method, and the results showed that the porous Ti presents a unique three-dimensional hierarchical porous structure after acid-base treatment, which contains three different pore size of pores, that is, large holes size 100-400μm, microporous with 20μm size and network-like pores with size of hundreds nanometers. Biomimetic mineralization and protein adsorption results indicated that the porous Ti has good bioactivity and biocompatibility. When the porous Ti was immersed in a simulated body fluid, HA can quickly deposit on the surface in 3 days, and its complex porous structure provides a large surface area and surface energy which greatly contributed to their protein adsorption capacity. When co-cultured with osteoblasts, the results showed that the hierarchical porous structure and surface chemical state have obvious impacts on cell growth, and it can promote the adhesion, proliferation and differentiation of osteoblast. Cells growed well on the surface of acid-base treated porous Ti, spreaded completely with more pseudo-feet, and growed into the pores.Animal experiment was conducted to further study its effects on bone integration. The results showed that the porous Ti had good biocompatibility and bone conduction capacity. HA coating and the porous structure had significant effect on the growth of bone tissue and promoted bone tissue ingrowth into the inner pores. When implanted in animals for 4 weeks and 12 weeks, the porous Ti with hierarchical porous structure showed the highest shear strength, new bone formation rate and best osseointegration.Finally, by adding yttrium oxide, the effect of rare-earth yttrium on properties of porous Ti was investigated in this study. The results showed that adding 0.2% and 0.5% Y2O3 can enhance the strength of porous Ti implants, while the adding amount was 1.0%, the compressive strength significantly decreased. Y-rich particles existed in Ti substrate as well as the gap of particles, and Y elements distributed uniformly in the matrix. Yttrium-rich particles contain not only the rare-earth oxides but also Ti/Y intermetallic compounds, which enable the improvement of mechanical properties. With good biomechanical compatibility, the yttrium contained porous Ti implants are expected to improve the long-term stability of the implant.更多还原