【作者】 黄福龙；

【导师】 李世普；

【作者基本信息】 武汉理工大学 ， 材料学， 2006， 博士

【摘要】 磷酸钙胶凝材料（CPC）具有可塑性、生物相容性好、骨传导性等优点，能直接通过注射器注入局部并快速固化，可作为药物缓释载体辅助治疗，载生长因子促进新骨的形成，是理想的骨替换及修复材料。随着研究的不断完善，这类骨替代材料将会得到越来越广泛的应用，成为生物材料的一个重要分支。但该类材料强度低、力学性能差的问题一直未能得到解决，且相关基础理论研究匾乏，限制了其应用范围，因此，临床仍以采用生物活性较差的PMMA骨水泥为主。针对目前的研究现状，开展CPC及其复合材料的相关理论研究，制备具有可操作性、力学性能好、可诱导成骨、降解速度与成骨速度匹配的CPC骨替代材料并研究其临床应用具有重要意义。为此，本文对CPC制备工艺、微观结构、力学性能及增强和生物学性能进行了研究。以磷酸氢钙和碳酸钙为原料，通过适宜的烧成工艺，合成了纯度高、性能稳定的α-磷酸三钙（α-TCP）。单纯α-TCP的水化硬化过程是溶解—析晶的过程，水化产物随pH值的不同而不同，当pH＜5.5时，水化产物为羟基磷灰石（HAP）、磷酸八钙（OCP）和磷酸二氢钙（DCPD）；当6＜pH＜8时，水化产物为HAP；NH₄H₂PO₄可促进α-TCP的水化反应，缩短凝固时间，改善抗压强度；当NH₄H₂PO₄的浓度为2.0M时，α-TCP凝固时间为17min，抗压、抗折强度分别为37.17MPa和6.2MPa。利用β-磷酸三钙（β-TCP）良好的降解性能和α-TCP的水化硬化性能，采用双氧水造孔法制备了可任意塑形、具有一定的强度的可降解多孔复合胶凝材料。α-TCP／β-TCP复合材料表面具有一定的生物活性，孔径受双氧水浓度影响，双氧水浓度越高，孔径越大；不同孔径材料在SBF中形成类骨磷灰石的能力不同：300～400μm＞200～300μm＞100～200μm＞400～500μm。根据晶体成核生长原理，采用两步湿法合成了高纯Ca₄（PO₄）₂O（TTCP）。在此基础上，选用合适的促凝剂，用X衍射、红外光谱及扫描电镜等测试手段研究α-Ca₃（PO₄）₂-Ca₄（PO₄）₂O双相体系泥的胶凝特性，发现80wt％α-TCP-20wt％TTCP硬化体抗压强度最高达38.76MPa，且水化较为完全，水化产物主要是HAP；通过对该组成复合胶凝材料水化硬化过程及其水化转化率的研究，建立了水化反应动力学模型，说明了水化反应过程前期由表面溶解控制、后期由扩散控制。同时探讨了影响α-TCP／TTCP复合胶凝材料水化硬化过程及抗压强度的因素。结果表明：改变柠檬酸浓度、提高胶凝材料颗粒度、降低液固比可以改善α-TCP／TTCP复合胶凝材料的性能；低结晶度的HAP可作为晶种加速水化反应，而高结晶度的HAP可作为“骨料”提高胶凝材料的强度。研究发现经过氧化处理的碳纤维（CF）表面氧含量增多，挠曲强度及拨出功增高。采用8wt％NaOH溶液氧化处理碳纤维，长径比为375，添加量为0.3wt％时，增强磷酸钙胶凝材料（CPC）的效果最为理想，抗压强度提高了55％，最大达63.46MPa；抗折强度提高近100％，最大可达11.95MPa；CF增强磷酸钙复合胶凝材料的界面结合方式主要为两种：一是弱化学结合力，利用经氧化后碳纤维表面带有的部分羟基、羧基、羰基及水分子，与基体材料形成有效的弱化学力结合；二是机械结合，当胶凝材料流入和填充经处理后纤维表面的刻蚀沟槽等物理缺陷时，形成的凹凸嵌合使这一作用得到提高，在两者的共同作用下复合材料获得了良好的界面结合。研究表明α-TCP／TTCP复合胶凝材料具有良好的生物相容性、生物活性、生物降解性和骨传导性。α-TCP／TTCP植入体内后，界面形成Ca-P富集层，随Ca-P富集层的消失，最终与骨组织融为一体；该胶凝材料能在生物体内逐步降解，并被生物体组织吸收取代，降解和新骨生成过程是同时进行，是既相互联系又相互制约的复杂而缓慢的生物转化过程。本文采用湿式反应法合成高纯度TTCP工艺，解决了TTCP制备困难、纯度低的问题，在合成工艺上有较大创新；探讨了钙磷材料的水化机理，简化了磷酸钙化合物的合成和加工工艺，为研究开发其它磷酸钙种类的胶凝材料开辟了新途径；采用α-TCP的水化产物粘结β-TCP颗粒制备双相多孔磷酸钙材料避免了烧结过程和高结晶度HAP的形成，保证了磷酸钙的生物活性，为多孔材料的制备提供了新工艺；采用生物相容相好、力学性能优良的碳纤维与CPC复合，提高了CPC的机械强度，为CPC的增强提供了一条切实可行的方法。该胶凝材料性质稳定、操作方便、能自行固化，适用于作盖髓材料、牙体修复材料及骨缺损充填材料和牙根管充填材料，可提高疗效，缩短疗程，简化操作，具有临床使用价值。更多还原

【Abstract】 Calcium phosphate cements （CPC） are the emerging class of perfect materials for bone substitution and reparation due to their excellent properties such as plasticity, biocompatibility and osteoconductibility. Calcium phosphate cements are more attractive than hydroxyapatite （HAP） ceramic granules because they can be molded and shaped to fill intricate bony cavities or narrow dental defect sites. The non-toxic and non-carcinogenic properties of CPC make them more advisable than polymethyl methacrylate （PMMA） bone cements. Other interesting properties of CPC are non-exothermic setting and negligible shrinkage. They can be directly injected in the local, rapidly set to hard mass, gradually replaced by new bone in vivo. They can also be used as drug deliver system in adjunctive therapy and growth factor carrier to promote new bone formation. With development of research, CPC have been widely used in restoration and orthopedics, and became an important part of biomaterials. However, the problems of low strength and bad mechanic performance for CPC have not been solved. Furthermore, the fundamental theories that are related to CPC are very deficient. CPC are only used to non-bearing bone and hard tissue repair due to the brittleness, so PMMA still remains a high priority in clinical application. As far as the actual research status of CPC is concerned, it is significant to develop the correlative theory research for CPC and their composites, prepare CPC substitutes which have maneuverability, good mechanic properties, osteoinductivity, matched rate between degradation and bone formation, and investigate the clinical application of CPC. Therefore, the preparation technology, microstructure, mechanic performance, strengthening method and biological properties for CPC were investigated in this paper.Via optimized preparation procedure, high pure and stableα-tricalcium phosphate （α-TCP） was synthesized by using dicalcium phosphate and calcium carbonate. The hydration and hardening process ofα-TCP is a dissolution-crystallization process, and the hydration products vary with the pH value. The products are HAP, octocalcium phosphate （OCP） and dicalcium phosphate dihydrate （pH＜5.0） or HAP （6＜pH＜8）. NH₄H₂PO₄^- can accelerate the hydration reaction rate, shorten setting time and improve compressive strength ofα-TCP. When the concentration of NH₄H₂PO₄ is 2.0M, the setting time ofα-TCP is 17rain, the compressive strength and bending strength is 37.17MPa and 6.2MPa, respectively.Owning to the excellent degradability ofβ-tricalcium phosphate （β-TCP） and the hydration-hardening performance ofα-TCP, degradable porous composite cement was prepared by using the hydrogen peroxide （H₂O₂） method, which can be shaped randomly and has certain mechanic strength. The surface ofα-TCP/β-TCP composite has appropriate bioactivity. The concentration of H202 has an influence on the pore size, which increases with the concentration of H202. The composites with diverse pore size show different potential of forming bone-like apatite in SBF: 300～400μm＞200～300μm＞100～200μm＞400～500μm.The high pure Ca₄（PO₄）₂O （TTCP） powders were synthesized by tow-step wet method according to the mechanism of crystal nucleation and growth, andα-TCP/TTCP composite bone cement was prepared. Furthermore, an appropriate set accelerator was selected. The properties ofα-Ca₃（PO₄）₂-Ca₄（PO₄）₂O （α-TCP/TTCP） composite cements were investigated by using X-ray diffraction, infrared absorption spectrum and scanning electron microscope etc. The results show that the highest compressive strength ofα-TCP/TTCP composites reaches 38.76MPa, （80wt%α-TCP-20wt%TTCP）, which has fully hydration reaction, and the main product is HAE The kinetics model of hydration reaction was illustrated by investigating the hydrating-hardening process and the transformation rate of hydration, which indicates that the reaction is controlled by surface dissolution during early stage and by diffusion during later stage. Furthermore, the effect factors on hydrating-hardening process and compressive strength ofα-TCP/TTCP were discussed. The results reveal that the properties ofα-TCP/TTCP composite cement can be improved when the concentration of citric acid is changed, the size of cement grains is increased or the ratio of liquid/solid was decreased. HAP with poor crystalline can accelerate the hydration reaction when used as crystal seed, while HAP with perfect crystalline can increase the strength of the cement as aggregate.As the results showed, the oxygen content of the fiber surfaces were increased, the flexural strength and pull-out load were improved after carbon fiber （CF） being oxidized. The flexure strength is strongly depending on the oxygen concentration incorporated into the fiber surfaces. The reinforcing effect is optimal by using 8wt% NaOH solution, an aspect ratio of 375, and an additive weight of 0.3wt%. Under these conditions, the compressive strength was increased 55% （the highest strength, is 63.46MPa） and the bending strength nearly increased 100% （the highest strength is 11.95MPa）. There are mainly two kinds of interface combination way after calcium phosphate composite cement being reinforced by CF, one way are weak chemical bonds, which form between CPC matrix and CFs by using the hydroxyl group, carboxyl, carbonyl and hydrone on the surface of CF; the other way are mechanical bonds, which are enhanced due to forming concave-convex mosaic when cement inpours and fills in the erosive groove on the surface of CF after oxidization treating. Thus, a favorable interface combination is available via the jointly action of above ways.The biological experiments showed thatα-TCP/TTCP composite cement has good biocompatibility, bioactivity, biodegradability and osteoconductivity. Ca-P rich layer formed on the interface afterα-TCP/TTCP being implanted,α-TCP/TTCP cement incorporated into bone tissue with gradual disappearance of the layer. The composite can be gradually degraded, absorbed and replaced in vivo. This indicated that the processes of the biodegradation of the materials and formation of new bone take place at the same time. These complex processes are slow, interdependent and complementary biotransformation.In Summary, the wet reaction method for high purity TTCP synthesizing solves the problem that TTCP of low purity is difficult to prepare, which is an innovative technology. The investigation of hydration mechanism and the simplification of synthesis technology for calcium phosphate offer an approach to develop other calcium phosphate cements. A brand-new technics that the hydration products ofα-TCP are used to adhere toβ-TCP grains is provided for preparing porous calcium phosphate double phase ceramics, which avoids formation of high crystallinity HAP in the sintering process and keeps up the bioactivity of calcium phosphate. A feasible technique was invented to strengthen CPC by using CF, which is a kind of biomaterials with excellent biocompatibility and mechanical performance. CPC that has stable properties, convenient operation and self-setting can be used as pulp capping, dental restoration, bone defect reparation and root canal filling materials, which can enhance curative effect, simplify operation and be used widely in clinic.更多还原