Reconstruction And Properties Control Of Calcium-Phosphate Based Biomaterial For Hard Tissue Repair

Human hard tissue repair and reconstruction has been hard to solve for modern medicine. Unfortunately, most current calcium-phosphate based biomaterials could not be biodegradated controllablly, be collapsed in the fluid and difficult to set, and loss suspension stability caused by solid-liquid separation. With controllable degradation and minimally invasive treatment for the entry point, the goal of the research presented in this dissertation is to reconstruct three kinds of calcium-phosphate based biomaterials for hard tissue repair and, the properties investigation and the preliminary research on their biological properties had been performed.Structure and properties of poprous calcium polyphosphate (CPP)——porous, high porosity of CPP was prepared by gravity sintering. Main factors affecting the structure change were explored from the viewpoint of chain structure, crystalline structure and group structure, and the degradation mechanism of CPP was investigated. Investigation of properties showed that the proportion of hydrolytic groups (QI groups) in polyphosphate chain was decreased as the sintering temperature increased. By controlling sintering temperature and particle size and altering the proportion of Q1 groups, CPP could be obtained respectively with different degradation rate. Cell viability test results showed that porous CPP exerted biocompatibility on C2C12 cells.Study on aqueous fast setting and anti-washout injectable calcium phosphate-based cement (fa-ICPC)——Based on the good injectability of the paste, anti-washout injectable calcium phosphate-based cement (aw-ICPC) was fabricated by introducing of anti-washout agents, and their effects on injectability, setting time, compressive strength, phase composition and microstructure were researched. The results showed that all the anti-washout agents studied in the dissertation imparted an effective anti-washout property to the ICPC, while prolonged the setting time. The aw-ICPC with white dextrin showed the best overall performance including anti-washout property.The setting time of aw-ICPC was adjusted by incorporating magnesium phosphate cement (MPC) and altering the ratio of solid to liquid, and the fast-setting mechanism was explored. It was found that MPC not only shortened the setting time but also significantly improved the anti-washout of the paste. The physical and chemical properties of the fa-ICPC could be regulated by adjusting the ratio of MPC to CPC. The increase of the ratio of liquid to solid would improve the injectability but declay the setting time. Biological experiment indicated that fa-ICMB was biocompatible and biodegradable, and showed the good ability to repair defects of the femur.High suspension stability of non-aqueous injectable calcium-phosphate based cement (n-ICPC) and its application in root canal filling——To meet the requirements of root canal therapy, nonaqueous but water-soluble organic liquid and calcium phosphate cement (CPC) powders were mixed to form n-ICPC which is stable in syringe and hardens in vivo. Focus on the setting mechanism, the effects of nonaqueous liquid, particle size and the ratio of solid to liquid on the setting time, injectability, rheology and compressive strength were systematic explored. It was found that n-ICPC could be set in SBF, although the setting time was much longer than that of the aqueous ICPC. n-ICPC with propylene glycol as a setting liquid had low viscosity, good thixotropy, shortened setting time which was in favor of injection. Reduction of particle size could effectively improve suspension stability of the n-ICPC.The effects of particle size, fumed silica and its content on the suspension behavior of n-ICPC were also investigated by concentrated system with fully functional stability analyzer. The results showed that 1 wt% fumed silica increased suspension stability by 10 times. The change rates of transmission light and back-scattering attenuation in n-ICPC with particle diameter≤75μm were small, and the sedimentation rate was only 0.27 mm/d. The addition of 10 wt% CTSAC improved the radiopacity and injectability of the n-ICPC significantly. In addition, CTSAC imparted excellent antibacterial property against common bacteria induced by gingival. Furthermore, the addition of CTSAC did not affect the setting characteristic and shear thinning behavior of the n-ICPC.In extracted teeth experiment, n-ICPC showed better sealability and were close intergrated with detine. Cytotoxicity results showed that n-ICPC were noncytotoxic and possess good biocompatibility. The developed n-ICPC could meet the requirements of root canal filling with a proper setting time, easy injection, improved suspension stability, potent radiopacity and effective antibacterial properties. The results obtained would provide basic data for the application of the n-ICPC in the root canal filling field.