| Calcium phosphate cement (Calcium phosphate cement, CPC) is a self-curing non-ceramic apatite-like material. As an important part of biomedical repair materials, calcium phosphate bone cement can be shaped arbitrarily,self-curing quickly under the conditions of humors and also have good biocompatibility.However, due to their brittle feature and less compressive strength of CPC, which was generally used only for non-weight-bearing bone in the repair area, and limited its clinical application. In this paper, a new CPC was developed by two ways, one was fiber-reinforced, the other one was in-situ-enhanced, and its properties were characterized.In this research, The was tetra-calcium phosphate (TTCP) and anhydrous calcium hydrogen phosphate (DCPA) was used as solid phase for the prepared of HAP, while the liquid phase was the weak acidic solution of chitosan. By carefully research, the setting cement synthetized by us could maintain the molding shape very good in the water; The initial setting time of CPC was 34min; with setting time extending, compressive strength also increased. After setting 6d,the maximum compressive strength was10.01±1.37MPa;The conversion rate was 94.3±0.3%; Porosity was 38.44±0.10%; the main phase of the setting cement was the hydroxyapatite.In the present study, a biodegradable PLLA(Ploy-L-lactic acid) nanofiber, which was prepared by spray-drying, was incorporated into CPC to reinforce its strength and fracture toughness. After combined with the PLLA fiber, the initial setting time of the CPC was shorter than that of unreinforced one; the main phase of the setting cement was the same hydroxyapatite as the unreinforced one. With an increase in nanofiber content from 0 to 15 wt%, the average compressive strength of CPC increased from 9.27±0.03 to 16.38±0.12 MPa, and the fracture toughness in wet achieved an increment of 90%. Both strength and fracture toughness followed a fall at a nanofiber fraction of 20 wt%. Fractographic observation and crack propagation test revealed that this increase could be correlated to energy-dissipating processes along fiber and bridge effect of fiber.degradation experiments In vitro showed that after degradated 120 day in the simulated body fluid(SBF), the pH value of SBF decreased, increased, and then declined; The mass loss rate and the porosity was rased with the increase of degradation, The mass loss rate and the porosity of CPC was respectively 23.6±5.2%and 52.78±1.31%, The mass loss rate and the porosity of CPC+15%PLLA was respectively 32.0±0.7%and 54.80±0.20%; The compressive strength of the material was decreased with the increase of degradation,after120 day, The compressive strength of CPC was 5.04±2.34MPa, The compressive strength of CPC +15%PLLA was 4.96±2.53 MPa.Because of HAP is similar to Human bone in the composition and structure, it is the ideal bone substitute material. but it was neglected of that the crystal structure of HAP was also a serious impact on its physiological functions and mechanical properties. In this paper, monoclinic HAP was prepared by adding organic inducers in the liquid phase, and form of lamellar structure. The crystal structure of HAP was effectively improved, and mechanical properties of CPC was also enhanced.The innovation of this paper was that:1.CPC was reinforced and toughened by using biodegradable PLLA fiber, the result showed that strenght could be increased to 60%, and toughness could be increased to 90%; 2.Using organic inducer, a ordering monoclinic HAP was in-situ formated to improve the performance of CPC-like materials, and its applications could be developed widely in the biomedical field.
|
PDF Full Text Request