Study On Calcium Phosphate Cement With Different Molar Ratio Of Ca/P And Multiple Porous

The calcium phosphate cement (CPC) have many advantages, such as, the excellent biocompatibility, self-setting under ambient conditions, and almost without heat release. Therefore it has attained more attentions and been applied in clinic to repair and replace the bone defects.However, the solid components of most CPC were insoluble calcium phosphate and the CPC had a lower molar ratio, which would slow down the dissolution CPC as well as changed to the hydroxyapatite(HA)and afected the biocompatibility and the degradation rate of CPC. Biocement D has been studied extensively because of its excellent performance, but it's solid components were insoluble calcium salt, and it's molar ratio of Ca/P was only 1.50. Meanwhile, the traditional CPC was lack of microporous for cell growth and macroporous for tissue ingrowth, and the biodegradable of CPC was slow. Therefore, many studies solved the problem by preparing porous CPC. However, the large size of the pore and fast rate of generating pores affect the mechanical properties of CPC implanted to human in the early. To preparing suitable pore size and rate of generating pores in CPC, the purpose of this study is preparation CPC with different molar ratio of Ca/P by adding easily dissolved calcium chloride particles and biodegradable chitosan particles to CPC, using dissolution of soluble calcium salt and degradation of chitosan formation multiple porous structure in CPC in the body at different times and different size.This study prepared CPC with 1.60,1.67 and 1.80 molar ratio of Ca/P by adding certain size (20-37.5μm) of soluble calcium salt (calcium chloride) to the solid of Biocement D. On this basis, multiple porous CPC was prepared by adding calcium chloride particles with size of 20-37.5μm and chloride particles with size of 150-300μm to CPC. The initial setting time (IT) and final setting time (FT) of CPC with different molar ratio of Ca/P and multiple porous CPC were studied. X-ray diffraction (XRD), mechanical testing, and scanning electron microscope (SEM) were used to characterize the phase composition, compressive strength and the morphology of the fracture surface of CPC with different Ca/P molar ratios and multiple porous CPC after soaking in phosphate buffer solution (PBS). Biological properties of CPC prepared in this study were evaluated by Cell experiment.The results show that:with the increase of molar ratio of Ca/P, initial and final setting time of CPC added calcium chloride increased significantly, initial setting time was 7-10 min, final setting time was 12-14 min, the setting time meet the needs of clinical applications except 1.80-CPC. After soaking in PBS for 3 and 7 days, the compressive strength of CPC added calcium chloride increased significantly, but no significant different compared with the control group. Provide more Ca2+ by adding calcium chloride promote the starting material of CPC to the final phase-HA in hydration and soaking in PBS,1.67-CPC and 1.80-CPC formed the poor crystalline apatite similar to those of the inorganic composition of bone after soaking in PBS, which have degradation and excellent biocompatibility. With the increase of molar ratio of Ca/P, the porosity of CPC has improved significantly after hydration for 24 hours, the largest porosity of CPC was 34.2±0.3% with Ca/P molar ratio of 1.80.The research indicates:the setting time of CPC added calcium chloride and chitosan was significantly reduced which initial setting time was 5-7 min, final setting time was 10-14 min. The maximum compressive strength of multiple porous CPC was 4.78±0.17 MPa after hydration for 24 hours. The maximum compressive strength of multiple porous CPC was 17.8±0.601 MPa after soaking in PBS for 7 days. The compressive strength decreased significantly compared with the control group. The porosity of multiple porous CPC improved significantly, the maximum porosity was 40.5±2.2% after hydration for 24 hours and 36.2±0.4% after soaking in PBS for 7 days. The multiple porous CPC formed the poor crystalline apatite with porous of hundreds of microns in diameter similar to those of the inorganic composition of boneThe results of cell culture in vitro showed that:after 7 days of cell culture, the cell numbers of CPC with Ca/P molar ratio of 1.60,1.67 and 1.80 were improved significantly than CPC with Ca/P molar ratio of 1.50. The alkaline phosphatase (ALP) activity of cells in the experimental group of CPC increased molar ratio of Ca/P improved significantly, it illustrated that promote the molar ratio of Ca/P would improve the biocompatibility of CPC. The osteoblasts in CPC with Ca/P molar ratio of 1.60,1.67 and 1.80 adhered and proliferationto the pore. From the cell experiment between CPC with different molar ratio of Ca/P and multiple porous CPC, the cell numbers of multiple porous CPC with Ca/P molar ratio of 1.60 and 1.67 were increased significantly after 7 days of cell culture; the ALP activity of multiple porous CPC with Ca/P molar ratio of 1.50 and 1.67 had improved significantly. It illustrated that the multiple porous CPC had better performance of biology than CPC with same molar ratio of Ca/P.The CPC added calcium chloride had high porosity and suitable strength, poor crystalline apatite similar to those of the inorganic composition of bone. The cell experiments showed more excellent biological properties of CPC added calcium chloride. The CPC added calcium chloride and chitosan had higher porosity and pores with hundreds of microns and poor crystalline apatite similar to those of the inorganic composition of bone. From the cell experiment between CPC added calcium chloride to CPC added calcium chloride and chitosan, it showed that CPC added calcium chloride and chitosan had more excellent biological properties.