Preparation And Properties Of Calcium Phosphate Cement Modified By Incorporating Silicon

Calcium phosphate cement(CPC)is a self-setting bone-repair material,which has been successfully applied to clinical hard tissue repair and replacement because of its good biological characteristics and low curing process.However,CPC has some disadvantages,such as long setting time,low mechanical strength,poor collapsibility and slow degradation,which limits its clinical application.In order to solve the above problems of CPC,this paper have prepared a CPC cement with excellent performance by process optimization,and modified by introducing silicon element through many ways.A new Si-CPC cement was prepared to meet the clinical needs.The preparation of CPC was completed by using different proportions of two powders of ?-TCP and DCPD as solid phase,and the solution of Na2HPO4 and citric acid in different ratio as liquid phase.The study showed that there was a plate-like CDHA in the hydrated product,and the mechanical property of CPC was best,the porosity was lowest,under the 5wt.%citric acid +0.5mol/L Na2HPO4 aqueous solution and the mixture with a-TCP and DCPD in molar ratio of 2:1.With the increase of liquid-to-powder ratio,the porosity and compressive strength of CPC both increased,at the same time,the more widely distributed plate-like CDHA was.The optimum liquid-to-powder ratio was 0.4mL/g under the conditions of this test.Adding proper concentration of citric acid in the liquid phase could increase the compressive strength of CPC,reduce its porosity,shorten setting time,and promote formation of the plate-like CDHA,too.When the liquid phase was 6wt.%citric acid +0.5mol/L Na2HPO4 aqueous solution,the performance of CPC was best.In the CPC,different crystallinity and content of TTCP was introduced.It was found that both HCTTCP/CPC and LCTTCP/CPC had generated a new phase of HA and showed nanoscale plate-like structure.The addition of LCTTCP increased the porosity of CPC,shortened the setting time,reduced the formation of HA,and led to decrease of compressive strength.The addition of HCTTCP reduced the porosity of CPC,increased the compressive strength and the formation of HA.When the amount of addition is 5wt.%,the performance of HCTTCP/CPC was the best.Si-CPC bone cement was prepared by adding CS and SiO2 directly into the solid phase and introducing Si into CPC by Si-a-TCP.The results showed that the sheet-like DCPD appeared on the surface of CPC directly,when the CS was added into solid phase of CPC.With the increase of CS,the liquid-to-solid ratio of 0.4mL/g could not meet solid phase wetting,make the setting time decreased,and appear the aggregation phenomenon.The mechanical properties of CPC decreased in a straight line,and the porosity increased.The addition of SiO2 promoted the plate-like HA and surface film formation of CPCThe Si-a-TCP with high bioactivity was prepared by adding Si to a-TCP at high-temperature sintering.The Si-CPC was formed with Si-a-TCP/DCPD/TTCP,whose mechanical properties improved significantly with the increase of Si.When the Si content was 2.5mol%in ?-TCP,the comprehensive performance of Si-CPC was best,the porosity was lowest,and whose the compressive strength was increased to 3 times than CPC.At the same time,the surface of Si-CPC was generated a dense film,and accoMPanied Si-HA formation.The Si-CPC and CPC bone repair materials were evaluated the bioactivity by immersing into SBF solution.The results showed that the degradation rate of Si-CPC increased negatively from immersing 1d,and the surface of Si-CPC was uniformLy distributed plate-like HA crystal.For immersing 7d,Si-CPC appeared amorphous silica-gel.However,the degradation of CPC increased first and then increased negatively.After soaking 7d,a small amount of plate-lik HA began to appear on the surface of CPC,but the crystallinity of HA was not high.During the immersing process,the solution pH of the Si-CPC and CPC immersed was the same change tendency.At the 6d,the solution pH was the lowest,but the solution pH value immersed in Si-CPC was higher than that of CPC,which prompted the formation of hydration products.The above results showed that not only Si-CPC had excellent mechanical properties,but the biological activity was also best.