Preparation And Performance Of ?-tricalcium Phosphate Bone Cement And Its Composite Materials

?-tricalcium phosphate(?-TCP)bone cement is an ideal bone defect repair material.It is non-toxic in vitro and in vivo and has excellent bone conductivity and biological activity.Compared with other calcium phosphate bone cement currently used in clinic,it is more bioabsorbable and easier to be replaced by new bone.However,?-TCP bone cement still has the shortcomings of long setting time,poor mechanical properties and too fast degradation rate.Therefore,it is significant to explore how to improve the mechanical and biological properties of ?-TCP bone cement.This thesis takes ?-TCP as the research object and prepared Sr2+ doped ?-TCP,calcium-deficient hydroxyapatite(CDHA)/?-TCP biphasic calcium phosphate and?-dicalcium silicate(?-Ca2SiO4)/?-TCP composite powder.The above materials are used as raw materials to prepare calcium phosphate bone cement.A series of basic researches have been carried out on the mechanical and biological properties of calcium phosphate bone cement.The main contents are as follows:(1)Using ?-cyclodextrin as template,Sr2+ doped ?-TCP powder was prepared by chemical precipitation method.The effect of Sr2+ doping on the performance of?-TCP was studied.The results show that with the increased of Sr2+ content,the size of ?-TCP particles increased and the specific surface area decreased,but the morphology changed little.With the increased of Sr2+ content,the setting time,compressive strength and cell activity of ?-TCP bone cement firstly increased and then decreased.When Sr2+ doping amount was 3 mol%,it reached the maximum value.At this point,the initial setting time was 24 min,the final setting time was 47 min and the compressive strength was 10.8 MPa.The cell survival rate of L928 cells after 3 days of culture was over 97%.Therefore,Sr2+ doped ?-TCP bone cement has excellent mechanical and biological properties.(2)Using ?-cyclodextrin and citric acid as templates,a controllable ratio of CDHA/?-TCP biphasic calcium phosphate powder was prepared by chemical precipitation method.The synthesis of CDHA/?-TCP biphasic calcium phosphate and the effect of CDHA on the performance of ?-TCP bone cement were studied.Research shows that citric acid promoted the formation of CDHA in biphasic calcium phosphate.With the increased of citric acid addition,The proportion of CDHA in CDHA/?-TCP biphasic calcium phosphate powder increased.For CDHA/?-TCP biphasic calcium phosphate bone cement,with the increased of CDHA content,the setting time,the compressive strength,the rate of mineralization and degradation of bone cement decreased and the cell activity increased at first and then decreased.When the ratio of CDHA/?-TCP was 50/50,the bone cement scaffold had the best cell viability.Under this ratio,The initial setting time of biphasic calcium phosphate bone cement was 7.1 min,the final setting time was 12.8 min and the compressive strength was 2.08 MPa.CDHA can affect the degradation rate of dual-phase calcium phosphate cement,so the degradation rate of dual-phase calcium phosphate cement can be controlled by controlling the ratio of CDHA/?-TCP to meet the needs of actual treatment.(3)The ?-Ca2SiO4 powder with high purity and good crystallinity was prepared by sol-gel method.The effect of ?-Ca2SiO4 on the properties of ?-TCP bone cement was studied.For ?-Ca2SiO4/?-TCP composite bone cement,with the increased of the content of ?-Ca2SiO4 in bone cement,the setting time,the compressive strength,the degradation rate of bone cement increased and the cell activity decreased.The addition of ?-Ca2SiO4 also changed the morphology of apatite deposited on the surface of the bone cement,from needle-like to spherical distribution.When?-Ca2SiO4 content was 50 wt%,the initial setting time of the bone cement was 15.2 min,the final setting time was 32.2 min,and the compressive strength was 14.98 MPa.Therefore,?-Ca2SiO4 can greatly improve the compressive strength of ?-TCP bone cement on the basis of ensuring cell viability.