Investigations On The Injectability Of Calcium Phosphate Cement Properties By Zirconia And Titanium Oxide

Calcium phosphate cements(CPCs)possess the excellent biocompatibility and osteoconductivity due to their similar component as those of the natural bone and have been used as bone replacement in clinic successfully.A major disadvantage of current CPC is that they exist in hardened forms,requiring the surgeon to fit the surgical site around the implant or to carve the graft to the desired shape.This can lead to increases in bone loss,trauma to the surrounding tissue,and prolong surgical time.The injectability of CPC is important in clinical applications that involve defects with limited accessibility or narrow cavities, when there is a need for precise placement of the paste to conform to a defect area.However,the drawbacks of injectable CPC,including the lack of low strength,have limited its clinical use.According to some studies,ZrO₂ and TiO₂ often were used to improve strength of materials and both of them have good biocompatibility.Citric Acid as the liquid component was used to prepare injectable CPC.In this study,ZrO₂ or TiO₂ were added into citirc acid CPC to improve CPC properties which including strength and injectability.In this study,the powder component of CPC contain 98 wt%α-TCP and HA 2 wt%and the liquid component were different concentrations citric acid(0.1 mol/1,0.2 mol/1,0.3 mol/1,0.5 mol/1)with different ratios of powder to liquid(2 g/ml,2.5 g/ml,3 g/ml,3.5 g/ml).The compress strength of CPC were tested by mechanical instrument(instron 5670).The extrusion method was used to test the injectability of CPC.The optimization concentration of citric acid and the ratio of powder to liquid were obtained.Then,different mass fracions ZrO₂ and TiO₂(5%,10%,15%,20%,wt)were added into the CPC,respectively,which named as ZCPC and TCPC.The CPC was used as the control.The Vicat was used to test the initial time and final time of as-received CPCs.The compressive strength and injectability were test as the previous description.X-ray diffraction(XRD)was employed to analyse the phase of as-prepared CPC.Scanning Electron Microscope(SEM)and Energy dispersive spertrum(EDS)were used to observe the morphology and indicate the element components of CPC.(Fourier transform infrared spectroscopy,FTIR)was worked to analyse the components of ZCPC and TCPC.X-ray Photoelectron Spectroscopy(XPS)were made to test element of Zr and Ti in the ZCPC and TCPC,respectively.The cell culture and immersed in simulation body solution(SBF)in vitro experiment were carried out to evaluate the biocompatibility and biodegradability of as-received CPCs.The present results show that the maximum compressive strength of CPC is 14 MPa and the injectability is 60%while citirc acid concentration was 0.5 mol/l and the powder to liquid ratio was 3 g/ml.The initial and final time of ZCPC and TCPC were 5-10 min,10-20 min and 10-15 min,20-30 min,respectivety.When the mass fraction of ZrO₂ and TiO₂ were 15 wt%,the maximum compressive strength are 23 MPa and 38 MPa for ZCPC and TCPC,respectivety,amd the injectability are 80%and 93%.XRD,SEM,FTIR and XPS analyse indicate that HA was the main product in the ZCPC and TCPC.Ca(HPO₄)₂·H₂O(DCPD)and calcium citric acid occured during CPC self-setting process.Zr(HPO₄)₂·H₂O also could be found in ZCPC.HA was the main product in the ZCPC and TCPC after immersion in SBF.Cell toxicity experiment illuminate that both of ZCPC and TCPC have good biocompatibility than normal CPC.Furthermore,ZCPC have better biocompatibility than TCPC.