Study On Mechanical Properties And Injectability Of α-Tricalcium Phosphate Bone Cement

α-tricalcium phosphate（α-TCP）bone cement has excellent biological activity and osteogenic properties,can self-cure in the human environment,which makes it a promising artificial bone repairing material.In this paper,metal-doped hydroxyapatite particles,graphene oxide,ZrO₂ and TiO₂,were added to the solid phase and then polyaspartic acid,ascorbic acid,sodium glucan sulfate and iconic acid were added to the liquid phase to prepare calcium phosphate bone cement,and the effects of these additives on the properties of bone cement were studied.Based on these facts,the injectability and mechanical properties of bone cements with good compressive strength were studied,and the effects of sodium alginate and chitosan as stabilizers on injectability and anti-collapsibility ofα-TCP bone cement were explored.The stability and crystallinity of HA crystals were affected by doping Ag⁺,Zn²⁺or Mg²⁺.The molar percentage range which making the HA phase stable of Ag⁺,Zn²⁺and Mg²⁺were0¹.5%,0¹.5%and 0².5%,repectively,among which 1Ag-HA had highest crystallinity,second 0.5Zn-HA,but doping Mg²⁺had little influence on HA crystallinity.Adding 1wt.%1Ag-HA into the solid phase obtained the maximum compressive strength of 51.31MPa,the curing time of 10.5min;Adding 0.5wt.%0.5Zn-HA obtained the second compressive strength of 50.67MPa,the curing time of 11min.In the bone cement with graphene oxide,the maximum compressive strength was55.62MPa and the curing time was 10.5min when the amount was 0.003wt.%.When ZrO₂powders were added to the solid phase,the curing time was reduced from 10min to 8-8.5min,and the compressive strength was the highest of 53.89MPa at the addition of 5wt.%,and the curing time was 8.5min.The mobility of bone cement with TiO₂ powders was increased,and the curing time was extended from 9min to 10.5min,but the compressive strength was not significantly enhanced.Polyaspartic acid,ascorbic acid,sodium glucan sulfate and iconic acid were added into the liquid phase,respectively,which mainly changed the pH of the liquid phase and affected the curing reaction,thus influenced the properties of bone cement.When the pH was in the range of 4.5⁵.9,the main hydration product was CDHA;pH was 4.1⁴.5,the main hydration products were CDHA and OCP;pH<4.1,the main hydration product was DCPD.When adding4wt.%ascorbic acid,the compressive strength of bone cement reached the maximum of39.3MPa,with the curing time of 9 min.Solid phase compositions,liquid phase compositions and liquid-solid ratios（L/S）were selected as investigate factors of L₉（3⁴）Taguchi method test.The results show that the main effecting factor of compression strength and injectability were solid phase compositions and L/S,respectively.Injectability and compressive strength are negatively-related properties of bone cement,thus the test obtained two bone cements,one with higher compressive strength and the other with preferable injectability.1.α-TCP was mixed with the liquid of 7%citric acid monohydrate,8%disodium hydrogen phosphate dodecahydrate and 0.003%graphene oxide,and the L/S was 0.45 mL/g.The bone cement obtained had high compressive strength of 44.38MPa and the injectability is 47.22%;2.5%ZrO₂ and 95%α-TCP were mixed with the liquid phase of 7%citric acid monohydrate,8%disodium hydrogen phosphate dodecahydrate and0.003%graphene oxide,and the L/S is 0.45 mL/g.The bone cement obtained had excellent injectability of 80.09%and the compressive strength of 34.28MPa.Both sodium alginate and chitosan could obviously improve the anti-collapsibility of bone cement,but the injectability was decreased.