Basic Research On 3D Printing Technology Of Biodegradable Composite Bone Plate

Bone plate is a common internal fixation method for the treatment of fractures.At present,the commonly used material of bone plate is titanium alloy.Although it has high strength,corrosion resistance and other advantages,its elastic modulus is much higher than that of human bone induced stress shielding,leading to osteoporosis,osteolysis and other conditions.At the same time,it still needs to be removed by a second operation after fracture healing.The biodegradable bone plate can effectively solve the defects of the traditional bone plate because of its advantages of good biocompatibility and no need for second operation.Therefore,this paper takes the degradable composite bone plate based on melt deposition molding(FDM)as the research object to conduct basic research on its 3D printing process.The 3D printing process parameters of PLA were studied.The influences of the printing layer height,printing speed and wire feeding speed on the single-channel cross-section morphology were studied.The results showed that the printing process was stable and the wire output was continuous when the middle layer height was0.1mm,the printing speed was 55 mm/s and the wire feeding speed was 0.8 mm/s.The influence of lap rate on the forming porosity,surface morphology,preparation time and warpage deformation of the specimen was studied.It was found that the minimum pore area of the specimen section was obtained when the lap rate was 30%,but the influence on the surface morphology,time efficiency and warpage deformation was not significant.The numerical simulation of temperature field at different printing speeds was studied.The results show that the molding temperature decreases with the increase of printing speed,and the simulation results are in good agreement with the experimental values.The effects of FDM 3D printing process parameters on the mechanical properties of PLA/HA composites were studied.The parameters of filling mode,layer height,lap rate,porosity and HA content were optimized by single factor analysis.The results show that the maximum tensile strength of the specimen is 59.6MPa when the length of the sheet is 0.1mm and HA content is 10%.The maximum bending strength of the specimen is 96.32 MPa.The biological properties of PLA/HA composites were studied.The effects of HA content on p H value,weight loss rate,hydrophilicity and cytotoxicity were studied.The results showed that the addition of HA neutralized the acid products generated by PLA degradation,slowed down the degradation rate,improved the hydrophilicity of PLA material,and was conducive to cell adhesion and proliferation without cytotoxicity.