Study On Mechanical And Biological Properties Of 3D Printing Biomimetic Porous Implants Based On TPMS

Objective: As a common way to treat dental implant restorations,the key to success is the osseointegration between the implant and bone interface.This experiment is based on Triply Periodic Minimal Surface(TPMS)to study the mechanical properties of GYROID structures with different porosity and gradient porosity,and to design and prepare new porous implants by adjusting the parameters of porosity and pore size to match the strength and elastic modulus of cortical bone and cancellous bone.Methods :(1)GYROID structures with 60%,65%,70%,75%,and 80% porosity were prepared by Selective Laser Melting(SLM),and the mechanical properties of GYROID structures with different porosity were analyzed by Finite Element Analysis(FEA)and mechanical compression tests.(2)The standard parts of gradient GYROID structure with60%-80% porosity were prepared by laser-selective melting technique and compared with the homogeneous porosity GYROID structure with 70% porosity,and finite element analysis and mechanical compression tests were performed to compare their mechanical properties.(3)Homogeneous porosity and gradient porosity GYROID structural implants were designed and prepared for implantation into the lateral femoral condyle of rabbits,and the implantation torque and kinematics were measured to obtain their initial stability,and post-operative 4w and 8w executions were performed to analyze their biocompatibility in roll-out experiments.Results :(1)finite element results showed that the homogeneous porosity GYROID structure had uniform stress distribution,and when the porosity increased,the equivalent force increased;the gradient porosity GYROID structure was subjected to a larger equivalent force at the larger pores.(2)Sand-blasted,Large grit,Acid-etched(SLA)treatment can form multi-layer nested primary and secondary pores on the surface of 3D printed titanium alloy.(3)The porosity analysis results show that the porosity of 3D printed specimens is 15% lower than the design porosity,and after SLA treatment the porosity of the specimens is improved to be similar to the design porosity.(4)Room temperature compression test results show that the homogeneous porosity GYROID structure produces uniform deformation until fracture in the densification stage,and its fracture line is obliquely distributed.Unlike the overall damage effect shown in the homogeneous porosity GYROID structure,the gradient GYROID structure undergoes local failure damage in a layer-by-layer deformation manner.As the porosity increases,the elastic modulus and compressive strength of the GYROID structure decreases.The increase of porosity causes the wall thickness of GYROID unit porous structure to decrease,which leads to the reduction of solid part of the sample,so the compressive capacity decreases.At the same porosity,the compressive strength of Ti-SLA group is significantly lower than that of Ti group.The compressive strength of the gradient porosity GYROID structure was lower than that of the homogeneous porosity GYROID structure,and its elastic modulus was similar to that of mandibular bone(0.56-12.7 GPa),and its strength was similar to that of human bone(180.5-211.1 MPa),which was suitable as an intraosseous implant material.(5)The results of the implantation experiments showed that both the homogeneous porosity implants and the gradient porosity implants have good initial stability.4w and 8w,the osseointegration strength of the gradient porosity GYROID structure implants were slightly higher than that of the homogeneous porosity implants.Conclusion :(1)3D printing will reduce the porosity of GYROID structure,SLA treatment can increase its porosity,while weakening its maximum compressive strength,but it has little effect on the elastic modulus.(2)homogeneous porosity GYROID structure stress distribution is more uniform,gradient GYROID structure stress peak is located at the large hole.(3)When the porosity increases,the elastic modulus and compressive strength of GYROID structure are reduced;the compressive strength of gradient GYROID structure is slightly lower than that of homogeneous porosity GYROID structure.