Study On Mechanical And Biological Properties Of 3D Printed TPMS Graded Porous Titanium Alloy Structures

In recent years,more and more patients choose dental implant for restoration after tooth loss or defect.However,titanium alloy implants commonly used in clinic are dense structures,whose elastic modulus is too different from that of human alveolar bone,which is easy to produce "stress shielding".Since human bone tissue is composed of cortical bone and spongy bone,more and more scholars began to study gradient porous implants to reduce the elastic modulus of implants and simulate the bone characteristics of human bone tissue.Studies have shown that the microstructure of implants is very important for their biological and biomechanical properties.However,when considering microstructure design,there is little research on which porous structure performs better in biology and biomechanics compared with uniform porous structures with gradient variations in different directions.In this study,two kinds of porous scaffolds with porosity gradient changes in different directions were designed based on three-period minimum surface structure(TPMS)to simulate the biomechanical properties of bones.Moreover,uniform porous scaffolds were designed as a control.Three groups of titanium alloy cylindrical scaffolds and disks with different porous structures were prepared by 3D printing technology.The mechanical properties of three groups of cylindrical titanium alloy scaffolds were evaluated,and a group of titanium alloy solid disks and three groups of porous titanium alloy disks were added to evaluate the biological properties in vitro.Compression tests revealed statistically significant differences in biomechanical properties of the three scaffolds.The scaffolds(Gz)with increasing porosity from top to bottom along the Z-axis had the highest elastic modulus and compressive strength among the three groups,and had excellent mechanical properties.The mechanical properties of scaffolds(Gxy)with increasing porosity from center to periphery along the xy plane showed no statistical significance between the scaffolds(Gxy)and the uniformly porous scaffolds(UN).However,the elastic modulus of the three groups of porous titanium alloy scaffolds was significantly lower than that of dense titanium alloy scaffolds.The scaffolds were cultured with r BMMSCs in vitro,and it was found that the Gxy group showed excellent biocompatibility in terms of cell proliferation and early osteogenesis,which may be conducive to the continuous expansion of bone tissue.The biocompatibility of the Gz group was slightly lower than that of the Gxy group,followed by the UN group,but in general,the biocompatibility of the three groups of porous structures was better than that of the solid group.Through the above experiments,this study found that the porous structure with different directional gradient changes can have different effects on the mechanical and biological properties of porous scaffolds.The results of this experiment provide the direction for future clinical customized dental implants for patients with different types of alveolar bone.