Fabrication And Characterization Of 3D Printed Interconnected Porous Titanium Surface

Objective :A growing demand of early and even immediate implantation has evolved the clinical field as great spreading of implantation techniques.In order to acquire rapid and stable osseointegration,optimizing design and fabrication of implants become an focus of research.There have been plenty of surface modifications for implants,but most of which are still lack in precision and susceptible to the bad effects caused by big difference between bone and implant.To optimize implant surface as well as reduce its elasticity modulus,this study was designed to fabricate poroustitanium implant surface by 3D printing technique.Methods:1.The three-dimensional models of porous titanium implant surface with optimum parameters were designed by computer,and fabricated by selective laser melting(SLM),resulting in interconnectedporous titanium surface species with different porosity.The surface morphology oftest species was observed by scanning electron microscopy,and differences between designed size and actual size of species were compared,thus comprehensively evaluating the print quality of titanium surface species.2.Scanning electron microscopy(SEM),atomic force microscopy(AFM),energy dispersive spectroscopy(EDS),and X-ray diffractometry(XRD)were used to examinesurface micromorphology and chemical composition of 3D printed titanium specimens,and the hydrophilicity was tested by contact angle experiments.In consequence,surface physicochemical properties were characterized.3.The nano-indentation technique was used to examine the mechanical properties of the precisely designed interconnected porous titanium surface to verify the effect of interconnected porous structure on the reduction of elastic modulus,as well as to select out the suitable porous titanium surface with exact porosity matched with the natural bone tissue elastic modulus.4.Fluorescent labeling technology was used to detect the protein adsorption capacity of 3D printed titanium specimens,and the ability of inducing apatite deposition before and after protein adsorption were compared.The biological activities of 3D titanium printed specimens were evaluated to optimize titanium implant surface design and fabrication scheme.Results :1.The interconnected porous titanium surface specimens with pore diameter of 500 ?m,strut size of at least 100 ?m,and porosity of 0,30%,50%,and 68% were successfully obtained by means of SLM.The specimens were of no defects,good in size reproducibility and attached with incompletely melted titanium powder.2.Results observed by SLM showed that the 3D printed interconnected porous titanium specimens appeared to be rough surfaceswith regularly arranged ‘linear array' morphology in microscale.EDS showed that there were few chemical impurities on the surface of 3D printed specimen,and XRD results showed that?-phase titanium grains are fine.The contact angle test showed that surfaces of 3D printed specimens were weakly hydrophilic,and there was no significant difference between 3D printed specimen with no pores and machined titaniumspecimen.As to 3D printed interconnected porous titanium specimens,the hydrophilicity decreased as the porosity increased.3.The elastic modulus of 3D printed interconnected porous titanium specimens were lower than that of non-porous titanium specimens,and the elastic modulus decreased with increasing porosity.Especially,the elastic modulus of 3D printed interconnected porous titanium specimen matched that of cancellous bone when the porosity was 68%.4.The protein adsorption and apatite deposition of 3D printed interconnected porous titanium specimens were significantly higher than those of machined titanium specimens,and increased with the increase of porosity.The presence of protein on titanium surface could significantly promote the deposition and maturity of apatite crystals.Conclusions :1.Interconnected porous titanium specimens with specific pore size and various porosities could be successfully obtained by SLM through reasonable control of parameters.2.The surface of 3D printed titanium specimen appeared to be stable in chemical composition,regular in micromorphology and weakly hydrophilic.3.The introduction of interconnected porous structure to the surface of titanium specimen could effectively reduce the elastic modulus to match the mechanical properties of bone tissues.4.The surface bioactivity of 3D printed titanium specimen was higher than that of machined titanium specimen,and increased with increasing porosity.