The Vivo Study On Porous Surface Of Titanium Specimens Fabricated By Selective Laser Melting

Objective In this study,the surface structure of the implant was improved by the computer aided design(CAD)with pure titanium powder as the materials,and the porous implant was prepared by selective laser melting(SLM).The mechanical properties of the structure and the abilities of the osseointegration were evaluated by the study of the elastic modulus of the implant and the experimental study of the animals.Methods 1.The second-grade spherical titanium powder with diameter of 0-45μm was selected to find the optimal laser parameters under the protection of Argon(Ar)by structural modification and CAD.The implants with different pore sizes were prepared under the proper conditions.At the same time,the traditional sandblasting and large-grits echting(SLA)implants was used as the control group.2.The surface morphology,pore size etc.were observed by field emission scanning electron microscopy(FE-SEM),and the surface elements of the implants were analyzed by X-ray energy dispersive spectroscopy(EDS).And the stress-strain curve was measured by MTS 810 universal electronic testing machine to compare the differences of elastic modulus.3.Three groups of implants were implanted into the rabbit femur and were sacrificed at 4,8 and 12 weeks.Bone tissue healing was observed by visual observation,X-ray observation and VG stain.The bone-implant contact(BIC)was studied on the formation of new bone.4.SPSS 16.0 software was used for statistical analysis.Results 1.The surface of macroporous group(SLML)were metal gloss,and the shape of the hole were approximately circular.The range of the diameter was between 200-250μm.The surface gloss of the microporous group(SLMS)is better than that of the first group,and the pore structure is not visible on the surface.Under the electron microscope,the pore range is between 150-200μm.Both the surfaces of SLM implants were accompanied by incomplete melting of titanium powder particles.The surface of the SLA implants was dark gray,no metallic luster,and the electron microscope had an irregular closed-cell foam structure.2.EDS results show that the carbon content on the surface of the SLA implants were higher than that of the laser cladding group.The elastic modulus of SLML was 27.7±1.3GPa,34.5±0.9GPa of SLMS and 101.6±1.1GPa of SLA specimen by "stress-strain curve".3.Bones were blinded in bone-implant interface,and the new bone was keen to grow in the pores of the implant.SLMS specimens did not show better biological properties than that of SLA specimens.However,SLML specimens had a bone exposure rate of 80.77% at week 8,compared with 71.91% for SLMS and 65.22% for SLA Differences(P <0.05).The ability of middle bone to induce bone formation was superior to the other two groups.Conclusion Through the software design,the laser under the prepared established procedures of the porous structure of the specimen,the elastic modulus close to the human cortical bone.The porous implant with pore size between 200-250μm has good biocompatibility and osteoinductive effect,shortens bone healing time,promotes new bone formation and enables new bone to grow into pores.The formation of the pores reduces the elastic modulus of the implants,which is closer to the elastic modulus of the human bone than the traditional implants,and the elastic modulus of the macroporous titanium implants is smaller than that of the small pore diamonds.