| Background:At present, the titanium alloy implants (Ti6Al4V) has become one of the mostimportant medical metalic implants, but their biological activity and the effect of boneinduction is not so good. How to make a new coating with high biological activity throughsurface modification, is critical to improve the biological activity and the organismosteogenic of medical metalic implants.By reviewing the literature, we believe that the anodic oxidation and micro-arcoxidation (MAO) are fit for improving the biological activity of medical titanium alloy.Anodic oxidation technique is based upon electro-chemical method, which can producetitanium dioxide (TiO2) nanotubes (NT) on titanium alloy materials. The anodizationprocess is quite simple, and is suitable for medical titanium alloy implants with verycomplex surfaces. TiO2-NT with different diameter (in tens to hundreds ofnanometers range) can be produced by altering the process parameters. On the otherhand, the MAO technology can produce microporous structure and oxide layer which isrich in calcium and phosphorus on titanium alloy material, so as to improve the biological activity of the implant surface. There were plenty of researchs about the above two kindsof surface modification techniques in vivo, and controvercial results were reported ontheir biological functions. In addition, TiO2-NT with which diameter has the bestbiological function is still in debate. What is more, the in vitro researchs were barelyreported. Therefore, which surface modification technology has better implant-boneinterface binding force and better osteogenic effect is still unclear.Our study intends to find an ideal modified surface topography, which may possessexcellent biological activity and has a solid implant-bone interface bonding. According tothe results of the in vivo and in vitro study, we can conclude a preliminary evaluation of itsclinical application.ObjectiveThrough the in vitro and in vivo sudy, to evaluate the influence of two surfacemodification technology on the function of osteoblast and the early osteogenic effect,and to draw a conclusion of the preliminary evaluation of the clinical application.Methods1. Using anodization and micro-arc oxidation to modify the surface of titanium alloymaterials.2. Observe the surface morphology with SE-SEM, and test the specimen surface crystalstructure, water contact angle and surface energy.3. The osteoblasts (OB) were co-cultured with different specimens, afterwards themorphology and the adhesion, proliferation and differentiation activities of the OBwere evaluated.4. Different specimens were implanted into femoral condyle defects of rabbits. At someperiods after surgery, macroscopic observation, fluorescence microscopy observation,histological evaluation, and implant push-out test were carried out.Results1. The anodic oxidation technique can successfully construct a nanometer-sizedmorphology with different diameter of TiO2-NT on the medical titanium alloymaterials, micro-arc oxidation technology can prepare a micron-sized morphology of oxide layer on the medical titanium alloy materials.2. In the morphology characterization study, XRD test indicated that TiO2-NT iscomposed of amorphous TiO2, the oxide layer of MAOed specimens was mostlyconsist of rutile TiO2and anatase TiO2; Compared with MAO group and the controlgroup, the water contact angle of anodic oxidation group decreased obviously and thesurface free energy increased significantly (p <0.05), compared with the controlgroup, the water contact angle of MAO group decreased slightly and the surface freeenergy increased slightly (p <0.05).3. The attachment, proliferation and differentiation ability of osteoblasts on the surfaceof anodic oxidation specimens are significantly better than MAO group and thecontrol group (p <0.05); In the three groups treated by anodic oxidation, osteoblastson the70nm TiO2-NT had the best adherent and proliferation ability in the earlystage (p <0.05).4. Fluorescence microscope observation showed:4weeks after implantation, quantity ofnewly generated bone tissue and orange markers could be seen on the surfaces ofanodic oxidation group. However, less bone tissue and no orange markers could beseen on the specimen surface of MAO and the control group;8weeks afterimplantation, there were more new bone tissue in every group than in4weeks, andthe bone tissue on the surface of anodic oxidation group were more uniform anddenser.5. Histological analysis manifested: the newly generated bone tissue on specimensurface of every group increased as the time prolonged, more uniform and denserbone tissue could be seen on the surface of anodic oxidation group at4weeks,8weeks and12weeks after implantation.6. The implant push-out test showed: the maximum push-out force and the shearstrength of specimens in anodic oxidation group were significantly higher than thosein MAO group and the control group at2weeks,4weeks and12weeks afterimplantation (p <0.05); In the three groups treated by anodic oxidation, specimensprocessed with20V had the highest maximum push-out force and shear strength at2 weeks and4weeks after implantation (p <0.05); At2weeks after implantation, themaximum push-out force and the shear strength of specimens in micro-arc oxidationgroup were a little higher than those in the control group (p>0.05).Conclusion1. The anodic oxidation technique can successfully construct a nanometer-sizedmorphology with different diameter of TiO2Nano-tubes (20–100nm) on themedical titanium alloy materials; Micro-arc oxidation technology can preparea micron-sized morphology of oxide layer on the medical titanium alloy materials.2. According to the in vitro cell experiment, the TiO2-NT topography could significantlyenhance the attachment, proliferation and differentiation ability of osteoblasts and the70nm TiO2-NT had the best biological activity.3. On the basis of in vivo animal experiments, the TiO2-NT topography could promotethe bone formation at early stage and had better implant-bone interface bindingforce;70nm was the optimal diameter for bone osteogenesis on implant surface.4. TiO2-NT topography could significantly enhance the bioactive ability of medicalmetallic implants, and could promote the bone formation at early stage. Besides, invirtue of its excellent implant-bone interface binding force, we can conclude thatTiO2-NT topography is suitable for the preliminary clinical application. |
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