| Titanium and its alloy have excellent biocompatibility and processability, they are the most extensively used oral implant materials in clinic. However, the titanium implant shows some drawbacks in practice due to its inert surface, low bioactivity, long cicatrisation period, weak resistant to wear and corrosion. In order to gain better titanium implant, we need to improve the surface of Titanium. The experiments were done to make the surface of Titanium to be bioactive by microarc oxidation technique associated with the general principles of surface modification and the requests of clinical application. Then the experiments were done to evaluate biological performance of the new surface.Objectives: In order to improve the bioactivity of titanium implant, to improve its abrasion performance and corrosion resistant and to promote the early bonding of the implant with bone tissue, samples of titanium discs were treated in different electrolytes by microarc oxidation technology. 2 kinds of TiO2 coatings with different chemical composition were got and biological evaluation were investigated. We hope to provide a theory base for surface modification of titanium implant.Methods and Results1. Surface treatment of titanium implant by microarc oxidation and surface analysisMethods: Titanium discs were treated using microarc oxidation technology in 2 different electrolytes. Electrical parameters and composition of electrolytic solution were specially chosen according to microarc oxidation (MAO) theories and clinical requirements. 2 kind of TiO2 coatings including MAO-Ca coating and MAO-Mg coating were got. The surface morphology of the TiO2 coatings were observed with SEM, the element distribution and composition of them were analyzed with X-ray energy dispersive analysis (EDX) and X-ray diffraction (XRD). The bonding strength of TiO2 coatings to titanium substrate were measured with the scratch test. Surface roughness of the coatings was also investigated.Results: SEM observation indicated that ceramic coatings with compact inner layer and porous outer layer were deposited on the surface of titanium samples after MAO treatment in different electrolytics. EDX analysis showed that the 2 kind of ceramic coatings contained Ti, Ca, P, O and Ti, Mg, O elements respectively. The XRD analysis showed that the one coating was consist of rutile TiO2, anatase TiO2 and CaTiO3, the other coating was consist of rutile, anatase and MgTiO3.The bonding strength of MAO-Ca coating to substrate were 26.5 N, and the bonding strength of MAO-Mg coating to substrate were 28.7 N. The average surface roughness of MAO-Ca coating was 0.756μm and was 0.691μm for MAO-Mg coating.2. The apatite deposition on the surface of coating in simulated body fluidMethods: The samples with MAO-Ca coating and MAO-Mg coating were dipped into simulated body fluid (SBF). The surface morphology of samples were observed with SEM at 7, 14 and 21 day. EDX and XRD were used to analyze the construction and composition of the deposition.Results: SEM observation indicated that the surface of MAO-Ca coating was covered with a layer of needle-like deposition. EDX analysis showed that the deposition was composed of Ca and P elements. XRD analysis showed that the deposition was mainly hydroxyapatite (HA). However, no new deposition was found on the surface of MAO-Mg coating.3. The biological evaluation of MAO-Ca coating and MAO-Mg coating Methods: following experiments were carried out:(1) Haemolysis experiment;(2) Cytotoxicity experiment;(3) The osteoblast's attachment and proliferation experiment.Results: The haemolysis rates were 0.81% for MAO-Ca coating and 0.96% for MAO-Mg coating. The cell proliferation rates of L929 exceeded 80% and no cytotoxicity was found for both of coatings. The initial attachment rate of osteoblast on MAO-Ca coating and MAO-Mg coating were obviously higher than the pure titanium, while no significant difference was found between MAO-Ca coating and MAO-Mg coating. The MAO-Ca coating showed positive effect on facilitating the proliferation of osteoblast compared with the MAO-Mg coating and pure titanium. Conclusion:The TiO2 coating with compact inner layer and porous outer layer were constructed on the surface of titanium discs by microarc oxidation treatment. The Ca2+ and Mg2+ ion was entered into TiO2 coating by MAO treatment in different electrolyte. The biocompatibility and bioactivity of TiO2 coating were improved with Ca2+ and Mg2+ ion. Both of coating had no cytotoxicity, showed good biocompatibility and increased osteoblasts attachment rate. The MAO-Ca coating could induce the deposition of apatite on it in simulated body fluid. It also found that MAO-Ca coating could facilitate proliferation of osteoblast. |
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