| Objective:Comparing the influence of different oxidation time on the structural properties of the titanium surface to explore the feasibility and superiority of the micro-arc oxidation (MAO) applied to the implant surface treatment.Methods:50 TA2 titanium plates with specification of 24mm×1.0mm were chosen and numbered randomly.40 were randomly chosen as experimental group, which were given micro-arc oxidation treatment. They were divided into four groups, namely, MAO-5、MAO-10、MAO-20 and MAO-30, according to different oxidation time(5minutes, 10minutes,20minutes and 30minutes). Ten titanium plates left were control group without micro-arc oxidation treatment. Sample surface morphology observation, roughness detection, composition and structure analysis were done by using scanning electron microscope (SEM), surface roughness tester, X-ray diffraction (XRD)and energy dispersive X-ray spectrometer (EDX). The data were statistically analyzed.Results:(1) Surface film of titanium plates in the experimental group presented gray-white and gritty appearance, with no metallic luster. While titanium plates in the control group showed bright and smooth surface, with silver metallic luster.(2) Surface views of titanium films in the experimental group under SEM were porous and honeycomb, with a three-layered section:the skin layer was loose while the inner layer was dense. Pores on the film were small and evenly distributed in MAO-5 group, while pores were bigger with uneven distribution in MAO-10 group; pores in MAO-20 group were very different in sizes, with ridgy rim like craters; pores in MAO-30 group were much bigger and overlapping, with uneven distribution, and sintering particles and liquation could be observed on the surface film. Surface of titanium plates in the control group appeared roughly parallel grooves under SEM.(3) Surface roughness measurements of titanium plates in the experimental group were (0.70±0.51)μm, (1.21±0.57)μm, (1.42±0.55)μm and (1.60±0.81)μm for the corresponding MAO-5. MAO-10, MAO-20 and MAO-30 group, while that in the control group was (0.32±0.33)μm. Surface roughness measurements were significantly different among the four MAO groups as well as between the experimental and control groups.(4) Titanium, oxygen, calcium and phosphorus elements were detected in the surface film of titanium plates in the experimental group, while no calcium and phosphorus elements in the control group. The ratios of atoms of calcium to phosphorus were 0.95,1.47,1.63 and 1.96 for group MAO-5, MAO-10, MAO-20 and MAO-30 respectively.(5) With the oxidation time extended, the diffraction peaks of rutile and anatase titanium dioxide in the micro-arc oxidation film were weakened, while the diffraction peak of crystal hydroxyapatite was enhanced. No diffraction peak of crystal hydroxyapatite was observed in the control group.Conclusions:(1) Micro-arc oxidation (MAO) films can form after different treated time (10min to 30min) at a voltage of 450 V in the electrolyte contained calcium acetate and sodium dihydrogen phosphate.(2) Different oxidation time has significant influence on pore size, morphology and thickness of the titanium film.(3) Surface roughness of the titanium plates is increased after micro-arc oxidation treatment, and will increase with the oxidation time prolonged.(4) The ratios of atoms of calcium to phosphorus is 1.63 in the micro-arc oxidation film, which is similar to that of hydroxyapatite in human body.(5) Surface film after micro-arc oxidation treatment contains rutile and anatase titanium dioxide as well as crystal hydroxyapatite.(6) The micro-arc oxidation (MAO) technology has certain advantages and feasibility in improving the surface properties of titanium implant. |
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