Papers by Author: Masazumi Okido

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Authors: Dai Yamamoto, Kensuke Kuroda, Ryoichi Ichino, Masazumi Okido
Abstract: Titanium and Ti alloys are widely used as substitutional materials for natural bone because of their good biocompatibility, high strength, and high corrosion resistance. In our previous studies, TiO2 coating on Ti with Ra (arithmetical means of roughness) < 0.1 μm formed by anodizing had much higher osteoconductivity than that of pure Ti. It can be expected that TiO2 coating with fine surface can improve the osteoconductivity of Ti alloys. In this study, the effects on the osteoconductivity of TiO2 coatings on different kinds of Ti alloys were investigated by in vivo study. TiO2 coatings with Ra < 0.1 μm were formed on 4 kinds of Ti alloys (Ti-6Al-4V (Ti64), Ti-6Al-7Nb (Ti67), Ti-29Nb-13Ta-4.6Zr (TNTZ), Ti-13Cr-1Fe-3Al (TCFA)) using anodizing in H3PO4 aqueous solution. Surface properties of these coatings were evaluated using SEM, XRD, and XPS. In in vivo study, samples were implanted in rats’ tibia for 14 days, and then removed. Cross section of the sample was observed with optical microscope and bone-implant contact ratio (RB-I) at the interface between body tissue and bone was used as a parameter of osteoconductivity. Anatase type TiO2 coatings with Ra < 0.1 μm were uniformly formed on all of the Ti alloys by anodizing at low voltage. These oxide coatings contained the ions of other alloy elements. TiO2 coatings on Ti64 and Ti67 indicated high osteoconductivity similar to that of TiO2 coating on pure Ti. On the contrary, TiO2 coating on TNTZ and TCFA showed low osteoconductivity. It was thought that ions of alloy elements brought bad influence on the osteoconductivity of TiO2.
Authors: S.J. Kim, Ryoichi Ichino, Masazumi Okido
Authors: K. Inoue, Kensuke Sassa, Yoshiyuki Yokogawa, Yoshio Sakka, Masazumi Okido, Shigeo Asai
Authors: S.A. Salman, N. Akira, Kensuke Kuroda, Masazumi Okido
Abstract: Self-assembled monolayer (SAM) was adsorbed on the surface of vanadate conversion coated AZ31 magnesium alloy. The SAM thin film was deposited using (Tridecafluoro-1, 1, 2, 2-tetrahydrooctyl) trimethoxysilane (FAS13) and Tetrakis (trimethylsiloxy) titanium as a catalyst. Contact angles measurement, SEM, XRD, EDS and XPS were employed to analyze the surface morphologies, molecular composition, phase structure and wettability of the coatings formed on Mg alloy substrate. Corrosion resistance property of the coatings was also examined using the anodic polarization method and salt spray test. The anticorrosion property was improved with SAM post treatment. Furthermore, the contact angle increases from 12 deg. to 165 deg. indicating to production of super hydrophobic surface with SAM post treatment.
Authors: Masazumi Okido, Ryoichi Ichino, Kotaro Kuroda
Abstract: Hydroxyapatite (Ca10(PO4)6(OH)2, HAp), carbonated HAp and titanium oxide are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants and investigated the in vitro and in vivo performance. HAp coatings were performed by the thermal substrate method in aqueous solutions. Titanium oxide film was also formed on the titanium implants by gaseous oxidation, or by anodizing in the acidic solution. All the specimens covered with HAp, carbonated HAp or TiO2 (rutile or anatase). were characterized by XRD, EDX, FT-IR and SEM. In the in vitro testing, the mouse osteoblast-like cells (MC3T3-E1) were cultured on the coated and non-coated specimens for up to 30 days. Moreover, the osseointegration was evaluated from the rod specimens implanted in rats femoral for up to 8 weeks. In in vivo evaluations two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, in order to evaluate of new bone formation, was significantly depended on the compound formed on the titanium implant.
Authors: Kotaro Kuroda, Yukio Miyashita, Ryoichi Ichino, Masazumi Okido
Authors: Kotaro Kuroda, Ryoichi Ichino, Masazumi Okido
Abstract: Hydroxyapatite (HAp) coatings were formed on cp titanium plates and rods by the thermal substrate method in an aqueous solution that included 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2. The coating experiments were conducted at 40-140 oC and pH = 8 for 15 or 30 min. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. All the specimens were covered with HAp, which had different surface morphologies such as net-like, plate-like and needle-like. After cleaning and sterilization, all the coated specimens were subjected to in vivo and vitro testing. In the in vitro testing, the mouse osteoblast-like cells (MC3T3-E1) were cultured on the coated and non-coated specimens for up to 30 days. Moreover, the specimens (φ2 x 5 mm) were implanted in rats femoral for up to 8 weeks, the osseoinductivity on them were evaluated. In in vitro evaluations, there were not significant differences between the different surface morphologies. In in vivo evaluations, however, two weeks postimplantation, new bone formed on both the HAp coated and non-coated titanium rods in the cancellous and cortical bone. The bone-implant contact ratio, which was used for the evaluation of new bone formation, was significantly dependent on the surface morphology of the HAp, and the results demonstrated that the needle-like coating appears to promote rapid bone formation.
Authors: Kensuke Kuroda, Ryoichi Ichino, Masazumi Okido
Abstract: In this study, anodizing of Ti in the various concentration of H3PO4 aqueous solutions gave TiO2 films, and the osteoconductivity was examined using in vivo testing. In the anodizing treatment, anodizing potential of < 200 V was applied to the Ti substrate in H3PO4 aqueous solutions with the concentration of 0.1 to 14 M at 298 K. The coatings were evaluated using SEM, XRD, FT-IR and XPS. In in vivo testing, the coated samples were implanted in the rats’ tibia for 14 d to evaluate the osteoconductivity. In H3PO4 aqueous solutions with any concentration, anatase-type TiO2 films were obtained on the Ti substrate by anodizing. The crystallinity of anodized TiO2 films depended on the concentration of H3PO4 and sparking. In less than 2 M H3PO4, anatase with high crystallinity was formed. On the other hand, anodizing with sparking in more than 4 M H3PO4, gave low crystallinity anatase film. In in vivo testing, osteoconductivity of the coatings with low crystallinity anatase was much higher than that with high crystallinity.
Authors: Kensuke Kuroda, Mansjur Zuldesmi, Masazumi Okido
Abstract: Anti-corroded valve metals, such as Ti, Nb, Ta, and Zr have been used as metallic biomaterials. However, as untreated surfaces, they do not have high osteoconductivity, and surface coatings with bioactive substances are needed for the implantation into the bone. Surface property, especially hydrophilicity, is considered to have a strong influence on the biological reactions. However, the influence of a hydrophilic surface on osteoconductivity is not completely clear. In this study, we produced super-hydrophilic surface on valve metals (Ti, Nb, Ta and Zr) using a hydrothermal treatment at 180 °C for 180 min. in the distilled water, and then the treated samples were stored in 5PBS(-). This maintained water contact angle less than 10 (deg.) in an apparent. The osteoconducivity of super-hydrophilic treated metals was evaluated with in vivo tests. The hard tissue formation on the samples increased with decreasing the water contact angle. That is to say that super-hydrophilic valve metals without coating of bioactive substances had high osteoconductivity, and the surface properties strongly affected on the osteoconductivity.
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