Journal of Biomaterials and Nanobiotechnology, 2013, 4, 229-236 http://dx.doi.org/10.4236/jbnb.2013.43028 Published Online July 2013 (http://www.scirp.org/journal/jbnb) 229 Influence of Alloy Elements on the Osteoconductivity of Anodized Ti-29Nb-13Ta-4.6Zr Alloy Dai Yamamoto 1 , Atsushi Waki 1 , Kensuke Kuroda 2 , Ryoichi Ichino 2 , Masazumi Okido 2 , Masato Ueda 3 , Masahiko Ikeda 3 , Mitsuo Niinomi 4 , Azusa Seki 5 1 Department of Materials Science & Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Japan; 2 EcoTopia Science Institute, Nagoya University, Nagoya, Japan; 3 Faculty of Chemistry, Materials and Bioengineering, Kansai University, Suita Japan; 4 Institute for Materials Research, Tohoku University, Sendai, Japan; 5 Hamri Co., Ltd., Tokyo, Japan. Email: yamamoto@f2.numse.nagoya-u.ac.jp Received March 31 st , 2013; revised May 20 th , 2013; accepted June 6 th , 2013 Copyright © 2013 Dai Yamamoto et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Anodizing is expected to be an effective method to improve the osteoconductivity of the Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy because the bioactivity of anodized Ti is good. However, it is not known how the alloy elements influence the surface roughness, composition, hydrophilicity, and osteoconductivity of the anodized film on the Ti alloy. In this study, we investigated the effects of anodizing on the surface properties and the osteoconductivity of the anodized TNTZ alloy, focusing on the functions of the individual alloy elements. The anodized oxides of the Nb, Ta, and Zr metals were hy- drophobic at all the voltages applied, in contrast to the anodized oxide of Ti. As well as pure Ti, a TiO 2 -based oxide film formed on TNTZ after anodizing. However, the oxide film also contained large amounts of Nb species and the molar Nb/Ti ratio in the TNTZ alloy was high, which makes the surface more hydrophobic than the anodized oxide on Ti. In vivo tests showed that the osteoconductivity of the TNTZ alloy was sensitive to both its surface roughness and hydrophilicity. When the TNTZ alloy was anodized, the process increased either the surface hydrophobicity or the sur- face roughness at the voltage used in this study. These changes in the surface properties did not improve its osteocon- ductivity. Keywords: Ti-29Nb-13Ta-4.6Zr; Anodizing; Titanium Dioxide; Alloy Element; Hydrophilicity; Osteoconductivity 1. Introduction A new single β type Ti alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), has been developed for biomedical applications [1,2]. Because this alloy has a lower Young’s modulus than pure Ti or conventional Ti alloys, such as the Ti- 6Al-4V alloy, the use of this alloy as a bone substitute is expected to suppress the bone resorption caused by the stress shielding effect, which arises when the Young’s modulus of the implant material is higher than that of natural bone. However, despite its improved mechanical biocompatibility, the problem remains that the osteocon- ductivity of TNTZ is as low as that of pure Ti and the Ti- 6Al-4V alloy [3]. Therefore, surface modification is re- quired to change the surface chemical properties of the TNTZ alloy to improve its osteoconductivity. Hydroxyapatite (HAp) coatings are widely used as a conventional surface modification for pure Ti to improve its osteoconductivity [4-12]. The anodizing process has also been investigated as a chemical surface treatment for pure Ti, and improves the osteoconductivity of Ti as much as HAp coatings do, by forming a TiO 2 film [13, 14]. Previous studies have shown that the chemical prop- erties of TiO 2 films, such as the surface roughness [13,15] crystal structure and crystallinity of TiO 2 [13,16,17] film thickness [13,18] and hydrophilicity [14,19,20] can differ depending on the anodizing conditions, resulting in dif- ferent osteoconductivities. In particular, a fine and hydro- philic surface was found to be better for the early fixation of bone onto anodized TiO 2 coatings. However, when we anodized the TNTZ alloy, Nb, Ta, and Zr are also contained in the oxide coating in addition to Ti [3] which may disturb the formation of a TiO 2 film on the TNTZ alloy. It is unclear how the alloy elements influence the surface roughness, composition, hydrophili- city, and osteoconductivity of the anodized film on the Ti alloy. Therefore, we investigated the influence of the Nb, Ta, and Zr species on the surface properties of the ano- dized TNTZ alloy in an aqueous solution of H 2 SO 4 , by Copyright © 2013 SciRes. JBNB