1. Department of Biomaterials Graduate School of Medicine Dentistry and Pharmaceutical Sciences Okayama University 2‐5‐1 Shikata‐cho, Kita‐ku Okayama 700‐8558 Japan
2. Department of Comprehensive Dentistry Okayama University Hospital 2‐5‐1 Shikata‐cho, Kita‐ku Okayama 700‐8558 Japan
3. Department of Applied Chemistry and Biotechnology Faculty of Engineering Okayama University 3‐1‐1 Tsushimanaka, Kita‐ku Okayama 700‐8530 Japan
4. Department of Conservative Dentistry Division of Biomaterials and Engineering Showa University School of Dentistry 1‐5‐8 Hatanodai, Shinagawa‐ku Tokyo 142‐8555 Japan
5. Division of Materials and Manufacturing Science Graduate School of Engineering Osaka University 2‐1 Yamadaoka, Suita Osaka 565‐0871 Japan