1. Department of Removable Prosthodontics and Occlusion, Osaka Dental University, 8-1 Kuzuha-hanazono-cho, Hirakata 573-1121, Osaka, Japan
2. Department of Advanced Hard Materials, SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki 567-0047, Osaka, Japan
3. Department of Oral Health Engineering, Faculty of Health Sciences, Osaka Dental University, 1-4-4, Makino-honmachi, Hirakata 573-1121, Osaka, Japan