1. Nihon University Graduate School of Dentistry at Matsudo, Removable Prosthodontics, Matsudo, Chiba 271– 8587, Japan
2. Departments of Removable Prosthodontics, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271 – 8587, Japan
3. Departments of Dental Biomaterials, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271 – 8587, Japan