1. Department of Removable Prosthodontics and Geriatric Oral Health, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
2. Nihon University Graduate School of Dentistry at Matsudo, Removable Prosthodontics, Matsudo, Chiba 271-8587, Japan
3. Department of Dental Biomaterials, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan