1. Department of Anatomy, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
2. Department of Special Needs Dentistry, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
3. Department of Oral Function and Fixed Prosthodontics, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan