1. Department of Dental and Oral Surgery, Zama General Hospital, Zama, Kanagawa 252-0011, Japan
2. Department of Community Oral Health, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
3. Department of Operative Dentistry, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
4. Department of Histology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
5. Nihon University Graduate School of Dentistry at Matsudo, Community Oral Health, Matsudo, Chiba 271-8587, Japan