1. Department of Oral and Maxillofacial Surgery University of Tsukuba Hospital Tsukuba Ibaraki Japan
2. Department of Oral and Maxillofacial Surgery Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba Tsukuba Ibaraki Japan
3. Department of Oral and Maxillofacial Surgery Ibaraki Prefectural Central Hospital, Ibaraki Cancer Center, Kasama Ibaraki Japan
4. Center for Medical Education and Training University of Tsukuba Hospital Tsukuba Ibaraki Japan
5. Department of oral and Maxillofacial Surgery, School of Dental Medicine Tsurumi University Yokohama Kanagawa Japan