1. Department of Oral and Maxillofacial Surgery, Unnan City Hospital, Unnan 699-1221, Japan
2. Department of Oral and Maxillofacial Surgery, Faculty of Medicine, Shimane University, Izumo 693-8501, Japan
3. Department of Community Care, Unnan City Hospital, Unnan 699-1221, Japan
4. Department of Community Medicine Management, Faculty of Medicine, Shimane University, Izumo 693-8501, Japan