1. Ominato Medical Service Unit, Japan Maritime Self-Defense Force, Mutsu 035-0093, Japan
2. Department of Fixed Prosthodontics, School of Dentistry, Kanagawa Dental University, Yokosuka 238-8580, Japan
3. Department of Liberal Arts Education, School of Dentistry, Kanagawa Dental University, Yokosuka 238-8580, Japan
4. Department of Education Planning, School of Dentistry, Kanagawa Dental University, Yokosuka 238-8580, Japan