1. Department of Fixed Prosthodontics, Kanagawa Dental University, Yokosuka 238-8580, Japan
2. Institute of Medical Sciences, Tokyo Medical University, Shinjuku 160-8402, Japan
3. Institute for Advanced Biosciences, Keio University, Tsuruoka 997-0052, Japan
4. Department of Education Planning, Kanagawa Dental University, Yokosuka 238-8580, Japan