1. Department of Physiology, Nihon University School of Dentistry, 1-8-13 Kanda-surugadai, Chiyoda-ku, Tokyo 101-8310, Japan
2. Division of Functional Morphology Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-surugadai, Chiyoda-ku, Tokyo 101-8310, Japan