H Hasegawa1, S Masui2, H Ishihata3. 1. Department of Dentistry and Oral Surgery, Fukushima Medical University Hospital, Fukushima, Japan. Electronic address: hi612hasegawa@gmail.com. 2. Department of Clinical Research Center, Fukushima Medical University Hospital, Fukushima, Japan. 3. Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan.