1. Department of Hygiene, Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan
2. R&D Division, Hayashibara Co., Ltd., Naka-ku, Okayama 702-8006, Japan
3. Department of Pathophysiology-Periodontal Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Kita-ku, Okayama 700-0867, Japan