1. Department of Periodontology, Tokyo Dental College, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
2. Department of Microbiology, Tokyo Dental College, 2-1-14 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan
3. Oral Health Science Center, 2-9-18 Kanda-Misakicho, Chiyoda-ku, Tokyo 101-0061, Japan