1. Department of Periodontology, The Nippon Dental University School of Life Dentistry at Tokyo, 1-9-20, Fujimi, Chiyoda-ku, Tokyo 1020071, Japan
2. Heartful Dental Clinic, 4-12-3, Mejirodai, Hachioji-shi, Tokyo 1930833, Japan
3. Lotus Dental Clinic, 3-13-11, Nishigotanda, Shinagawa-ku, Tokyo 1410031, Japan
4. Kawanabe Dental Clinic, T Building 1F, 4-21-4, Nishikojiya, Ota-ku, Tokyo 1440034, Japan