1. Department of Preventive Dentistry, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan.
2. Department of Dentistry, Japan Self Defense Forces Fukuoka Hospital, 1-61 Kokurahigashi, Kasuga-shi, Fukuoka 816-0826, Japan.
3. Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan.