1. Division of Periodontology, Department of Oral Biological Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
2. Shimizu Dental Clinic, Takasaki, Japan
3. General Dentistry and Clinical Education Unit, Niigata University Medical and Dental Hospital, 2-5274 Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan
4. Food Science & Technology Institute, Morinaga Milk Industry Co., Ltd., Zama, Japan