1. Department of Preventive Dentistry, Academic Field of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan
2. Department of Preventive Dentistry, Okayama University Hospital, Okayama 700-8558, Japan
3. Department of Foods and Human Nutrition, Notre Dame Seishin University, Okayama 700-0013, Japan