1. Biological Science Laboratories, Kao Corporation, Tochigi, Japan
2. Materials Development Research Laboratories, Kao Corporation, Wakayama, Japan
3. Safety and Microbial Control Research Center, Kao Corporation, Tochigi, Japan
4. Health Care Products Research Laboratories No. 1, Kao Corporation, Tokyo, Japan
5. Department of Clinical Pathophysiology, Tokyo Dental College, Chiba, Japan
6. Department of Epidemiology and Public Health, Tokyo Dental College, Chiba, Japan