1. Division of Oral Molecular Microbiology; Hokkaido University Graduate School of Dental Medicine; Sapporo; Japan
2. Department of Oral Microbiology; Showa University School of Dentistry; Tokyo; Japan
3. Division of Oral Functional Prosthodontics; Department of Oral Pathobiological Science; Hokkaido University Graduate School of Dental Medicine; Sapporo; Japan