1. Nihon University Graduate School of Dentistry at Matsudo, Special Needs Dentistry, Matsudo, Chiba 271-8587, Japan
2. Department of Special Needs Dentistry, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
3. Department of Microbiology and Immunology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271- 8587, Japan