1. Department of Periodontology; Showa University School of Dentistry; Ohta-ku Tokyo Japan
2. Department of Oral Pathology and Diagnosis; Showa University School of Dentistry; Shinagawa-ku Tokyo Japan
3. Department of Periodontology; Kyushu Dental College; Kokurakita-ku Kitakyushu city Fukuoka Japan
4. Comprehensive Research Center of Oral Cancer; Showa University School of Dentistry; Shinagawa-ku Tokyo Japan