1. Department of Bacteriology, School of Dental Medicine; Tsurumi University; Tsurumi Yokohama, Kanagawa 230 Japan
2. The Second Department of Oral and Maxillofacial Surgery, School of Dental Medicine; Tsurumi University; Tsurumi Yokohama, Kanagawa 230 Japan
3. Department of Oral Biology, College of Dentistry; University of Florida; Gainesville FL U.S.A.