1. Departments of Periodontology, Institute of Dental Surgery, 256 Gray's Inn Road, London, WC1X 8LD, UK
2. Department of Oral Medicine and Pathology, United Medical and Dental Schools, Guy's and St Thomas's Hospitals, London Bridge, London, SE1 9RT, UK
3. Departments of Community Dental Health, Institute of Dental Surgery, 256 Gray's Inn Road, London, WC1X 8LD, UK