A Villa1, L Strohmenger2, S Abati2, N S Treister1. 1. Division of Oral Medicine and Dentistry, Brigham and Women's Hospital, and Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, USA. 2. Dental Clinic, Department of Health Sciences and WHO Collaborating Centre of Milan for Epidemiology and Community Dentistry, University of Milan, Italy.