1. Department of Oral and Maxillofacial Surgery, Massachusetts General
Hospital and Harvard School of Dental Medicine, 55 Fruit Street, Warren 1201, Boston,
MA 02114;
2. Department of Oral Health Policy and Epidemiology, Harvard School of
Dental Medicine, 188 Longwood Avenue, Boston, MA 02115; and
3. Department of Biostatistics, Harvard School of Public Health, 677
Huntington Avenue, Boston, MA 02115;