1. Department of Epidemiology and Health Promotion, New York University College of Dentistry, 250 Park Avenue South—6th Floor, New York, NY 10003-1402, USA
2. Department of Oral Medicine, King's College London, Denmark Hill Campus, London SE5 9RW, UK
3. Department of Clinical Biochemistry, King's College London, Denmark Hill Campus, London SE5 9RW, UK
4. The Welcome Trust Centre for the History of Medicine at UCL, 210 Euston Road, London NW1 2BE, UK