1. School of Dental Medicine University of Pennsylvania Philadelphia PA USA
2. Leonard Davis Institute of Health Economics University of Pennsylvania Philadelphia PA USA
3. Division of Epidemiology and Community Health School of Public Health University of Minnesota Minneapolis MN USA
4. Department of Epidemiology Mailman School of Public Health Columbia University New York NY USA
5. Herbert Irving Comprehensive Cancer Center Columbia University New York NY USA
6. Division of Periodontics Section of Oral and Diagnostic Sciences College of Dental Medicine Columbia University New York NY USA