1. Department of Preventive Sciences, University of Minnesota School of Dentistry, Minneapolis, MN.
2. Craniofacial Epidemiology and Genetics Branch, National Institute of Dental and Craniofacial Research, Bethesda, MD.
3. Clinical Research Center for Periodontal Diseases, School of Dentistry, Virginia Commonwealth University, Richmond, VA.
4. Department of Periodontics, University of Maryland School of Dentistry, Baltimore, MD.