1. Unit of Periodontology; Department of Restorative Dentistry, Periodontology, and Endodontology; University Medicine Greifswald; Ernst Moritz Arndt University Greifswald; Greifswald Germany
2. Department of Periodontology and Oral Implantology; Temple University School of Dentistry; Philadelphia PA USA
3. Department of Oral Surgery; School of Dentistry; College of Medical and Dental Sciences; University of Birmingham; Birmingham UK
4. Division of Health and Nutrition Examination Surveys; National Center for Health Statistics; Centers for Disease Control and Prevention (CDC); Hyattsville MD USA
5. Eastman Dental Institute; University College London; London UK
6. King's College London Dental Institute; London UK
7. Centre for Professional Practice; University of Kent; Kent UK
8. Division of Population Health; National Center for Chronic Disease Prevention and Health Promotion; Centers for Disease Control and Prevention; Atlanta GA USA
9. Section of Oral and Diagnostics Sciences; Division of Periodontics, College of Dental Medicine; Columbia University; New York NY USA