1. Departments of Clinical Dentistry and
2. Biomedicine, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway
3. Department of Periodontology, The Forsyth Institute, Cambridge, MA, USA
4. Department of Periodontics, University of Science and Technology, Khartoum, Sudan
5. Division of Periodontology, Department of Oral Medicine, Infection, and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
6. Oral Health Centre of Expertise in Western Norway, Hordaland, Bergen, Norway