1. The Public Dental Health Service Competence Centre of Northern Norway Tromsø Norway
2. Department of Community Medicine, Faculty of Health Sciences UiT The Arctic University of Norway Tromsø Norway
3. Department of Clinical Dentistry, Faculty of Health Sciences UiT The Arctic University of Norway Tromsø Norway
4. Clinic of Periodontology, The Public Dental Service Region Västra Götaland Skövde Sweden
5. Department of Periodontology, Institute of Odontology, The Sahlgrenska Academy University of Gothenburg Gothenburg Sweden