1. Department of Clinical Dentistry, Faculty of Medicine University of Bergen Bergen Norway
2. Tandvårdsenheten Region Östergotland Linköping Sweden
3. Tandvårdsenheten Region Örebro län Örebro Sweden
4. Department of Dentistry Örebro Sweden
5. Research Department of Epidemiology and Public Health, WHO Collaborating Center for Oral Health Inequalities and Public Health University College London London UK