1. Research Unit of Oral Health Sciences, Faculty of Medicine, University of Oulu, Oulu, Finland;
2. Social Sciences, Faculty of Education, University of Oulu, Oulu, Finland;
3. Periodontology and Geriatric Dentistry, Research Unit of Oral Health Sciences, University of Oulu, Oulu, Finland;
4. Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland;
5. Kallio Public Health Care, Ylivieska, Finland