1. Department of Oral and Maxillofacial Diseases, Institute of Dentistry, Kuopio University Hospital, University of Eastern Finland, Kuopio, Finland;
2. Health and Social Bureau, City of Vantaa, Vantaa, Finland;
3. Institute of Dentistry, University of Turku, Turku, Finland;
4. Department of General Practising and Primary Care, University of Helsinki, Helsinki, Finland