1. Department of Periodontology, Institute of Dentistry, University of Turku, 20500 Turku, Finland
2. Welfare Division, Oral Health Care, 20101 Turku, Finland
3. Finnish Institute for Health and Welfare, 00271 Helsinki, Finland
4. Institute of Dentistry, University of Eastern Finland, 70211 Kuopio, Finland
5. Oral Health Services, 33101 City of Tampere, Finland