1. Department of Public Health, University of Helsinki, Helsinki, Finland
2. Social and health bureau, Espoo, Finland
3. Department of Oral and Maxillofacial Diseases, Head and Neck Center, University of Helsinki, Helsinki, Finland
4. Department of Oral and Maxillofacial Diseases, Helsingin yliopisto, Tampere, Finland
5. Social and health bureau, Vantaa, Finland