1. King’s College London Dental Institute at Guy’s, King’s College and St. Thomas’ Hospitals, Division of Population and Patient Health, London, UK
2. Department of Oral and Maxillofacial Diseases, Faculty of Medicine, University of Helsinki, Helsinki, Finland
3. Department of Epidemiology and Public Health, University College London, London, UK
4. National Institute for Health and Welfare, Helsinki, Finland
5. Department of Oral Public Health, Institute of Dentistry, University of Eastern Finland, Kuopio, Finland
6. Department of Oral and Maxillofacial Surgery, Kuopio University Hospital, Kuopio, Finland