1. Institute of Dentistry; University of Eastern Finland; Kuopio Finland
2. Oral Health Care; Social Services and Health Care; Department of Social Services and Health Care; Helsinki Finland
3. Oral and Maxillofacial Department; Kuopio University Hospital; Kuopio Finland
4. Research Unit of Oral Health Sciences; Faculty of Medicine; University of Oulu; Oulu Finland
5. Department of Oral and Maxillofacial Surgery; Medical Research Centre Oulu; Oulu University Hospital; Oulu Finland
6. Korea Education Fund; Pyongyang city Democratic People's Republic of Korea
7. Dental Faculty; Pyongyang Medical College; Kim Il Sung University; Pyongyang city Democratic People's Republic of Korea
8. Faculty of Health Sciences; University of Eastern Finland; Kuopio Finland