1. Institute of Clinical Dentistry, University of Tromsø, Tromsø, Norway
2. Institute of Dentistry, University of Oulu, Oulu
3. Oral and Maxillofacial Department, Oulu University Hospital, Oulu
4. Department of Oral and Maxillofacial Surgery, Surgical Hospital, Helsinki and Uusimaa Hospital District, Helsinki
5. Health Centre of Kirkkonummi, Kirkkonummi, Finland