1. Department of Periodontology and Geriatric Dentistry; Institute of Dentistry; University of Oulu; Oulu Finland
2. National Institute for Health and Welfare (THL); Kuopio Finland
3. Institute of Dentistry; University of Eastern Finland; Kuopio Finland
4. Oral and Maxillofacial Department; Kuopio University Hospital; Kuopio Finland
5. National Institute for Health and Welfare (THL); Turku Finland
6. Department of Oral and Maxillofacial; Oulu University Hospital; Oulu Finland