[1] Univ Turku, Inst Dent, Dept Periodontol, FIN-20520 Turku, Finland
[2] Natl Inst Hlth & Welf, Dept Infect Dis Surveillance & Control, Helsinki, Finland
[3] Univ Helsinki, Dept Periodontol, Inst Dent, SF-00300 Helsinki, Finland
[4] Univ Helsinki, Cent Hosp, Dept Oral & Maxillofacial Surg, Helsinki, Finland