[1] Univ Torino, Dept Maxillofacial Surg, Turin, Italy
[2] Univ Michigan, Dept Periodont & Oral Med, Ann Arbor, MI 48109 USA
[3] Univ Bern, Sch Dent Med, Dept Periodontol, Freiburgstr 7, CH-3010 Bern, Switzerland
[4] Copenhagen Univ Hosp, Dept Oral & Maxillofacial Surg, Rigshosp, Copenhagen, Denmark