[1] Univ Bonn, Dept Periodontol Operat & Prevent Dent, Welschnonnenstr 17, D-53111 Bonn, Germany
[2] Univ Iuliu Hatieganu, Dept Prosthet Dent, Str Clinicilor 32, Cluj Napoca 400006, Romania
[3] Philipps Univ Marburg, Dept Periodontol & Peri Implant Dis, Georg Voigt Str 3, D-35033 Marburg, Germany
[4] Univ Bonn, Inst Med Biometry Informat & Epidemiol, Venusberg Campus 1, D-53127 Bonn, Germany
[5] Periodontal Private Practice Periodontol, Gheorghe Doja Str 9, Cluj Napoca 400068, Romania
[6] Univ Bern, Dept Periodontol, Freiburgstr 7, CH-3010 Bern, Switzerland