[1] Cairo Univ, Fac Oral & Dent Med, Oral Med & Periodontol Dept, Giza, Egypt
[2] Univ Kiel, Sch Dent Med, Clin Conservat Dent & Periodontol, Kiel, Germany
[3] Univ Bonn, Dept Periodontol Operat & Prevent Dent, Bonn, Germany
[4] Philips Univ Marburg, Dept Periodontol & Periimplant Dis, Marburg, Germany
[5] Univ Iuliu Hatieganu, Clin Prosthet Dent, Cluj Napoca, Romania
[6] Univ Bern, Dept Periodontol, Bern, Switzerland
[7] Christian Albrechts Univ Kiel, Sch Dent Med, Clin Conservat Dent & Periodontol, Arnold Heller Str 3,Haus 26, D-24105 Kiel, Germany