1. Oral Medicine and Periodontology Department, Faculty of Oral and Dental Medicine Cairo University Giza Egypt
2. Clinic for Conservative Dentistry and Periodontology, School of Dental Medicine Christian Albrechts University Kiel Germany
3. Department of Periodontology, Operative and Preventive Dentistry University of Bonn Bonn Germany
4. Department of Periodontology and Peri‐implant Diseases Philips University Marburg Marburg Germany
5. Clinic for Prosthetic Dentistry University Iuliu‐Hatieganu Cluj‐Napoca Romania
6. Department of Periodontology University of Bern Bern Switzerland