1. Department of Periodontology, School of Dental Medicine University of Bern Bern Switzerland
2. Department of Oral and Maxillofacial Surgery Copenhagen University Hospital (Rigshospitalet) Copenhagen Denmark
3. Department of Periodontology and Operative Dentistry University Medical CenterUniversity of Mainz Mainz Germany
4. Department of Oral and Maxillofacial Surgery, School of Dentistry, Faculty of Health Sciences University of Copenhagen Copenhagen Denmark