1. Department of Oral Surgery and Implantology; Carolinum; Johann Wolfgang Goethe-University Frankfurt; Frankfurt Germany
2. Department of Periodontology; Institute of Odontology; The Sahlgrenska Academy at University of Gothenburg; Gothenburg Sweden
3. Department of Oral Surgery and Stomatology; ZMK School of Dentistry; University of Bern; Bern Switzerland
4. Department of Periodontics and Oral Medicine; University of Michigan School of Dentistry; Ann Arbor MI, USA