1. Department of Orthodontics and Dentofacial Orthopedics; University of Bern; Bern Switzerland
2. Section of Periodontology; University of Aarhus; Aarhus Denmark
3. Robert K. Schenk Laboratory of Oral Histology; University of Bern; Bern Switzerland
4. Department of Periodontology; Faculty of Odontology; Malmö University; Malmö Sweden