1. Department of Periodontology; Faculty of Odontology; University of Malmö; Malmö Sweden
2. Division of Oral Surgery; Bernhard Gottlieb School of Dentistry; Medical University of Vienna; Vienna Austria
3. Division of Conservative Dentistry and Periodontology; Bernhard Gottlieb School of Dentistry; Medical University of Vienna; Vienna Austria
4. Department of Statistics; Lund University School of Economics and Management; Lund University; Lund Sweden
5. Department of Oral Rehabilitation; School of Dentistry; Faculty of Health Sciences; University of Copenhagen; Copenhagen Denmark