1. Clinic of Preventive Dentistry, Periodontology and Cariology, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
2. Department of Oral and Maxillofacial Diseases, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
3. Karolinska Institutet, Department of Dental Medicine, Division of Periodontology, Stockholm, Sweden
4. Institute of Molecular Diagnostics, Dentognostics GmbH, Solingen and Jena, Germany