1. Institute of Preventive Dentistry and Oral Microbiology, School of Dental Medicine, University of Basel, Hebelstrasse 3, CH-4056 Basel, Switzerland
2. Department of Hematology, University Hospital Basel, Switzerland
3. Department of Oral Medicine, Clinical Oral Physiology, Oral Pathology & Anatomy, University of Copenhagen, Denmark
4. Department of Hematology, Leiden University Medical Center, the Netherlands
5. Department of Periodontology, Endodontology and Cariology, School of Dentistry, University of Basel, Switzerland