1. Department of Periodontology, Laboratory of Oral Microbiology, School of Dental Medicine, University of Bern, Freiburgstrasse 7, 3010 Bern, Switzerland
2. Center of Electron Microscopy, University Hospital of Jena, Ziegelmühlenweg 1, 07743 Jena, Germany
3. Heraeus Medical GmbH, Philipp-Reis-Str. 8/13, 61273 Wehrheim, Germany