1. Department of Dental Materials and Biomaterials Research RWTH Aachen University Hospital Pauwelsstrasse 30 52074 Aachen Germany
2. Institute for Molecular Biotechnology RWTH Aachen University Worringerweg 1 52074 Aachen Germany
3. Electron Microscopy Facility Institute of Pathology RWTH Aachen University Hospital Pauwelsstrasse 30 52074 Aachen Germany