1. Department of Reconstructive Dentistry, University Center for Dental Medicine Basel, University of Basel, 4058 Basel, Switzerland
2. Clinic of Reconstructive Dentistry, Center of Dental Medicine, University of Zurich, 8032 Zurich, Switzerland
3. Department of Prosthodontics and Biomaterials, Center of Implantology, RWTH University Hospital Aachen, 52074 Aachen, Germany