Eberhard Frisch1, Petra Ratka-Krüger2, Dirk Ziebolz3. 1. 1 Northern Hessia Implant Center, Hofgeismar, Germany. 2. 2 Department of Operative Dentistry and Periodontology, University of Freiburg, Freiburg, Germany. 3. 3 Department of Cariology, Endodontology, and Periodontology, University of Leipzig, Leipzig, Germany.