1. Department of Oral and Maxillofacial Surgery, Head and Neck Cancer Center, University Hospital Schleswig-Holstein (Campus Lübeck), D-23562 Luebeck, Germany
2. Department of Oral and Maxillofacial Surgery, Helios Medical Center, D-19055 Schwerin, Germany
3. Division of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong