1. Department of Oral and Cranio-Maxillofacial Surgery, University of Heidelberg, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany
2. Institute of Medical Biometry, University of Heidelberg, Im Neuenheimer Feld 130.3, D-69120 Heidelberg, Germany
3. Department of Oral and Cranio-Maxillofacial Surgery, Saarland University Hospital, Kirrberger Straße, D-66424 Homburg, Germany