1. Department of Oral and Plastic Maxillofacial Surgery, Heinrich Heine University Hospital Düsseldorf, Moorenstraße 5, 40225 Düsseldorf, Germany
2. Brainlab AG, Olof-Palme-Str. 9, 81829 München, Germany
3. Department of Oral and Maxillofacial Surgery, National Dental Centre Singapore, 5 Second Hospital Ave., Singapore 168938, Singapore