1. Department of Oral and Maxillofacial Surgery; Hannover Medical School; Carl-Neuberg-Strasse 1 30625 Hannover Germany
2. Institute for Biostatistics; Hannover Medical School; Carl-Neuberg-Strasse 1 30625 Hannover Germany
3. Ursapharm Arzneimittel GmbH; Industriestraße 35 66129 Saarbrücken Germany