1. Department of Oral and Maxillofacial SurgeryUniversity of Groningen GroningenThe Netherlands
2. Department of Pathology & Medical BiologyUniversity of Groningen GroningenThe Netherlands
3. Department of Otorhinolaryngology/Head & Neck SurgeryUniversity of Groningen GroningenThe Netherlands
4. Department of Epidemiology University Medical Centre Groningen, University of Groningen GroningenThe Netherlands
5. Department of Research Comprehensive Cancer Organization of The Netherlands (IKNL) Utrecht The Netherlands