1. Department of Oral and Maxillofacial Surgery; University Medical Center Groningen; University of Groningen; Groningen The Netherlands
2. Department of Oral and Maxillofacial Surgery; Nij Smellinghe Hospital; Drachten The Netherlands
3. Dental School; Department of Fixed and Removable Prosthodontics; University Medical Center Groningen; University of Groningen; Groningen The Netherlands