1. Department of Oral and Maxillofacial Surgery; University Medical Center Groningen; University of Groningen; Groningen The Netherlands
2. Department of Dental Materials Science; Academic Centre for Dentistry Amsterdam (ACTA); Universiteit van Amsterdam and Vrije Universiteit; Amsterdam The Netherlands
3. Department of Fixed and Removable Prosthodontics; University Medical Center Groningen; University of Groningen; Groningen The Netherlands