1. Department of Oral Implantology and Prosthetic Dentistry at the Academic Centre for Dentistry Amsterdam (ACTA); Amsterdam The Netherlands
2. University of Zurich, Dental Materials Unit, Center for Dental and Oral Medicine; Clinic for Fixed and Removable Prosthodontics and Dental Materials Science; Zurich Switzerland
3. Department of Buccofacial Prostheses (Stomatology I); Faculty of Odontology, Complutense University of Madrid; Madrid Spain