1. School of Dentistry Universita' di Ferrara; Ferrara Italy
2. Clinic of Fixed and Removable Prosthodontics and Dental Material Science; Center of Dental Medicine; University of Zurich; Zurich Switzerland
3. Akademie für Orale Implantologie; Private Practice; Vienna Austria
4. Aesthetic Dent; Private Practice; Szczecin Poland
5. University of Santiago de Compostela; Santiago de Compostela Spain
6. Division of Prosthodontics; School of Dental Medicine; University of Connecticut; Farmington CT USA