1. Oral and Maxillo-Facial Prosthodontics, Section of Prosthodontics, Department of Biomedical and Neuromotor Science, Alma Mater Studiorum University of Bologna, Bologna, Italy.
2. Department of Management and Engineering, University of Padova, Vicenza, Italy.
3. Department of Statistical Sciences, Alma Mater Studiorum University of Bologna, Bologna, Italy.