1. Department of Prosthodontics, University of Ferrara, 44100 Ferrara, Italy
2. Apollonia s.r.l., Specialist Private Practice, 06061 Castiglione del Lago (PG), Italy
3. Centro Odontotecnico di Ortensi Gianni, 40126 Bologna, Italy
4. Laboratorio Odontotecnico Borromeo Carlo, 20831 Seregno (MB), Italy