1. Department of Biomedical, Surgical and Dental Science, University of Milan, Via Beldiletto 1, 20142 Milan, Italy
2. Department of Restorative Dentistry and Endodontology, Justus-Liebig-University Giessen, 35392 Giessen, Germany
3. Department of Restorative, Preventive and Pediatric Dentistry, University of Bern, Freiburgstrasse 7, 3012 Bern, Switzerland