1. Department of Prosthetic Dentistry, Dental Division, Faculty of Medicine , University of Ljubljana , Vrazov trg 2, 1000 Ljubljana , Slovenia
2. Department of Diagnostic and Biological Sciences, School of Dentistry , University of Minnesota , Minneapolis , USA
3. Biostatistical Design and Analysis Center, Clinical and Translational Science Institute , University of Minnesota , Minneapolis , USA
4. Department of Prosthodontics , University Dental Clinics, University Medical Center Ljubljana , Ljubljana , Slovenia