1. Department of Prosthodontics, Peking University School and Hospital of Stomatology, National Clinical Research Center for Oral Diseases, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital StomatologyBeijing P.R. China
2. Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine University of Zurich Zurich Switzerland