1. Danube Private University, Department for Posthetic Dentistry, Krems, Austria.
2. Danube Private University, Center for CAD/CAM and Digital Technologies, Krems, Austria.
3. Saarland University, Department for Posthetic Dentistry, Saarbrücken, Germany.
4. Charité-Universitätsmedizin Berlin, Department of Prosthodontics, Berlin, Germany.