1. Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/163 MC, 1060 Vienna, Austria
2. Christian-Doppler-Laboratory for Photopolymers in Digital and Restorative Dentistry, Getreidemarkt 9, 1060 Vienna, Austria
3. Ivoclar Vivadent AG, 9494 Schaan, Liechtenstein
4. Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria