1. Institute of Inorganic Chemistry; Technische Universität Graz; Stremayrgasse 9/IV 8010 Graz Austria
2. Institute of Physical and Theoretical Chemistry; Technische Universität Graz; Austria
3. Institute of Applied Synthetic Chemistry and Christian Doppler Laboratory for Photopolymers in Digital and Restorative Dentistry; Technische Universität Wien; Austria
4. Ivoclar Vivadent AG; Schaan Liechtenstein