1. Department of Chemistry and Chemical Engineering; Applied Chemistry, Chalmers University of Technology; Göteborg 412 96 Sweden
2. Department of Prosthodontics; Faculty of Odontology, Malmö University; Malmö 205 06 Sweden
3. Department of Applied Physics; Biological Physics, Chalmers University of Technology; Göteborg 412 96 Sweden
4. Department of Chemistry and Molecular Biology; Biomedical Photonics, University of Gothenburg; Göteborg 412 96 Sweden
5. Department of Clinical Dentistry; University of Bergen; P.O. Box 7800 Bergen NO-5020 Norway