1. University of Pennsylvania, School of Dental Medicine, 4001 Spruce Street, Philadelphia, PA 19104
2. Harvard University, School of Dental Medicine, Boston, MA, University of Berne, School of Dental Medicine, Berne, Switzerland
3. University of Lausanne, Department of Experimental Physics, Lausanne, Switzerland
4. University of Hamburg, Institute of Pathology, Hamburg, Germany
5. University of Berne, School of Dental Medicine, Berne, Switzerland
6. Harvard University, School of Dental Medicine, Boston, MA