1. Department of Prosthodontics and Materials Science; School of Dentistry; University of Leipzig; Leipzig Germany
2. Department of Diagnostic and Biological Sciences; School of Dentistry; University of Minnesota; Minneapolis MN USA
3. Division of Epidemiology and Community Health; University of Minnesota; Minneapolis MN USA
4. Department of Pediatric Dentistry; School of Dentistry; University of Leipzig; Leipzig Germany
5. Department of Prosthetic Dentistry; School of Dentistry; University Medical Center Hamburg-Eppendorf; Hamburg Germany