1. Department of Operative Dentistry and Periodontology; University Medical Center; Johannes Gutenberg University; Mainz Germany
2. Department of Cell Biology and Histology; Academic Medical Center; University of Amsterdam; Amsterdam The Netherlands
3. Private Practice; Fiorano al Serio Bergamo Italy
4. Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI); Johannes Gutenberg University; Mainz Germany
5. Accademia Toscana di Ricerca Odontostomatologica (ATRO); Florence Italy