1. Section of Periodontology; Faculty of Odontology; University Complutense of Madrid; Madrid Spain
2. Department of Dental Ecology; University of North Carolina at Chapel Hill School of Dentistry; Chapel Hill NC USA
3. Department of Periodontology; University of North Carolina at Chapel Hill School of Dentistry; Chapel Hill NC USA
4. Department of Applied Oral Sciences; The Forsyth Institute; Cambridge MA USA
5. Department of Dental Medicine; Karolinska Institute; Stockholm Sweden
6. Clinic of Fixed and Removable Prosthodontics and Dental Material Science; Center of Dental Medicine; University of Zürich; Zürich Switzerland