1. Section of Graduate Periodontology; University Complutense; Madrid Spain
2. ETEP (Etiology and Therapy of Periodontal Diseases) Research Group; University Complutense; Madrid Spain
3. Department of Oral Surgery; Universitätsklinikum Düsseldorf; Düsseldorf Germany
4. Department of Oral Surgery and Implantology; Carolinum; Johann Wolfgang Goethe-University Frankfurt; Frankfurt Germany
5. Clinic of Fixed and Removable Prosthodontics and Dental Material Science; University of Zurich; Zurich Switzerland