1. Department of Implant Dentistry; University of Loma Linda; Loma Linda California
2. ETEP (Etiology and Therapy of Periodontal Diseases) Research Group; University Complutense; Madrid Spain
3. Department of Periodontology; School of Dentistry; International University of Catalonia; Barcelona Spain
4. Department of Oral Surgery and Stomatology; ZMK School of Dentistry; University of Bern; Bern Switzerland