1. Department of Oral Biology; Medical University of Vienna; Vienna Austria
2. Department of Preventive, Restorative and Pediatric Dentistry; School of Dental Medicine; University of Bern; Bern Switzerland
3. Clinic of Cranio-Maxillofacial and Oral Surgery; University of Zurich; Zurich Switzerland
4. Department of Oral & Maxillofacial Surgery; Red Cross Hospital; Kassel Germany