1. Department of Periodontology, Operative and Preventive Dentistry; University Hospital Bonn; Bonn Germany
2. Faculty of Dentistry, The University of Sydney; Sydney Dental Hospital; Sydney Australia
3. Unit of Periodontology and International Centre for Evidence-Based Oral Health; UCL Eastman Dental Institute; London UK
4. Cochrane Oral Health; Division of Dentistry, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester; Manchester UK