1. Unit of Periodontology; University College London Eastman Dental Institute; London UK
2. Department of Health Policy and Health Services Research; Boston University Henry M. Goldman School of Dental Medicine; Boston MA USA
3. Centre for Oral Clinical Research, Institute of Dentistry; Barts and The London School of Medicine and Dentistry, Queen Mary University of London; London UK
4. Department of Oral Biology; University at Buffalo, State University of New York; Buffalo NY USA
5. Department of Restorative Dentistry, Periodontology, Endodontology, Preventive and Pediatric Dentistry; Dental School of the University Medicine Greifswald; Greifswald Germany
6. UCL Library Services; University College London; London UK
7. Biostatistics Unit; University College London Eastman Dental Institute; London UK