1. The University of Manchester; School of Dentistry; Higher Cambridge Street Manchester UK M15 6FH
2. Ministry of Health, Bahrain; UKCC (Bahrain Branch); Box 25438 Awali Bahrain
3. Dental Department; Naval Medical Center San Diego; 1465 C Street Unit 3512 San Diego USA CA 92101
4. Institute for Quality and Efficiency in Health care; Department of Health Information; Dillenburger Street 27, D-51105 Cologne Germany D-51105
5. University College London Medical School; Department of Epidemiology and Public Health; 1-19 Torrington Place, Gower Street London UK WC1E 6BT
6. KCL Dental Institute; Division of Health and Social Care Research; Caldecot Road London UK SE5 9RW
7. School of Dentistry, The University of Manchester; Department of Oral and Maxillofacial Surgery; Higher Cambridge Street Manchester UK M15 6FH