1. School of Dentistry, The University of Manchester; Coupland III Building Oxford Road Manchester UK M13 9PL
2. The University of Manchester; School of Dentistry; Manchester UK
3. School of Dentistry, The University of Manchester; Cochrane Oral Health Group; Coupland III Building, Oxford Road Manchester UK M13 9PL
4. Faculty of Health Sciences, McMaster University; Centre for Health Economics and Policy Analysis, Department of Clinical Epidemiology and Biostatistics; 1280 Main Street West Hamilton Ontario Canada L8S 4K1
5. San Francisco School of Dentistry, University of California; Preventative and Restorative Dental Sciences, Suite 410; 3333 California Street San Francisco USA CA 94118
6. University of Oslo; Department of Community Dentistry; Box 1052 Blindern Oslo Norway 0316