1. Department of Orthodontics, Leeds Dental Institute, Clarendon Way, UK
2. Holywell House Orthodontics, Hinckley, Leicestershire, UK
3. Department of Orthodontics, St Luke’s Hospital, Bradford, UK
4. Department of Orthodontics, Montagu Hospital, Mexborough, Doncaster and Bassetlaw NHS Trust, UK
5. Department of Orthodontics, The Charles Clifford Dental Hospital, Sheffield, UK
6. Department of Biostatistics, School of Dentistry, University of Leeds, UK