Z Shehabi1, C Flood2, L Matthew3. 1. Barts Health NHS Trust, Special Care Dentistry, Barts Health Dental Hospital, Department of Restorative Dentistry, London, E1 1BB. 2. School of Health Sciences City, University of London, Northampton Square, London, EC1V 0HB. 3. Aintree University Hospital NHS Foundation Trust, Lower Lane, Aintree Lower Lane, Aintree, Liverpool, L9 7AL.