1. School of Dentistry, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
2. School of Oral Health Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Johannesburg, South Africa
3. Department of Radiation Oncology, University of the Witwatersrand, Johannesburg and Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa