1. University of Witwatersrand, Fir Avenue, Bantry Bay, Cape Town 2050, South Africa
2. Department of Community Dentistry, School of Dentistry, University of Pretoria, Pretoria 0084, South Africa
3. Department of Radiation Oncology, University of Witwatersrand, Johannesburg and Charlotte Maxeke Academic Hospital, Johannesburg 2193, South Africa
4. Department of Periodontics and Oral Medicine, School of Dentistry, Faculty of Health Sciences, University of Pretoria, Pretoria 0084, South Africa
5. Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, University of Pretoria, Pretoria 0084, South Africa