Radiotherapy to the head and neck region has oral side effects and can lead to catastrophic dental deterioration, but this is largely preventable. This article describes the case of a patient whose dentition was irreparably compromised after radical radiotherapy for a soft palate cancer. The patient had a fairly well maintained dentition at the pre-radiotherapy dental screen, but the side effects of radiotherapy – notably dry mouth and reduced access to the mouth for cleaning – coupled with a high-sugar diet intended to aid recovery, led to the rapid progression of dental caries and tooth wear. Additionally, service restrictions due to the coronavirus disease 2019 pandemic meant that his dental care was delayed. Eight months after completion of radiotherapy, all his teeth were deemed unrestorable. The authors discuss the importance of frequent and regular dental reviews to prevent rapid dental deterioration in patients undergoing radiotherapy for head and neck cancer.