The effect of dental and salivary gland radiation dose on the occurrence of post-radiotherapy dental disease in patients with head and neck cancer

  • Ciaran Moore

Student thesis: Doctoral ThesisDoctor of Philosophy


Head and neck cancer (HANC) patients are at increased risk of post-radiotherapy dental caries and periodontitis due to radiation-related salivary gland hypofunction and direct radiation damage to dental and periodontal tissues, however, the exact aetiology is poorly understood. Patients’ non-compliance with preventive oral hygiene and dietary advice may also play a role. Robust research is therefore required to enhance knowledge in this area. In addition, the development of dental caries and periodontal disease can affect patients’ long-term quality of life, and dental extractions in irradiated patients may precipitate the debilitating condition of osteoradionecrosis. Current guidelines regarding the dental management of pre- and post-radiotherapy HANC patients lack an evidence-base and existing advice in relation to pre-radiotherapy dental extractions is vague and ambiguous.

The overall aim of this research programme was to address knowledge gaps in relation to disease aetiology and provide evidence that would inform the improvement of the dental care pathway for HANC patients.

The first ever systematic review and meta-analysis of post-radiotherapy dental caries incidence sourced data from 23 studies and determined that approximately one-third (29-37%) of head and neck radiotherapy patients are at risk of developing new carious lesions post-treatment. Moreover, meta regression analyses indicated that an increased incidence of post-radiotherapy dental caries may be associated with increased radiotherapy dose, and chemotherapy treatment in addition to radiotherapy.

A prospective cohort study of 151 HANC patients assessed at baseline (pre-radiotherapy), rendered dentally fit, and followed up at 6-months and 12-months post-radiotherapy, demonstrated that increased mean and maximum dental radiation doses at the dental-sextant level were both associated with an increased odds of post-radiotherapy dental caries after adjusting for potential confounding variables. The radiation dose exposures of the parotid glands, however, were found to have no impact on the incidence of post-radiotherapy dental caries or post-radiotherapy periodontitis. In addition, the continued consumption of dietary nutritional supplements and patients’ non-compliance with clinical oral hygiene and dietary advice for the prevention of post-radiotherapy dental disease, were also found to be associated with an increased incidence and severity of post-radiotherapy dental caries.

A separate qualitative investigation of a subgroup of participants (n=12) recruited to the prospective cohort study was also conducted, and determined that patients’ non-compliance with dietary sugar restriction and the use of high fluoride toothpaste may be related to issues regarding communication, inadequate supplies of preventive oral hygiene products, and treatment-related oral discomfort (e.g. oral mucositis).

Furthermore, a health economics study of costs associated with the management of pre- and post-radiotherapy dental disease was also completed – the first of its kind in the United Kingdom (UK) – and found that HANC patients experience two-three times greater personal dental treatment costs compared to patients from the general population. In addition, the micro-costings analysis also determined substantial healthcare service costs associated with the management of pre- and post-radiotherapy dental disease.

Finally, a three-round Delphi survey of 24 Consultants in Restorative Dentistry generated 89 consensus statements concerning the types of teeth that should be extracted prior to radiotherapy. The results of this Delphi study represent the majority view of Consultants in Restorative Dentistry in the UK and Ireland, and it is anticipated that they will be used to inform the development of national and international guidelines regarding the dental management of HANC patients.
Date of AwardDec 2023
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsHealth and Social Care (Northern Ireland) Research and Development & Royal College of Physicians & Surgeons of Glasgow
SupervisorCiaran O'Neill (Supervisor), Michael Donnelly (Supervisor) & Gerry McKenna (Supervisor)


  • Head and neck cancer
  • dental caries
  • radiotherapy
  • periodontitis

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