A summary of: Kovarik, J., Voborna, I., Barclay, S. et al. Dental loss after radiotherapy for head and neck cancer. Br Dent J 231, 473–478 (2021). https://doi.org/10.1038/s41415-021-3536-4
Introduction:
Every year, more than 600,000 people worldwide are diagnosed with head and neck cancer (HNC). Patients with HNC raise additional challenges, such as an increased risk of dental issues. Oral toxicity caused by radiation can be acute or chronic with acute side effects including taste disorder and xerostomia, and chronic side effects include trismus, osteoradionecrosis and dental caries leading to tooth loss.
The aim of this clinical study was to determine the prevalence of tooth loss over time and its association with radiotherapy (RT) dose and other risk factors in patients with HNC treated with radical RT.
Material and methods:
Records of 78 patients (with HNC treated with radical or adjuvant RT) with 1,566 teeth in which all the details of post-treatment interventions were available was used for analysis. After dental examination by experienced restorative dentistry clinicians, 40 of the 78 patients required dental extractions prior to RT. The median number of extracted teeth was three (range: 1–14).
During RT, dental care, non-surgical periodontal treatment and the use of fluoride varnish if caries was present was offered. Following completion of RT treatment, all patients were seen by the head and neck or maxillofacial surgery teams every three months for the first two years, then every six months for the next three years.
Dose mapping was performed to determine the exact dose of RT in each of the 1,566 teeth. Knowing the precise location of each tooth, exact RT dose mapping was performed to explore the relationship of RT dose distribution with the extraction site. Figure 1 demonstrates an example of RT dose mapping.
Results:
Out of a total of 1,566 teeth, 253 (16.2%) were extracted. The median interval between completion of RT and extraction was 25.0 months (range: 1–101 months). There were several causes to the extraction of teeth including extensive caries, periodontal disease, osteoradionecrosis, prosthetic work, and tooth causing trauma to adjacent buccal mucosa.
The following risk factors were considered statistically significant: gender (p = 0.0001), xerostomia (p<0.0001), RT dose (p<0.0001) and smoking (p<0.0001). Non-significant factors were age, RT delivery technique and the addition of cisplatin. When analysing p values, <0.05 was considered significant.
The most widely accepted aetiology of post-radiation dentition breakdown is the indirect effect of radiation-induced xerostomia. However, a direct effect is thought to occur in locations with high radiation dosage.Tooth damage seems to occur at RT doses greater than 60 Gray (Gy). There appears to be a 2–3 times increase in tooth damage at doses of 30–60 Gy, which is likely related to salivary gland impact. Analysis revealed a significant difference in tooth loss development between groups of patients treated with RT doses of 40 Gy, 41-60 Gy, and >60 Gy, confirming the hypothesis that the damaging effect on tooth structure is dose-dependent.
Conclusion:
Tooth loss is a recognised complication of RT in HNC treatment. It is associated with smoking status, the presence and severity of xerostomia and RT dose. Smoking cessation advice and provision of regular dental care should be considered to reduce the incidence of tooth loss. Every effort should be made to reduce the dose of RT to the teeth and salivary glands in order to reduce the risk of xerostomia and, hence, tooth loss.
Summary by Safa Shareef, University of Manchester, BDS 2