Impact of Radiotherapy Dose on Dentition Breakdown in Head and Neck Cancer Patients

PURPOSE: To evaluate the severity of post-radiation dental lesions and possible correlation with radiation dose to the teeth in patients treated for head and neck cancers. METHODS AND MATERIALS: Data from 93 head and neck radiotherapy patients treated between 1997 and 2008 were analyzed retrospectively. The main effect, radiation dose to the individual teeth, was evaluated with covariates of elapsed time after radiation, xerostomia, topical fluoride use, and oral hygiene status included. Patients' radiotherapy plans were used to calculate cumulative exposure for each tooth. Patients' teeth were evaluated using a validated index and then categorized as having none/slight or moderate/severe post-radiation damage. RESULTS: Patients (31 females, 62 males) ranged in age from 18-82 yrs (mean=57). The number of teeth/patient ranged from 3-30 (mean=20) with a total of 1873 teeth evaluated. Overall, 51% of teeth had moderate/severe damage, with the remaining having little or none. Using odds ratios and 95% confidence intervals, the odds for moderate/severe damage were 2-3x greater for teeth exposed to between 30-60 Gy as compared to no radiation. However, for teeth exposed to ≥60 Gy as compared to no radiation the odds of moderate/severe tooth damage was greater by a magnitude of 10 times. CONCLUSIONS: The results indicate that there is minimal tooth damage below 30 Gy (salivary gland threshold), a greater than 1:1 increased dose-response between 30-60y likely related to salivary gland damage, and a critical threshold of ≥60Gy which may be linked to direct effects of radiation on tooth structure. These findings suggest that care should be taken during the treatment planning process to limit tooth dose, and when clinically possible to limit tooth dose to less than 60 Gy.