Background: Treatment for head and neck cancer (HNC) such as radiotherapy (RT) can lead to numerous acute and chronic head and neck sequelae, including dental caries. The goal of the present study was to measure 2-y changes in dental caries after radiotherapy in patients with HNC and test risk factors for caries increment.

Methods: Cancer and dental disease characteristics, demographics, and oral health practices were documented before and 6, 12, 18, and 24 mo after the start of RT for 572 adult patients with HNC. Patients were eligible if they were age 18 y or older, diagnosed with HNC, and planned to receive RT for treatment of HNC. Caries prevalence was measured as decayed, missing, and filled surfaces (DMFS). The association between change in DMFS and risk factors was evaluated using linear mixed models.

Results: On average, DMFS increased from baseline to each follow-up visit: 6 mo, +1.11; 12 mo, +2.47; 18 mo, +3.43; and 24 mo, +4.29 (P < 0.0001). The increase in DMFS during follow-up was significantly smaller for the following patient characteristics: compliant with daily fluoride use (P = 0.0004) and daily oral hygiene (brushing twice daily and flossing daily; P = 0.015), dental insurance (P = 0.004), and greater than high school education (P = 0.001). DMFS change was not significantly associated with average or maximum RT dose to the parotids (P > 0.6) or salivary flow (P > 0.1). In the subset of patients who had salivary hypofunction at baseline (n = 164), lower salivary flow at follow-up visits was associated with increased DMFS.

Conclusion: Increased caries is a complication soon after RT in HNC. Fluoride, oral hygiene, dental insurance, and education level had the strongest association with caries increment after radiotherapy to the head and neck region. Thus, intensive oral hygiene measures, including fluoride and greater accessibility of dental care, may contribute to reducing the caries burden after RT in HNC.