Influence of head and neck radiotherapy doses on apical periodontitis progression: An animal-based study

AIM: The aim of this study was to assess the dose-dependent effects of radiotherapy on the progression of apical periodontitis (AP) in rats. METHODS: Forty-five animals were divided into five groups based on radiation dose and apical periodontitis induction (n = 9): AP-RT7 (irradiated with a dose of 7.5 Gy + AP); AP-RT10 (10 Gy dose + AP); AP-RT15 (15 Gy dose + AP); AP (AP without radiation), and Control (no intervention). Radiation therapy was administered on the first day of the experiment. After seven days, the apical periodontitis induction was carried out in all groups except Control. All animals were euthanized after 21 days of AP progression (day 28), and the area and volume of AP were analyzed using radiography, micro-CT, and histological analyses. Inflammation intensity and extent were assessed histologically. Statistical analysis was performed using ANOVA and Student's t test for quantitative data, and Kruskal-Wallis for ordinal data (P < 0.05). RESULTS: The AP-RT15 group exhibited significantly larger apical periodontitis lesions compared to the AP-RT7.5, AP-RT10, and AP groups, as demonstrated by radiographic (p < 0.05), micro-CT (p < 0.0001), and histological analyses (p < 0.0001). Histological examination further revealed a more extensive and intense inflammatory response in the AP-RT15 group (p < 0.01). Overall, radiotherapy contributed to increased apical bone resorption and exacerbated inflammation in a dose-dependent manner. CONCLUSIONS: The progression of apical periodontitis in irradiated animals follows a dose-dependent pattern, with higher radiation doses markedly amplifying the lesion's area, volume, and inflammatory severity.