Effects of different doses of ionizing radiation on alveolar bone repair in post-extraction tooth socket: an experimental study in rats

Objective This study aimed to evaluate the dose-response effects of ionizing radiation (IR) on alveolar bone repair and bone strength after tooth extraction.Materials and methods A total of 32 male Wistar rats were used in the study, 28 animals were included in the final analysis, and n = 7 for each experimental group. Mandibular first molars were extracted. After 7 days, the animals were randomly divided into four groups according to single-dose irradiation: NIr, control group; Ir15, irradiated at 15 Gy; Ir20, irradiated at 20 Gy; and Ir30, irradiated at 30 Gy. The tooth extraction sites were subjected to micro-computed tomography (micro-CT), histological, histomorphometric, and biomechanical analyses 14 days after extraction. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test (alpha = 0.05).Results Micro-CT analysis revealed that IR led to lower values of bone volume (BV, in mm(3)) (0.68 +/- 0.08, P < 0.001) and bone volume fraction, ratio of the segmented bone volume to the total volume of the region of interest (BV/TV, in %) (44.1 +/- 8.3, P < 0.001) for the Ir30 group compared to the control group. A significantly lower amount of newly formed bone was observed in the Ir30 (P = 0.005) than in the Ir15 group. The histomorphometric results of quantification of bone matrix neoformation and the micro-CT were in agreement, demonstrating greater damage to the Ir30 group. IR30 cells showed a lower percentage of densely packed collagen than control cells. No significant differences were found in the biomechanical parameters.Conclusion IR affects alveolar bone repair. A dose of 30 Gy reduced the bone healing process owing to a smaller amount of newly formed bone and a lower percentage of densely packed collagen. Therefore, a dose of 30 Gy can be used to successfully establish an animal model of an irradiated mandible that mimics the irradiated clinical conditions.Clinical relevance Radiotherapy can lead to severe side effects and tooth extraction is a major risk factor. A proper understanding of the pathological mechanisms of radiation in alveolar bone repair requires the establishment of a suitable animal model of clinical conditions.