Abstract：
OBJECTIVE: This study aimed to evaluate the dose-response effects of ionizing radiation (IR) on alveolar bone repair and bone strength after tooth extraction.
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 (α = 0.05).
RESULTS: Micro-CT analysis revealed that IR led to lower values of bone volume (BV, in mm3) (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.
CONCLUSIONS: 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.
CONCLUSIONS: 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.
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 (α = 0.05).
RESULTS: Micro-CT analysis revealed that IR led to lower values of bone volume (BV, in mm3) (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.
CONCLUSIONS: 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.
CONCLUSIONS: 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.
摘要：
目的：本研究旨在评估电离辐射（IR）对拔牙后牙槽骨修复和骨强度的剂量反应效应。
方法：研究中使用了32只雄性Wistar大鼠，28只动物被纳入最终分析，每个实验组n=7。拔除下颌第一磨牙。7天后,根据单剂量照射将动物随机分为四组:NIr,对照组;Ir15,以15Gy照射;Ir20,以20Gy照射;和Ir30,以30Gy照射。拔牙部位进行了显微计算机断层扫描（micro-CT），组织学,组织形态计量学,提取后14天进行生物力学分析。数据采用单向方差分析，然后进行Tukey的事后检验(α=0.05)。
结果：Micro-CT分析显示IR导致较低的骨体积值（BV，单位为mm3)(0.68±0.08,P<0.001)和骨体积分数,分段骨体积与感兴趣区域总体积的比率(BV/TV，与对照组相比，Ir30组（44.1±8.3，P<0.001）。在Ir30中观察到新形成的骨的量明显低于Ir15组(P=0.005)。骨基质瘤形成定量的组织形态计量学结果与显微CT一致，显示对Ir30组的伤害更大。IR30细胞显示出比对照细胞更低的致密堆积胶原蛋白百分比。生物力学参数没有发现显着差异。
结论：IR影响牙槽骨修复。30Gy的剂量减少了骨愈合过程,这是由于较少量的新形成的骨和较低百分比的致密堆积的胶原。因此,30Gy的剂量可用于成功地建立模拟照射的临床条件的照射的下颌骨的动物模型。
结论：放疗可导致严重的副作用，拔牙是一个主要的危险因素。要正确理解辐射在牙槽骨修复中的病理机制，需要建立合适的临床条件动物模型。
方法：研究中使用了32只雄性Wistar大鼠，28只动物被纳入最终分析，每个实验组n=7。拔除下颌第一磨牙。7天后,根据单剂量照射将动物随机分为四组:NIr,对照组;Ir15,以15Gy照射;Ir20,以20Gy照射;和Ir30,以30Gy照射。拔牙部位进行了显微计算机断层扫描（micro-CT），组织学,组织形态计量学,提取后14天进行生物力学分析。数据采用单向方差分析，然后进行Tukey的事后检验(α=0.05)。
结果：Micro-CT分析显示IR导致较低的骨体积值（BV，单位为mm3)(0.68±0.08,P<0.001)和骨体积分数,分段骨体积与感兴趣区域总体积的比率(BV/TV，与对照组相比，Ir30组（44.1±8.3，P<0.001）。在Ir30中观察到新形成的骨的量明显低于Ir15组(P=0.005)。骨基质瘤形成定量的组织形态计量学结果与显微CT一致，显示对Ir30组的伤害更大。IR30细胞显示出比对照细胞更低的致密堆积胶原蛋白百分比。生物力学参数没有发现显着差异。
结论：IR影响牙槽骨修复。30Gy的剂量减少了骨愈合过程,这是由于较少量的新形成的骨和较低百分比的致密堆积的胶原。因此,30Gy的剂量可用于成功地建立模拟照射的临床条件的照射的下颌骨的动物模型。
结论：放疗可导致严重的副作用，拔牙是一个主要的危险因素。要正确理解辐射在牙槽骨修复中的病理机制，需要建立合适的临床条件动物模型。
