RESUMO
BACKGROUND: Nowadays, the ray types, animal species, irradiation modes and sites used in the establishment of animal models of radioactive skin injury in China are not consistent. Meanwhile, there is no uniform standard for the prevention and treatment of radioactive skin injury in clinical practice. OBJECTIVE: To establish an ideal rat model of acute radioactive skin injury. METHODS: Sixty Wistar rats were randomly divided into 32, 38, 45 Gy X-ray groups (n=18) and non-irradiated group (n=6). Three X-ray irradiated groups (32, 38, 45 Gy) received single irradiation of the right posterior buttock, 300 cGy/min, 100 cm between the skin and irradiated source, for 10.67, 12.67, and 15 minutes respectively. No irradiation was given in the non-irradiated group. The study protocol was approved by the Animal Ethic Committee of Shanxi Cancer Hospital (approval No. GDY2018001). RESULTS AND CONCLUSION: There was no accidental death after irradiation. The body mass of the rats decreased within 3 days after irradiation, and then increased. Irradiated wound was severest at about 15 days after irradiation, and the body mass dropped again, and returned to normal 2 days later. Two weeks after radiation, with the increase of X-ray dose, the structures of rat’s skin appendages were destroyed and a large number of inflammatory cells were infiltrated, indicating that the acute radiation skin injury was dose-dependent within a certain range. On the other hand, with the increase of irradiation time, the skin wound in the 38 and 45 Gy groups gradually deepened. At the same dose, the severity of acute radiation skin injury was also positively correlated with the irradiation time. After 6 hours to 15 days of 38 Gy irradiation on the rat skin, macrophages were activated, and the expression of Nod-like receptor pyrin domain-containing protein 3 was enhanced, indicating obvious inflammatory response, and thereby verifying the reliability of the model. To conclude, it is an ideal animal model of acute X-ray skin injury model made by the X-ray linear accelerator, which is easily observed and obtained, with obvious skin inflammation expression. This model is also of high safety and strong tolerance.
RESUMO
PURPOSE: On maxillofacial tumor patients, oral implant placement prior to postoperative radiotherapy can shorten the period of prosthetic reconstruction. There is still lack of research on effects of post-implant radiotherapy such as healing process or loading time, which is important for prosthodontic treatment planning. Therefore, this study evaluated the effects of post-implant local irradiation on the osseointegration of implants during different healing stages. MATERIALS AND METHODS: Custom-made implants were placed bilaterally on maxillary posterior edentulous area 4 weeks after extraction of the maxillary first molars in Forty-eight Sprague-Dawley rats. Experimental group (exp.) received radiation after implant surgery and the other group (control) didn't. Each group was divided into three sub-groups according to the healing time (2, 4, and 8 week) from implant placement. The exp. group 1, 2 received 15-Gy radiation 1 day after implant placement (immediate irradiation). The exp. group 3 received 15-Gy radiation 4 weeks after implant placement (delayed irradiation). RESULTS: The bone mineral density (BMD) was significantly lower in the immediate irradiation groups. BMD was similar in the delayed irradiation group and the control group. The irradiated groups exhibited a lower bone-to-implant contact ratio, although the difference was not statistically significant. The irradiated groups also exhibited a significantly lower bone volume and higher empty lacuna count than the control groups. No implant failure due to local irradiation was found in this study. CONCLUSION: Within the limits of this study, the timing of local irradiation critically influences the bone healing mechanism, which is related to loading time of prostheses.