OBJECTIVE: To investigate the effects of radiotherapy on bone tissues and the accuracy of gray level measurements on radiographic images. MATERIALS AND METHODS: Four Wistar rats were submitted to external radiotherapy (single 3000 cGy dose) on an area of 2 cm × 2 cm of their right legs. The animals were sacrificed six weeks after radiotherapy, and both irradiated and contralateral (non-irradiated) legs were removed, dissected, evaluated for thickness, x-rayed in a standardized form and histologically processed (stained with hematoxylin-eosin and picrosirius red). The radiographs were digitalized and the gray level average was measured with the ImageTool® software. RESULTS: The femur thickness of non-irradiated legs was greater than that of the irradiated legs (p < 0.05). Radiographically, the findings indicated a higher bone density in the non-irradiated legs, although with no statistically significant difference (p > 0.05). Histological analysis of the irradiated legs demonstrated a decrease in the number of osteocytes and Haversian canals, although with no statistically significance (p > 0.05). On the other hand, a significant increase in adipocytes was observed, resulting in a reduction of medullary tissue in the irradiated legs (p < 0.05), besides a higher osteoblastic activity in the non-irradiated legs (p < 0.05). CONCLUSION: Radiotherapy within the above mentioned parameters determined a decrease in activity of bone remodeling, which could be radiographically detected in the majority of the evaluated specimens.

Keywords: Radiotherapy, Ionizing radiation, Bone tissue

Head and neck radiotherapy causes countless sequelae in irradiated patients, affecting the stomatognathic system, with significant systemic implications. Sequelae of exposure to ionizing radiation may be extensive and sometimes permanent, particularly in the salivary glands and bone tissue. It is of utmost importance that the surgeon dentist be aware of adverse reactions and appropriate forms of treatment to alleviate discomfort and improve the quality of life of the irradiated patient. Therefore, awareness and motivation of the patient, with promotion of oral health through the adaptation of the oral environment and guidance on preventive measures are essential to get a better prognosis.

Keywords: Head and neck tumors; Radiotherapy; Acute effects; Late effects.