OBJECTIVE: The objective of the present study was to evaluate both immediate and late effects of fractionated cobalt-60 teletherapy over the mean percentage of empty osteocyte lacunae in rats mandibles. MATERIALS AND METHODS: The animals sampling (n = 45) was divided into three groups with 15 specimens each: group 1 - submitted to fractionated teletherapy (60 Gy) and sacrificed following the last irradiation dose; group 2 - the specimens were submitted to the same procedure as group 1, however were sacrificed 30 days after finishing radiotherapy; group 3 - non-irradiated specimens, control group. The radiotherapy protocol consisted of a course of 30 radiotherapy sessions, fractionated in 2 Gy/day-doses, totalling 60 Gy. After specimens perfusion with 4% paraformaldehyde, the left hemimandibles were histologically processed and 5 mm serial sections were hematoxylin-eosin stained. Duplicate calculation of the mean percentage of empty osteocyte lacunae was performed in the areas adjacent to the first and second molar roots with the Image Tool software. RESULTS: The analysis of variance supplemented with the Turkey's multiple comparison test indicated that irradiated groups 1 and 2 showed no difference, presenting higher rates of empty osteocyte lacunae (p = 0.005) in comparison with the control group. CONCLUSION: Fractionated cobalt-60 teletherapy causes an increase in the number of osteoplasts in bone tissues of rats' mandibles.

Keywords: Radiotherapy, External beam radiation therapy, Late effects, Radiation damage, Osteoradionecrosis, Rats

OBJECTIVE: The aim of this study was to quantitatively evaluate the histological changes produced by radiation therapy both on the stroma and the parenchyma of submandibular gland in rats. MATERIALS AND METHODS: The sample size consisted of 30 Wistar rats, divided in two groups: test and control. The 15 animals of the test group were irradiated daily on the head and neck region with a dose of 2 Gy for six weeks using a rotational fractionated modality of 60Co-gamma rays. At the end of the experimental period the animals had received a total dose of 60 Gy. Sixty hours after the last radiation therapy session the submandibular glands of the animals from both groups were excised, processed using paraffin technique, stained with hematoxiline-eosin and analyzed by optical microscopy. RESULTS: The mean proportional volume of the glandular parenchyma and stroma was obtained using a stereological method of manual point counting. The proportional volume of the acini on the irradiated group (60.67% ± 6.43) was significantly lower than the control group (67.42% ± 10.90) (p = 0.048), however there was no statistical difference between the groups for parenchyma, ducts and stroma (Student t test, p > 0.05). CONCLUSION: The radiation therapy produced acinar atrophy in submandibular glands. No total quantitative changes in the stroma or in the parenchyma were observed.

Keywords: Rats, Salivary gland, Radiotherapy, Microscopy