The effect of head-fractioned teletherapy on pulp tissue.

AIM: To evaluate the early and delayed effects of fractioned teletherapy (radiotherapy) on the dental pulps of rats using Co(60). METHODOLOGY: In group 1 - rats (n = 15) were subjected to fractioned teletherapy by 30 daily sessions fractioned in doses of 200 cGy day(-1), totaling 60 Gy and the rats were killed immediately after the final dose of irradiation; group 2 - same protocol but killed 30 days following the final irradiation dose; groups 3 (n = 7) and 4 (n = 8) - formed controls without irradiation. Following perfusion, the left mandible of each rat was dissected and processed for histopathology. Serial sections (5 microm) were obtained and stained with HE or picrosirius. Observations were recorded for the coronal pulp tissue. A blinded observer evaluated HE sections using pre-defined indices of inflammation, nuclear alterations and extracellular matrix (ECM) hyalinization. Images of sections stained with picrosirius were converted to black and white for analysis by image-pro plus; areas in black (collagen) were measured as percentage area. The pulps of mandibular incisors of the specimens prepared for transmission electron microscopy (TEM) were subjected to descriptive analysis. Magnifications of 6300 and 10000 x were used to observe 10 pulp fibroblasts from each group. RESULTS: No inflammatory reactions or modification of the ECM status were found (P = 0.428) in any specimens. The collagen content also displayed no significant changes (P = 0.067) as a result of treatment. Groups 1 and 2 displayed significantly more nuclear alterations than the control groups (P < 0.05). The bubble-like aspect was more pronounced in group 1, and the bubbles looked smaller in group 2. The ECM showed no differences in the hyalinization status and there were no differences in the collagen area within the pulps. Under TEM, the pulp fibroblasts in group 1 displayed nuclear alterations that resembled circular, oval or elongated perforations; perforations also appeared in the cytoplasm. CONCLUSION: Fractioned teletherapy is capable of producing nuclear alterations in the dental pulp tissue of rats.