The effects of irradiation on the periodontal tissues of rats with the low calcium diet

The purpose of this study was to investigate the changes of periodontal tissues in the irradiated mandibular bone in rats which were fed normal diet and low calcium diet. In order to carry out this experiment, 64 seven-week old Sprague-Dawley strain rats weighing about 150 gms were selected and equally divided into one experimental group of 32 rats and one control group with the remainder. The experimental group and the control group were then subdivided into two groups when the rats reached the age of 10 weeks, 16 rats were allotted for each subdivided group was composed of 16 rats and exposed to irradiation. The two groups were irradiated a single dose of 20 Gy on the only jaw area and irradiated with a cobalt-60 teletherapy unit. The rats in the control and experimental groups were warily dissected by fours on the 3rd, 7th, the 14th, and the 21st day after irradiation. After each dissection, both sides of the dead rat mandibular bodies were removed and fixed with 10% neutral formalin. The specimens sectioned and observed in histopathological, histochemical, and immunocellular chemical methods. The obtained results were as follows: 1. In the mandibles of rats with low calcium diet the increased number of fibroblasts of periodontal ligaments, many small capillaries and irregular arrangement of loose collagen fibers were detected and the partial resorption of dentin and cementum could be found by the microscopic studies. 2. In the group of irradiated rats, deaerated periodontal tissues led to the condition of irregular arrangement of collagen fibers and the decreased number of fibroblasts. But this condition was somewhat restored after 21 days of experiment. 3. Periodontal tissues of the irradiated rat group with low calcium diet were destroyed earlier than those of the irradiated rat group with normal diet. Soon this condition was restored and then high cellularity and dense collagen fibers were observed. 4. Many periodontal cells bearing tumor necrosis factor could be clearly observed in the nonirradiated group of rats with normal diet, whereas could not be observed on the 7th day and reappeared on 14th day in the irradiated group of rats with normal diet. A few of them could be observed in the group of rats with low calcium diet, but they could be clearly observed in the both groups after 21 days of experiment.