[Effect of long-term methotrexate-induced neutropenia on experimental periodontal lesion in rats]

The purpose of the present study was to investigate histologically and histometrically the effect of a long-term methotrexate-induced neutropenia on the periodontal lesion in rats. Forty rats were used in this study. The control side (the interdental area between the left maxillary 1st and 2nd molars) of the rats received no treatment. In the experimental side (the interdental area between the right maxillary 1st and 2nd molars) of the same animals, a suturing nylon thread was inserted into the interdental space between these two molars for 3 weeks to produce a slight inflammation of the gingival tissue. Then, the animals were divided equally into Group A and Group B. Group A received no injection of methotrexate, whereas Group B was injected with 1.0 mg/kg of methotrexate 3 times per week for 1 to 9 weeks. Animals of both groups were killed at 1, 3, 5, 7, and 9 weeks. During the sacrifice, peripheral blood was taken from all animals. White blood cells and neutrophils were counted and the periodontal tissues were examined by light microscopy. 1. Blood findings In Group A, the white blood cell count and neutrophil count did not show any changes for 9 weeks. In Group B, however, the white blood cell count and neutrophil count decreased at 3 to 9 weeks. 2. Histological findings In Group A, the control side did not show any changes for 9 weeks, but the experimental side showed a slight gingival inflammation and a moderate alveolar bone resorption at 7 and 9 weeks. In Group B, the control side was similar to that in Group A for 9 weeks, but the experimental side displayed a slight gingival inflammation and a severe alveolar bone resorption at 7 and 9 weeks. 3. Histometrical findings In Groups A and B, the control sides did not show any changes for 9 weeks in the gingival ressection. However, in both groups, the experimental sides showed an increased gingival ressection from 1 to 9 weeks. In the experimental sides, the gingival ressecion between these two groups did not show any differences statistically. In Groups A and B, the control sides did not show any changes for 9 weeks in alveolar bone loss. However, in both groups, the experimental sides showed increasing alveolar bone loss from 1 to 9 weeks. In the experimental sides, the alveolar bone loss in Group B at 7 and 9 weeks was significantly severer (p less than 0.01) than that in Group A for the same weeks.(ABSTRACT TRUNCATED AT 400 WORDS)