EFFECT OF LONG-TERM METHOTREXATE-INDUCED NEUTROPENIA ON EXPERIMENTAL PERIODONTAL LESION IN RATS

The effects of long-term methotrexate (MTX)-induced neutropenia on the periodontal lesion in rats were investigated histologically, histometrically and bacteriologically. A nylon thread was inserted into the interdental gingiva between the Ist and 2nd right maxillary molars of the animals 3 weeks before an application of MTX. The animals were then divided into Groups A and B. Group B were injected intraperitoneally with 1.0 mg/kg of MTX 3 times per week for 9 weeks. Group A. received saline as a control. Five animals were killed at the 1st, 3rd, 5th, 7th, and 9th week. In Group A, the neutrophils did not decrease during these 9 weeks. In Group B, however, the neutrophils decreased during the 3rd to 9th week. Whereas the experimental side of Group A. showed only moderate alveolar bone resorption between the 7th and 9th week, [in Group B] a marked alveolar bone resorption occurred in Group B occurred in the same period. Alveolar bone loss in the experimental side of Group B was significantly greater (p<0.01) than in Group A in the 7th to 9th weeks. The percentage of gram-negative rods increased in both control and experimental sides of Group B at the 9th week. The results of the present study indicate that neutropenia is induced by a long-term application of MTX in rats and that alveolar bone destruction increases as lime goes by in the area where a nylon thread was inserted.