RESUMO
AIM: The main aim of the study was to evaluate the inflammatory response and development of apical periodontitis in rats chronically treated with glucocorticoids. METHODOLOGY: Male Wistar rats (Rattus novergicus) were randomly divided into two groups: the experimental group, which was treated with prednisone (5 mg/kg/day) and a control group, which was administered saline solution for 30 days before induction of apical periodontitis, continuing until the day of euthanasia days 0, 7, 14 and 28 after injury induction. The mandibles were subjected to histological evaluation to determine the size of the lesion, was also performed for the presence and absence of pulp necrosis, bone resorption and micro abscesses, and histomorphometric analyses were performed based on the number of polymorphonuclear cells and mononuclear cells. Histochemical analysis was also performed to assess the percentage of collagen fibres and their typification, in addition to immunohistochemistry for the inflammatory markers interleukin IL-1ß, IL-6, TNF-α and TRAP. RESULTS: Despite after 7 days, there was no differences between groups, a significant increase in the root pulp necrosis (p = .001), micro-abscesses (p = .026) and the size of the apical lesion on the 14th day of treatment with prednisone (p = .008). On the same day, there was also an increase in the number of polymorphonuclear cells (p = .042) and cells immunostained for IL-1ß (p = .006), IL-6 (p < .001) and TRAP (p = .002) in animals treated with prednisone. The numbers of mononuclear cells also increase in 28 days (p = .025) and TNF-α ± increases in the prednisone group on the 7th day (p = .041). The prednisone group also showed a decrease in collagen after 14 (both type I [p = .041] and type III [p = .046]) and 28 type III (p = .002) days after the coronary opening. CONCLUSIONS: The glucocorticoids modified the development of experimental apical periodontitis induced in rats, causing an early increase in periapical bone resorption and pulp necrosis. These effects are associated with alterations in cytokine levels, in the inflammatory response and in collagen deposition, in the 14th day after injury induction.