Anti-inflammatory effects of dexamethasone on periapical tissues following endodontic overinstrumentation

An animal model was developed in which the ant-iinflammatory effects of dexamethasone could be examined histologically in periapical tissues following endodontic overinstrumentation. Mandibular first molars containing vital or partially necrotic pulp tissue were instrumented beyond the apical foramen in rats. Fifty microliters of sterile saline or dexamethasone sodium phosphate (0.4 mg/ml) were administered in a blind manner by supraperiosteal infiltration into the buccal vestibule. The rats were killed after 6, 24, and 48 h. Block sections of the mandibular molars were processed for histological examination and stained with hematoxylin and eosin. The number of polymorphonuclear neutrophils present in the periapical tissues was counted in a blind manner and statistical analysis of the results was performed by two-way analysis of variance. Following endodontic overinstrumentation, local infiltration of dexamethasone produced a significant anti-inflammatory effect on the periapical tissues of teeth with vital or partially necrotic pulp tissue.