The role of reactive oxygen intermediates in the pathogenesis of chronic apical periodontitis.

The level of malondialdehyde, a stable end product of lipid peroxidation induced by reactive oxygen intermediates and the activity of two potent antioxidant enzymes, superoxide dismutase and glutathione peroxidase, was investigated in tissue homogenates of 22 surgical periapical granuloma specimens. Malondialdehyde levels were significantly higher and glutathione peroxidase activity was significantly lower in periapical granuloma samples than in healthy gingival tissue homogenates, which were used as controls. The activity of superoxide dismutase was similar in periapical granuloma and in control samples. Our results indicate an altered balance between the production and the elimination of toxic oxygen metabolites in chronic apical periodontitis. We hypothesize that reactive oxygen intermediates, which are being produced by activated phagocytic cells abundantly present in periapical granulomas, can contribute to periapical tissue injury and bone loss in this disease.