Tetracycline conditioning augments the in vivo inflammatory response induced by cementum extracts

Background: Studies have shown that extracts of cementum from periodontally involved teeth stimulated cytokine secretion from cultured human monocytes and that this stimulatory effect is inhibited by conditioning of the cementum with tetracycline. Using the subcutaneous chamber model in mice, the present study was designed to test the ability of cementum extracts from periodontally diseased teeth to induce an inflammatory response in vivo and to evaluate the effect of cementum conditioning with tetracycline. Methods: Subcutaneous chambers were implanted in 24 mice. Two weeks later, the animals received intrachamber injection of one of the following: diseased-cementum extract, healthy-cementum extract, diseased-cementum extract preconditioned with tetracycline, or medium alone. Chamber exudates were harvested and analyzed for leukocyte levels, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin-10 (IL-10). Results: Injection of healthy- or diseased-cementum extracts increased the intrachamber levels of leukocytes. Extracts of diseased cementum were found to significantly increase the levels of TNF-α, IFN-γ, and IL-10, compared with extracts of healthy cementum or media alone. Peak cytokine levels were observed 2 hours postinjection. Conditioning of diseased cementum with tetracycline before extraction resulted in augmented levels of TNF-α and IFN-γ, and reduced levels of IL-10, compared with untreated diseased cementum. Conclusions: The present results demonstrate that conditioning of diseased cementum with tetracycline may induce an intense inflammatory response in a mouse model, and they suggest that local application of tetracycline for root conditioning should be carefully reinvestigated.