Up-regulation of receptor activator nuclear factor-kappaB ligand expression by root canal sealers in human osteoblastic cells.

Histologic investigations have demonstrated that root canal sealers can induce mild to severe inflammatory alternations. A recently identified tumor necrosis factor family molecule, receptor activator of nuclear factor-kappaB ligand (RANKL), plays a critical role in the development of osteoclasts that result in bone resorption. The aim of this study was to investigate the effects of root canal sealers AH26, Canals, and N2 on the expression of RANKL in human osteoblast cell line U2OS cells. Freshly mixed materials were filled in glass rings (4 mm height and 10 mm in diameter) and eluted in 10 mL of culture medium for 1 day. Subsequently, various dilutions (final dilution: 1/2, 1/4, and 1/8) of these extraction media were prepared for this study. Cytotoxicity was measured by the propidium iodide fluorescence assay. The expression of RANKL was measured by reverse transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. The results showed that AH26, Canals, and N2 were cytotoxic to U2OS cells in a concentration-dependent manner (P < .05). The exposure of U2OS cells to root canal sealers resulted in the up-regulation of RANKL mRNA and protein expression (P < .05). The expression of RANKL was up-regulated by root canal sealers in the following order: N2 > AH26 > Canals. Taken together, the activation of RANKL might play an important role in the pathogenesis of periapical bone destruction induced by root canal sealers.