Effects of root canal sealers on alkaline phosphatase in human osteoblastic cells

Histologic investigations have demonstrated that root canal sealers can induce mild to severe bone resorption. Alkaline phosphatase (ALP) is a membrane-bound glycoprotein, which is one of the osteogenic differentiation markers considered to indicate the formation of new bone. The aim of this study was to investigate the effects of an epoxy resin-based sealer AH26, a zinc oxide-eugenol-based sealer Canals, and a paste sealer N2 on the expression of ALP in human osteoblastic cell line U2OS cells.

Freshly mixed materials were filled in glass rings 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 almar blue dye assay. Gene expression of ALP was examined by using reverse transcription-polymerase chain reaction. ALP activity was further evaluated by using substrate 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 AH26 and N2 resulted in the down-regulation of ALP mRNA gene expression (P < .05). ALP activity was significantly suppressed by 3 root canal sealers (P < .05).

The inhibition of ALP expression might play an important role in the pathogenesis of root canal sealer-induced periapical bone destruction.