Objective: To compare the effect on human gingival cell proliferation (HGC) exposed to an epoxy resin-based sealer at different temperatures. Materials and methods: Human gingival fibroblasts (HGFs) were established from explants of healthy gingival tissue, exposed to heat-treated sealer (150°C) and at room temperature (14°C). Cellular responses were recorded using flow cytometry at different times of assessment - 12 h, 24 h, 48 h and 72 h. Results: Cells exposed to room temperature sealer showed an increase proliferation at 12 h and 24 h. However, at both experimental temperatures there was not a significant difference in cellular response at 72 h, but there was a decrease proliferation compared to the control group. At both experimental conditions there was a significant increase in the rate of cell death, compared with the control group at 72 h. Conclusions: In vitro experimental assay showed a cytotoxic effect on HGFs after being exposed to resin epoxy sealer at 72 h. Clinical Significance: Elevated temperature changes in root canal sealers during warm vertical compaction techniques should not impact periapical cellular responses adversely, if any sealer is inadvertently expressed beyond the confines of the root canal system.