Resin based dental materials are not stable in the oral environment and may release their components into biological media. These components may include substances such as triethylene glycol dimethacrylate (TEGDMA), which is a major co-monomer of dental resin materials. This release can trigger host immune and inflammatory responses against foreign materials, mediated by monocytes. The aim of this study was to investigate the possible cytotoxic effects of TEGDMA on human THP-1 monocytes.