Polymer-based composite materials have replaced the use of amalgam as filling material of choice in modern dentistry. Methacrylate monomers are key constituents in the polymer-based composite materials. The monomers are found to be airborne in dental practices, making airway exposure likely. Human bronchial epithelial cells, BEAS-2B, were therefore used as an in vitro model system. Methacrylate monomers have been associated with cell growth disturbances, glutathione depletion, DNA damage and cell death in different human cell lines. The detailed cellular mechanisms underlying these effects are still unclear. Oxidative stress caused by glutathione depletion is suggested as a possible mechanism in the development of cytotoxic effects. However, resent findings indicate other mechanisms to be of importance. In the current study, the mechanisms involved in the cellular response to the two commonly used methacrylate monomers glycerol dimethacrylate (GDMA) and 2-hydroxyethyl methacrylate (HEMA) were investigated. The main focus was to map DNA damage response and the involvement of glutathione depletion. In order to investigate the role of glutathione depletion and oxidative stress, the effect of the monomers were compared to two glutathione depleting agents, diethyl maleate (DEM) and buthionine sulfoximine (BSO). Glutathione depletion, oxidative stress, cell cycle disturbances and DNA damage were observed in BEAS-2B cells following exposure to both GDMA and HEMA. Similar effects on glutathione depletion and increased oxidative stress were seen in the two exposure scenarios. The effects on cell growth, cyclin levels and activation of DNA damage signalling proteins differed between the monomers, indicating differences in cellular response mechanisms. The results show that oxidative stress caused by glutathione depletion cannot alone explain the monomer-induced cytotoxicity in vitro.