Indiana University-Purdue University Indianapolis (IUPUI) / Monomers like triethylene glycol dimethacrylate (TEGDMA) leach from dental composites and adhesives due to incomplete polymerization or polymer degradation. The release of these monomers causes a variety of reactions that can lead to cell death. This death can be either necrotic, which is characterized mainly by inflammation and injury to the surrounding tissues, or apoptotic, which elicits little inflammatory responses, if any at all. TEGDMA-induced apoptosis in human pulp has been reported recently. However, the molecular mechanisms and the apoptotic (pro and anti) proteins involved in this process remain unclear. The objective of this study was to determine the apoptotic proteins expressed or suppressed during TEGDMA-induced apoptosis. Human pulp fibroblasts (HPFs) were incubated for 24 hours with different TEGDMA concentrations (0.125-1.0 mM). Cytotoxicity was determined using the cytotoxicity Detection KitPLUS (Roche Applied Science, Mannheim, Germany). TEGDMA was shown to cause cell cytotoxicity at concentrations of 0.50 mM and up. The highest concentration with no significant cytotoxicity was used. Cells were incubated with or without 0.25 mM TEGDMA for 6 h and 24 h. Cell lysates were then prepared and the protein concentrations determined using the Bradford protein assay. A Human Apoptosis Array kit (Bio-Rad Hercules, CA ) was utilized to detect the relative levels of 43 apoptotic proteins. The results of this study showed statistically significant increases of multiple examined pro-apoptotic proteins. The anti-apoptotic proteins were also altered. Pro-apoptotic proteins involved in the intrinsic and extrinsic apoptotic pathways were increased significantly. The results indicated that TEGDMA has effects on both the extrinsic and intrinsic apoptotic pathways.