Orthodontic adhesive systems, also knows as denture resin, consist of many different substances which can be released from those systems if not hardened enough.Out of all those substances, the main focus in this research is on monomers HEMA (2-hydroxyethylmethacrylate) and TEGDMA (triethylene glycol dimethacrylate). Both monomers are colorless fluirs that can cause cell apoptosis, disrupt or delay cell cycles, merge with glutathione to produce free oxygen radicals (which will cause oxidative cell shock within the cell) or may damage the DNA molecule (be it by deleting certain base pairs or by causing double strand breaks along the DNA molecule). The aim of this study was to investigate the influence of these monomers on the viability and metabolic activity of yeast cells from Saccharomycs cevevisiae W303. The viability was observed by the change in the number of the cells while they grew in media for 20 hours. Out of three media, two of them were treated with monomers; one with HEMA monomer and the other one with TEGDMA monomer. The last medium was left untreated. The results showed that both monomers slowed down the reproduction of yeast cells or killed the cells, since the numbers of newly reproduced cells in both media (which were treated by those monomers) were lower than the number of cells in the contol group. Also, HEMA monomer showed a greater impact on the viability of the yeast cells, compared to TEGDMA monomer. Monomer's impact on methabolic activity of the yeast cells was examined by the LIVE/DEAD Yeast Viability Kit, which was used to stain the cells. Afterwards, those cells were microscoped by a fluorescence microscopy. The monomers ended up producing a similar number of metabolically active (viewed as red cells) and dead cells (viewed as green cells), but it was shown that HEMA monomer produces a lesser number of metabolically inactive cells, compared to the number produced by TEGDMA. Also,TEGDMA monomer somehow created special cells with a green crescent edge, whose creation and fromation couldn't be explained jet.