Dental bonding agents may affect the cell cycle patterns and induce cell cycle arrest by blocking its progression. This study tested the cell cycle effects through cyclin-dependent kinase (cdc2) and Rb phosphorylation. Human lung fibroblasts (MRC5) were used for the experiments. The bonding agent tested was the total-etch XP bond. Extracts of the bonding agent were prepared and serial dilutions were tested. The effects of the bonding agent on cell survival, proliferation and DNA synthesis were tested by the SRB and BrdU assays. Analysis of cell cycle distribution was performed by flow cytometry. XP bond exhibited strong inhibition of DNA synthesis and after 48 h of exposure cells were accumulated in the G2/M phase. Cells exposed to the half maximal cell growth inhibitory concentration (IC50) showed an increase in cdc2 kinase and Rb phosphorylation. The results most likely indicate mutagenic effect of the tested agent.