Objectives: The purpose of this study was to investigate the antibacterial properties of different temporary fillings. Methods: The direct contact test was used to evaluate the antibacterial properties of 4 temporary filling materials Revoltek LC, Tempit, Systemp inlay and IRM. The materials were tested in contact with two bacteria: Streptococcus Mutans and Enterococcus Faecalis. The materials were examined immediately after setting, 1,7,14 and 30 days after aging in PBS. Two ways ANOVA, ANOVA and Tukey multiple comparison procedures were applied on the results. Results: Systemp inlay, Tempit and IRM exhibited antibacterial properties when in contact with S.Mutans for at least 7 days, Tempit and IRM sustained this ability for at least 14 days. When in contact with E. Faecalis Tempit and IRM were antibacterial immediately after setting, IRM sustained this ability for 1 day. Conclusions: Our study suggests that the difference in temporary filling materials may determine which microorganism will be allowed to grow, thus proposing an explanation for E. Faecalis becoming a dominant pathogen in failed endodontic treatments.