Description:
<jats:p><jats:bold>Abstract – </jats:bold> <jats:italic>Aim</jats:italic>: The objective of this study was to compare <jats:italic>in vitro</jats:italic> the antibacterial activity of Tetraclean (mixture of doxycycline, citric acid and polypropylene glycol), Niclor 5 (5.25% sodium hypochlorite solution), Cloreximid (0.2% chlorhexidine and 0.2% cetrimide solution) and hydrogen peroxide 12 volumes on three endodontic pathogens associated with primary endodontic infections. <jats:italic>Enterococcus faecalis</jats:italic>, <jats:italic>Streptococcus mutans and Staphylococcus aureus</jats:italic> strains were selected to evaluate the antibacterial activity of endodontic irrigants by the agar disc‐diffusion test. <jats:italic>Material and methods</jats:italic>: Paper discs were saturated with each one of the test solutions (at room temperature and preheating at 50°C) and placed onto culture agar‐plates preadsorbed with bacterial cells and further incubated for 24 h at 37°C. The growth inhibition zones around each irrigant were recorded and compared for each bacterial strain. Kruskal–Wallis and Mann–Whitney tests were applied to compare the various groups. <jats:italic>Results</jats:italic>: At room temperature, Tetraclean showed significantly higher inhibition of bacteria growth than all other irrigants tested. Preheating at 50°C significantly increased growth inhibition for all the groups tested. At 50°C, hydrogen peroxide 12 volumes and Tetraclean showed significantly higher efficacy than all other irrigants tested. <jats:italic>Conclusions</jats:italic>: 50°C‐preheated hydrogen peroxide 12 volumes and Tetraclean showed highest inhibition of the bacterial growth.</jats:p>