Effect of various mixing ratios on antibacterial properties and hardness of endodontic sealers

Most chemically cured two-component dental materials, including endodontic sealers, are marketed with mixing instructions but with no strict mixing ratios. The present study evaluated the antibacterial properties and hardness of three endodontic sealers: Roth's cement (RC), CRCS, and AH26, mixed to four controlled consistencies within the range of the manufacturer recommendations. Using Enterococcus faecalis as the test microorganism, antibacterial activity was evaluated by agar diffusion and direct contact test. Surface hardness of sealers with the same consistency was evaluated on week-old specimens by the Knoop Hardness Number tester. In the agar diffusion test, light consistency of RC showed larger zones of inhibition than heavier consistency, whereas no significant differences were found with AH26 or CRCS. In the direct contact test, RC and CRCS exhibited complete inhibition of bacterial growth at all consistencies, whereas AH26 with the heavier consistencies did not inhibit bacterial growth at 24 h samples. The hardness of AH26 and CRCS was significantly lower with lighter consistencies. It is concluded that endodontic sealers possess different antibacterial and physical properties according to their mixing consistencies.