Assessment of antibacterial activity of endodontic sealers by a direct contact test

It is recognized that endodontic success depends on bacterial elimination from the root and root canal system. Antibacterial activity of endodontic sealers can improve the success rate of endodontic treatment, provided the physical properties are not compromised. The aim of this study was to evaluate the antimicrobial properties of two endodontic sealers (AH26 and Endoflas) using a direct contact test (DCT) which was designed for this purpose. The DCT is based on measuring the effect of close contact between test bacteria and the tested material on the kinetics of bacterial outgrowth using a temperature controlled microplate spectrophotometer (THERMOmax). For comparison, the agar diffusion test (ADT) was performed for both materials. The results of the DCT showed that Endoflas was a significantly more potent bacterial growth inhibitor than AH26, whereas when assessed with the ADT, AH26 was capable of producing a larger inhibition zone than Endoflas. The DCT, by being quantitative and virtually independent of solubility and diffusion, was found more suitable to assay solid surfaces. The results demonstrated the added value of DCT in the study of the antimicrobial properties of endodontic sealers.