Objective: To compare the sealing ability of ProRoot mineral trioxide aggregate (MTA) to the sealing ability of EndoSequence Bioceramic Root Repair Material (ES-BCRR) putty using a bacterial leakage model. Method and Materials: Root canals of 60 single-rooted extracted teeth were enlarged to an apical diameter of 0.5 mm using EndoSequence files. The apical 3 mm of each root was sectioned at 90 degrees to the long axis of the root. An ultrasonic surgical tip was used to prepare a 3-mm deep root-end preparation in all teeth. Teeth were equally divided into four groups: Group 1, MTA; Group 2, ES-BCRR putty; Group 3, positive control, gutta-percha without sealer; Group 4, negative control, sealed with wax and nail varnish. Prepared teeth were kept moist for 48 hours to allow for initial setting of the materials. After ethylene oxide sterilization, the teeth were suspended in sterilized vials containing 3% phenol lactose broth and inoculated with Enterococcus faecalis through the occlusal access openings. The samples were observed daily for leakage to a maximum of 28 days. Chi-square and Fisher exact tests were used to compare the experimental groups and an alpha level of significance was set at P = .05. Results: In the ES-BCRR group 93% of samples leaked, compared to only 20% of samples in the MTA group. There was a significant difference in leakage between the experimental groups (P .0001). Also there were no significant differences between the negative control group and MTA group and between the positive control group and ES-BCRR group (P = 1.00). Conclusion: Samples in the ES-BCRR group leaked significantly more than samples in the MTA group. Schlagwörter: bacteria, EndoSequence Root Repair Material, Enterococcus faecalis, leakage, MTA