The aim of this ex vivo study was to evaluate bacterial penetration after filling root canals using 3 different techniques. Three experimental groups of 25 teeth each, obturated with lateral-warm-vertical condensation of gutta-percha, Microseal technique and EndoREZ system, respectively, were tested in a split chamber model system using Enterococcus faecalis and monitored for 180 days to determine bacterial penetration. A statistical analysis was performed using the Kaplan-Meier method. Median survival time was 25 days for Microseal system, 41 for lateral-warm-vertical condensation and 81 for EndoREZ®. Significant differences were demonstrated between Microseal and EndoREZ (p less than 0.001) and between Microseal and lateral-warm-vertical condensation technique (p less than 0.05). No statistically significant differences were observed between EndoREZ and lateral-warm-vertical condensation. After 180 days of assessment, 20 percent of the EndoREZ samples resisted bacterial penetration and furthermore, the EndoREZ system has the potential to be a filler system compatible with other currently used systems.