Materials and methods. This experimental study was performed on 90 extracted maxillary central incisors. Rotary files were used for preparation of the canals. Root canals were filled with a single gutta percha cone, using one of the four seal-ers, under dry and moist root canal conditions (10 teeth in each group). Orifices were sealed with glue wax and all root sur-faces were covered with nail polish except the positive control group. After ten days in 100% humidity, teeth were placed in methylene blue, and then were cut in longitudinal axis. Blue color permeability was measured by stereomicroscope in mi-crometers. Data were analyzed by t-test, ANOVA and Scheffe post hoc test using SPSS V.18 software at P < 0.05. 

Results. Mean apical micro-leakage was significantly lower in the dry groups (P < 0.001). Minimum and maximum micro-leakage was seen in AH26 and ZOE, respectively. MTA Fillapex did not exhibit a significant difference in apical micro-leakage between dry and moist conditions (P > 0.05). Apical micro-leakage was significantly higher in the Excite DSC groups (P < 0.001).

Conclusion. AH26 provided the least apical micro-leakage under dry conditions while ZOE had the highest micro-leakage under moist conditions. MTA Fillapex provided acceptable apical seal regardless of moisture.