The apical sealing ability of root canal fillings is an important issue for desirable outcome of treatment. The aim of this in-vitro study was to assess the apical microleakage of root canal obturation with MF and .02 tapered gutta-percha as accessory cones using lateral condensation., Fifty six extracted human anterior teeth with single, straight canals were randomly divided in to two experimental groups of 23 teeth each and two control groups of 5 teeth each. The teeth were instrumented with Race rotary Ni-Ti files to a master apical file of #30. Teeth in group 1 were obturated with.06 tapered master cone and.02 tapered gutta-percha as accessory cone with AH26 sealer using lateral condensation. Teeth in group 2 were obturated similarly, except MF gutta-percha was used as accessory cones. Positive control teeth were instrumented but not filled. Negative control teeth were instrumented, obturated and externally sealed. All the specimens were sectioned buccolingually and the maximum of leakage was measured using a stereomicroscope at 8X magnification. Data were analyzed using T-test and 0.1 mm accuracy.The positive and negative controls validated the testing model. There was significant differences between two groups. The average dye penetration in group 1 and group 2 were 3.5-12.5 and 1.75-10.5 mm, respectively.,The most dye penetration was in group 1 and the lowest level of leakage was in group 2, which obturated laterally with.06 master cone and MF accessory gutta-percha.

Key words: 0.06 gutta-percha, standard gutta-percha, lateral condensation, microleakage