A good apical seal is one of the criteria for the success of the endodontic treatment. The most common causes of failure in endodontic treatment are referred to the lack of proper apical seal. The aim of this in vitro study was to evaluate the apical sealing ability where the canals were prepared by wave one and recipro systems. Material & Method: Fifty one extracted human teeth with single root were divided randomly into 3 similar groups of fifteen of each. Group I: the teeth were instrumented with wave one (Dentsply Maillefer, Ballaigues, Switzerland), Group II: the teeth were instrumented with reciproc (VDW, Munich, Germany), and group III: the teeth were instrumented by hand instruments of K-files (Dentsply,maillefer,switzerland); then, the teeth were obturated with lateral condensation techniques. Six teeth were divided as positive and negative control groups; three in each one. AH26 was used as a root canal sealer in this study. A dye penetration method was used to evaluate the apical seal after the longitudinal section, using stereomicroscope at 40X magnification. The data were analyzed using ANOVA and LSD post-hoc test at 0.05 level of significance. Results: The Lsd statistical analysis of the results demonstrated that there was no statistically significant difference in micro leakage between the two different rotary instruments in each wave one and reciproc. While there was a significant difference between the rotary instruments, and the Hand instrument K-files. Conclusion: It could be concluded from this study that the use of the NiTi rotary instrument for root canal preparation showed the least apical micro leakage, in comparison with the hand instrument.
