Abstract: Objective: To evaluate the apical microleakage with three root canal sealers after root canal filling, and to provide experimental evidence for selecting the appropriate root canal sealers to reduce microleakage in clinic work. Methods: Forty straight single root canal teeth were prepared by crown-down technique, and then divided randomly into four experimental groups (10 teeth in each group). Group A was filled with iRoot SP. Group B was filled with AH-plus. Group C was filled with Roekoseal. Group D was the control group. All teeth were immersed in India ink, demineralized, and dehydrated. The apical microleakages were observed with microscope, and the length of stained apical was recorded. Meanwhile, ultrastrucatral evaluation between filling materials and dentin was observed with scanning electron microscope. Results: There were significant difference in the leaked lengths among four groups (P<0.05). The length of group A was less than those of B, C and D group. There was statistically significant difference among B, C, and D group for apical leakage (P<0.05). The length of group B was longer than that of group C, but there was not significant difference in the leaked lengths between two groups. Scanning electron microscope revealed that group A (iRoot SP) had the best bonding between the sealer and dentin among four groups. Conclusion: iRoot SP can effectively reduce the microleakage in our study, and it has value in clinical application.

Key words: Root canal therapy, Root canal sealers, Apical microleakage, Apical seal