Abstract: To investigate the sealing ability of biological root canal sealer iRoot SP in over-root canal filling. METHODS：After completion of root canal preparation, 48 extracted human single-canal teeth were used. The ratio of mesio-distal root canal diameter to bucco-lingual diameter was less than 0.5. The teeth were randomly divided into group A, B and C. The root canals were obturated with root canal filling agent (group A), AH Plus (group B) and iRoot SP (group C), respectively; the apical leakage was evaluated by dye penetration method and transparent teeth technique. The data were analyzed using SPSS 19.0 software package. RESULTS: The depth of dye penetration in group A was significantly higher than that in group B and C (P<0.05); there was no significant difference in the depth of dye penetration between group B and group C (P>0.05). CONCLUSIONS: The apical sealing ability of iRoot SP is equivalent to AH Plus in oval-root canal, both are better than that of root canal filling agent．

Key words: Root canal sealer, Oval-root canal, Microleakage