Abstract: Objective: To evaluate the effect of immediate and delayed post space preparation on apical sealing ability of iRoot SP single-cone obturation technique. Methods: Seventy single root premolars removed by orthodontics were collected, and randomly assigned to eight groups after crown resection. The root canals in groups A1, B1and C1were obturated with warm vertical technique, and the groups A2, B2 and C2 were obturated with single-cone technique.The canals in the former groups(A1, B1and C1) were filled with AH Plus and the latter groups(A2, B2andC2) were filled with iRoot SP, respectively. The group D was positive control and the group E was negative control. The post space was prepared either immediately after obturation groups (A1 and A2) or 7 days later groups (B1 and B2), and the groups (C1 and C2) were not prepared.The extent of dye penetration was evaluated in different groups by Indian ink dyeing treatment and transparent dental technology. Results: Dye penetration was observed in all experimental groups. Under the same filling method with different post space preparation, there were no significant differences(P>0.05) between groups (A1-B1, A2-B2) . Similar results(P>0.05) were also seen between groups (A1-A2, B1-B2) under different filling methods with the same post space preparation.There were no significant differences(P>0.05) between the non post space preparation groups and the immediate post space preparation groups (C1-A1,C2-A2), but there were significant differences(P<0.05) between the non post space preparation groups and the delayed post space preparation groups(C1-B1,C2-B2). Conclusion: Both iRoot SP with single-cone technique and AH Plus with warm vertical technique had similar performances on root canal seal. There was no significant difference between immediate and delayed post space preparation on the apical sealing ability of iRoot SP single-cone obturation technique.

Key words: iRoot SP, single-cone technique, microleakage, post space preparation