Efficacy of five irrigation techniques in removing calcium hydroxide from simulated S-shaped root canals

Calcium hydroxide [Ca(OH)2], a wildly used intracanal medicament, should be completely removed from the root canal before obturation to avoid negative effects on the treatment. This study evaluated the effectiveness of conventional needle irrigation (CNI), passive ultrasonic activation (PUI), photon-induced photoacoustic streaming (PIPS), XP-endo Finisher (XP) and EDDY for the removal of Ca(OH)2 from S-shaped root canal.Eighty-four S-shaped root canals in resin blocks were prepared using Protaper Gold up to size #25/0.08 and filled with Ca(OH)2. Five groups were established according to the removal techniques (n = 16): CNI, PUI, PIPS, XP and EDDY group. The positive and negative control group (n = 2) were also established. Sodium hypochlorite 3% was used as the irrigant. Digital radiographs were used to measure the remaining Ca(OH)2. Statistical analysis of the data was performed by using the Kruskal-Wallis test, followed by Dunn's post hoc test with Bonferroni correction (α = 0.05).All the tested techniques completely removed Ca(OH)2 from the straight portion and coronal curve of the S-shaped root canal in 100% of cases. Regarding the apical curve, PUI, EDDY, PIPS and XP removed significantly more Ca(OH)2 than CNI (P < 0.05), with no significant differences among these four groups (P > 0.05). The complete clearance of Ca(OH)2 from the apical curve was observed in 75%, 62.5%, 56.3%, 43.8% and 0% of cases of PUI, EDDY, PIPS, XP and CNI group, respectively.Irrigant activation enhanced Ca(OH)2 removal from the apical region of the S-shaped root canal. CNI was significantly less effective than all activation techniques.