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The complex configuration of C-shaped canals in mandibular second molars make root canal treatment unusually difficult. The present case highlights their unpredictable canal anatomy and describes the use of two pluggers simultaneously to downpack the main canals. The effect of such a modification on the high-flow characteristics of thermosoftened gutta-percha in vertical condensation is discussed.

Aim To compare two preparation systems and two sonic irrigation devices during the removal of root filling material from oval distal canals of extracted mandibular molars. Methodology The distal canals in 40 extracted mandibular molars were shaped using the ProTaper Next system (Dentslpy Sirona, Ballaigues, Switzerland), filled with Gutta Percha X2 (Dentsply Sirona), along with AH Plus sealer (Dentsply De Trey, Konstanz, Germany) and randomly divided into two groups (n = 20) according to volume of initial filling, preparation diameter and working length. One group was retreated using the Reciproc system (VDW, Munich, Germany), and the other using the 2Shape system (Micro‐Mega, Besançon, France). A micro‐CT scan was taken after the initial root filling and after retreatment to evaluate the volume of filling material remnants. The teeth were divided into four groups to test the supplementary effect of two sonic irrigation devices on removing filling material: Eddy (VDW) and MM1500 (Micro‐Mega). In the first and second groups, 2Shape was followed subsequently by MM1500 and Eddy; in the third and fourth groups, Reciproc was followed by MM1500 and Eddy. A third micro‐CT was taken to compare the remaining root filling material in all groups. Wilcoxon's signed rank tests, Mann–Whitney and Kruskal–Wallis tests were used for statistical analysis. Results No significant difference was found for the volume of filling material removed between the Reciproc and 2Shape in the entire canal (P = 0.355). The volume dropped significantly from its initial value after removing the bulk of the root filling by 95.8% (from 4.71 to 0.22 mm3) with the 2Shape (P < 0.001) and by 94.0% (from 5.05 to 0.33 mm3) with the Reciproc (P < 0.001). Sonic activation significantly decreased the residual volume of filling material remnants by 3.21% (P = 0.013) in the first group, 1.38% (P = 0.012) in the second group, 1.83% (P = 0.008) in the third group and 1.83% (P = 0.012) in the fourth group. At the end, the percentage of residual material was not significantly different among the groups in the entire canal (P = 0.163). Conclusion In the distal oval canals of extracted mandibular molar teeth, there was no significant difference between the 2Shape and Reciproc systems in removing gutta‐percha/sealer. Sonic activation with MM1500 and Eddy significantly improved filling material removal.

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