Cleaning Efficacy, Debris Extrusion, and Instrument Separation during Root Canal Filling Removal using Continuous Rotation, Reciprocation, and Optimum Torque Reverse Motions: An In Vitro Study

Abstract This study aims to address the Optimum Torque Reverse (OTR) efficacy in root canal obturationmaterials removal, the amount of apically extruded debris, and separating instruments (SI) as a complication compared to continuous rotational motion (CRM) and reciprocating motion (RM). The sample involved 45 straight mandibular first premolars. The crowns were decoronated to standardize the length to 16 mm. The root canals were prepared up to a size 25 taper 0.06, obturated using the lateral compaction technique with a resin-based sealer, stored for 7 days, and divided according to the motion type used during retreatment into three groups (each group consisted of 15 samples); Group 1: CRM using Protaper Universal Retreatment system (D3 20 0.07 last file reach apical third), Group 2: RM using WaveOne Gold system Medium 25 0.07 variant taper, and Group 3: OTR motion using Protaper Universal Retreatment system (D3 20 0.07 last file reach apical third). The extruded debris weight was measured using an analytical balance. Samples were sectioned longitudinally and photographed at 20X magnification using an optical microscope. The images were analyzed in ImageJ to assess the percentage of residual obturation material. The number of SI during retreatment was recorded. Statistical Analysis Data were statistically analyzed using one-way analysis of variance (ANOVA) and chi-square tests at an α = 0.05 significance level. The results indicate that the incidence of SI during retreatment in the OTR motion group was higher than the CRM group and the RM group (p = 0.001). There were no significant differences among the groups regarding the amount of apically extruded debris and the percentage of residual obturation material (p >0.05). The effectiveness of root canal obturation material removal and the amount of extruded debris during retreatment do not depend on the motion used. However, the OTR motion is associated with an increased risk of SI during retreatment.