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Introduction:The aim of this study is to compare the effectiveness of reciprocating and continuous rotary nickel-titanium instruments during retreatment performed through two different access outlines.Methodology:A total of 48 freshly extracted mandibular first and second premolars with single root and canal were selected. Initial root canal treatment was completed through a contracted endodontic cavity (CEC) design. Canals were instrumented with F2 ProTaper instrument, obturated with warm lateral condensation of gutta-percha with AH Plus sealer, and allowed to set for 30 days at 37°C and 100% humidity. For retreatment, specimens were divided into two groups (n = 24) on the basis of access outline, CEC or traditional endodontic cavity. Retreatment was initiated using ProTaper Retreatment instruments (D1–D3). Specimens were further divided (n = 12) and reinstrumented up to Neoniti 25/0.08 or WaveOne 25/0.08. Irrigation was performed using 3% sodium hypochlorite and 17% ethylene diamine tetraacetic acid. Retreatment time was recorded. Teeth were sectioned and photographed, and the percentage of remaining obturation material was measured.Results:Data were collected, and statistical analysis was performed using one-way analysis of variance and Tukey honestly significant difference multiple post hoc procedures (P < 0.05).Conclusion:None of the systems completely removed the root filling material from root canals. However, ProTaper/Neoniti instruments removed more GP when compared to Protaper/WaveOne instruments with both the access outlines. Both the instruments with traditional access outline required less time for removal of obturating material when compared to CEC.

Introduction:The aim of this study was to compare canal transportation of two single-file systems, WaveOne Gold and Neoniti, using cone-beam computed tomography (CBCT).Methodology:A total of 40 mesiobuccal canals of maxillary first molars with curvatures of 15°–30° were chosen and randomly divided into two experimental groups (n = 20). In both groups, glide path was established using ProGlider. In group 1, canals were shaped with WaveOne Gold and in group 2 with Neoniti A1, respectively. According to manufacturer's instructions, canal preparation was made. Canals were scanned before and after instrumentation using CBCT scanner to evaluate root canal transportation at 3, 5, and 7 mm from the apex. Data were statistically analyzed, and significance level was set at P < 0.05.Results:Mesiodistal and buccolingual transportation showed a statistically significant difference at 3 mm (P = 0.009) and 7 mm (P = 0.002), respectively, when instrumented with Neoniti than WaveOne Gold.Conclusion:WaveOne Gold single reciprocation file respected original canal anatomy better than Neoniti single continuous file