Background: In endodontics, glide Path creation has been extensively considered a mandatory clinical step to improve the safety and efficiency of rotary nickel–, titanium instruments. The high anatomic variations in the mesiobuccal (MB) root of the maxillary molars are observed in the form of canal configuration, number, and position. The aim of this study was to evaluate the negotiability of MB canals in maxillary molars using different Pathfiling systems (ProGlider, R‑, pilot, HyFlex electrical discharge machining [EDM], WaveOne Gold Glider, and C‑, Pilot). Materials and Methods: This in vitro study included 125 maxillary first molars with closed apex. Before preparation, all teeth were scanned by periapical radiograph for review of the presence of second MB (MB2) canals, without any resorption or calcification, and moderate curve of MB root canal. Subsequently, the access cavity was prepared with a Diamond Fissure Bur. Then, the samples were divided into five groups (ProGlider, R‑, pilot, HyFlex EDM, WaveOne Gold Glider, and C‑, Pilot). Certain relevant indices were recorded for analysis, such as the negotiability of the glide Path file in the MB canals, file fracture rate, and negotiation speed. The level of significance P value was set at 0. 05. Results: In this study, HyFlex EDM was the only Path file that could not reach the full working length (WL) in some cases. The highest frequency of file fracture in the MB2 was observed with HyFlex EDM (24%),nevertheless, R‑, Pilot presented an intermediate fracture rate (16%), and both ProGlider and WaveOne Gold Glider were the safest files (4%) in this regard. However, there were no significant differences between the groups (P = 0. 065). The lowest and the highest average time of reaching full WL was observed with WaveOne Gold Glider and HyFlex EDM,nonetheless, there was no significant difference between the four rotary groups. The average number of pecks in HyFlex EDM was significantly higher in comparison to those reported for WaveOne Gold Glider and ProGlider. Conclusion: Path files used for glide Path preparation in the MB2 canals of maxillary molars should be flexible with low taper. The use of HyFlex EDM in the MB2 canals is not recommended due to its high taper.

Objectives: This study aimed to assess root canal transportation of curved canals following glide Path preparation by Pathfile and Scout RaCe rotary systems compared with manual instrumentation with stainless steel (SS) hand files using cone-beam computed tomography (CBCT). Materials and Methods: This in-vitro experimental study was conducted on extracted human mandibular first and second molars (n=51) with 25-45° canal curvature in their mesiobuccal root. All teeth underwent CBCT and were randomly divided into three groups (n=17). In group 1, a glide Path in the mesiobuccal canal was created using SS hand files to the working length. In groups 2 and 3, after canal negotiation with a #8 SS hand file, a glide Path was created with Pathfile and Scout RaCe systems, respectively. The teeth underwent CBCT. Pre-and postoperative CBCT scans were compared to calculate the magnitude of canal transportation at 3, 6, and 9 mm from the apex. The results were analyzed using the Kruskal-Wallis and Freedman tests (P<0. 05). Results: Manual instrumentation caused significantly higher canal transportation at 3 and 9 mm from the apex compared with rotary systems (P<0. 05). Pathfile and Scout RaCe were not significantly different at 3 (P=0. 39) or 9 mm (P=0. 99). No significant difference was noted in canal transportation among the three groups at 6 mm (P=0. 15). Conclusion: Scout RaCe and Pathfile cause less canal transportation than manual instrumentation with SS files when used for glide Path preparation in curved canals, especially in the apical third.