This study compared the torque generation during canal shaping with a nickel-titanium\nendodontic instrument according to the extent of glide-path establishment. Seventy-five simulated\nS-shaped canal blocks were divided into five groups (n = 15) according to the number of repetitive\ninsertions to the working length using a One G glide-path instrument: groups with 5, 10, 15, and 20\ninsertions as well as group Z without glide-path establishment. When the tip of the One G file\nreached the working length, the file was moved back and forth repetitively at the working length\nfor the designated number of times for each group. The instrumentation procedure with HyFlex\nEDM had 15 pecking strokes. During instrumentation, the generated torque was transmitted to a\ncustomized data acquisition module and collected using customized software. Data were computed\nto determine the maximum torque and total stress. The maximum screw-in forces were statistically\nanalyzed using one-way analysis of variance and Tukeyâ??s post hoc comparison test with a\nsignificance level of 95%. While the maximum stress did not have significant differences among the\nfive groups (p > 0.05), groups with more than 10 repetitive insertions generated lower total stress\nduring instrumentation than did the group with 5 insertions and group Z (p < 0.05). Under the\nlimitations of this study, repetitive insertions of glide-path establishment files at the working length\nreduced stress generation during the shaping using nickel-titanium instruments.
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