Comparison of torque, force generation and canal shaping ability between manual and nickel-titanium glide path instruments in rotary and optimum glide path motion
This study aimed to analyze force/torque generation and canal volume changes of NiTi rotary glide path preparation using HyFlex EDM Glide Path File in comparison to manual stainless steel K-file instrumentation. Thirty extracted mandibular incisors with a minimally curved and narrow root canal were randomly divided into three groups (n = 10) according to the instrumentation kinematics: Optimum Glide Path motion (OGP) or continuous rotation (CR) with HyFlex EDM Glide Path Files using a custom-made automated-root-canal-preparation device and manual instrumentation with stainless steel K-files (SS) in watch-winding motion. Torque and force were monitored with a custom-made torque/force analyzing device. Canal volume changes and transportation values were measured on micro-computed tomographic images taken before and after the glide path preparation. The data were statistically evaluated using Kruskal–Wallis test and Mann–Whitney U test with Bonferroni correction, with a significance level set at 5%. Maximum upward apical force, representing the screw-in force, was lower in groups OGP and CR compared with that in group SS (P < 0.05). Group CR showed the highest maximum clockwise torque value and canal volume changes, followed by groups OGP and SS (P < 0.05). Canal transportation values at 1 and 3 mm from the apex were not significantly different among groups. Within the limitations of this study, rotary glide path preparation generated smaller screw-in force, larger torque and larger canal volume changes than manual preparation. OGP motion generated smaller torque and less canal volume changes than CR.
KeywordsCanal volume changes Optimum glide path motion Rotary glide path preparation Screw-in force Torque
This study was supported in part by Grants-in-Aid for Young Scientists from the Ministry of Education, Culture, Sports, Science and Technology, Japan (B)(15K20400).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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