Comparison of In Vitro Torque Generation during Instrumentation with Adaptive Versus Continuous Movement

doi:10.1016/j.joen.2019.02.010

Journal of Endodontics

Volume 45, Issue 6, June 2019, Pages 803-807

https://doi.org/10.1016/j.joen.2019.02.010 Get rights and content

Highlights

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This study analyzed in vitro torque generation during canal shaping.
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K3XF file system generated more torque compared with TF-adaptive file.
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Adaptive movement reduced torque generation during instrumentation.
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Adaptive movement did not increase the required preparation time.

Abstract

Introduction

The purpose of this in vitro study was to compare the torque generated by continuous and adaptive movements of 2 nickel-titanium rotary file systems.

Methods

Forty-five simulated resin blocks with an S-shaped canal were randomly divided into 3 groups (n = 15) according to the file system and kinematics: the K3XF rotary system (Kerr Endodontics, Orange, CA) with continuous rotary movement, the K3XF with adaptive movement, and the Twisted File (Kerr Endodontics) adaptive file with adaptive movement. After creating a glide path, the canal was instrumented to the same size (.04/#20 for K3XF or SM1 for the Twisted File with adaptive movement) before torque measurement. During the final instrumentation procedure with the .06/25 sized file (K3XF or SM2), the generated torque and the preparation time were recorded. The total torque experienced and the maximum torque value were calculated. The data were statistically analyzed using 1-way analysis of variance and the Tukey post hoc comparison test at a significance level of 95%.

Results

The K3XF file system used with adaptive motion group showed significantly lower total and maximum torque values compared with the K3XF with continuous rotary movement group. The Twisted File adaptive file with adaptive motion showed significantly lower torque generation and shorter preparation time than the K3XF groups with adaptive or continuous rotation (P < .05).

Conclusions

Under the conditions of this study, adaptive movement for nickel-titanium files may reduce torque generation without increasing preparation time. Nickel-titanium files with a smaller cross-sectional area using adaptive movement may be helpful to reduce the potential risk of root dentin damage.

Section snippets

Materials and Methods

Endo-training resin blocks (Dentsply Sirona, York, PA) that contained an S-shaped artificial canal with a coronal curvature of 30° and a 5-mm radius and an apical curvature of 20° and a 4.5-mm radius were used in this study (Fig. 1A–D). A #10 size K-file was inserted into the artificial canal until the file tip was just visible at the apical foramen under an operating microscope (Leica S6D; Leica Microsystems, Wetzlar, Germany). The working length was determined to be 16 mm, which was 0.5 mm

Results

The mean generated total and maximum torque during instrumentation in each group are summarized in Table 1. Representative plots of the torque generated in each group are presented in Figure 2A–C.

The total torque experienced by the K3XF file system with continuous rotary movement (group XFC) was the greatest among the 3 groups (P < .05), and the maximum torque value was the highest also. The XFA group showed less total torque and a lower maximum torque value than the XFC group (P < .05) with

Discussion

The reaction torque generated during root canal instrumentation may be considered as the stress on the NiTi files and forces sustained by the root dentin 19, 20, 21. Previous studies have correlated the occurrence of dentinal cracks with higher torque (21), and that large amount of generated torque may induce file fracture or dentinal crack formation 19, 21. To prevent excessive torque generation, motors designed for endodontic use nowadays generally have an “auto-reverse” function whereby the

Conclusion

Within the limitations of this study, it may be concluded that the kinematics and geometric design of NiTi files would affect the torque generated during root canal instrumentation. Adaptive motion, which may relieve the stress by rotating reversely when a threshold of torque is experienced, is able to reduce torque generation. It would seem advantageous to adopt the adaptive movement to other NiTi file systems during instrumentation procedures. Further study should extend to in vivo torque

Acknowledgments

Sung Kyo Kim and Hyeon-Cheol Kim contributed equally to this study.

This work was supported by the National Research Foundation of Korea grant funded by the Korean government (MSIT) (grant no. 2017R1C1B5015074).

The authors deny any conflicts of interest related to this study.

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Cited by (17)

Impact of Sequential Use of Reciprocating Files on the Shaping Load During Root Canal Treatment
2024, Journal of Endodontics
The purpose of this in vitro study was to investigate the apical and coronal loads generated during shaping canals with 2 successive reciprocating files in comparison to a single reciprocating file from the same system.
A total of 40 narrow and straight canals were distributed into two groups: R-Motion with single file (RMS) and R-Motion with multiple files (RMM). In both groups, the R-Motion system was used in a reciprocating motion. After establishing glide path, the RMS canals were shaped down to working length with a single file (25/.06) in two insertions while the RMM canals were shaped with two files (20/.04 and 25/.06) to the working length. The shaping time and effects of tested groups on the apical and coronal peak loads were statistically analyzed using the t-test and Mann-Whitney U test, respectively, at a 95% confidence level.
All canals were completely shaped in three insertions and no file deformation or fracture was observed. The RMS and RMM were able to shape canals in 117.3 ± 15.1 and 123.7 ± 7.3 seconds, respectively (P < .05). Within each group, the shaping load appeared to increase with the successive insertions of the file. In both groups, the ranges of apical and coronal peak loads were 0.41–1.87 N and 0.38–1.03 N, respectively. The RMM and RMS had comparable apical and coronal peak loads (P > .05) except in the last insertion where RMM showed clearly lower apical peak load than RMS (P < .01).
Under the current laboratory conditions using the R-Motion system, preshaping the canal with a smaller reciprocating file was shown to favorably reduce the apical peak loads induced during canal shaping of extracted teeth.
Effect of Periodic Changes in Rotation Speed on Torsional Stress and Screw-in Force by Alternative Rotation Technique
2023, Journal of Endodontics
Citation Excerpt :
Although the reciprocating movement periodically changed the rotational direction from the counterclockwise to the clockwise direction, the ART motion did not change the rotational direction but changed the rotation speed. Motors that have operating modes with periodic direction changes have been shown to have lower maximum torque generation19,33. Similar to these studies, the novel ART motion in this study resulted in a significantly lower maximum screw-in force than CR without direction change.
This study evaluated the effect of periodic changes in rotation speed on torsional stress and screw-in force using the dedicated alternative rotation technique (ART) motion of the EQ-M (Metabiomed, Cheongju, Korea) endodontic motor.
Two ART modes of the EQ-M motor in 2 alternative techniques (ART30 and ART50) and continuous rotation were compared using ProTaper Next X2 (Dentsply Sirona, Charlotte, NC) files and simulated resin blocks (n = 12 per group). ART30 and ART50 were operated by continuous rotation of 350 rpm for 360° and then rotated at 30% increased speed from the base speed for 180° and at 50% increased speed for 180°, respectively. Before the test, the simulated resin blocks were pre-enlarged using ProTaper Gold S1 and S2 (Dentsply Sirona) and fixed on a metal stage connected to the force- and torque-measuring unit. During shaping the simulated canal in an automatic up-and-down manner, the parameters of maximum torque, sum of torque, maximum screw-in force, and maximum apical force were measured. The data were statistically analyzed using 1-way analysis of variance and the Tukey post hoc comparison test at the 95% significance level.
The ART30 and ART50 groups showed a lower maximum torque, sum of torques, screw-in force, and apical drive force than the continuous rotation group. There was no significant difference between the ART30 and ART50 groups (P > .05). When the screw-in force increased suddenly, the torque correspondently increased.
Under the limitations of this study, the ART mode could reduce the torsional stress and apical forces of the screw-in during instrumentation in comparison with continuous rotation.
Kinematics of “Adaptive Motion” under Constant Torque Values
2022, Journal of Endodontics
Citation Excerpt :
The greater maximum and total torque value measurement in the S-shaped canals than moderate canal curvature could be explained by the reported relationship in the previous study27. The constant 100-gcm torque value (minimum for the Elements motor) selected for the present study covers those reported intraoperative real-time maximum and total torque values3,5 during shaping with adaptive motion. Concerning the TFA-100 findings and the reported real-time torque values, it can be assumed that the adaptive motion generates a mixed type of motion in clinical use with TF Adaptive instruments.
To demonstrate the unknown kinematics of complex adaptive motion with respect to disclosed values, the aim of this study was (1) to analyze the adaptive motion and (2) to compare the effects of constant torque values on kinematics.
A new endodontic motor (Aseptico AEU-28SYB Elements; SybronEndo, Orange, CA) and 8:1 contra-angle handpiece were used for analysis. A pilot test was conducted for synchronizing the external experimental stress on the shaft of the target object and the built-in torque sensor of the motor source. A load setup was developed by attaching universal precision weights to the shaft of the of the target object. The groups were adaptive motion with no load (TFA-0), adaptive motion with a 100-gcm constant load (TFA-100), and adaptive motion with a 200-gcm constant load (TFA-200). The peak-to-peak–based phase identification method was used to analyze the kinematics. Student t and Mann-Whitney U tests were used where applicable (α = 0.05).
A noteworthy observation was the inconsistent kinematics of TFA-100 compared with the kinematics of TFA-0 and TFA-200. TFA-100 presented mixed-phased kinematics, which consisted of both a quaternary phase (n = 33) similar to that of TFA-200 and a dual phase (n = 17) similar to that of TFA-0. The sequence of these quaternary and dual phases of TFA-100 was arbitrarily changing. The kinematic parameters of dual-phase intermittent motion of TFA-0 and TFA-100 and quaternary-phase reciprocating motion of TFA-100 and TFA-200 revealed significant differences (P < .05).
The main conclusions of the present study are the kinematics of adaptive motion was demonstrated, and the 100-gcm load is not sufficient for predictable and constant operation in the reciprocating mode.
Effects of Root Canal Curvature and Mechanical Properties of Nickel-Titanium Files on Torque Generation
2021, Journal of Endodontics
Citation Excerpt :
The generated torque is considered to be the power needed to keep the file at a constant rotational speed and is essential for removing the root dentin. Torque is inevitably generated during root canal procedures with engine-driven NiTi files, even if the file rotates freely in the air.21 The geometry of the root canal, such as the canal curvature and the degree of calcification, is the cause of the fracture of the NiTi file.22
This study aimed to compare the torque generated by 4 different files in root canals with 4 different curvature angles.
Four brands of nickel-titanium (NiTi) endodontic files were selected: WaveOne Primary (Dentsply Sirona, Ballaigues, Switzerland), WaveOne Gold Primary (Dentsply Sirona), ProTaper Universal F2 (Dentsply Sirona), and ProTaper Next X2 (Dentsply Sirona). A tempered steel block containing artificial canals with 4 different canal curvatures (15°, 25°, 35°, and 45°) was constructed. Each file was used according to the manufacturer’s instructions in the dynamic model, with an added 15 axial up-and-down movements of 4 mm at the end of the canal. The generated torque was recorded, and the total and maximum torque values were measured. Two-way analysis of variance and the Duncan post hoc comparison test were performed at a significance level of 95%.
A significant correlation between the curvature angle and the type of file system was observed (P < .05). As the degree of canal curvature increased, the generated total and maximum torque increased. At 15° and 25°, the NiTi files with reciprocating motion generated a higher total and maximum torque than files with continuous rotation. ProTaper Universal of conventional NiTi alloy showed the steepest increase in the generated total and maximum torque with the increasing curvature angle. The ProTaper Next file had the lowest torque values at the higher canal angles of 35° and 45° (P < .05).
Despite the study limitations, it can be concluded that root canal curvature, design, and heat treatment of NiTi files and file kinematics affect the generated torque during instrumentation.
Comparison of Torque, Screw-in Force, and Shaping Ability of Glide Path Instruments in Continuous Rotation and Optimum Glide Path Motion
2021, Journal of Endodontics
Citation Excerpt :
Moreover, OGP motion exhibited lower maximum screw-in force than CR during both preparation phases, possibly because the OGP motion reduced the contact time and stress on both the instrument and the dentin wall. Reducing clockwise torque can decrease the torsional fatigue that leads to instrument separation9,11,16. Regarding the pattern of torque/force generation, CR exhibited that clockwise torque and screw-in force increased continuously and peaked during the last 15 seconds of the 22-mm preparation (Fig. 2A–D).
This study aimed to analyze torque/force generation and transportation in double-curved canals instrumented with 3 types of glide path files using optimum glide path (OGP) motion in comparison with continuous rotation.
Sixty simulated double-curved canals were prepared with #10/0.05 or #15/0.03 HyFlex EDM Glidepath files (Coltene/Whaledent, Altstätten, Switzerland) or a #13/0.04 prototype MANI Glidepath file (Tochigi, Japan) using OGP motion or continuous rotation (n = 10 each). Canals were sequentially prepared to 20 mm and 22 mm (full working length) using automated root canal instrumentation and a torque/force analyzing device. Transportation was calculated at 1–9 mm from the apex. Data were compared using 2-way analysis of variance followed by a post hoc simple main effect test with Bonferroni correction and a Kruskal-Wallis test (α = 5%).
All #10/0.05 instruments fractured. In the 22-mm preparation, the OGP motion resulted in lower clockwise torque and screw-in force than did continuous rotation (P < .05). In the 20-mm preparation, #15/0.03 instruments recorded a lower screw-in force for OGP motion than for continuous rotation (P < .05). Comparing the 2 preparation phases, OGP motion generated no significant differences; however, continuous rotation developed higher clockwise torque and screw-in force in the 22-mm preparation than in the 20-mm preparation (P < .05). There was no significant difference among the tested groups for transportation values.
Compared with continuous rotation, OGP motion generated less screw-in force, lower clockwise torque, and similar transportation. The #15/0.03 HyFlex EDM instrument and the #13/0.04 prototype MANI instrument performed similarly well.
Apically extruded debris of different file systems used with various kinematic movements during retreatment: An in vitro study
2023, Australian Endodontic Journal

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Basic ResearchComparison of In Vitro Torque Generation during Instrumentation with Adaptive Versus Continuous Movement

Highlights

Abstract

Introduction

Methods

Results

Conclusions

Section snippets

Materials and Methods

Results

Discussion

Conclusion

Acknowledgments

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Basic Research
Comparison of In Vitro Torque Generation during Instrumentation with Adaptive Versus Continuous Movement