Restor Dent Endod.  2016 Nov;41(4):304-309. 10.5395/rde.2016.41.4.304.

Screw-in forces during instrumentation by various file systems

• Ha JH
• Kwak SW
• Kim SK
• Kim HC

• KMID: 2356007
• DOI: http://doi.org/10.5395/rde.2016.41.4.304

Abstract

OBJECTIVES
The purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems.
MATERIALS AND METHODS
Forty simulated canals in resin blocks were randomly divided into 4 groups for the following instruments: Mtwo size 25/0.07 (MTW, VDW GmbH), Reciproc R25 (RPR, VDW GmbH), ProTaper Universal F2 (PTU, Dentsply Maillefer), and ProTaper Next X2 (PTN, Dentsply Maillefer, n = 10). All the artificial canals were prepared to obtain a standardized lumen by using ProTaper Universal F1. Screw-in forces were measured using a custom-made experimental device (AEndoS-k, DMJ system) during instrumentation with each NiTi file system using the designated movement. The rotation speed was set at 350 rpm with an automatic 4 mm pecking motion at a speed of 1 mm/sec. The pecking depth was increased by 1 mm for each pecking motion until the file reach the working length. Forces were recorded during file movement, and the maximum force was extracted from the data. Maximum screw-in forces were analyzed by one-way ANOVA and Tukey's post hoc comparison at a significance level of 95%.
RESULTS
Reciproc and ProTaper Universal files generated the highest maximum screw-in forces among all the instruments while M-two and ProTaper Next showed the lowest (p < 0.05).
CONCLUSIONS
Geometrical differences rather than shaping motion and alloys may affect the screw-in force during canal instrumentation. To reduce screw-in forces, the use of NiTi files with smaller cross-sectional area for higher flexibility is recommended.

Keyword

Continuous rotation; Geometry; Nickel-titanium file; Reciprocating; Screw-in force

MeSH Terms

Alloys
Pliability
Alloys

Figure

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  Figure 1 Longitudinal geometries of the instruments showing helical angle and pitch length. (a) Mtwo size 25/0.07; (b) Reciproc R25; (c) ProTaper Universal F2; (d) ProTaper Next X2.

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  Figure 2 A custom-made test device (AEndoS-k, DMJ system, Busan, Korea). Simulated canal, force sensor and engine-driven motor unit are shown in box.

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  Figure 3 Representative chart of screw-in forces during instrumentation using Reciproc R25. Negative values indicate the screw-in forces and the deepest depth in force with negative value indicates the maximum screw-in forces. Repeating 5 mm downward (black arrow) and 4 mm upward (white arrow) movement, the files approach the working length (16 mm) as the laps of time.

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