J Korean Acad Conserv Dent.  2010 Sep;35(5):380-386. 10.5395/JKACD.2010.35.5.380.

Influence of taper on the screw-in effect of nickel-titanium rotary files in simulated resin root canal

• Sung HJ
• Ha JH
• Kim SK

• KMID: 2176437
• DOI: http://doi.org/10.5395/JKACD.2010.35.5.380

Abstract

OBJECTIVES
The introduction of nickel-titanium alloy endodontic instruments has greatly simplified shaping the root canal systems. However, these new instruments have several unexpected disadvantages. One of these is tendency to screw into the canal. In this study, the influence of taper on the screw-in effect of the Ni-Ti rotary instrument were evaluated.
MATERIALS AND METHODS
A total of 20 simulated root canals with an S-shaped curvature in clear resin blocks were divided into two groups. ProFile .02, .04, .06 (Dentsply-Maillefer) and GT rotary files .08, .10, .12 (Dentsply) were used in Profile group, and K3 .04, .06, .08, .10, and .12 (SybronEndo, Glendora) were used in K3 group. Files were used with a single pecking motion at a constant speed of 300 rpm. A special device was made to measure the force of screw-in effect. A dynamometer of the device recorded the screw-in force during simulated canal preparation and the recorded data was stored in computer with designed software. The data were subjected to one-way ANOVA and Tukey's multiple range test for post-hoc test. p value of less than 0.05 was regarded significant.
RESULTS
The more tapered instruments generated more screw-in forces in Profile group (p < 0.05). In K3 group, 0.08, 0.10. and 0.12 tapered instruments showed more screw-in force than 0.04 tapered one, and 0.08 and 0.12 tapered instruments showed more screw-in force than 0.06 tapered one (p < 0.05).
CONCLUSIONS
The more tapered instruments seems to produce more screw-in force. To avoid this screw-in force during instrumentation, more attention may be needed when using more tapered instruments.

Keyword

Dynamometer; Nickel-titanium rotary file; Screw-in effect; Simulated resin root canal; Taper

MeSH Terms

Alloys
Dental Pulp Cavity
Nickel
Titanium
Alloys
Nickel
Titanium

Figure

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  Figure 1 The custom-made device for the measurement of the screw-in effect. The device was composed of a part generating a single pecking movement of the handpiece (a) with a constant speed of 300 rpm, compression/tension sensor (b) and computer (c) for data storage, analysis.

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  Figure 2 Screw-in force according to the taper of each rotary file systems (mean ± S.D.).

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