J Korean Acad Conserv Dent.  2010 Sep;35(5):374-379. 10.5395/JKACD.2010.35.5.374.

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

• Son JY
• Ha JH
• Kim YK

• KMID: 2176436
• DOI: http://doi.org/10.5395/JKACD.2010.35.5.374

Abstract

OBJECTIVES
Nickel-titanium (Ni-Ti) rotary instruments have some unexpected disadvantages including the tendency to screw-in to the canal. The purpose of this study was to evaluate the influence of root canal curvatures on the screw-in effect of Ni-Ti rotary files.
MATERIALS AND METHODS
A total of 80 simulated root canals in clear resin blocks were used in the study. Canals with curvature of 0, 10, 20 and 30 degrees were instrumented with ProTaper instruments SX, S1, S2 and a ProFile of #25/0.06 to 1.0-2.0 mm beyond the initial point of root curvature. The screw-in force was measured with a specially designed device while canal was instrumented with a ProFile of #30/0.06 at a constant speed of 300 rpm. The data were subjected to one-way ANOVA and Scheffe multiple range test for post-hoc test.
RESULTS
Larger degree of canal curvature generated significantly lesser screw-in forces in all groups (p < 0.001).
CONCLUSIONS
More attention needs to be paid when using rotary instruments in canals with less curvature than canals with more curvatures to prevent or reduce any accidental overinstrumentation.

Keyword

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

MeSH Terms

Dental Pulp Cavity
Nickel
Titanium
Nickel
Titanium

Figure

• 

  Figure 1 The custom-made device for the measurement of the screw-in effect. The device is 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 root canal curvature of each resin block (mean ± S.D.). a, b, c, d: Letters indicate significant differences between materials by Scheffe multiple range test; p < 0.001.

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