'Screw-in' tendency of rotary nickel-titanium files due to design geometry

J. H. Ha, G. S.P. Cheung, Antheunis Versluis, C. J. Lee, S. W. Kwak, H. C. Kim

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

To examine the effect of several standard geometric characteristics of rotary instruments on the 'screw-in' forces and stresses generated on root dentine using 3D finite element analysis (FEA). Methodology: Four cross-sectional designs (triangular, slender-rectangular, rectangular and square) were evaluated. The area of the triangular cross-section and of the slender-rectangular model were the same. Another rectangular model had the same centre-core diameter as the triangular one. Each design was twisted into a file model with 5, 10 or 15 threads over its 16-mm-long working section. Three curved root canals were simulated as rigid surface models: θ = 15 degrees/R = 36 mm radius; θ = 30/R = 18; and θ = 45/R = 12. A commercial FEA package was used to simulate the file rotating in the canal to determine the 'screw-in' force and reaction torque on the instrument. Results: Instruments of a square cross-section had the highest 'screw-in' force and reaction torsional stresses followed by the rectangle, the triangle design and the slender-rectangle design, respectively. The file with closer pitch generated lower stresses, compared with that with longer pitch. The greater the root canal curvature, the higher the 'screw-in' force and reaction torque generated. Conclusion: This study demonstrated that the 'screw-in' tendency depends on both the instrument geometry and canal curvature. Clinicians should be aware that certain instrument designs are prone to develop high 'screw-in' forces, requiring the operator to maintain control of the handpiece or to use a brushing action to prevent instruments being pulled into the canal.

Original languageEnglish (US)
Pages (from-to)666-672
Number of pages7
JournalInternational Endodontic Journal
Volume48
Issue number7
DOIs
StatePublished - Jul 1 2015

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Finite Element Analysis
Dental Pulp Cavity
Torque
Mechanical Torsion
Dentin
nitinol

All Science Journal Classification (ASJC) codes

  • Dentistry(all)

Cite this

'Screw-in' tendency of rotary nickel-titanium files due to design geometry. / Ha, J. H.; Cheung, G. S.P.; Versluis, Antheunis; Lee, C. J.; Kwak, S. W.; Kim, H. C.

In: International Endodontic Journal, Vol. 48, No. 7, 01.07.2015, p. 666-672.

Research output: Contribution to journalArticle

Ha, J. H. ; Cheung, G. S.P. ; Versluis, Antheunis ; Lee, C. J. ; Kwak, S. W. ; Kim, H. C. / 'Screw-in' tendency of rotary nickel-titanium files due to design geometry. In: International Endodontic Journal. 2015 ; Vol. 48, No. 7. pp. 666-672.
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