Stress Generation during Pecking Motion of Rotary Nickel-titanium Instruments with Different Pecking Depth

Jung Hong Ha, Sang Won Kwak, Asgeir Sigurdsson, Seok Woo Chang, Sung Kyo Kim, Hyeon Cheol Kim

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Abstract

Introduction The aim of this study was to evaluate the effect of different pecking depth on the stress generated by the screw-in forces of a rotating endodontic file in simulated canals. Methods Twenty simulated resin blocks with a J-shaped curvature were used. Twenty OneG files (MicroMega, Besançon, France) were assigned for a screw-in test depending on the pecking depth in 2 groups (n = 10). The files were operated at 300 rpm, and the up and down speed was controlled at 1 mm/s stroke velocity and a 10-millisecond dwell time using a customized device. The distances (pecking depth) for the pecking motion were 2 mm or 4 mm for each group; “6 mm forward and 4 mm backward” and “6 mm forward and 2 mm backward” movements were applied, respectively, for the 2 pecking groups. During the operation, the positive and negative apical loads were recorded at a rate of 50 Hz using customized software attached to the device. The maximum negative apical load (screw-in force [SF]) was recorded, and the total energy during pecking motion until the file reached the working length (cumulative screw-in forces [CSFs]) was computed. The data were analyzed using an independent t test at a significance level of 95%. Results No significant difference in SF was found between the 2 groups of pecking depths. However, the longer pecking depth (4-mm group) showed a significantly larger CSF compared with the shorter pecking depth group (P < .05). Conclusions The shorter pecking depth may generate lower overall stresses for the root dentin as well as the instrument.

Original languageEnglish (US)
Pages (from-to)1688-1691
Number of pages4
JournalJournal of endodontics
Volume43
Issue number10
DOIs
StatePublished - Oct 2017

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Keywords

  • Instrument fracture
  • nickel-titanium rotary file
  • pecking depth
  • screw-in force
  • stress generation

ASJC Scopus subject areas

  • Dentistry(all)

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