Characterisation of deformed or separated nickel-titanium retreatment instruments after clinical use - A multicentre experience: Defect profiles of clinically-used retreatment instruments

He Liu, Kiarash Shabehpour, Zhejun Wang, Tyler Sobotkiewicz, Sang Won Kwak, Markus Haapasalo, N. Dorin Ruse, Jeffrey M. Coil, Franklin R. Tay, Ya Shen

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Objectives: The present study examined the defect characteristics of clinically-used, discarded nickel titanium rotary retreatment instruments and analysed the impact of clinical use on their metallurgical properties. Methods: 92 XP-endo Shaper (XPS; FKG Dentaire) and 20 XP-endo Finisher (XPFR; FKG Dentaire) instruments with structural deformation or separation were collected after retreatment from four endodontic clinics over a 20-month period. The types of defects and their relative locations were recorded. The lateral and fractured surfaces of the separated instruments were examined with scanning electron microscopy. Differential scanning calorimetry was used to investigate the thermal behaviour of new, deformed and fractured instruments. Results: 77 (84%) XPS and 4 (20%) XPFR had an area with structural change while 15 (16%) XPS and 16 (80%) XPFR were fractured. All unfractured, deformed XPFR showed unwinding close to the coronal end of the flute. Fractures in XPS and XPFR were often close to the coronal end of the flutes or the expanding segments of the insruments. Most of the XPS fractures were torsional failure (67%) while XPFR failed predominantly by cyclic fatigue (81%). The austenite-finishing temperature of XPFR (40 °C) was higher than that of XPS (35 °C). Both XPS and XPFR exhibited 2-stage phase transformations. Conclusions: Torsional failure was more prevalent in XPS instruments and fatigue failure was more prevalent in XPFR instruments. amongst the investigated instruments, XPFR were more likely to separate without warning whereas XPS frequently exhibited plastic deformation. The latter may be used as a pre-separation forewarning sign during clinical retreatment. Clinical significance: The failure mode of XP-endo Shaper and XP-endo Finisher used clinically for retreatment appeared to be different. Plastic deformation, the forewarning sign of instrument seaparation, occurs when XP-endo instruments are used for retreatment.

Original languageEnglish (US)
Article number103939
JournalJournal of Dentistry
Volume117
DOIs
StatePublished - Feb 2022

Keywords

  • Clinical use
  • Defects
  • Nickel-titanium instrument
  • Retreatment
  • XP-endo Finisher R
  • XP-endo Shaper

ASJC Scopus subject areas

  • General Dentistry

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