Duration of ultrasonic activation causing secondary fractures during the removal of the separated instruments with different tapers

  • Hakan ArslanEmail author
  • Ezgi Doğanay Yıldız
  • Gizem Taş
  • Nuray Akbıyık
  • Hüseyin Sinan Topçuoğlu
Original Article



The aim of the present study was to determine the effect of taper (.08, .06, and .04) of separated K3XF instruments on duration taken for the secondary fracture formation during ultrasonic activation.

Materials and methods

Ten 25/.08 K3XF (SybronEndo, Orange, CA, USA), ten 25/.06 K3XF, and ten 25/.04 K3XF instruments were used for the study. The apical 5 mm of the instruments was cut to simulate the fragments in root canals. Fragments of the instruments were sandwiched between two straight dentin blocks. An ultrasonic tip was used to cause a secondary fracture of the fragment. The time needed for the secondary fracture was recorded for each instrument. The data were statistically analyzed using the Kruskal-Wallis H test (alpha = 0.05).


Secondary fractures occurred in all instruments. In the .08 taper group, secondary fractures took longer than in the case of the .06 and the .04 taper groups (P < 0.05). There were no significant differences between the .06 and the .04 taper groups in terms of the time required for the occurrence of a secondary fracture (P > 0.05).


In the .08 taper group, secondary fracture took longer time than in the case of the .06 and the .04 taper groups due to its larger cross-sectional area involved.

Clinical relevance

Typically, when removing separated instruments, a much lower power setting is chosen. The purpose of this in vitro study was to determine which tapered files were more resilient to secondary fracture, thus allowing a higher power setting to be chosen. Thus, the results of the present study cannot be used in clinical practice. If the clinician knows the taper of the broken file, the clinician should be very careful with regard to secondary fractures when using ultrasonics to remove the separated smaller tapered instruments.


K3XF Nickel titanium Secondary fracture Separated file Taper Ultrasonics 


Compliance with ethical standards

Conflict of interest

All authors declare that they have no conflict of interest.

Ethical approval

The research described in this article did not involve human participants.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Hakan Arslan
    • 1
    Email author
  • Ezgi Doğanay Yıldız
    • 2
  • Gizem Taş
    • 3
  • Nuray Akbıyık
    • 3
  • Hüseyin Sinan Topçuoğlu
    • 4
  1. 1.Department of Endodontics, Faculty of DentistryHealth Sciences UniversityİstanbulTurkey
  2. 2.Department of Endodontics, Faculty of DentistryKırıkkale UniversityKırıkkaleTurkey
  3. 3.Department of Endodontics, Faculty of DentistryAtaturk UniversityErzurumTurkey
  4. 4.Department of Endodontics, Faculty of DentistryErciyes UniversityKayseriTurkey

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