• 1 Department of Restorative Dentistry, Faculty of Dentistry, The National University of Malaysia, Kuala Lumpur, Malaysia
  • 2 Department of Mechanical & Manufacturing Engineering, Faculty of Engineering & Built Environment, The National University of Malaysia, Bangi, Malaysia
  • 3 Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston, UK
Aust Endod J, 2021 Dec;47(3):520-530.
PMID: 33956372 DOI: 10.1111/aej.12516


This study aimed to evaluate and compare the frequency of microcracks and its severity at different root canal dentin locations, after preparation with thermomechanically heat-treated engine-driven nickel-titanium instruments. Forty mandibular premolars were assigned to four experimental groups (n = 10): ProTaper Next, ProTaper Gold, WaveOne Gold and Reciproc Blue. After pre-instrumentation micro-computed tomography scans, the root canals were prepared to size 25. Following post-instrumentation scans, pre- and post-instrumentation scanned images were analysed for the presence and extent of dentinal defects. A total of 56 500 cross-sectional images were obtained, showing that less than 2.3% with pre-existing dentinal microcracks. No new microcracks were identified during the post-instrumentation analyses. No significant association was found between the types of dentinal defects, file motions and sequences. Thermomechanically heat-treated rotary files did not induce the formation of new microcracks. There was also no association between the kinematic motions and sequences of the rotary instruments to the types of dentinal defects.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.