{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T16:23:48Z","timestamp":1788971028093,"version":"build-2803163510"},"reference-count":56,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2022,1,17]],"date-time":"2022-01-17T00:00:00Z","timestamp":1642377600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>As the use of nickel-titanium (NiTi) file systems for root canal therapy has become popular; hence, knowledge and understanding of the characteristics of NiTi files is essential for dentists. Unintended sudden fracture can occur during root canal shaping, and it is important to understand the conditions that may cause instrument fractures. Torque is defined as the force required to rotate the NiTi file and can be considered of as a parameter for the stress generated. The endodontic engine maintains a constant rotational speed by adjusting torque regardless of the root canal conditions. The process of root canal shaping by rotary instruments is a series of actions that requires torque and generates stress to both the teeth and the NiTi instruments. The generated stress may induce the strain accumulation on NiTi instrument and the canal wall and lead to the development of microcrack in the instrument and dentinal wall. Therefore, understanding of torque and stress generated is important to prevent the fractures to the instrument and the teeth. This stress has been measured using various experimental approaches, including microcrack observation by using a microscope or computed tomography, attaching strain gauges to the teeth, and finite element analysis. This review focuses on the stress generated to the teeth and the instrument during instrumentation under various experimental conditions. The factors related to torque generation are also discussed.<\/jats:p>","DOI":"10.3390\/ma15020664","type":"journal-article","created":{"date-parts":[[2022,1,17]],"date-time":"2022-01-17T20:46:03Z","timestamp":1642452363000},"page":"664","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Torque Generation of the Endodontic Instruments: A Narrative Review"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7965-977X","authenticated-orcid":false,"given":"Sang Won","family":"Kwak","sequence":"first","affiliation":[{"name":"Department of Conservative Dentistry, Dental and Life Science Institute, Dental Research Institute, School of Dentistry, Pusan National University, Yangsan 50612, Korea"},{"name":"Department of Oral Biological and Medical Sciences, Division of Endodontics, Faculty of Dentistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0792-4279","authenticated-orcid":false,"given":"Ya","family":"Shen","sequence":"additional","affiliation":[{"name":"Department of Oral Biological and Medical Sciences, Division of Endodontics, Faculty of Dentistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9416-6372","authenticated-orcid":false,"given":"He","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Oral Biological and Medical Sciences, Division of Endodontics, Faculty of Dentistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada"},{"name":"Department of Stomatology, Affiliated Hospital of Jining Medical University, Jining 272000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8032-1194","authenticated-orcid":false,"given":"Hyeon-Cheol","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Conservative Dentistry, Dental and Life Science Institute, Dental Research Institute, School of Dentistry, Pusan National University, Yangsan 50612, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Markus","family":"Haapasalo","sequence":"additional","affiliation":[{"name":"Department of Oral Biological and Medical Sciences, Division of Endodontics, Faculty of Dentistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"346","DOI":"10.1016\/S0099-2399(88)80196-1","article-title":"An initial investigation of the bending and torsional properties of nitinol root canal files","volume":"14","author":"Walia","year":"1988","journal-title":"J. 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