{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T11:08:21Z","timestamp":1775646501962,"version":"3.50.1"},"reference-count":38,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T00:00:00Z","timestamp":1775606400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Dentistry Journal"],"abstract":"<jats:p>Background\/Objectives: Instrument fracture remains a significant complication in endodontics. This study compared the resistance to cyclic fatigue failure between rotary and reciprocating nickel\u2013titanium file systems, as well as differences related to file size and taper. Methods: Nineteen rotary and reciprocating file types (n = 10 per group) were evaluated in three independent test series, harmonized according to file size and system. Cyclic fatigue testing was conducted using a static model with a stainless-steel artificial canal, with an internal diameter of 0.9 mm, a 75\u00b0 curvature angle, and a fixed radius for each series. Files were operated using preset programs on the X-Smart Plus, Rooter X3000, and Sendoline Endo torque-controlled motors. Time to fracture was recorded digitally, and the total number of full rotations to failure was calculated. The fractured fragments were examined with scanning electron microscopy and fractographic analysis. The data were analyzed using linear models in Stata version 19, with significance set at p \u2264 0.05. Results: Reciprocating file systems demonstrated greater time-to-fracture fatigue resistance than rotary systems. However, these differences were diminished or, in some cases, eliminated when normalized to the number of complete rotations. Fractographic analysis indicated that fractures predominantly resulted from tensile stress rather than shear forces. Conclusions: Reciprocating kinematics generally enhanced fatigue resistance compared with continuous rotation. The results suggest that fatigue resistance in machine-driven nickel\u2013titanium instruments cannot be predicted by motion type or file design alone but reflects a complex interaction between alloy composition, heat treatment, and cross-sectional geometry.<\/jats:p>","DOI":"10.3390\/dj14040216","type":"journal-article","created":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T09:49:44Z","timestamp":1775641784000},"page":"216","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Cyclic Fatigue of Rotary Versus Reciprocating Endodontic Files: An In Vitro Study of Engine-Driven Endodontic Files"],"prefix":"10.3390","volume":"14","author":[{"given":"Sverre","family":"Brun","sequence":"first","affiliation":[{"name":"Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, \u00c5rstadveien 19, 5009 Bergen, Norway"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andrine Rebni","family":"Kristoffersen","sequence":"additional","affiliation":[{"name":"Public Dental Health Service in Vestland, \u00c5rstadveien 21, 5009 Bergen, Norway"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Malene Nerb\u00f8berg","family":"Solsvik","sequence":"additional","affiliation":[{"name":"Public Dental Health Service in Vestland, Gamle Dalavegen 15, 5600 Norheimsund, Norway"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7134-6485","authenticated-orcid":false,"given":"Marit","family":"\u00d8ilo","sequence":"additional","affiliation":[{"name":"Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, \u00c5rstadveien 19, 5009 Bergen, Norway"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3054-6501","authenticated-orcid":false,"given":"Inge","family":"Fristad","sequence":"additional","affiliation":[{"name":"Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, \u00c5rstadveien 19, 5009 Bergen, Norway"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1211","DOI":"10.1016\/0030-4220(55)90385-6","article-title":"The need for endodontic instrument standardization","volume":"8","author":"Ingle","year":"1955","journal-title":"Oral Surg. 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