{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,8]],"date-time":"2026-03-08T19:30:39Z","timestamp":1772998239887,"version":"3.50.1"},"reference-count":30,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2024,9,30]],"date-time":"2024-09-30T00:00:00Z","timestamp":1727654400000},"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>Objectives: The objective of the present study was to evaluate the cyclic fatigue strength of clockwise cutting rotary endodontic instruments when subjected to two different kinematics: continuous clockwise rotation and clockwise reciprocation movement under optimum torque reverse (OTR) motion. Methods: New ProTaper Next X1 (n = 20) and X2 (n = 20) instruments were randomly divided into two subgroups (n = 10) based on kinematics (continuous rotation or OTR). The specimens were tested using a custom-made device with a non-tapered stainless-steel artificial canal measuring 19 mm in length, featuring a 6 mm radius and an 86-degree curvature. All instruments were tested with a lubricant at room temperature until a fracture occurred. The time to fracture and the length of the separated fragment were recorded. Subsequently, the fractured instruments were inspected under a scanning electron microscope for signs of cyclic fatigue failure, plastic deformation, and\/or crack propagation. The subgroup comparisons for time to fracture and instrument length were performed using the independent samples t-test, with the level of statistical significance set at 0.05. Results: When using OTR movement, the ProTaper Next X1 increased the time to fracture from 52.9 to 125.8 s (p &lt; 0.001), while the ProTaper Next X2 increased from 45.4 to 66.0 s (p &lt; 0.001). No subgroup exhibited plastic deformations, but both showed dimpling marks indicative of cyclic fatigue as the primary mode of failure. Additionally, OTR movement resulted in more metal alloy microcracks. Conclusions: The use of OTR motion extended the lifespan of the tested instruments and resulted in a higher number of metal microcracks. This suggests that OTR motion helped to distribute the mechanical stress more evenly across the instrument, thereby relieving localized tension. As a result, it delayed the formation of a single catastrophic crack, enhancing the overall performance of the instruments during the experimental procedures.<\/jats:p>","DOI":"10.3390\/dj12100317","type":"journal-article","created":{"date-parts":[[2024,9,30]],"date-time":"2024-09-30T04:57:28Z","timestamp":1727672248000},"page":"317","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Influence of Continuous Rotation and Optimal Torque Reverse Kinematics on the Cyclic Fatigue Strength of Endodontic NiTi Clockwise Cutting Rotary Instruments"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6932-2038","authenticated-orcid":false,"given":"Jorge N. R.","family":"Martins","sequence":"first","affiliation":[{"name":"Faculdade de Medicina Dent\u00e1ria, Universidade de Lisboa, 1600-277 Lisboa, Portugal"},{"name":"LIBPhys-FCT UID\/FIS\/04559\/2013, 1600-277 Lisboa, Portugal"},{"name":"Grupo de Investiga\u00e7\u00e3o em Bioquimica e Biologia Oral (GIBBO), Unidade de Investiga\u00e7\u00e3o em Ci\u00eancias Orais e Biom\u00e9dicas (UICOB), 1600-277 Lisboa, Portugal"},{"name":"Centro de Estudos de Medicina Dent\u00e1ria Baseada na Evid\u00eancia (CEMDBE), 1600-277 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6445-8243","authenticated-orcid":false,"given":"Emmanuel J. N. L.","family":"Silva","sequence":"additional","affiliation":[{"name":"Department of Endodontics, School of Dentistry, Grande Rio University (UNIGRANRIO), Rio de Janeiro 21210-623, Brazil"},{"name":"Department of Endodontics, Fluminense Federal University, Rio de Janeiro 24220-900, Brazil"},{"name":"Department of Endodontics, Rio de Janeiro University (UERJ), Rio de Janeiro 20550-013, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1966-8281","authenticated-orcid":false,"given":"Duarte","family":"Marques","sequence":"additional","affiliation":[{"name":"Faculdade de Medicina Dent\u00e1ria, Universidade de Lisboa, 1600-277 Lisboa, Portugal"},{"name":"LIBPhys-FCT UID\/FIS\/04559\/2013, 1600-277 Lisboa, Portugal"},{"name":"Grupo de Investiga\u00e7\u00e3o em Bioquimica e Biologia Oral (GIBBO), Unidade de Investiga\u00e7\u00e3o em Ci\u00eancias Orais e Biom\u00e9dicas (UICOB), 1600-277 Lisboa, Portugal"},{"name":"Centro de Estudos de Medicina Dent\u00e1ria Baseada na Evid\u00eancia (CEMDBE), 1600-277 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marco A.","family":"Versiani","sequence":"additional","affiliation":[{"name":"Dental Specialty Center, Brazilian Military Police, Belo Horizonte 30350-190, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2024,9,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1111\/j.1601-1546.2005.00152.x","article-title":"Mechanical preparation of root canals: Shaping goals, techniques and means","volume":"10","author":"Peters","year":"2005","journal-title":"Endod. 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