{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,20]],"date-time":"2026-01-20T00:13:10Z","timestamp":1768867990464,"version":"3.49.0"},"reference-count":17,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T00:00:00Z","timestamp":1768694400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia, I.P.","doi-asserted-by":"publisher","award":["UIDB\/50025\/2020-2023"],"award-info":[{"award-number":["UIDB\/50025\/2020-2023"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Faculty of Dental Medicine of the University of Lisbon Scholarship for Open Access Publications"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>This study evaluated the effect of clockwise reciprocation motion used in the original Optimum Torque Reverse kinematics, compared with clockwise continuous rotation, on the cyclic fatigue strength of nickel\u2013titanium rotary instruments (NiTi) with different metallurgical characteristics. A total of 120 instruments, ProFile and EndoSequence in sizes 25\/.04, 30\/.04, and 35\/.04, were tested under continuous rotation or reciprocation motions (n = 10 per subgroup). Instruments were examined by optical and scanning electron microscopy to exclude manufacturing defects. Phase transformation temperatures were determined by differential scanning calorimetry, and cyclic fatigue testing was conducted using a custom device simulating a curved canal with a 6 mm radius and an 86\u00b0 curvature. The time to fracture was recorded, and the number of cycles to fracture was calculated. Statistical comparisons were performed using the Mann\u2013Whitney U test with a significance level of p &lt; 0.05. Differential scanning calorimetry showed that ProFile instruments were fully austenitic at the test temperature, while EndoSequence instruments exhibited a mixed R-phase and austenitic structure. Clockwise reciprocation motion significantly increased cyclic fatigue resistance in all groups compared with clockwise continuous rotation. Time to fracture increased by 241.3% to 337.5%, and EndoSequence instruments consistently demonstrated higher fatigue resistance. The greatest relative improvement was observed in ProFile 35\/.04, with a 422.4% increase in the number of cycles to fracture. Overall, the reciprocation motion markedly enhanced cyclic fatigue strength irrespective of metallurgical phase composition, indicating a practical mechanical benefit that may reduce the risk of instrument separation during endodontic procedures.<\/jats:p>","DOI":"10.3390\/ma19020387","type":"journal-article","created":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T11:35:27Z","timestamp":1768822527000},"page":"387","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Effect of Clockwise Reciprocation Motion of Optimum Torque Reverse Kinematic on the Cyclic Fatigue Resistance of Nickel\u2013Titanium Rotary Instruments with Different Metallurgical Properties"],"prefix":"10.3390","volume":"19","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\/2020, Universidade de Lisboa, 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"}]},{"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"}]},{"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\/2020, Universidade de Lisboa, 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"}]},{"given":"Jo\u00e3o","family":"Caram\u00eas","sequence":"additional","affiliation":[{"name":"Faculdade de Medicina Dent\u00e1ria, Universidade de Lisboa, 1600-277 Lisboa, Portugal"},{"name":"LIBPhys-FCT UID\/FIS\/04559\/2020, Universidade de Lisboa, 1600-277 Lisboa, Portugal"}]},{"given":"Francisco M.","family":"Braz Fernandes","sequence":"additional","affiliation":[{"name":"CENIMAT\/I3N, Department of Materials Science, NOVA School of Science and Technology, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5277-9827","authenticated-orcid":false,"given":"Marco A.","family":"Versiani","sequence":"additional","affiliation":[{"name":"Dental Specialty Center, Brazilian Military Police, Belo Horizonte 30350-190, Brazil"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,18]]},"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. Top."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"161","DOI":"10.1097\/00004770-200003000-00008","article-title":"Defects in rotary nickel-titanium files after clinical use","volume":"26","author":"Sattapan","year":"2000","journal-title":"J. Endod."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"775","DOI":"10.1111\/iej.13915","article-title":"Multimethod analysis of three rotary instruments produced by electric discharge machining technology","volume":"56","author":"Silva","year":"2023","journal-title":"Int. Endod. J."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1111\/j.1365-2591.2007.01256.x","article-title":"Fatigue testing of a NiTi rotary instrument. Part 2: Fractographic analysis","volume":"40","author":"Cheung","year":"2007","journal-title":"Int. Endod. J."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1063","DOI":"10.1111\/j.1365-2591.2010.01756.x","article-title":"Extended cyclic fatigue life of F2 ProTaper instruments used in reciprocating movement","volume":"43","author":"Moreira","year":"2010","journal-title":"Int. Endod. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"522","DOI":"10.1111\/iej.12769","article-title":"Influence of continuous rotation or reciprocation of Optimum Torque Reverse motion on cyclic fatigue resistance of nickel-titanium rotary instruments","volume":"51","author":"Corsentino","year":"2018","journal-title":"Int. Endod. J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1088","DOI":"10.1111\/iej.12924","article-title":"New thermomechanically treated NiTi alloys\u2014A review","volume":"51","author":"Zupanc","year":"2018","journal-title":"Int. Endod. J."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1046\/j.1365-2591.2000.00339.x","article-title":"An overview of nickel-titanium alloys used in dentistry","volume":"33","author":"Thompson","year":"2000","journal-title":"Int. Endod. J."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1136","DOI":"10.1016\/j.joen.2020.05.001","article-title":"Influence of Kinematics on the Cyclic Fatigue Resistance of Replicalike and Original Brand Rotary Instruments","volume":"46","author":"Martins","year":"2020","journal-title":"J. Endod."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Martins, J.N.R., Silva, E., Marques, D., and Versiani, M.A. (2024). Influence of Continuous Rotation and Optimal Torque Reverse Kinematics on the Cyclic Fatigue Strength of Endodontic NiTi Clockwise Cutting Rotary Instruments. Dent. J., 12.","DOI":"10.3390\/dj12100317"},{"key":"ref_11","unstructured":"(2004). Standard Test Method for Transformation Temperature of Nickel-Titanium Alloys by Thermal Analysis (Standard No. ASTM:F2004-17)."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"251","DOI":"10.4012\/dmj.2018-428","article-title":"Enhanced root canal-centering ability and reduced screw-in force generation of reciprocating nickel-titanium instruments with a post-machining thermal treatment","volume":"39","author":"Maki","year":"2020","journal-title":"Dent. Mater. J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1948","DOI":"10.1111\/iej.70027","article-title":"The Cost of Instrument Retrieval on the Root Integrity","volume":"58","author":"Versiani","year":"2025","journal-title":"Int. Endod. J."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"569","DOI":"10.1016\/j.joen.2012.12.033","article-title":"Management of intracanal separated instruments","volume":"39","author":"Madarati","year":"2013","journal-title":"J. Endod."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1111\/etp.12045","article-title":"An overview of the mechanical properties of nickel-titanium endodontic instruments","volume":"29","author":"Zhou","year":"2013","journal-title":"Endod. Top."},{"key":"ref_16","unstructured":"McSpadden, J.T. (2007). Mastering the concepts. Mastering Endodontics Instrumentation, Cloudland Institute."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1031","DOI":"10.1016\/j.joen.2006.06.008","article-title":"Rotary NiTi instrument fracture and its consequences","volume":"32","author":"Parashos","year":"2006","journal-title":"J. Endod."}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/2\/387\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T11:41:14Z","timestamp":1768822874000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/19\/2\/387"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,18]]},"references-count":17,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["ma19020387"],"URL":"https:\/\/doi.org\/10.3390\/ma19020387","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,18]]}}}