Fracture Resistance of Heat-Treated Nickel-Titanium Rotary Files After Usage and Autoclave Sterilization: An In Vitro Study

Published:August 17, 2022DOI:



      This study aimed to evaluate the dynamic cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) files after usage and autoclaving.


      Two heat-treated NiTi file systems with tip sizes of #25 (ie, ProTaper Gold F2 [Dentsply Sirona, Charlotte, NC] and TruNatomy Prime [Dentsply Sirona]) were selected. Files of each system were divided into 3 experimental subgroups (n = 10). For subgroup 1, new files were tested to establish the baseline number of cycles to failure (NCF). For subgroup 2, files underwent canal instrumentation in a simulated J-shaped canal block with 35° of curvature and a 16.5-mm length. The simulated canals were pre-enlarged using stainless steel files #10K and #15K. After instrumentation, the files were tested. For subgroup 3, files underwent canal instrumentation as in subgroup 2 followed by autoclave sterilization and then were tested for cyclic failure. The cyclic fatigue test was performed in dynamic pecking motion under body temperature. The time to fracture was recorded and calculated into NCF. Fracture fragment lengths were measured using a digital microcaliper. Statistical analysis was conducted using the independent t test and multifactorial analysis of variance with 95% significance. Scanning electron microscopy was used to examine the topographic characteristics after cyclic fatigue tests.


      There were no significant differences between file systems in subgroup 1 using new files (P < .05). Although PG reduced the NCF after use, TN showed a significantly increased NCF (P < .05). However, after sterilization, TN showed a reduced NCF compared with the used one (P < .05).


      Cyclic loading by usage and heat treatment during sterilization may result in different cyclic fatigue resistance according to the geometry and alloy characteristics.

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        • Walia H.M.
        • Brantley W.A.
        • Gerstein H.
        An initial investigation of the bending and torsional properties of nitinol root canal files.
        J Endod. 1988; 14: 346-351
        • Es-Souni M.
        • Es-Souni M.
        • Brandies H.F.
        On the transformation behaviour, mechanical properties and biocompatibility of two niti-based shape memory alloys: NiTi42 and NiTi42Cu7.
        Biomaterials. 2001; 22: 2153-2161
        • Cheung G.S.
        • Liu C.S.
        A retrospective study of endodontic treatment outcome between nickel-titanium rotary and stainless steel hand filing techniques.
        J Endod. 2009; 35: 938-943
        • Peters O.A.
        • Schönenberger K.
        • Laib A.
        Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography.
        Int Endod J. 2001; 34: 221-230
        • Shen Y.
        • Cheung G.S.
        Methods and models to study nickel–titanium instruments.
        Endod Topics. 2013; 29: 18-41
        • Zinelis S.
        • Eliades T.
        • Eliades G.
        A metallurgical characterization of ten endodontic Ni-Ti instruments: assessing the clinical relevance of shape memory and superelastic properties of Ni-Ti endodontic instruments.
        Int Endod J. 2010; 43: 125-134
        • Ashok L.
        • Krishnan V.
        • Nair R.S.
        • Angelo M.C.
        An overview of thermomechanically heat-treated nickel–titanium alloy used in endodontics.
        Cons Dent Endod J. 2019; 4: 34-38
        • Shen Y.
        • Zhou H.M.
        • Zheng Y.F.
        • et al.
        Current challenges and concepts of the thermomechanical treatment of nickel-titanium instruments.
        J Endod. 2013; 39: 163-172
        • Bulem Ü K.
        • Kececi A.D.
        • Guldas H.E.
        Experimental evaluation of cyclic fatigue resistance of four different nickel-titanium instruments after immersion in sodium hypochlorite and/or sterilization.
        J Appl Oral Sci. 2013; 21: 505-510
        • Silva E.
        • Zanon M.
        • Hecksher F.
        • et al.
        Influence of autoclave sterilization procedures on the cyclic fatigue resistance of heat-treated nickel-titanium instruments: a systematic review.
        Restor Dent Endod. 2020; 45: e25
        • Özyürek T.
        • Yılmaz K.
        • Uslu G.
        The effects of autoclave sterilization on the cyclic fatigue resistance of ProTaper Universal, ProTaper Next, and ProTaper Gold nickel-titanium instruments.
        Restor Dent Endod. 2017; 42: 301-308
        • Al Raeesi D.
        • Kwak S.W.
        • Ha J.H.
        • et al.
        Mechanical properties of glide path preparation instruments with different pitch lengths.
        J Endod. 2018; 44: 864-868
        • Kim T.O.
        • Cheung G.S.
        • Lee J.M.
        • et al.
        Stress distribution of three NiTi rotary files under bending and torsional conditions using a mathematic analysis.
        Int Endod J. 2009; 42: 14-21
        • Sattapan B.
        • Nervo G.J.
        • Palamara J.E.
        • Messer H.H.
        Defects in rotary nickel-titanium files after clinical use.
        J Endod. 2000; 26: 161-165
        • Setzer F.C.
        • Böhme C.P.
        Influence of combined cyclic fatigue and torsional stress on the fracture point of nickel-titanium rotary instruments.
        J Endod. 2013; 39: 133-137
        • Bürklein S.
        • Zupanc L.
        • Donnermeyer D.
        • et al.
        Effect of core mass and alloy on cyclic fatigue resistance of different nickel-titanium endodontic instruments in matching artificial canals.
        Materials (Basel). 2021; 14: 5734
        • Pedullà E.
        • Benites A.
        • La Rosa G.M.
        • et al.
        Cyclic fatigue resistance of heat-treated nickel-titanium instruments after immersion in sodium hypochlorite and/or sterilization.
        J Endod. 2018; 44: 648-653
        • Hayashi Y.
        • Yoneyama T.
        • Yahata Y.
        • et al.
        Phase transformation behaviour and bending properties of hybrid nickel-titanium rotary endodontic instruments.
        Int Endod J. 2007; 40: 247-253
        • Plotino G.
        • Costanzo A.
        • Grande N.M.
        • et al.
        Experimental evaluation on the influence of autoclave sterilization on the cyclic fatigue of new nickel-titanium rotary instruments.
        J Endod. 2012; 38: 222-225
        • Valois C.R.
        • Silva L.P.
        • Azevedo R.B.
        Multiple autoclave cycles affect the surface of rotary nickel-titanium files: an atomic force microscopy study.
        J Endod. 2008; 34: 859-862
        • Silvaggio J.
        • Hicks M.L.
        Effect of heat sterilization on the torsional properties of rotary nickel-titanium endodontic files.
        J Endod. 1997; 23: 731-734
        • Ha J.H.
        • Sigurdsson A.
        • De-Deus G.
        • et al.
        Torsional behavior of WaveOne Gold endodontic file with the dedicated motor of the original WaveOne file.
        Materials (Basel). 2018; 11: 1150
        • Plotino G.
        • Grande N.M.
        • Cordaro M.
        • et al.
        A review of cyclic fatigue testing of nickel-titanium rotary instruments.
        J Endod. 2009; 35: 1469-1476
        • Elnaghy A.M.
        • Elsaka S.E.
        Laboratory comparison of the mechanical properties of TRUShape with several nickel-titanium rotary instruments.
        Int Endod J. 2017; 50: 805-812
        • Elnaghy A.M.
        • Elsaka S.E.
        Mechanical properties of ProTaper Gold nickel-titanium rotary instruments.
        Int Endod J. 2016; 49: 1073-1078
        • Goo H.J.
        • Kwak S.W.
        • Ha J.H.
        • et al.
        Mechanical properties of various heat-treated nickel-titanium rotary instruments.
        J Endod. 2017; 43: 1872-1877
        • Silva E.J.
        • Lima C.O.
        • Barbosa A.F.
        • et al.
        The impact of TruNatomy and ProTaper Gold instruments on the preservation of the periradicular dentin and on the enlargement of the apical canal of mandibular molars.
        J Endod. 2022; 48: 650-658
        • Mize S.B.
        • Clement D.J.
        • Pruett J.P.
        • Carnes Jr., D.L.
        Effect of sterilization on cyclic fatigue of rotary nickel-titanium endodontic instruments.
        J Endod. 1998; 24: 843-847
        • Hilfer P.B.
        • Bergeron B.E.
        • Mayerchak M.J.
        • et al.
        Multiple autoclave cycle effects on cyclic fatigue of nickel-titanium rotary files produced by new manufacturing methods.
        J Endod. 2011; 37: 72-74
        • Lopes H.P.
        • Ferreira A.A.
        • Elias C.N.
        • et al.
        Influence of rotational speed on the cyclic fatigue of rotary nickel-titanium endodontic instruments.
        J Endod. 2009; 35: 1013-1016
        • Daugherty D.W.
        • Gound T.G.
        • Comer T.L.
        Comparison of fracture rate, deformation rate, and efficiency between rotary endodontic instruments driven at 150 rpm and 350 rpm.
        J Endod. 2001; 27: 93-95
        • Zelada G.
        • Varela P.
        • Martín B.
        • et al.
        The effect of rotational speed and the curvature of root canals on the breakage of rotary endodontic instruments.
        J Endod. 2002; 28: 540-542