Mechanical and Metallurgical Properties of Various Nickel-Titanium Rotary Instruments

The aim of this study was to investigate the effect of thermomechanical treatment on mechanical and metallurgical properties of nickel-titanium (NiTi) rotary instruments. Eight kinds of NiTi rotary instruments with sizes of ISO #25 were selected: ProFile, K3, and One Shape for the conventional alloy; ProTaper NEXT, Reciproc, and WaveOne for the M-wire alloy; HyFlex CM for the controlled memory- (CM-) wire; and TF for the R-phase alloy. Torsional fracture and cyclic fatigue fracture tests were performed. Products underwent a differential scanning calorimetry (DSC) analysis. The CM-wire and R-phase groups had the lowest elastic modulus, followed by the M-wire group. The maximum torque of the M-wire instrument was comparable to that of a conventional instrument, while those of the CM-wire and R-phase instruments were lower. The angular displacement at failure (ADF) for the CM-wire and R-phase instruments was higher than that of conventional instruments, and ADF of the M-wire instruments was lower. The cyclic fatigue resistance of the thermomechanically treated NiTi instruments was higher. DSC plots revealed that NiTi instruments made with the conventional alloy were primarily composed of austenite at room temperature; stable martensite and R-phase were found in thermomechanically treated instruments.

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Torsional Resistance of Heat-Treated Nickel-Titanium Instruments under Different Temperature Conditions

Materials ◽

10.3390/ma14185295 ◽

2021 ◽

Vol 14 (18) ◽

pp. 5295

Author(s):

Hyo Jin Jo ◽

Sang Won Kwak ◽

Hyeon-Cheol Kim ◽

Sung Kyo Kim ◽

Jung-Hong Ha

Keyword(s):

Nickel Titanium ◽

Phase Transformation Temperature ◽

Scanning Calorimetry ◽

Temperature Conditions ◽

Torsional Resistance ◽

Heat Treated ◽

Rotary Instruments ◽

Single Use ◽

Niti Instruments ◽

Niti Rotary Instruments

This study compared the torsional resistance of heat-treated nickel-titanium (NiTi) instruments under different temperature conditions. Four thermomechanically treated single-use NiTi rotary instruments were selected for this study: OneShape (OS), OneCurve (OC), WaveOne Gold (WOG) and HyFlex EDM (HFE). Each instrument was further subdivided by temperature into 2 subgroups. Maximum torque and the distortion angle until fracture occurred were evaluated. Differential scanning calorimetry analysis was performed to measure the phase transformation temperature. Statistical analysis was performed using a two-way ANOVA and t-test (p < 0.05). Fractured fragments were observed using scanning electron microscopy (SEM). The two-way ANOVA showed no significant differences for different temperature conditions. At both room (RT) and body temperature (BT), OS was predominantly austenite while HFE was martensite. OC and WOG were predominantly martensite at RT and mixed phase at BT. At BT, more than half of WOG was martensite, while half of OC was austenite. SEM examination showed no topographical differences between instruments in different temperature groups. In relation to a limitation of this study, there was no difference in torsional resistance of NiTi rotary instruments between the BT and RT conditions. This implies that clinicians do not need to consider a decrease of torsional resistance of heat-treated NiTi instruments at BT.

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Role of the Flat-Designed Surface in Improving the Cyclic Fatigue Resistance of Endodontic NiTi Rotary Instruments

Materials ◽

10.3390/ma12162523 ◽

2019 ◽

Vol 12 (16) ◽

pp. 2523 ◽

Cited By ~ 6

Author(s):

Gianluca Gambarini ◽

Gabriele Miccoli ◽

Marco Seracchiani ◽

Tatyana Khrenova ◽

Orlando Donfrancesco ◽

...

Keyword(s):

Cyclic Fatigue ◽

Nickel Titanium ◽

Segment Length ◽

Flat Side ◽

Heat Treated ◽

Rotary Instruments ◽

Time To Fracture ◽

Niti Instruments ◽

Niti Rotary Instruments

The aim of this study was to investigate the role of the flat-designed surface in improving the resistance to cyclic fatigue by comparing heat-treated F-One (Fanta Dental, Shanghai, China) nickel–titanium (NiTi) rotary instruments and similar prototypes, differing only by the absence of the flat side. The null hypothesis was that there were no differences between the two tested instruments in terms of cyclic fatigue lifespan. A total of 40 new NiTi instruments (20 F-One and 20 prototypes) were tested in the present study. The instruments were rotated with the same speed (500 rpm) and torque (2 N) using an endodontic motor (Elements Motor, Kerr, Orange, CA, USA) in the same stainless steel, artificial canal (90° angle of curvature and 5 mm radius). A Wilcoxon–Mann–Whitney test was performed to assess the differences in terms of time to fracture and the length of the fractured segment between the flat- and non-flat-sided instruments. Significance was set at p = 0.05. The differences in terms of time to fracture between non-flat and flat were statistically significant (p < 0.001). In addition, the differences in terms of fractured segment length were statistically significant (p = 0.034). The results of this study highlight the importance of flat-sided design in increasing the cyclic fatigue lifespan of NiTi rotary instruments.

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Advancement of Mechanical Properties of Nickel-Titanium Rotary Endodontic Instruments by Spring Machining on the File Shaft

Materials ◽

10.3390/ma13225246 ◽

2020 ◽

Vol 13 (22) ◽

pp. 5246

Author(s):

Sangmi Ahn ◽

Jung-Hong Ha ◽

Sang Won Kwak ◽

Hyeon-Cheol Kim

Keyword(s):

Fatigue Resistance ◽

Cyclic Fatigue ◽

Nickel Titanium ◽

Significance Level ◽

Rotary Instruments ◽

Niti Instruments ◽

General Dentists ◽

Niti Rotary Instruments ◽

Distortion Angle ◽

Paired T Test

Nickel-titanium (NiTi) endodontic rotary instruments are used extensively in root canal procedures by both general dentists and specialists. However, their vulnerability to fracture is the major reason for clinicians’ concern regarding their use. The objective of this study was to investigate the potential effects of spring machining of the file shaft on the fatigue and torsional resistances of NiTi rotary instruments. Three types of NiTi rotary systems with (S) and without (NS) spring machining were used in this study (n = 15 each): a spring file (SPR; #25/.06, SPR-S, SPR-NS), a ProTaper Next X2 (PTN; #25/variable taper, PTN-S, PTN-NS), and a ProTaper Gold F2 (PTG; #25/variable taper, PTG-S, PTG-NS). Spring machining was adjusted on the 6 mm of each file system’s shaft via a laser cutting process. The number of rotation cycles until fracture (i.e., cyclic fatigue resistance), ultimate torsional strength, the distortion angle, and the toughness of each subgroup were estimated with specially designed devices. The results were analyzed using a paired t-test at a significance level of 95%. NiTi rotary instruments with spring machining exhibited a higher cyclic fatigue resistance than instruments without spring machining. The groups with spring machining exhibited a higher toughness and larger distortion angle than the groups without it (p < 0.05). In conclusion, spring machining on the shank of NiTi instruments may provide a stress-bearing area and attenuate the torsional and cyclic fatigue of NiTi rotary instruments.

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Evolution of Nickel–titanium Alloys in Endodontics

The Journal of Contemporary Dental Practice ◽

10.5005/jp-journals-10024-2181 ◽

2017 ◽

Vol 18 (11) ◽

pp. 1090-1096 ◽

Cited By ~ 5

Author(s):

Sukumaran Anil ◽

Prasanna Neelakantan ◽

Wadih Nassif

Keyword(s):

Titanium Alloys ◽

Clinical Performance ◽

Surface Hardness ◽

Cyclic Fatigue ◽

Surface Treatments ◽

Nickel Titanium ◽

Fatigue Properties ◽

Rotary Instruments ◽

Nickel Titanium Alloys ◽

Niti Instruments

ABSTRACT To improve clinical use of nickel–titanium (NiTi) endodontic rotary instruments by better understanding the alloys that compose them. A large number of engine-driven NiTi shaping instruments already exists on the market and newer generations are being introduced regularly. While emphasis is being put on design and technique, manufacturers are more discreet about alloy characteristics that dictate instrument behavior. Along with design and technique, alloy characteristics of endodontic instruments is one of the main variables affecting clinical performance. Modification in NiTi alloys is numerous and may yield improvements, but also drawbacks. Martensitic instruments seem to display better cyclic fatigue properties at the expense of surface hardness, prompting the need for surface treatments. On the contrary, such surface treatments may improve cutting efficiency but are detrimental to the gain in cyclic fatigue resistance. Although the design of the instrument is vital, it should in no way cloud the importance of the properties of the alloy and how they influence the clinical behavior of NiTi instruments. Clinical significance Dentists are mostly clinicians rather than engineers. With the advances in instrumentation design and alloys, they have an obligation to deal more intimately with engineering consideration to not only take advantage of their possibilities but also acknowledge their limitations. How to cite this article Ounsi HF, Nassif W, Grandini S, Salameh Z, Neelakantan P, Anil S. Evolution of Nickel–titanium Alloys in Endodontics. J Contemp Dent Pract 2017;18(11):1090-1096.

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Information regarding use of rotary nickel -titanium endodontic instruments among general dental practitioners: a questionnaire survey

Journal of Research in Dentistry ◽

10.19177/jrd.v4e120164-8 ◽

2016 ◽

Vol 4 (1) ◽

pp. 4

Author(s):

Ritu Meel ◽

Deepak Raisingani ◽

Ashwini Prasad ◽

Rachit Mathur ◽

Nidha Madan ◽

...

Keyword(s):

Questionnaire Survey ◽

Nickel Titanium ◽

Cross Sectional ◽

Rotary Instruments ◽

Dental Practitioners ◽

Instruments And Techniques ◽

Niti Instruments ◽

General Dentists ◽

Niti Rotary Instruments

Aim: A cross-sectional questionnaire survey was conducted to obtain information on the use of rotary nickel –titanium endodontic instruments was conducted among General Dental Practioner A two sectioned questionnaire was mailed to 200 randomly general practioners to obtain information on usage of Nickel –Titanium endodontic instrument and data was collected.Results: Forty-six percent of the general practioners had used rotary NiTi instruments. 76% dentists use NiTi files for five or more times a week. Most of the dentist used NiTi file coronally &apically. General dentists experienced more file fracture at size 20 and 25 with 0.02 and 0.04 taper.Conclusions: Dentists are familiar with limitations of NiTi instruments and techniques. Current study showed the awareness of dentists about benefits of NiTi rotary instruments application comparing to traditional techniques and also the high percent usage of these instruments among general dentists.

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Cyclic fatigue resistance of reduced-taper nickel-titanium (NiTi)instruments in doubled-curved (S-shaped) canals at body temperature

Journal of Dental Research Dental Clinics Dental Prospects ◽

10.34172/joddd.2020.024 ◽

2020 ◽

Vol 14 (2) ◽

pp. 111-115 ◽

Cited By ~ 1

Author(s):

Gülsah Uslu ◽

Mustafa Gündoğar ◽

Taha Özyürek ◽

Gianluca Plotino

Keyword(s):

Fatigue Resistance ◽

Fatigue Testing ◽

Cyclic Fatigue ◽

Nickel Titanium ◽

Clinical Environment ◽

Root Canals ◽

Rotary Instruments ◽

Niti Instruments ◽

Student’S T ◽

Number Of Cycles

Background. This study was conducted to compare the cyclic fatigue resistance of VDW.ROTATE,TruNatomy Prime, HyFlex CM, and 2Shape nickel-titanium (NiTi) rotary instruments in doublecurvedcanals in a simulated clinical environment. Methods. Eighty NiTi files were used for the fatigue testing in stainless steel canals compatible withinstrument sizes until fracture occurred (n=20): VDW.ROTATE (04./25#), TruNatomy Prime (04./26#),HyFlex CM (04./25#) and 2Shape TS04./25#( 1). For each instrument, the number of cycles to fracture(NCF) was calculated, and the fractured fragment length (FL) was measured. To verify that the fileswere fractured due to cyclic fatigue, the fractured surfaces of the files were evaluated under a scanningelectron microscope. Data were statistically analyzed using the Kruskal–Wallis and Student’s t-tests atthe %95 confidence level. Results. The failure of the files due to cyclic fatigue was first seen in the apical curvature before thecoronal curvature (P<0.05). The highest fatigue resistance was observed in VDW.ROTATE and HyFlexCM files in both curvatures (P<0.05). There were no significant differences in the fatigue resistancebetween the HyFlex CM and VDW.ROTATE files or between the 2Shape and the TruNatomy files(P>0.05). There was no difference in the fractured lengths of the files between the apical and coronalcurvatures (P>0.05). Conclusion. In artificial S-shaped root canals, VDW.ROTATE and HyFlex CM files exhibited higherfatigue resistance compared to 2Shape and TruNatomy files.

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Automatic Electronic Device Used for the Evaluation of Cyclic-Fatigue Resistance of Nickel-Titanium Instruments

Odovtos - International Journal of Dental Sciences ◽

10.15517/ijds.v0i0.27288 ◽

2017 ◽

Vol 19 (1) ◽

pp. 51

Author(s):

Cesar Gaitán-Fonseca DDS, MSc, PhD ◽

Edith Lara-Alvarado DDS, MSc ◽

Héctor Flores-Reyes DDS, MSc, PhD ◽

Amaury Pozos-Guillén DDS, MSc, PhD ◽

Verónica Méndez-González DDS, MSc

Keyword(s):

Human Factor ◽

Electronic Device ◽

Cyclic Fatigue ◽

Nickel Titanium ◽

Cycle Number ◽

Fracture Pressure ◽

Group Data ◽

Rotary Instruments ◽

Two Parameters ◽

Pressure Changes

The aim of this study was to evaluate the cyclic-fatigue fracture of different Nickel-Titanium motor-driven rotary instruments (ProTaper® Universal, ProFile®, and Mtwo® systems) in artificial canals by means of an Automatic Electronic Device (AED). The study was performed using Nickel-Titanium instruments 25/0.06 evaluated in canals with a 45-degree curvature and 2-mm radius. The analyses evaluated two parameters: fracture by cyclic fatigue, and time of fracture; in addition, the length of separated fragment was evaluated. Medians and range values were calculated for each group. Data were analyzed by the Kruskall–Wallis and Mann–Whitney U tests to determine statistical difference. The ProFile motor-driven rotator system exhibited highest resistance to fracture due to cyclic fatigue and highest fracture time compared with the ProTaper and Mtwo systems (p <0.05). The equipment proposed in this study (AED) demonstrated efficiency for recording information, automation, scheduled work times and durations, cycle number, time of fracture, pressure changes and, principally control of the human factor.

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