A Review of Cyclic Fatigue Testing of Nickel-Titanium Rotary Instruments (original) (raw)
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An In Vitro Cyclic Fatigue Analysis of Different Endodontic Nickel-Titanium Rotary Instruments
Journal of Endodontics, 2012
Introduction: The study compared Twisted File (TF) with 3 traditionally manufactured systems to determine whether changes in the manufacturing process improved the cyclic fatigue resistance. Methods: Four rotary file systems, (1) ProFile (PF), (2) Mtwo, (3) K3, and (4) TF, were tested in artificial canals with 45 and 90 angles of curvature. Ten instruments each of the 4 file systems were tested in both angles of curvature (n = 10). All instruments had identical size and taper (.06/0.25 tip diameter). Results: A statistically significant difference (P < .05) was noted between TF and other nickel-titanium instruments in both 45 and 90 angles of curvature. TF showed the greatest mean number of cycles to failure. There was no statistical difference between PF and K3 (P > .05) in both canal curvatures; however, statistically significant difference (P < .05) was observed between Mtwo and the other 2 traditionally manufactured instruments. Mtwo showed the lowest mean number of cycles to failure. Conclusions: Under the conditions of this study, size .06/0.25 TF was significantly more resistant to fatigue than the other 3 instrument systems produced with the traditional grinding process.
Journal of Endodontics, 2011
Introduction: The aim of this study was to evaluate, by static and dynamic cyclic fatigue tests, the number of cycles to fracture (NCF) 2 types of rotary NiTi instruments: Twisted File (SybronEndo, Orange, CA), which is manufactured by a proprietary twisting process, and RaCe files (FKG Dentaire, La Chaux-de-Fonds, Switzerland), which are manufactured by grinding. Methods: Twenty Twisted Files (TFs) and 20 RaCe files #25/.006 taper instruments were allowed to rotate freely in an artificial curved canal at 310 rpm in a static or a dynamic model until fracture occurred. Results: Measurements of the fractured fragments showed that fracture occurred at the point of maximum flexure in the midpoint of the curved segment. The NCF was significantly lower for RaCe instruments compared with TFs. The NCF was also lower for instruments subjected to the static test compared with the dynamic model in both groups. Scanning electron microscopic analysis revealed ductile morphologic characteristics on the fractured surfaces of all instruments and no plastic deformation in their helical shafts. Conclusions: Rotary NiTi endodontic instruments manufactured by twisting present greater resistance to cyclic fatigue compared with instruments manufactured by grinding. The fracture mode observed in all instruments was of the ductile type. (J Endod 2011;37:1553-1557
Influence of Rotational Speed on the Cyclic Fatigue of Rotary Nickel-Titanium Endodontic Instruments
Journal of Endodontics, 2009
Introduction: During the preparation of curved canals, rotary nickel-titanium (NiTi) instruments are subjected to cyclic fatigue, which can lead to instrument fracture. Although several factors may influence the cyclic fatigue resistance of instruments, the role of the rotational speed remains uncertain. This study was intended to evaluate the effects of rotational speed on the number of cycles to fracture of rotary NiTi instruments. Methods: ProTaper Universal instruments F3 and F4 (Maillefer SA, Ballaigues, Switzerland) were used in an artificial curved canal under rotational speeds of 300 rpm or 600 rpm. The artificial canal was made of stainless steel, with an inner diameter of 1.5 mm, total length of 20 mm, and arc at the end with a curvature radius of 6 mm. The arc length was 9.4 mm and 10.6 mm on the straight part. The number of cycles required to fracture was recorded. Fractured surfaces and the helical shafts of the fractured instruments were analyzed by scanning electron microscopy. Results: The results showed approximately a 30% reduction in the observed number of cycles to fracture as rotational speed was increased from 300 to 600 RPM (p < 0.05). The morphology of the fractured surface was always of ductile type, and no plastic deformation was observed on the helical shaft of fractured instruments. Conclusions: The present findings for both F3 and F4 ProTaper instruments revealed that the increase in rotational speed significantly reduced the number of cycles to fracture. (J Endod 2009;35:1013-1016
Frontiers in Dental Medicine, 2021
Introduction: Cyclic fatigue resistance of rotary endodontic instruments has been extensively studied in the last two decades, yet with no standardization. While new low-cost instruments are now manufactured, a standard is lacking to guarantee a minimum quality. This study aimed to validate a new model for CF testing through a fixture proposed for ISO Specification 3630-1 and to establish a minimum quality standard based on testing conditions and material characteristics.Materials and methods: Size 25/0.06 instruments of ProFile Vortex (PF) and Vortex Blue (VB) were run until failure in curved metallic fixtures (5 or 7.5 mm radius) built according to a proposal for an additional test for the ISO 3630-1 standard. High resolution videos were recorded, number of cycles to failure (NCF) registered and apical fragments measured with a digital caliper. Surface strain was determined from test dimensions and fragment lengths. Mean life, β and η parameters were calculated with Weibull analys...
Cyclic fatigue of different nickel-titanium endodontic rotary instruments
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 2006
A comparative study of the fatigue resistance of rotary nickel-titanium endodontic instruments was performed with the aim of assessing the influence of both instrument design and surface treatment on flexural fracture. Study design. To evaluate fatigue resistance of different rotary instruments, a total of 120 instruments were tested; these came from different sources: ProFile, RaCe, K3, Hero, and Mtwo. To compare the effect of electro-polishing procedures on fatigue resistance, a group of RaCe instruments (which are normally electro-polished) without surface treatment was used. A scanning electron microscope (SEM) study for each instrument was performed before and after fatigue study to determine the mode of fracture and the aspect of tips and cross-sectional surface areas. Results. ProFile instruments gave the best values for fatigue resistance. It was seen that for RaCe instruments the surface treatment reduces the presence of micro-cracks, surface debris, and machining damage.
Cyclic Fatigue of Different Nickel-Titanium Rotary Instruments: A Comparative Study
The Open Dentistry Journal, 2009
Since the introduction of nickel-titanium alloy to endodontics, there have been many changes in instrument design, but no significant improvements in the raw material properties, or enhancements in the manufacturing process. Recently, a new method to produce nickel-titanium rotary (NTR) instruments has been developed, in an attempt to obtain instruments that are more flexible and resistant to fatigue. NTR instruments produced using the process of twisting (TF, SybronEndo, Orange, CA) were compared to NTR instruments from different manufacturers produced by a traditional grinding process. The aim of the study was to investigate whether cyclic fatigue resistance is increased for TF NTR files. Tests were performed with a cyclic fatigue device that evaluated cycles to failure of rotary instruments inside curved artificial canals. Results indicated that size 06-25 TF instruments showed a significant increase (P< .05). In the mean number of cycles to failure when compared to the other tested 06-25 NTR. Hence, it can be concluded that size 06-25 TF NTR instruments were found to be significantly more resistant to fatigue than those produced with the traditional grinding process.
Survival Analysis of Factors Influencing Cyclic Fatigue of Nickel-Titanium Endodontic Instruments
Advances in Materials Science and Engineering, 2015
Objective. The aim of this study was to validate a survival analysis assessing the effect of type of rotary system, canal curvature, and instrument size on cyclic resistance.Materials and Methods. Cyclic fatigue testing was carried out in stainless steel artificial canals with radii of curvature of 3 or 5 mm and the angle of curvature of 60 degrees. All the instruments were new and 25 mm in working length, and ISO colour coding indicated the instrument size (yellow for size 20; red for size 25).Wizard Navigatorinstruments,Mtwoinstruments,ProTaperinstruments, andRevo-Sinstruments were passively rotated at 250 rotations per minute, and the time fracture was being recorded. Subsequently, fractographic analysis of broken tips was performed by scanning electron microscope. The data were then analysed by the Kaplan-Meier estimator of the survival function, the Cox proportional hazards model, the Wald test for regression covariates, and the Wald test for significance of regression model.Co...
Applied Sciences
Background: To evaluate the cyclic fatigue resistance of rotary endodontic nickel-titanium instruments using both experimental and finite element methods. Methodology: Four different proprietary rotary endodontic instruments (PTG, PTU, VB, and TRN) were subjected to cyclic fatigue tests through a custom-built fixture (n = 30 for each group) and tested until failure according to the manufacturer’s recommended settings, and the number of cycles to failure (NCF) was measured. Separated fragments were measured to determine the location of the fracture event. Finite element modeling replicated this experiment in silico via a two-step method, modeling the dynamic motion via an initial insertion step, then followed by rotation. Results: TRN showed the highest NCF (2027.94 ± 452.50) with the lowest values for strain (4.49% ± 0.23%) and fragment lengths (3.26 mm ± 0.47 mm), whereas PTU showed the lowest NCF (600.90 ± 80.86) and highest values for strain (6.29% ± 0.47%) and fragment lengths (...
Influence of cyclical fatigue on torsional fracture morphology in endodontic instruments
Acta odontológica latinoamericana : AOL, 2013
Cyclical fatigue may influence the appearance and propagation of the type of fracture of an endodontic instrument. The aim of this study was to assess the influence of cyclic fatigue on morphological features of torsional fracture in Pathfile nickel-titanium rotary instruments for surgical preparation in endodontics. Thirty new Pathfile instruments (Dentsply- Maillefer. Ballaigues-Switzerland) diameter .13 and taper .02 were randomly divided into 5 groups (n = 6). Twenty-four of them were subject to cyclical fatigue by continuous rotation using a stainless steel cylinder with internal bore 0.5 mm, length 25 mm, with a curve of 45 degrees and radius 8 mm at 5 mm from the tip, at 300 rpm and 1 Ncm torque for different times: A: 15 sec, B: 75 sec, C: 150 sec and D: 300 sec, while the fifth group was kept as a control (group N). As a second step, the instruments were rotated at 2 rpm and 1 Ncm torque, with their apical 3 mm fixed in a resin block until they suffered torsional fracture. ...
Predicting in vivo failure of rotary nickel-titanium endodontic instruments under cyclic fatigue
Dental Materials Journal, 2012
The aim of this study was to examine the lifespan or number of cycles to failure of tapered rotary nickel-titanium (Ni-Ti) endodontic instruments. Simulated root canals with different curvatures were used to determine a relation between canal curvature and instrument lifespan. Using a novel mathematical model for the deformation of pseudoelastic Ni-Ti alloy, it was shown that maximum stress need not necessarily occur at the outer layer. On the basis of this observation, the Coffi n-Manson relation was modifi ed with parameters determined from this experiment. Results showed that the number of cycles to failure was infl uenced by the angle and radius of canal curvature and the size of instrument at the beginning of canal curvature. The resulting quantitative mathematical relation could be used to predict the lifespan of rotary Ni-Ti endodontic instruments under clinical conditions and thereby reduce the incidence of instrument failure in vivo.