Fatigue Resistance Of NiTi Files Research Articles

Influence of Anatomical Root Factors on Cyclic Fatigue Resistance of Heat Treated NiTi Instrument: A Review

Endodontic treatments have been improved over the last decade by the use of nickel titanium (NiTi) alloys. NiTi instrument had shape memory and superelastic properties which made the instrument more flexible, so the treatment quality was enhanced by eliminating the procedural errors. Although the numerous benefits of the NiTi instruments, the fracture was the most frequent failure that may be happened during its use due to flexural (cyclic) or torsional fatigue. Various thermo-mechanical heat treatments have been applied to NiTi instruments to improve fracture resistance and clinical performance. Several parameters influenced the fatigue resistance of NiTi files, and the most important factor that affected the likelihood of NiTi instrument fatigue was the root canal shape. Data collected of 100 papers from the Goggle scholar and Scien ceDirect database. After excluding 60 unrelated papers, thi s review of 40 included related studies aims to evaluate an overview of the anatomical root-related factors affecting t he cyclic fatigue of heat-treated NiTi instruments. Concl uded that the separation rates of file increased when the radius of curvature decreases and when the angle of curvature increased. Canals with the double curvatures increase the risk of cyclic fatigue. Also, the resistance to cyclic fatigue of NiTi files was affected by the canal curvature posit ion, with a short failure life coronally. So even in the improve ment of wire metallurgy and designs of instrument, the anatomy of canal still impact on the cyclic fatigue and should be considered during preparation especially with th e new concept of minimally invasive endodontic treatmen t.

Cyclic fatigue resistance for six types of nickel titanium instruments at artificial canals with different angles and radii of curvature.

This study evaluated the cyclic fatigue resistance for six types of 25# NiTi instruments. A traditional manufacturing instrument, an M wire instrument, a gold treatment instrument, a controlled memory (CM) wire instrument, a CM wire instrument with electrical discharge machining (EDM), and an R-phase heat treatment instrument, were operated in the different curved artificial canals. The fracture time (FT) and number of cycles to fracture (NCF) of the NiTi instruments were higher at 45° angles and double-curvature canals than at 60° angles. Except for the instruments with gold technology and EDM technology, others showed the longest FT and the highest NCF at an 8 mm radius of curvature. Morphological characteristics of cyclic fatigue were exhibited on the cross-section and lateral view of fracture fragments. The use of M-wire, R-phase wire, CM-wire, gold technology, EDM technology, and reciprocating movement were beneficial to enhance the cyclic fatigue resistance of NiTi files.

Comparison of cyclic fatigue resistance of heat-treated nickel-titanium reciprocating instruments at the intracanal temperature

Background/Aim: The aim of the present study was to compare the cyclic fatigue resistance of NiTi files running with reciprocal motion and having different characteristics (RPC Blue, WOG, EndoArt Wise Reciproc Gold, EndoArt Wise Reciproc Blue) at the intracanal temperature (35°C) by using NaOCl irrigation solution. Material and Methods: Totally 60 WaveOne GOLD (Dentsply-Sirona, Ballaigues, Switzerland), Reciproc Blue (VDW, Munich, Germany), EndoArt Wise Reciproc Gold, and EndoArt Wise Blue (Inci Dental Productions Co, Istanbul, Turkey) (n= 15) files were used. Each of the rotary files were tested at the intracanal temperature (35°C) using a dynamic model in a stainless-steel artificial canal with an inner diameter of 1.5 mm, 60° angle of curvature, and 2mm radius of curvature until fracture occurred. The device automatically stopped at the moment of fracture and the number of cycles to the fracture was calculated as per second. The lengths of fractured parts were measured using a digital microcaliper. The One-Way Analysis of Variance (ANOVA) and Tukey's posthoc tests were used for intergroup comparisons. Results: In 2 mm Radius of curvature, the EndoArt Wise Reciproc Blue group had a significantly higher time to fracture followed by the EndoArt Wise Reciproc Gold, Resiproc Blue, WaveOne Gold. No significant difference was found between EndoArt Wise Reciproc Gold and Resiproc Blue groups (P>0.05). Among the groups, there was no statistically significant difference in the lengths of fractured parts of the instruments (P> 0.05). Conclusions: EndoArt Wise Reciproc Blue files exhibited significantly higher cyclic fatigue resistance compared with other files tested in a 2-mm radius of curvature and a 600 angle in an artificial canal at the intracanal temperature.

Effect of different kinematics and operational temperature on cyclic fatigue resistance of rotary NiTi systems

BackgroundThe aim of this study was to compare the effect of different kinematics and operational temperature on cyclic fatigue resistance of Protaper Next, WaveOne Gold, and Twisted File Adaptive files in a static model.MethodologyAn artificial canal, made of stainless steel with an inner diameter of 1.5 mm, a 60° angle of curvature, and a curvature radius of 2 mm, was used for the cyclic fatigue test immersed in a water bath for temperature adjustment (37 °C and 20 °C). A total of 120 files were divided into three groups according to the type of motion continuous rotation motion (CRM), adaptive motion (AM), and reciprocation motion (RM). Each group was further subdivided into two subgroups according to the operational temperature (37 °C and 20 °C), All instruments were operated until fracture occurred, and the time to fracture was recorded in seconds. Mean number of cycles to failure and standard deviations were calculated for each group, and data were analyzed statistically using two-way ANOVA followed by Tukey’s post hoc test (P ≤ 0.05).ResultsThe continuous rotation motion exhibited significantly lower cyclic fatigue resistance than reciprocating or adaptive motion (p ≤ 0.001) at 37 °C and 20 °C.ConclusionsCyclic fatigue resistance of NiTi files was affected by the motion used during root canal preparation. Reciprocation motion and adaptive motion resulted in extended fatigue. The operational temperature affects the cyclic fatigue resistance of the twisted file.

Effect of surface treatment on the mechanical properties of nickel-titanium files with a similar cross-section

ObjectivesThe aim of this study was to compare the mechanical properties of various nickel-titanium (NiTi) files with similar tapers and cross-sectional areas depending on whether they were surface-treated.Materials and MethodsThree NiTi file systems with a similar convex triangular cross-section and the same ISO #25 tip size were selected for this study: G6 (G6), ProTaper Universal (PTU), and Dia-PT (DPT). To test torsional resistance, 5 mm of the straightened file's tip was fixed between polycarbonate blocks (n = 15/group) and continuous clockwise rotation until fracture was conducted using a customized device. To evaluate cyclic fatigue resistance, files were rotated in an artificial curved canal until fracture in a dynamic mode (n = 15/group). The torsional data were analyzed using 1-way analysis of variance and the Tukey post-hoc comparison test, while the cyclic fatigue data were analyzed using the Mann-Whitney U test at a significance level of 95%.ResultsPTU showed significantly greater toughness, followed by DPT and G6 (p < 0.05). G6 showed the lowest resistance in ultimate torsional strength, while it showed a higher fracture angle than the other files (p < 0.05). In the cyclic fatigue test, DPT showed a significantly higher number of cycles to failure than PTU or G6 (p < 0.05).ConclusionsWithin the limitations of this study, it can be concluded that the torsional resistance of NiTi files was affected by the cross-sectional area, while the cyclic fatigue resistance of NiTi files was influenced by the surface treatment.

Comparative Evaluation of the Effects of Different Sterilization Methods on Cyclic Fatigue Resistance of NiTi Files: An in vitro Study

evaluated. A total of new 50 ProTaper files nickel-titanium (NiTi) files (Tulsa-dentsply, USA), of standard # 20 size with taper of 0.06 and 25 mm length were taken, and divided into five groups according to method of sterilization employed with 10 files in each group. Group 1: Control with no sterilization of files. Group 2: Autoclaved files at 121oC at 15 psi for 15 minutes. Group 3: Files wiped with 90% ethyl alcohol solution. Group 4: Files submerged in glass bead sterilizer at 425o Ffor 10 seconds. Group 5: Files immersed in 2% glutaral dehyde solution for 4 hours. After five cycles of sterilization, in custom made cyclic fatigue testing model, time taken for fracture of files and number of cycles to failure (NCF) was calculated in each group. Results were analyzed statistically using analysis of variance (ANOVA) test at the 95% confidence level (p < 0.05). Conclusion: Changes in the mechanical properties of NiTi endodontic instruments after five cycles of common sterilization procedures were insignificant.

Effect of heat treatment on cyclic fatigue resistance, thermal behavior and microstructures of K3 NiTi rotary instruments

Objective. The aim of this study was to investigate the effect of heat treatment on the cyclic fatigue resistance, thermal behavior and microstructural changes of K3 NiTi rotary instruments. Materials and methods. Twelve control (as-received) and 12 experimental (heat-treated) K3 NiTi rotary instruments were compared in this study. Those experimental K3 instruments were heated in a furnace for 30 min at 450°C and then quenched in water. The cyclic fatigue resistance was measured with a fatigue tester. The thermal characteristic and the microstructures of both instruments were investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. Results. There was a significant increase in the cyclic fatigue resistance between the heat-treated instruments and the as-received instruments (T-test, p < 0.05). DSC showed that the as-received and heat-treated samples were different, with an increased Af (austenite-finish temperature) for the latter. TEM analysis revealed that both as-received and heat-treated instruments were composed mainly of an austenite phase. However, the heat-treated samples had an increased appearance of larger grains, twinning martensite, TiO2 surface layer and a Ni-rich inner layer. Conclusions. Heat treatment increased the cyclic fatigue resistance of NiTi files and changed the thermal behavior of the instruments without marked changes in the constituting phases of NiTi alloy.

Cyclic fatigue resistance of two reciprocating nickel–titanium instruments after immersion in sodium hypochlorite

To assess resistance to cyclic fatigue of reciprocating nickel-titanium ( NiTi ) files (Reciproc and WaveOne) after immersion in NaOCl solution over several time periods. A total of 90 new Reciproc R25 and WaveOne Primary were tested. The 45 files of the same brand were randomly assigned to three groups (n = 15) and submitted to the following immersion protocol in 5% NaOCl at 37 °C for 16 mm: no immersion (control), 1 or 5 min dynamically. The dynamic immersion and the following cyclic fatigue tests were performed using the appropriate preset reciprocation modes ('RECIPROC ALL' or 'WAVEONE ALL') in a specially designed endodontic motor. Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The artificial canal was manufactured reproducing the instrument's size and taper. Data were analysed by 2-way analyses of variance. Resistance to cyclic fatigue of the same NiTi file was not significantly affected by immersion in NaOCl . Reciproc R25 was associated with a higher cyclic fatigue resistance in all groups compared to WaveOne Primary (P < 0.0001). Reciprocating dynamic immersion in NaOCl for 1 or 5 min did not reduce the cyclic fatigue resistance of NiTi files significantly. However, the type of reciprocating instrument influenced cyclic fatigue resistance with Reciproc R25 being more resistant than WaveOne Primary.