Influence of size and taper of artificial canals on the trajectory of NiTi rotary instruments in cyclic fatigue studies (original) (raw)
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Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 2009
Objective. The objective of this study was to investigate the trajectory of NiTi rotary instruments of the same size but different design in an artificial root canal manufactured for cyclic fatigue test. Study design. Eight groups of instruments with tip size 25, 0.06 taper with different design were tested in a simulated root canal with an angle of curvature of 60 degrees and radius of curvature of 5 mm milled in a stainless steel block with a tapered shape corresponding to the dimensions of the instruments tested. Geometric analysis of the trajectory that each instrument followed inside the artificial canal was performed on digital images, determining 3 parameters: angle and radius of the curvature and the position of the center of the curvature. Mean values were then calculated for each group. Data were analyzed using 1-way ANOVA and Holm t test to determine any statistical difference (P Ͻ .05).
Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology, 2011
Objectives. This study evaluated the effects of curvature location along an artificial canal on cyclic fatigue (CF) of an Mtwo rotary instrument, verifying the number of cycles to fatigue fracture (NCF) and morphologic characteristics of the fractured instruments. Study design. CF testing of instruments was performed in artificial canals with curvature radii of 10 mm and arc lengths of 11 mm. Mtwo rotary instruments size 40, 0.04 taper were used in 2 groups (n ϭ 10): group A, curvature positioned on middle part; group B, apical curvature. All instruments were rotated until fracture. The number of cycles to failure was registered. Data were analyzed by independent sample t test. Fractured surfaces and the helical shafts of the instruments were analyzed by scanning electron microscopy. Results. NCF for groups A and B had significant statistic differences (P Ͻ .05). The highest values were found in the group where the curvature was positioned on the apical part of the canal. No plastic deformation was observed on the helical shafts. Conclusions. The number of cycles to fracture of the Mtwo instruments increased when the arc was changed from the middle to the apical part of the canal. The morphologic characteristics of the fractured surfaces were of the ductile type.
Journal of Endodontics, 2013
Introduction: This study evaluated the influence of different features of canal curvature geometry on the number of cycles to fracture of a rotary nickel-titanium endodontic instrument subjected to a cyclic fatigue test. Methods: BioRaCe BR4C instruments (FKG Dentaire, La Chaux-de Fonds, Switzerland) were tested in 4 grooves simulating curved metallic artificial canals, each one measuring 1.5 mm in width, 20 mm in total length, and 3.5 mm in depth with a U-shaped bottom. The parameters of curvature including the radius and arc lengths and the position of the arc differed in the 4 canal designs. Fractured surfaces and helical shafts of the separated instruments were analyzed by scanning electron microscopy. Results: The Student's t test showed that a significantly lower number of cycles to fracture values were observed for instruments tested in canals with the smallest radius, the longest arc, and the arc located in the middle portion of the canal. Scanning electron microscopic analysis of the fracture surfaces revealed morphologic characteristics of ductile fracture. Plastic deformation was not observed in the helical shaft of the fractured instruments. Conclusions: Curvature geometry including the radius and arc lengths and the position of the arc along the root canal influence the number of cycles to fracture of rotary nickel-titanium instruments subjected to flexural load.
Australian Endodontic Journal, 2010
The fracture of nickel‐titanium rotary instruments is a serious problem that can jeopardise the outcome of root canal treatment. The aim of this study was to compare the cyclic fatigue resistance of new and used Mtwo rotary nickel‐titanium instruments in artificial canals with two different radii of curvature. Four hundred and twenty Mtwo instruments were used in the present study. Thirty new and 30 used instruments of each size were tested for cyclic fatigue in artificial canals with radii of curvature of 5 or 10 mm. Each instrument was rotated until fracture occurred and the number of cycles to fracture was calculated by multiplying time to fracture and rotational speed. Data were analysed using a t‐test. According to the results of the study, radius of curvature was an important factor on cyclic fatigue resistance and clinical use significantly reduced the instrument lifespan.
The fracture of instruments within root canal during endodontic treatment is a common incidence, fracture because of fatigue through flexure occurs because of metal fatigue, this study aimed to assess the effect of curvature angle and rotational speed on the cyclic fatigue of different type of Endodontic NiTi Rotary Instruments and compare among them. Materials and method: three types of rotary instruments with tip size 0.25: ProTaPer F2 (Densply,Malifier) Revo-S SU ( 0.06 taper, MicroMega) and RaCe system (0.06 taper, FKG,Dentaire), Forty file of each instrument were used within two canals with angle of curvature (40 &60 )at two speed (250&400)RPM, twelve group were formed for all instruments(total number=120),ten file for each group. The testing canals customized within stainless steel block covered with glass face, the time to fracture recorded and the mean of cycles to fracture (MCF) detected for each instrument .Data were analyzed statistically by ANOVA, LSD and Independent T-test at 5% significant level. Result: there was a highly significant difference of curvature angle and significant difference of rotational speed on the fracture resistance of instruments. RaCe revealed the best fracture resistance followed by ProTaper then Revo-s that showed the less resistance. Conclusion: the rotary instruments more prone to fracture when used at more curvature angle and higher rotational speed, as well as the rotary instruments differ from each other according to manufacturing process, taper ,cross section and other factors.
2021
BackgroundThe aim of this study was to compare cyclic fatigue resistance (CFR) and separation patterns during rotating movement of five heat-treated nickel titanium files in both single and double-curved canals. MethodsCFR was compared between five groups of 24 files each: HyFlex® EDM, HyFlex™ CM, Vortex Blue®, Protaper Next®, and One Curve, by determining the time needed to fracture (TTF) and the number of cycles to failure (NCF) in a cyclic fatigue testing device with a single 5-mm radius of curvature (ROC) and 60° angle, and a double curvature; coronal curvature (5 mm ROC and 60° angle) and apical curvature (2 mm ROC and 70° angle). The separation pattern was evaluated, and file fragment separated length were measured. One-way ANOVA and Tukey’s post-hoc were used to compare statistical differences between the groups. Scanning Electron Microscope (SEM) was used to investigate the fracture sites. Results HyFlex™ CM files displayed significantly higher CFR, followed by HyFlex® EDM a...
Journal of Endodontics, 2015
Introduction: The purpose of this study was to evaluate the cyclic fatigue resistance of 3 different nickeltitanium reciprocating instruments. Methods: A total of 45 nickel-titanium instruments were tested and divided into 3 experimental groups (n = 15): group 1, WaveOne Primary instruments; group 2, Reciproc R25 instruments; and group 3, Twisted File (TF) Adaptive M-L1 instruments. The instruments were then subjected to cyclic fatigue test on a static model consisting of a metal block with a simulated canal with 60 angle of curvature and a 5-mm radius of curvature. WaveOne Primary, Reciproc R25, and TF Adaptive instruments were activated by using their proprietary movements, Wave-One ALL, Reciproc ALL, and TF Adaptive, respectively. All instruments were activated until fracture occurred, and the time to fracture was recorded visually for each file with a 1/100-second chronometer. Mean number of cycles to failure and standard deviations were calculated for each group, and data were statistically analyzed (P < .05). Instruments were also observed through scanning electron microscopy to evaluate type of fracture. Results: Cyclic fatigue resistance of Reciproc R25 and TF Adaptive M-L1 was significantly higher than that of WaveOne Primary (P = .009 and P = .002, respectively). The results showed no statistically significant difference between TF Adaptive M-L1 and Reciproc R25 (P = .686). Analysis of the fractured portion under scanning electron microscopy indicated that all instruments showed morphologic characteristics of ductile fracture that were due to accumulation of metal fatigue. Conclusions: No statistically significant differences were found between the instruments tested except for WaveOne Primary, which showed the lowest resistance to cyclic fatigue.
Brazilian oral research, 2015
The cyclic resistance of ProTaper Universal (size 25/08) and ProTaper Next (size 25/06) instruments was compared in artificial canals with different curvatures in this study. A total of 30 ProTaper Universal and 30 ProTaper Next instruments were divided into 6 groups (n = 10) and were operated into artificial canals with 3 different angles of curvature (45°, 60°, 90°). The canal length was kept consistent in this study. The number of cycles to fracture (NCF) was counted until file fracture occurred, at which point, the length of the fragment was measured. The data were analyzed statistically using ANOVA complemented by the Tukey test (p < 0.05). Cross sections of the fractured files were scanned by an electron microscope. In the fatigue test, the ProTaper Next displayed more resistance in 45° and 60° canals (p < 0.05), whereas ProTaper Universal exhibited a better operability in 90° canals (p <…