Influence of the Geometry of Curved Artificial Canals on the Fracture of Rotary Nickel-Titanium Instruments Subjected to Cyclic Fatigue Tests

Lopes, Hélio Pereira; Vieira, Márcia Valéria Boussada; Elias, Carlos Nelson; Gonçalves, Lúcio Souza; Siqueira, José F.; Moreira, Edson Jorge Lima; Vieira, Víctor Talarico Leal; Souza, Letícia Chaves de

doi:10.1016/j.joen.2012.12.027

Cited by 38 publications

(30 citation statements)

References 29 publications

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“…The Weibull analysis showed that Hyflex CM instruments subjected to the continuous rotating bending test presented a lower probability of survival, according to the usage of the time (Figure 1). SEM analysis revealed that all instruments displayed morphological characteristics of ductile fracture as found in other studies, 10,[12][13][14][15] regardless of the number of times the instrument was sterilized (Figure 2 A, B, and C). It can be observed that the instruments subjected to a cumulative rotating bending test showed multiple cracks in the region corresponding to the center of the arc of the metallic artificial canal (Figure 2 D).…”

Section: Resultssupporting

confidence: 80%

“…This is in accordance with the results found in other studies. 10,[12][13][14][15] Studies reported that not all Hyflex CM instruments regained their original shape after autoclaving. 4,16 The inability to regain shape can be associated with altered metallurgical properties of the deformed instruments.…”

Section: Discussionmentioning

confidence: 99%

“…10,[12][13][14][15] The mounting rod allowed the fixation of the handpiece, which was regulated by a manual adjustment screw. The device allows vertical movement of the instrument in the longitudinal axis of the straight part of the metallic canal.…”

Section: • Continuous Cyclic Fatigue Testmentioning

confidence: 99%

“…The arc was located in the apical portion of the canal. 14 The instruments were placed in the contra-angle gear unit and inserted into the channel so that its tip touched a shield positioned at the end of the arc. This shield aimed to standardize the distance of penetration of the instrument inside the channel and was removed after final adjustment of the instrument.…”

Section: • Continuous Cyclic Fatigue Testmentioning

confidence: 99%

“…10,[12][13][14][15] Different magnifications were used (300×-500×) to obtain photomicrographs at the point of maximum stress concentration (half the arc of 9.42 mm from the instrument end) to study the nucleation and propagation of cracks.…”

Section: • Scanning Electron Microscopymentioning

confidence: 99%

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Effect of autoclave cycles on cyclic fatigue resistance of control memory NiTi files observed by scanning electron microscopy

Vieira

Lopes

Elias

et al. 2017

Rev. Bras. Odontol.

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Objective: Hyflex CM instruments were developed for debridement of the root canal system. The control-memory alloy recovers its shape on sterilization, thereby allowing instrument reuse. This study investigated the effect of shape recovery by sterilization on the fatigue life and crack formation of Hyflex CM NiTi instruments. Material and Methods: the cyclic fatigue test was performed in two groups: In the first, it was continuously performed to establish the fatigue life (group 1, n = 10); in the second, it was performed with outages of 30s to evaluate cracks' nucleation and propagation (group 2, n = 10). The test was performed using a stainless steel canal that was 1.5mm in diameter and 3.5mm in depth, with an arc of 9.42mm and radius of curvature of 6mm. The instruments were driven at 300 rpm. The fatigue time was recorded using a digital stopwatch (Technos). An electronic microscope (Quanta 250) was used to observe the crack formation and growth during the cyclic fatigue. Results: the autoclaved instruments endured 1196.67+214.63 cycles, and the non-autoclaved endured 1000+199.42 cycles until the occurrence of fracture. The t-student test (α=5%) revealed a significant difference. The cyclic fatigue test with pauses demonstrated a significantly longer cyclic fatigue life than the continuous cyclic fatigue test (p<0.05). Conclusion: as revealed by SEM images, cracks grow with an increase in the number of cycles to fracture (NCF). It can be concluded that the shape of Hyflex CM instruments recovered by autoclaving withstood significantly more NCF than non-autoclaved instruments (p<0.05), demonstrating an improvement of approximately 16%.

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