Citations

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• Effect of autoclave sterilization on the cyclic fatigue resistance of EdgeFile X7, 2Shape, and F-one nickel–titanium endodontic instruments
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  Journal of Conservative Dentistry.2023; 26(1): 26.     CrossRef
• Investigation of cyclic fatigue of rotary endodontic instruments
  Z. S. Khabadze, F. R. Ismailov
  Endodontics Today.2022; 20(1): 28.     CrossRef
• Torsional Resistance of Heat-Treated Nickel-Titanium Instruments under Different Temperature Conditions
  Hyo Jin Jo, Sang Won Kwak, Hyeon-Cheol Kim, Sung Kyo Kim, Jung-Hong Ha
  Materials.2021; 14(18): 5295.     CrossRef
• Effect of surface treatment on the mechanical properties of nickel-titanium files with a similar cross-section
  Sang Won Kwak, Joo Yeong Lee, Hye-Jin Goo, Hyeon-Cheol Kim
  Restorative Dentistry & Endodontics.2017; 42(3): 216.     CrossRef
• Effect from Rotational Speed on Torsional Resistance of the Nickel-titanium Instruments
  Jung-Hong Ha, Sang Won Kwak, Sung Kyo Kim, Asgeir Sigurdsson, Hyeon-Cheol Kim
  Journal of Endodontics.2017; 43(3): 443.     CrossRef
• Mechanical Properties of Various Heat-treated Nickel-titanium Rotary Instruments
  Hye-Jin Goo, Sang Won Kwak, Jung-Hong Ha, Eugenio Pedullà, Hyeon-Cheol Kim
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The purpose of this study was to determine the effect of sodium hypochlorite and steam autoclaving on the cyclic fatigue of nickel-titanium endodontic files.

Two types of files with a .06 taper and #30 were used, K3^® (SybronEndo, Glendora, California, USA) and Hero642^®(Micro-Mega, Besançon, France).

The files were divided into 6 experimental groups containing 10 files each group depending the soaking time in 6% sodium hypochlorite solution and number of cycles of steam autoclave. After sterilization, a cyclic fatigue test was performed on each file, and the fracture time was recorded in seconds. The control group underwent the cyclic fatigue test only. After the test, the surface characteristics of the files were observed using scanning electron microscopy (SEM).

All groups containing the Hero 642^® files showed a similar cyclic fatigue fracture time. However, the cyclic fatigue fracture time with the K3^® files was significantly shorter in groups which were treated with sodium hypochlorite than in the control group (P < 0.05). SEM revealed both Hero642^® and K3^® files to have significant corrosion on the file surface in groups treated with sodium hypochlorite, compared with the sharp and regular blades of the control group. K3^® files showed more corrosion than the Hero642^® files. Bluntness of the blades of the K3^® file was observed in groups treated with steam autoclave. Although there was no obvious destruction on the surface of steam autoclaved Hero642^® files, slight bluntness was observed.

Sterilizing with a steam autoclave is much less destructive to K3^® files than sodium hypochlorite. The longer time exposed to sodium hypochlorite, the more destructive pattern was shown on the blades of the files. Therefore, when using sodium hypochlorite solution, the exposure time should be as short as possible in order to prevent corrosion and increase the cyclic fatigue fracture time.

This in vitro study examined the effect of surface defects on cutting blades on the extent of the cyclic fatigue fracture of HEROShaper Ni-Ti rotary files using fractographic analysis of the fractured surfaces. A total of 45 HEROShaper (MicroMega) Ni-Ti rotary files with a #30/.04 taper were divided into three groups of 15 each. Group 1 contained new HEROShapers without any surface defects. Group 2 contained HEROShapers with manufacturing defects such as metal rollover and machining marks. Group 3 contained HEROShapers that had been clinically used for the canal preparation of 4-6 molars. A fatigue-testing device was designed to allow cyclic tension and compressive stress on the tip of the instrument whilst maintaining similar conditions to those experienced in a clinic. The level of fatigue fracture time was measured using a computer connected the system. Statistical analysis was performed using a Tukey's test. Scanning electron microscopy (SEM) was used for fractographic analysis of the fractured surfaces. The fatigue fracture time between groups 1 and 2, and between groups 1 and 3 was significantly different (p < 0.05) but there was no significant difference between groups 2 and 3 (p > 0.05). A low magnification SEM views show brittle fracture as the main initial failure mode. At higher magnification, the brittle fracture region showed clusters of fatigue striations and a large number of secondary cracks. These fractures typically led to a central region of catastrophic ductile failure. Qualitatively, the ductile fracture region was characterized by the formation of microvoids and dimpling. The fractured surfaces of the HEROShapers in groups 2 and 3 were always associated with pre-existing surface defects. Typically, the fractured surface in the brittle fracture region showed evidence of cleavage (transgranular) facets across the grains, as well as intergranular facets along the grain boundaries. These results show that surface defects on cutting blades of Ni-Ti rotary files might be the preferred sites for the origin of fatigue fracture under experimental conditions. Furthermore, this work demonstrates the utility of fractography in evaluating the failure of Ni-Ti rotary files.

Citations

Citations to this article as recorded by  

• The Effect of Canal Curvature and Different Manufacturing Processes of Five Different NiTi Rotary Files on Cyclic Fatigue Resistance
  Panupat Phumpatrakom, Awiruth Klaisiri, Sukitti Techapatiphandee, Thippawan Saekow, Panuroot Aguilar
  European Journal of General Dentistry.2024;[Epub]     CrossRef
• Effect of internal stress on cyclic fatigue failure in .06 taper ProFile
  Hye-Rim Jung, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
  Restorative Dentistry & Endodontics.2012; 37(2): 79.     CrossRef
• Effect of internal stress on cyclic fatigue failure in K3
  Jun-Young Kim, Jin-Woo Kim, Kyung-Mo Cho, Se-Hee Park
  Restorative Dentistry & Endodontics.2012; 37(2): 74.     CrossRef
• Stress distribution for NiTi files of triangular based and rectangular based cross-sections using 3-dimensional finite element analysis
  Hyun-Ju Kim, Chan-Joo Lee, Byung-Min Kim, Jeong-Kil Park, Bock Hur, Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2009; 34(1): 1.     CrossRef
• Comparative analysis of various corrosive environmental conditions for NiTi rotary files
  Ji-Wan Yum, Jeong-Kil Park, Bock Hur, Hyeon-Cheol Kim
  Journal of Korean Academy of Conservative Dentistry.2008; 33(4): 377.     CrossRef

There are various factors affecting the fracture of NiTi rotary files. This study was performed to evaluate the effect of cross sectional area, pecking motion and pecking distance on the cyclic fatigue fracture of different NiTi files. Five different NiTi files-Profile®(Maillefer, Ballaigue, Switzerland), ProTaper™ (Maillefer, Ballaigue, Switzerland), K3® (SybronEndo, Orange, CA), Hero 642® (Micro-mega, Besancon, France), Hero Shaper®(Micro-mega, Besancon, France)-were used. Each file was embedded in temporary resin, sectioned horizontally and observed with scanning electron microscope. The ratio of cross-sectional area to the circumscribed circle was calculated. Special device was fabricated to simulate the cyclic fatigue fracture of NiTi file in the curved canal,. On this device, NiTi files were rotated (300rpm) with different pecking distances (3 mm or 6 mm) and with different motions (static motion or dynamic pecking motion). Time until fracture occurs was measured. The results demonstrated that cross-sectional area didn't have any effect on the time of file fracture. Among the files, Profile® took the longest time to be fractured. Between the pecking motions, dynamic motion took the longer time to be fractured than static motion. There was no significant difference between the pecking distances with dynamic motion, however with static motion, the longer time was taken at 3mm distance. In this study, we could suggest that dynamic pecking motion would lengthen the time for NiTi file to be fractured from cyclic fatigue.

Citations

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• Comparative Study Assessing the Canal Cleanliness Using Automated Device and Conventional Syringe Needle for Root Canal Irrigation—An Ex-Vivo Study
  Keerthika Rajamanickam, Kavalipurapu Venkata Teja, Sindhu Ramesh, Abdulaziz S. AbuMelha, Mazen F. Alkahtany, Khalid H. Almadi, Sarah Ahmed Bahammam, Krishnamachari Janani, Sahil Choudhari, Jerry Jose, Kumar Chandan Srivastava, Deepti Shrivastava, Shankarg
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• Vibrations Generated by Several Nickel-titanium Endodontic File Systems during Canal Shaping in an Ex Vivo Model
  Dong-Min Choi, Jin-Woo Kim, Se-Hee Park, Kyung-Mo Cho, Sang Won Kwak, Hyeon-Cheol Kim
  Journal of Endodontics.2017; 43(7): 1197.     CrossRef
• Effect of cross-sectional area of 6 nickel-titanium rotary instruments on the fatigue fracture under cyclic flexural stress: A fractographic analysis
  Soo-Youn Hwang, So-Ram Oh, Yoon Lee, Sang-Min Lim, Kee-Yeon Kum
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