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ORIGINAL RESEARCH
Year : 2022 | Volume
: 13
| Issue : 4 | Page : 121-123
Effects of Chitosan, NaOCl, and EDTA Irrigation Solutions on the Cyclic Fatigue Resistance of Three Nickel–Titanium Endodontic Rotary Files: An In Vitro Study
Wisam S Salloom1, Biland M.S Shukri2
1 Ministry of Health, Baghdad, Iraq
2 Department of Conservative Dentistry, College of Dentistry, Mustansiriyah University, Baghdad, Iraq
Correspondence Address:
Wisam S Salloom
Ministry of Health, Baghdad
Iraq
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/denthyp.denthyp_86_22
Introduction The goal of this study was to compare the impact of NaOCl, EDTA, and chitosan on the cyclic fatigue of 2Shape, HyFlex EDM, and RACE EVO.
Methods A total of 120 new 2Shape (n = 40), HyFlex EDM (n = 40), and RACE EVO (n = 40) files were subdivided randomly into four groups (n = 10): Group (A) with no immersion, Group (B) with immersion in 5.25% NaOCl for 5 min, Group (C) with immersion in 17% EDTA for 5 min, and Group (D) with immersion in 0.2% chitosan for 5 min. The files were rotated in an artificial canal with a 5 mm radius and a 60° curvature at body temperature until they fractured, and the number of cycles to fracture was measured. ANOVA test and Tukey post-hoc test were used to analyze the data.
Results Immersion of the files in NaOCl, EDTA, or chitosan solutions had no significant effect on the number of cycles to fracture (P > 0.05).
Conclusion The irrigation solutions did not have any influence on the cyclic fatigue of the tested files.
Keywords: chitosan, cyclic fatigue, endodontics, ethylenediaminetetraacetic acid nickel–titanium (niti) alloys, irrigants, root canal therapy, rotary file, sodium hypochlorite
Nickel–titanium (Ni–Ti) instruments are commonly used in endodontic treatments because of their super-elastic features, excellent cutting efficiency, and greater protection of the original canal anatomy.[1] However, the most significant drawback of Ni–Ti instruments is that they can break during canal preparation without warning. The fracture of Ni–Ti files might occur because of either cyclic fatigue or torsional loading. A torsional fracture occurs when the file becomes locked in the canal as the handpiece continues to rotate. On the other hand, cyclic fatigue fracture occurs when the freely rotating file within the canal is subjected to repetitive compression/tensile stress cycles at the section of the canal with the steepest incline.[2]
The Ni–Ti files come into contact with the irrigation solutions used during root canal preparation, which can corrode files and might lead to areas of stress concentration and decrease fatigue resistance.[3] NaOCl is the most widely used irrigating solution due to its antibacterial properties and ability to dissolve necrotic tissue. EDTA is a polycarboxylic amino acid − a colorless and water-soluble material. Because of its capacity to remove the smear layer, EDTA was considered a chelating agent. NaOCl and EDTA solutions were shown to have a significant negative effect on the fatigue resistance of Ni–Ti files.[4],[5] Chitosan is a natural polysaccharide derived from chitin. It has chelation and antibacterial effects.[6],[7] To our knowledge, no study has yet compared the impact of chitosan on the cyclic fatigue of instruments.
2Shape files (TS; Micro-Mega, Besancon, France) are manufactured by a special heat treatment (T-Wire) that is claimed to improve flexibility and fatigue resistance.[8] HyFlex EDM files (HEDM; Coltene-Whaledent, Allstetten, Switzerland) are electro-discharge machining (EDM) files composed of controlled memory alloy. Fatigue resistance was found to be enhanced by using the EDM method.[9] RACE EVO files (RE; FKG Dentaire, La Chaux-de-Fonds, Switzerland) are manufactured by exclusive blue heat treatment.[10] There is still no research about the impact of NaOCl, EDTA, and chitosan on RE fatigue resistance.
The objective of this study was to assess the impact of 5.25% NaOCl, 17% EDTA, and 0.2% chitosan on the cyclic fatigue of 2Shape, HyFlex EDM, and RACE EVO files at body temperature.
Materials and MethodsThe study protocol was approved by the local ethical committee of the Mustansiriyah University (Reference number: 4680). A total of 120 new 2Shape (TS, 0.25/0.06) (n = 40), HyFlex EDM (HEDM, 0.25/0.08), (n = 40), and RACE EVO (RE 0.25/0.06) (n = 40) Ni–Ti files were used in this study. Each file type group was further randomly (using www.random.org) divided into four subgroups (n = 10): (A) Control (no immersion), (B) NaOCl 5.25% (Cerkamed, Stalowa Wola, Poland), (C) EDTA 17% (Cerkamed, Stalowa Wola, Poland), and (D) Chitosan 0.2%.
Chitosan 0.2% was made by dissolving 0.2 g of chitosan (Central Drug House, New Delhi, India) in 100 ml of 1% acetic acid (Gainland Chemical Company, Flintshire, UK), and the mixture was stirred using a magnetic stirrer (Four E′S, Guangdong, China) for 2 h.[6]
The 19 mm working part of the instruments in groups B, C, and D were immersed in irrigating solutions at 37 ± 1°C for 5 min. To neutralize the solutions’ effects, the instruments were washed with distilled water immediately after immersion. The instruments were then tested for cyclic fatigue in a stainless steel block with an artificial canal.[11] The canal was designed in AutoCAD 2017 (Autodesk co, CA, USA) and then converted to AutoCAD 2004 (Autodesk co, CA, USA) to be understood by cutting machine. By using wire cutting machine of electrical discharge machining type (Suzhou Baoma Numerical Control Equipment Co., Suzhou, China), the artificial canal was milled in a stainless steel block. The dimensions of the canal were about 19 mm in length, with a single 60° curve and a 5 mm radius.[11] The diameter of the canal was 1.5 mm coronally and 1 mm apically.
The stainless steel model was fixed inside a beaker filled with water at 37 ± 1°C. The temperature of the water was controlled using a hot plate (Four E′S, Guangdong, China). To decrease heat generation, the canal was filled with glycerin (Applichem GmbH Olloweg D-64291, Darmstadt, Germany) before each file was introduced.[2] Each instrument was adapted to the desired length (19 mm) from the upper orifice of the canal.
A 16:1 reduction endo-motor (Dentsply Maillefer, Ballaigues, Switzerland) was used to activate the instruments inside the canal, at the manufacturers’ recommended speed until the fracture occurred (2Shape files: 300 rpm; HyFlex EDM files: 500 rpm; RACE EVO files: 1000 rpm). The number of cycles to fracture for each file was obtained by multiplying the recommended speed by the time to fracture in seconds after being converted to minutes.
Statistical analysis
The data of number of cycles to fracture were analyzed using SPSS23 software (IBM-SPSS Inc., Chicago, IL, USA). A one-way ANOVA and Tukey post-hoc test were then performed for comparison between groups.
ResultsThe descriptive statistics for the number of cycles to fracture for each file group are shown in [Figure 1]. There was no significant difference among the various irrigation solutions (control, NaOCl, EDTA, and chitosan) in number of cycles to fracture for 2Shape (P = 0.37), RACE EVO (P = 0.26), and Hyflex EDM (P = 0.61) files.
DiscussionThe extracted tooth model more closely resembles the clinical situation, but it is impossible to standardize experimental conditions because the tooth can only be used one time and the canal shape will change during cleaning and shaping. Moreover, no two root canals are perfectly identical.[2] The stainless steel model is most commonly used to make artificial canals in non-clinical tests for examining the cyclic fatigue for assurance of standardization.[9] There are two types of stainless steel cyclic fatigue test models: static and dynamic models.[12] In this study, a static model was used.
According to the results of the present study, the immersion of 2Shape, Race EVO, and Hyflex EDM in NaOCl, EDTA, and chitosan solutions had no significant effect on the cyclic fatigue of files. These findings are in agreement with the results of previous investigations which reported that the immersion of HyFlex CM and M3 files in 5.25% NaOCl and 17% EDTA had no impact on their cyclic fatigue.[13] According to Erik and Özyürek,[14] 17% EDTA and 6% NaOCl did not affect the fatigue resistance of the RPC Blue, Hyflex EDM, and WaveOne Gold.
Conversely, Pedullà et al.[4] reported that when WaveOne, Reciproc, and ProTaper Universal were exposed to 17% EDTA, the cyclic fatigue resistance actually decreased. Nogueira et al.[5] found that when the sequence files, Hyflex EDM, and Protaper Next were immersed in 5.25% NaOCl, the cyclic fatigue resistance of the tested files was reduced. As a reason for these results, the researchers stated that the irrigants caused micropitting on the surface of instruments, which could have caused the weakening of the files. The discrepancy between these findings and those of the present study might be due to the difference in methodologies, as well as the temperature utilized throughout procedures. There are no studies about the impact of chitosan on cyclic fatigue, but many studies have reported that the chitosan improved the corrosion resistance of the Ni–Ti alloy. [15]
As a suggestion for future study, conduction of a meta-analysis to summarize results of currently available studies greatly encouraged.
The main limitation of the present study was that both the immersion in irrigation solutions and cyclic fatigue test were done in a static model rather than a dynamic motion. A dynamic model replicates the natural clinical situation more than a static model. With respect to in vitro nature of this study, usage of our results to predict clinical situation must be done with great caution and further in vivo studies are necessary.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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