Restor Dent Endod.  2021 Feb;46(1):e6. 10.5395/rde.2021.46.e6.

Corrosion resistance assessment of nickel-titanium endodontic files with and without heat treatment

• Costa TD
• Silva EdFe
• Caetano PL
• Campos MJdS
• Resende LM
• Machado AG
• Carmo AMRd

• KMID: 2548056
• DOI: http://doi.org/10.5395/rde.2021.46.e6

Abstract

Objectives
The aim of this study was to evaluate the corrosion resistance of heat-treated (Reciproc and WaveOne) and non-heat-treated (ProTaper and Mtwo) superelastic nickeltitanium endodontic files when immersed in a 5.25% sodium hypochlorite solution.
Materials and Methods
Anodic polarization curves were obtained with potential sweeps that began at the open circuit potential or corrosion potential (E_corr ). The pitting potential (E_pit ) was identified on the anodic polarization curve as the potential at which a sudden increase in current was observed. The micromorphology of the 28 tested files was analyzed before and after the electrochemical assay using scanning electron microscope (SEM). The data were analyzed using 1-way analysis of variance with the post hoc Bonferroni test (for E_corr ) and the Student t-test for independent samples (for E_pit ).
Results
The mean E_corr values were 0.506 V for ProTaper, 0.348 V for Mtwo, 0.542 V for Reciproc, and 0.321 V for WaveOne files. Only WaveOne and Protaper files exhibited pitting corrosion, with E_pit values of 0.879 V and 0.904 V, respectively. On the SEM images of the ProTaper and WaveOne files, cavities suggestive of pitting corrosion were detected.
Conclusions
Signs of corrosion were observed in both heat-treated and non-heat-treated files. Of the evaluated files, WaveOne (a heat-treated file) and ProTaper (a non-heat-treated file) exhibited the lowest corrosion resistance.

Keyword

Corrosion; Endodontics; Root Canal

Figure

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  Figure 1 Representative diagram of the experimental design.SEM, scanning electron microscope.

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  Figure 2 Anodic polarization curves of the Reciproc files in 5.25% sodium hypochlorite (NaOCl) solution.

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  Figure 3 Anodic polarization curves of the Mtwo files in 5.25% sodium hypochlorite (NaOCl) solution.

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  Figure 4 Anodic polarization curves of the ProTaper files in 5.25% sodium hypochlorite (NaOCl) solution. The arrow indicates the cavity of pitting.

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  Figure 5 Anodic polarization curves of the Mtwo files in 5.25% sodium hypochlorite (NaOCl) solution. The arrow indicates the cavity of pitting.

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  Figure 6 Scanning electron microscopic image of Reciproc files. (A) Before (×304) and (B) after the electrochemical test (×306).

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  Figure 7 Scanning electron microscopic image of Mtwo files. (A) Before (×296) and (B) after the electrochemical test (×298).

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  Figure 8 Scanning electron microscopic image of ProTaper files. (A) Before (×256) and (B) after the electrochemical test, with the presence of corrosion by pitting (×250).

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  Figure 9 Scanning electron microscopic image of WaveOne files. (A) Before (×304) and (B) after the electrochemical test, with the presence of corrosion by pitting (×306).

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