The effect of root canal preparation on the surface roughness of WaveOne and WaveOne Gold files: atomic force microscopy study

Impact of endodontic irrigants on surface roughness of various nickel-titanium rotary endodontic instruments

BACKGROUND

The aim of the current study is to assess the surface roughness of several recent nickel-titanium (Ni-Ti) rotary endodontic instruments, namely: Protaper next (PTN); Hyflex CM (CM); Hyflex EDM (EDM); WaveOne gold (WOG); and trunatomy (TN), before and after application of 5.25% sodium hypochlorite (NaOCl) irrigant solution.

METHODS

In this in vitro study, five recently introduced rotary endodontic instruments of different metallurgical properties and designs were subjected to Atomic Force Microscopy (AFM) analysis, and then each file was rotated in 5.25% NaOCl for 15 min., with speed and torque according to manufacturer's instructions. The instruments were then subjected to AFM analysis again. The surface roughness average (Sa) parameter was calculated. Data were analyzed by Paired T test, One-way ANOVA and Tukey tests.

RESULTS

There was a statistically significant decrease in the surface roughness of all rotary endodontic instruments after immersion in irrigants (P ≤ 0.05).

CONCLUSION

The new TN and PTN instruments showed the least surface roughness. All tested Ni-Ti rotary endodontic instruments after irrigants exposure showed a varying increase in surface roughness.

Surface profile of different heat-treated nickel-titanium files before and after root canal preparation

The aim of this study was to evaluate surface wear, presence of microcracks and surface irregularities of WaveOne (WO) and WaveOne Gold (WOG) instruments before and after multiple uses. Eight Primary instruments of the WO and WOG systems were evaluated, each one was used to prepare six mesial canals of extracted human mandibular molars. The surface of the instruments was evaluated before use (T0), after instrumentation of three (T1) and six (T2) root canals. Surface wear was analyzed using a three-dimensional optical profiler and the presence of microcracks and surface irregularities were evaluated using a tabletop scanning electron microscopy. The Friedman test was used to assess surface wear and Kruskal-Wallis test to evaluate the presence of microcracks and surface irregularities, with a 5% significance level. There was a significant increase in wear in both groups at T2, compared to T0 (p=0.0003). The surface wear after instrumentation of six canals (T2-T0) was statistically greater in the WOG group, than in the WO group (p=0.02), where the presence of microcracks was significantly greater and increased after multiple uses (p<0.05). The presence of surface irregularities in the cutting blade before and after use was statistically greater in the WOG group than WO group (p<0.05). Wear of the cutting blade, microcracks and surface irregularities were observed on the surface topography of all the instruments after multiple uses. These surface changes may affect the cutting efficiency of WOG files and increase the risk of fracture of WO files.

Metallurgical Tests in Endodontics: A Narrative Review

Since there are no reviews of the literature on this theme, the aim of this narrative review is to summarize the metallurgical tests used in endodontics, pointing out their functional use and their pros and cons and giving readers a user-friendly guide to serve as an orientation aid in the plethora of metallurgical tests. With this purpose, a literature search for articles published between January 2001 and December 2021 was conducted, using the electronic database PubMed to collect all published articles regarding the metallurgical tests used in endodontics for the evaluation of NiTi rotary instruments. The search was conducted using the following keywords: “metallurgy”, “differential scanning calorimetry” (DSC), “X-ray diffraction” (XRD), “atomic force microscopy” (AFM), “energy-dispersive X-ray spectroscopy” (EDS), “focused ion beam analysis” (FIB) and “Auger electron spectroscopy” (AES) combined with the term “endodontics” or “NiTi rotary instruments”. Considering the inclusion and exclusion criteria, of the 248 articles found, only 81 were included in the narrative review. According to the results, more than 50% of the selected articles were published in one of the two most relevant journals in endodontics: International Endodontic Journal (22.2%) and Journal of Endodontics (29.6%). The most popular metallurgical test was DSC, with 43 related articles, followed by EDS (33 articles), AFM (22 articles) and XRD (21 articles). Few studies were conducted using other tests such as FIB (2 articles), micro-Raman spectroscopy (4 articles), metallographic analysis (7 articles) and Auger electron spectroscopy (2 articles).

Impact of Endodontic Instrumentation on Surface Roughness of Various Nickel-Titanium Rotary Files

OBJECTIVES

 The aim of the present study was to evaluate the surface roughness (SR) of various nickel-titanium (NiTi) rotary endodontic instruments (ProTaper Next [PTN], WaveOne Gold [WOG], and ProTaper Gold [PTG]) before and after root canal instrumentation.

MATERIALS AND METHODS

 For each type (PTN, WOG, and PTG), the endodontic instrumentation was performed using extracted mandibular molar teeth's curved mesial root canals (curvature: 20-40 degrees) after determining the working length. Each NiTi file was cleaned, and sterilized following preparation of four root canals and characterized for surface properties before and after endodontic instrumentation using a contact-mode three-dimensional surface profiler. The data were analyzed statistically using Statistical Package for the Social Sciences for SR parameters including average surface roughness value (Sa), root mean square roughness (Sq), and peak to valley height (Sz).

RESULTS

 Preinstrumentation assessment revealed a significant difference for all the three SR variables (p < 0.05) for the cutting blade and the flute area. WOG instruments showed the highest SR values (p = 0.000). The postinstrumentation assessment revealed significant differences in SR values in the blade and the flute between the three groups (p < 0.05), with WOG and PTG exhibiting the highest values in the blade and flute sections, respectively.

CONCLUSIONS

 The SR parameters of intact PTN, WOG, and PTG NiTi files vary and that was increased following the endodontic instrumentation.

A new method for assessment of nickel-titanium endodontic instrument surface roughness using field emission scanning electronic microscope

BACKGROUND

To introduce a new method for measurement of surface roughness of the endodontic instrument, before and after instrumentation, using the Field Emission Scanning Electronic Microscope (FE-SEM) combined with the ImageJ software.

METHODS

Twenty J-shape resin blocks were divided into two groups, ten blocks of each group. Simulated root canal inside the resin block was 16 mm length, 60⁰ angle of curvature, and radius of 4.5 mm. Ten WaveOne Gold Primary and 10 Reciproc Blue R25 instruments were used for root canal instrumentation. The instruments were scanned before and after instrumentation with special molds made to ensure the same areas at the point located 3 mm from the tips of the instruments using the FE-SEM. These scanned images were analyzed using the ImageJ. The arithmetical mean roughness (R_a), root mean square roughness (R_q), and the average distance between the highest peak and lowest valley in each sampling length (R_z) were calculated by ImageJ for quantitative analyses. The paired-t test was performed to analyze the data using the SPSS 22.0 at the significance of .05.

RESULTS

Almost all surface roughness values were decreased. However, these decreases were not statistically significant (P > .05).

CONCLUSIONS

The FE-SEM combined with the ImageJ was the reliable and appropriate modality for measurement surface roughness of instruments.

Surface Alterations Induced on Endodontic Instruments by Sterilization Processes, Analyzed with Atomic Force Microscopy: A Systematic Review

Endodontic canal disinfection procedures that use sodium hypochlorite, and subsequently, heat sterilization procedures can alter the surface of endodontic instruments, described as corrosion and micropitting. These phenomena can be visualized on the surface of the instruments by SEM and atomic force microscopy analyses. The endodontic instruments used in probing, pre-enlargement, and shaping phases are made of steel alloy or nickel-titanium alloy (NiTi) and are subject to torsional, flexor, and cyclic fatigue; indeed, reuse of these instruments must be done with the knowledge that these instruments are subject to fracture following stress caused during their use. Fracture of the instrument within the canal is an eventuality that can lead to failure of the treatment, and therefore it is important to try to reduce situations that can contribute to the fracture. This review was performed based on the PRISMA protocol. Studies were identified through bibliographic research using electronic databases. A total of 1036 records were identified on the PubMed and Scopus databases. After screening the articles, restricted by year of publication (1979 to 2019), there were 946 records. With the application of the eligibility criteria (all the articles pertaining to the issue of sterilization in endodontics), there were 228 articles. There were 104 articles after eliminating overlaps. There were 50 articles that discussed the influence of sterilization procedures on the surface characteristics of endodontic instruments, and 26 articles that measured parameters on surface alteration. Applying the inclusion and exclusion criteria resulted in a total of eleven articles for quantitative analysis. Four articles were in reference to the primary outcome, eight articles to secondary outcome, and five articles to tertiary outcome. The meta-analysis showed a statistically significant surface alteration effect after five autoclaves and after immersion in the canal irrigants after 10 min.

Atomic force microscopy and energy dispersive X-ray spectrophotometry analysis of reciprocating and continuous rotary nickel-titanium instruments following root canal retreatment

The aim was to examine the effect of retreatment process on the surface roughness and nickel titanium (NiTi) composition of ProTaper Universal Retreatment (PTUR; consists of 3 files; D1, D2, D3) and WaveOne Gold (WOG) (primary) instruments. Twenty extracted mandibular molar teeth with severe curved (30-40°) mesial roots were selected and divided into two groups (n = 10) based on the instrument used for the removal of the root canal filling. Before and after using the instruments in two canals, they were subjected to atomic force microscopy (AFM) and energy dispersive X-ray spectrophotometry (EDX) analysis. The EDX analysis data and roughness average (Ra) and root mean square (RMS) values were analyzed statistically using a one-way analysis of variance and post hoc Tukey's test at the 5% significant level. There was no significant difference between the new and used D1 and D2 PTUR and WOG instruments in terms of the Ni composition (p > .05). The Ti contents of the used D2 and D3 PTUR instruments were lower those of the new instruments (p < .05). In both new and used instruments, PTUR and WOG have no difference in terms of Ra and RMS values. (p > .05). The Ra and RMS values of the PTUR and WOG systems significantly increased after removal of the root canal filling (p < .05). The use of PTUR and WOG instruments for removal of root canal filling in severely curved root canals affected the surface topography of the files. The NiTi composition of the WOG instruments was unaffected by the retreatment process.