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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 34  |  Issue : 4  |  Page : 288-292

An in vitro evaluation of canal transportation and centering ability of ProTaper Universal, Hyflex EDM, and WaveOne gold using microcomputed tomography


1 Department of Conservative Dentistry and Endodontics, SRM Kattankulathur Dental College and Hospital, SRM Institute of Science and Technology, Chennai, Tamil Nadu, India
2 Department of Conservative Dentistry and Endodontics, Ragas Dental College and Hospital, The Tamil Nadu Dr. M.G.R Medical University, Chennai, Tamil Nadu, India

Date of Submission19-Apr-2022
Date of Decision03-Jul-2022
Date of Acceptance28-Aug-2022
Date of Web Publication28-Dec-2022

Correspondence Address:
Dr. Ashwin Ravichandran
Department of Conservative Dentistry and Endodontics, SRM Kattankulathur Dental College and Hospital, SRM Institute of Science and Technology, SRM Nagar, Kattankulatur, Chennai - 603 203, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_108_22

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  Abstract 


Aim: The study was to determine and compare the values of canal transportation and centering ability of ProTaper Universal (PTU), Hyflex EDM (HEDM), and WaveOne GOLD (WOG) using microcomputed tomography (Micro-CT).
Methods: Sixty mandibular molar mesiobuccal canals were randomly allocated into three groups, each with 20 samples: PTU (group one), HEDM (group two), and WOG (group three). Micro-CT was used to scan samples before and after instrumentation. Three-dimensional scans of root cross-sections at 3 mm, 6 mm, and 9 mm from the apex were obtained to measure canal transportation and centering ability. For statistical analysis, SPSS software was utilized. P = 0.05 was used as the significance level.
Results: When compared all three systems, PTU files had the highest transportation and were less centered. HEDM and WOG showed no significant difference (P > 0.05).
Conclusion: Curved roots canals were shaped without any significant canal transportation by Hyflex EDM and WOG when compared with PTU files.

Keywords: Canal transportation, centering ability, microcomputed tomography


How to cite this article:
Ravichandran A, Baskaran VA, Gopal SN, Motilal VS, Rajasekaran M, Ramachandran AK. An in vitro evaluation of canal transportation and centering ability of ProTaper Universal, Hyflex EDM, and WaveOne gold using microcomputed tomography. Endodontology 2022;34:288-92

How to cite this URL:
Ravichandran A, Baskaran VA, Gopal SN, Motilal VS, Rajasekaran M, Ramachandran AK. An in vitro evaluation of canal transportation and centering ability of ProTaper Universal, Hyflex EDM, and WaveOne gold using microcomputed tomography. Endodontology [serial online] 2022 [cited 2023 Jan 28];34:288-92. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/4/288/365805




  Introduction Top


The three basic processes of endodontic treatment are mechanical preparation, disinfection, and a three-dimensional obturation of the root canal system. Chemomechanical preparation, on the other hand, is an important part of the endodontic therapy since it entails removing any leftover pulp tissue and debris, as well as create space for the irrigation solutions and medicaments to function on the bacteria and disinfect the root canal.[1],[2] However, due to the widely varied root canal morphology, these goals are hard to attain. It is more difficult to achieve a good taper in a curved canal since there is a risk of canal transportation and loss of centering ability. Excessive dentin removal within the canal in a single direction rather than in all directions equidistant from the primary tooth axis results in canal transportation which is an unwanted deviation from the natural canal course. The capacity of the instrument to keep centered in the canal is known as centering ability.[3],[4]

Walia et al. invented NITI files in year 1988. NiTi is well known for its outstanding super elasticity and shape memory properties. Over the years, NiTi instruments have undergone many modifications to improve fracture resistance, flexibility, and treatment time.[5],[6],[7]

The ProTaper file system (PT; Dentsply Maillefer, Ballaigues, Switzerland) is one of the most widely used rotary file systems today.[8] The instrument design features a convex triangular cross-section, progressive taper, variable helical angle, and a noncutting, modified guiding tip. These features may serve to increase the file's flexibility and aid in the creation of a centered preparation.[9]

HyFlex EDM [HEDM]; Coltene/Whaledent AG, Altstaetten, Switzerland is created by a controlled memory treatment and an EDM process.[10],[11] It hardens the NiTi file's surface, resulting in increased fracture resistance and cutting efficiency. HEDM features three different cross-sections in its file shaft: triangular in the coronal third, trapezoidal in the middle third, and practically quadratic in the apical third.[12],[13]

WaveOne GOLD [WOG]; Dentsply Maillefer, Ballaigues, Switzerland is made using the GOLD treatment technique and has the same movement kinematics as Wave One, but the cross section of the file has been changed to a parallelogram structure with two cutting edges to make it more flexible.[12] The most notable point is that WOG is manufactured with GOLD alloy technology, which involves heating and then slowly cooling the file. This new heat treatment procedure, according to the manufacturer, improves the flexibility of files.[14],[15]

The introduction of microcomputed tomography (Micro-CT) into the field of endodontics has opened up new possibilities. The micro-CT is a nondestructive and noninvasive technology for evaluating root canal anatomy, endodontic procedures, and materials.[16],[17] The goal of this in vitro study was to use micro-CT imaging to compare the canal transportation and centering abilities of three rotary systems: ProTaper Universal (PTU), HEDM, and WOG in the preparation of curved mesial root canals of mandibular molars.


  Materials and Methods Top


The study included 60 human mandibular molars with a fully formed apex, two independent mesial canals, and an apical foramen. The sample size was determined based on previous studies of this nature.[18] A diamond disc with water coolant was utilized to decoronate all of the teeth at the cemento-enamel junction to standardize canal instrumentation. The curvatures of the root canals were not standardized. The distal roots of mandibular molars were then detached, leaving the mesial roots. Instrumentation was limited to the mesiobuccal canals. Files of size #10 K were used to generate the glide path. Working length was determined by extending the file into the canal until the apical foramen was just visible, then subtracting 1 mm.

The 60 teeth were then allocated into three instrumentation groups, each with 20 teeth (n = 20): Group 1 (PTU), Group 2 (HEDM), and Group 3 (WOG). To replicate the periodontal ligament, a thin coating of polyether impression material was applied to the roots and placed in an acrylic resin holder, which sped up the core registration process. Micro-CT scanning is used for preoperative operative scanning. All groups were instrumented after being increased to a size 20 K-file: rotary files in Groups 1 and 2, and reciprocating files in Group 3. A 6:1 reduction hand piece powered by a torque-limited endomotor (X-smartTMplus, Dentsply Tulsa Dental) was utilized with rotary and reciprocating instruments. The torque limit and rotating speed recommended by the manufacturer were used for each file. In a reciprocating working motion generated by the motor, reciprocating files were used. The manufacturer's instructions were followed for preparing the canals.

Microcomputed tomography scanning

Samples were embedded in high-precision impression material with the orifice facing down for exact repositioning during pre- and post-operative scans. Five mesial roots were placed in a sample holder and transported to the micro-CT scanner's carbon fiber bed (SkyScan 1174 v2: Bruker microCT, Kontich, Belgium). Samples were scanned at 50 kV and 800 mA with a 19.6 μm isotropic resolution. To obtain scans in the same sagittal positions, the long axes of the mesial roots were changed to be perpendicular to the beam. The roots were then scanned by rotating them 360° around the vertical axis with a camera exposure period of 7000 msonds. A 1-mm thick aluminum filter was used to filter the X-rays. With NRecon v. 1.6.9 software (Bruker micro-CT) and 15% beam hardening, ring artifact correction of 5%, and a comparable contrast limit, images were reconstructed into cross-sectional slices, resulting in the capture of 700–900 (pixel size 18 μ) transverse cross-sections per tooth. [Figure 1] shows reconstructed Micro-CT cross-sectional images of the tooth.
Figure 1: Reconstructed Micro-CT cross-sectional images. Micro-CT: Microcomputed tomography

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Methodology of evaluation

CTAn v. 1.14.4 software (Bruker micro-CT) was used to calculate quantitative parameters and create visual 3D models from the acquired images. By integrating regions of interest in all cross-sections, the volume of interest for each specimen was determined, extending from the furcation region to the apex of the mesial root. Using a density histogram and the global threshold approach, the gray scale range required to detect the dentin before and after instrumentation was calculated. To guarantee the correctness of the segmentation, comparisons were made with the original segmented scan. Using a custom-processing program, task lists were used to generate separated binary pictures of the root canal space and dentin.

Analysis of root canal transportation

Axial sections corresponding to distances of 3, 6, and 9 mm from the anatomic apex were chosen for root canal transportation study. The Gambill et al. formula was used to compute canal transportation in millimeters [Figure 1].

Gambill et al.[19] defined ([X1-X2]-[Y1-Y2]) as ([X1-X2]-[Y1-Y2]).

Where X1 is the shortest distance between the mesial portions of the root and uninstrumented canal, X2 is the shortest distance between the mesial portions of the root and instrumented canal, Y1 is the shortest distance between the distal portions of the root and uninstrumented canal, and Y2 is the shortest distance between the distal portions of the root and instrumented canal, and Y3 is the shortest distance between the distal portions of the root.

According to this formula, a result of 0 indicated no canal transportation. A positive result indicated transportation away from the furcation region. Moreover, a negative result indicated transportation toward the furcation region.

Centering ability

It was calculated for each cross section using the values obtained in the assessment of root canal transportation with the ratio of (X1-X2) to (Y1-Y2). If these numbers were not equal, then the lower figure was considered to be the numerator of the ratio. According to this formula, a result of 1 indicated the optimal centering ability. The data obtained were subjected to statistical analysis. Canal transportation was analyzed using Kruskal–Wallis test followed by Tukey's post hoc test. Centering ability was analyzed using one way ANOVA followed by Tukey's post hoc test.


  Results Top


The mean and standard deviation (SD) values of canal transportation at 3 mm of PTU group, HEDM group, and WOG group were 0.195 (±0.1538), 0.030 (±0.0571), and 0.060 (±0.0940), respectively. The mean and SD values of canal transportation at 6 mm of PTU group, HEDM group and WOG group were 0.175 (±0.1682), 0.055 (±0.0887), and 0.080 (±0.1005), respectively. The mean and SD values of canal transportation at 9 mm of PTU group, HEDM group, and WOG group were 0.20 (±0.1654), 0.060 (±0.1095), and 0.085 (±0.1040), respectively [Table 1].
Table 1: Comparison of transportation and centering ability at 3, 6, 9 mm among ProTaper group, Hyflex EDM group, and WaveOne GOLD group

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The mean and SD values of the centering ratio at 3 mm of PTU group, HEDM group, and WOG group were 0.4230 (±0.20329), 0.8000 (±0.25131), and 0.7325 (±0.30893), respectively. The mean and SD values of centering ratio at 6 mm of PTU group, HEDM group, and group 3 were 0.4405 (±0.22700), 0.6745 (±0.27888), and 0.6655 (±0.31660), respectively. The mean and SD values of centering ratio at 9 mm of PTU group, HEDM group, and WOG group were 0 [Table 1].


  Discussion Top


A smooth and gradually tapering preparation is required for a successful endodontic treatment. In curved canals, achieving the tapering preparation is difficult.[20] Stainless steel hand files have been used in root canal instrumentation in the past, which caused procedural errors such as elbows, zips, and danger zones, as well as canal transportation, might occur.[21] NiTi alloy has been proposed for use in endodontics to alleviate this disadvantage.

To investigate the efficiency of instrument, invasive procedures, and noninvasive methods were available. Exact repositioning of pre- and postinstrumented samples is challenging in invasive procedures; they are technique sensitive, resulting in specimen loss.[19] Because of the smaller voxel size and higher resolution than standard clinical scanners, the micro-CT technology employed in this investigation which showed the full three-dimensional morphology of the root canal.[16],[17] The mandibular molars mesial canals are often moderately curvy, and they are among the teeth that need root canal therapy the most.[22] As a result, this study used human mandibular molar teeth.

At all three levels (3 mm, 6 mm, and 9 mm), the PTU system (group one) showed more canal transportation and a lower centering ratio. The PTU system exhibited positive transportation (movement away from the furcation) at 3 mm and 6 mm, but negative transportation at 9 mm. According to Schäfer et al.,[23] the percentage of taper is one of the primary causes involved in canal transportation, therefore, the transportation of PTU can be linked to the greater taper (8%) and less flexibility of the instruments.

At 9 mm ProTaper group removed more dentin toward the furcation, this may be due to the thin distal (furcal) root wall of the mesiobuccal canal of a mandibular molar, especially in long roots (24 mm) than in short-rooted teeth (19 mm) Stern et al.;[18] it can therefore be assumed that strip perforations might occur more frequently in mandibular teeth with long roots than short-rooted mandibular teeth when using greater taper instruments.

In more samples, HEDM demonstrated flawless shaping abilities with no canal transportation and was more centered in the canal than PTU. HEDM's superior performance in this study can be attributed to the electro-discharge machining procedure, the file shaft's variable cross sections design: quadratic in the apical third, trapezoidal in the middle third, and almost triangular in the coronal third, and the fact that it uses controlled memory wires.[24] When compared to the ProTaper next system, Venino et al.[25] discovered that HEDM showed less transportation at all three levels and was more centered. Pinheiro et al.[26] recently evaluated five newer heat treated NiTi files, namely ProTaper Gold, ProDesign S, Hyflex CM, HEDM, and ProDesign Logic, and found identical results for canal transportation and canal centering ability. They reported that the original canal anatomy was maintained in all five fresh heat-treated files.

At all three levels, WOG showed less transportation and was more centered, which could be related to the high austenite finish temperature value and two-stage transformation behavior of the WOG file.[27],[28] As a result, the WOG's successful performance in curved canal may be due to the GOLD heat treatment procedure. Between HEDM and WOG, there is no discernible difference. Another study by Özyürek et al. reported no difference in canal transportation between HEDM and WOG; however, unlike the previous study, which employed artificial resin canals, this study used natural canals and was examined with a highly accurate micro-CT.[12]

According to Wu et al.,[29] the essential canal transportation value is 0.3 mm since leakage happens more frequently when the apical transportation index is more than 0.3 mm. Peters et al.[30] showed in a comparable investigation that apical transportation of <0.1 mm is clinically acceptable. This limit was not exceeded by any of the transportation values measured in this study. The followings were the study's limitations: The instruments employed in this study are of various taper. Because the taper of instruments varies by manufacturer, it is impossible to standardize it. In this investigation, only the instrument tip was standardized to size 25, while the curvatures of the root canals were not standardized.


  Conclusion Top


Within the scope of the investigation, it was determined that the HEDM and WOG NiTi systems outperformed the PTU system in terms of canal centering ability at all levels (3 mm, 6 mm, and 9 mm) with minimal canal transportation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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