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 Table of Contents  
ORIGINAL ARTICLE
Year : 2023  |  Volume : 13  |  Issue : 1  |  Page : 80-87

Evaluation and comparison of transportation and centering ability of various pathfiles in the second mesiobuccal canal of maxillary first molars


1 Associated Professor, Department of Endodontics, School of Dentistry, Mashhad University of Medical Science, Mashhad, Iran
2 Professor, Department of Oral and Maxilofacial Radiology, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran
3 Dental Student, Department of Endodontics, Faculty of Dentistry, Mashhad University of Medical Sciences (MUMS), Mashhad, Iran
4 Assistant Professor, Department of Endodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran

Date of Submission01-Jul-2022
Date of Decision31-Aug-2022
Date of Acceptance01-Sep-2022
Date of Web Publication11-Jan-2023

Correspondence Address:
Dr. Maryam Peighoun
Dental Research Center, Faculty of Dentistry, Mashhad University of Medical Science, VakilAbad Avenue, Mashhad
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_123_22

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  Abstract 

Introduction: In root canal treatment, the glide path process is considered a primary action to increase the safety and efficiency of nickel–titanium rotary files and prevent preparation errors. The present study aimed to evaluate and compare different glide paths in terms of transportation and centering ability of the curved, narrow second mesiobuccal (MB2) canal of maxillary first molars using cone-beam computed tomography (CBCT).
Materials and Methods: First, periapical radiographs and CBCT were obtained from extracted maxillary first molars, and 125 teeth, whose mesiobuccal root curve was in the medium range (a curve angle of 20°–40°) and had separate MB2 canal, were selected. However, teeth <17 mm and more than 21 mm in length were excluded from the study. Afterward, the access cavity was prepared with a round diamond bur, and the MB2 canal was negotiated using a manual size 6–8 C-pilot. In the next stage, were randomly divided to five groups of 25, and each group was prepared by using one of the files of ProGlider, R-Pilot, Hyflex EDM, WaveOne Gold Glider, and C-Pilot. Following that, CBCT was taken from all teeth again, and the levels of canal transportation and centering ability were evaluated at five levels (distances of furcation, 1 and 2 mm from the furcation, the crest of the curvature, and 1 mm from the apex).
Results: In this study, there was no statistically significant difference in canal transportation and centering ability among five PathFile systems in all sections (P > 0.05).
Conclusions: All five PathFile systems carry out Glide path preparation similarly and appropriately in terms of canal transportation and centering ability.

Keywords: Canal transportation, centering ability, cone-beam computed tomography, PathFile, root canal preparation


How to cite this article:
Gharechahi M, Bagherpour A, Behzadi S, Gharechahi MM, Peighoun M. Evaluation and comparison of transportation and centering ability of various pathfiles in the second mesiobuccal canal of maxillary first molars. Saudi Endod J 2023;13:80-7

How to cite this URL:
Gharechahi M, Bagherpour A, Behzadi S, Gharechahi MM, Peighoun M. Evaluation and comparison of transportation and centering ability of various pathfiles in the second mesiobuccal canal of maxillary first molars. Saudi Endod J [serial online] 2023 [cited 2023 Feb 3];13:80-7. Available from: https://www.saudiendodj.com/text.asp?2023/13/1/80/367511


  Introduction Top


One of the successful root canal treatments is the elimination or minimization of root canal system microorganisms while maintaining the original shape and path of the canal.[1],[2] In fact, suitable root canal preparation is one of the most important roots canal treatment stages, some of the principles of which include proper mechanical debridement while preserving the original shape of the root canal, creating enough space from the orifice to the apex for cleaning and obturation the cavity.[3],[4] However, observing the mentioned principles is difficult in narrow and curved canals.[5] Since instrumentation techniques can cause the canal to deviate from its original path and lead to errors such as ledge, transportation, zipping, and instrument fraction during the preparation process, which jeopardizes the success of root canal treatment.[6] One of these narrow and curved canals is the second mesiobuccal (MB2) canal of the maxillary first molars.[7] Therefore, various manual and mechanical rotary files have been introduced under the general title of Glide path.[8],[9],[10]

Stainless steel files No. 10–15 and nickel–titanium rotary files are applied in manual and mechanical types of the Glide path method, respectively.[9],[11]

The mechanical type of Glide path is used with different rotary motions, some of the most important of which are continuous rotary and reciprocal motions. In the latter, the file moves slowly along the canal toward the apex in reciprocating motions. These motions reduce torsional stresses while increasing cyclic fatigue resistance, compared to the former.[12],[13] Moreover, there is a higher rate of centering maintenance and less transportation in reciprocal files, compared to rotary files.[14],[15] In terms of different types of Glide path files, R-Pilot and WaveOne gold glider are of reciprocating rotary system type, whereas Hyflex EDM and ProGlider files are of continuous rotary system type.

In addition to the difference in the type of motion, various PathFiles can be designed in single- or multiple-file form for the Glide path process. In this regard, R-Pilot, WaveOne gold glide, Hyflex EDM, and ProGlider files are used in the single-file form, while Profile, Scout Race, and M3 files are applied in multi-file form. One of the advantages of the single-file system is accelerating the pace of the Glide path process.[16] Treatment of the MB canal of maxillary first molars is extremely challenging in 96% of the cases due to the existence of the MB2 canal.[17]

With this background in mind, the present study aimed to compare the transportation and preservation of root canal centrality by five systems; the ProGlider file, R-Pilot file, Hyflex EDM file, WaveOne Gold Glider file, and C-Pilot file in the MB2 root canal of maxillary first molars using cone-beam computed tomography (CBCT).


  Materials and Methods Top


Study protocol and registration

This article was approved by Mashhad University of Medical Sciences' Ethics and Research Committee with the ethical code of IR.MUMS.DENTISTRY.REC.1398.052.

Specimen selection and preparation

This was an ex vivo study performed on 125 mature permanent maxillary first molars extracted due to severe caries or periodontal problems.[7] The teeth were first immersed in 2.5% sodium hypochlorite solution for 48 h for sterilization and then kept in saline solution for the experiment.[18] Afterward, a parallel periapical radiograph was taken to measure the curvature of the canal and the possibility of MB2 canal, absence of calcification, and measuring root lengths of teeth. Teeth with root lengths between 17 and 21 mm and whose curvature angle in the mesiodistal plane were in the range of 20° to 40° according to the Schneider method[19] were included in the study.

To ensure the fixed position of teeth in both CBCTs before and after canal preparation, the samples were mounted in putty. Afterward, CBCT (Planmeca ProMax 3D Classic) was prepared (FOX = 8 cm × 8 cm, voxel size = 160 μm, KVP = 70, and MA = 8) in the axial, coronal, and sagittal sections to evaluate root and canal anatomy and ensure the existence of MB2 canal and its positioning. Finally, out of 325 maxillary first molar teeth, 125 teeth were approved and numbered to enter the study.[7] Therefore, after removing carious tissues and previous restorations, a standard access cavity was prepared using a high-speed handpiece and a flat-end fissure bur. In the next stage, the undercuts on the MB2 canal were removed by Muller bur, and the location of the MB2 canal was determined using size 6 and 8 C-files. Contrary to some studies, where the crown was cut at the cemento-enamel junction level or other roots,[20],[21] in the present study to further simulate clinical conditions the crown and other roots were preserved. In addition, the working length was determined by applying a size-6 C-file; in this regard, the entire file was entered into the canal and 1 mm of it was reduced after observing the tip of the file in the apical foramen and the result was recorded as the working length. In the next stage, the samples were randomly divided into five groups of 25, and each group was negotiated with one of the systems of Proglider (Dentsply Sirona, Ballaigues, Switzerland), R-pilot (VDW, Munich, Germany), Hyflex EDM (Coltene/Whaledent, Switzerland), WaveOne Gold Glider (Dentsply Maillefer, Switzerland), and C-Pilot (VDW, Germany).

In the manual group (negative control), the filing was done by C-pilot file up to number 15 with watch winding and balanced force motions following determining the length of the canal. In addition, root canals of all groups were flushed with 5.25% sodium hypochlorite, and RC prep (Meta Biomed Co., Seoul, Korea) was used to lubricate the canal during filing. In the other four Glide path groups, files were used in single file and disposable form without pressuring the walls and with mild apical pressure. In this study, we used the Silver Reciproc motor (VDW Silver, VDW, Munich, Germany). According to the factory recommendation, the Hyflex EDM file was used with a speed of 300 rpm and a torque of 2 n.cm, and the Proglider file was applied with a speed of 300 rpm and a torque of 1.8 n.cm. Given that, WaveOne Gold Glider and R-Pilot files have reciprocal motion, the device was set to WaveOne all mode and Reciproc all mode when using these files, respectively.

Each file was removed from the canal after pecking three times and cleaned with gauze, and the canal was flushed with 5.25% sodium hypochlorite and lubricated with EDTA. The sequence was repeated until the file reached the working length.[22] File fracture in the root canal would result in the elimination of the tooth from the research and replacing it with a new maxillary molar. Notably, all canal preparation stages and evaluations were carried out by an endodontist.

Afterward, the molars were re-mounted on the putty, and CBCT was prepared with the same characteristics before the operation. Ultimately, centering ability and transportation were assessed using CBCT.

Image J software (version 1.52v, Java 1.8.0_112 Wayen Rasband, U.S. National Institutes of Health, Bethesda, MD, USA) was used to examine the variables in this study. In this regard, the Planmeca Romexis Viewer software was applied to observe CBCT images of molars. In CBCT images sections were prepared at one mm from the apex as an apical cross-section, maximum curvature as intermediate cross-section and furcation section, and 1- and 2-mm furcation section, and measurements were taken. [Figure 1], [Figure 2], [Figure 3] show images of samples before and after canal preparation. A red line with a specified length was drawn on the palatal root of each section to equalize the measurement scale in CBCT and image J software, using the measure length option in the mentioned viewer. Following that, the sections were transferred to the Image J software to measure the desired variables. Data measurement was carried out by a researcher who was blinded to the sample allocation, and data analysis was performed by an analyzer.
Figure 1: Axial sections of root at apical region before and after preparation (from left to right, respectively) MB2 canal (a red line was drawn on the palatal root in the viewer with Image J software. To match the CBCT scale). MB2: Second mesiobuccal, CBCT: Cone-beam computed tomography

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Figure 2: Axial section of the root in the middle section before and after MB2 canal preparation (from left to right, respectively). MB2: Second mesiobuccal

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Figure 3: Axial sections of the root in furcation and 1- and 2-mm from furcation (from left to right, respectively) before (up) and after (down) the MB2 canal preparation. MB2: Second mesiobuccal

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In this study, the centering ability was estimated using the equation below:[23]

CT = (M1-M2)/(D1-D2), if (D1-D2>M1-M2)

CT = (D1-D2)/(M1-M2), if (M1-M2)>(D1-D2)

M1 is the shortest distance between the mesial of the tooth to the mesial edge of the uninstrumented canal, and M2 is the shortest distance between the mesial of the tooth to the mesial edge of the instrumented canal. Accordingly, D1 is the shortest distance between the distal wall of the tooth to the distal edge of the uninstrumented canal, and D2 is the shortest distance between the distal wall of the tooth to the distal edge of the instrumented canal. The closer the value to one, the better the centering ability. On the other hand, the closer the value to 0, the weaker the centering ability. The following equation, presented by Gambill et al., was used to assess the transportation of the mentioned sections.[23]

T = (M1-M2) – (D1-D2)

There will be no transportation if the values obtained from the equation are close to 0. Positive values show transportation in the mesial, whereas negative values demonstrate transportation in the distal, i.e., the furcation section (danger zone). The absolute value of the numbers obtained was analyzed to evaluate the level of transportation, and the values themselves were analyzed to determine transportation in each group.

Statistical methods and sample size

Data analysis was performed using Kruskal–Wallis test and one-way ANOVA. It is worth noting that a P = 0.05 was considered statistically significant.

The sample size was estimated at 25 with a 95% confidence interval and 80% test power to have an 80% effect.


  Results Top


Centering ability

[Table 1] shows the mean, standard deviation, and lowest and highest scores of ANOVA test results for the variable of centering in apical, middle, furcation, and 1- and 2-mm furcation sections in different groups. As observed, the lowest centering level was observed in the Hyflex EDM group, whereas the highest centering level was detected in WaveOne Gold Glider and C-Pilot groups. Based on the Kruskal–Wallis test results, there was no significant difference among the groups in terms of centering (P = 0.232). In the 1 mm furcation section, the lowest mean centering preservation was observed in the R-Pilot group, while the highest rate was found in the ProGlider group, even though the difference among the groups was insignificant (P = 0.316). In the 2-mm furcation section, the lowest and highest mean preservation of centering in the canal was related to the R-Pilot and Hyflex EDM groups, respectively. In this regard, no significant difference was observed among the groups (P = 0.711). In the crest of curvature, the lowest and highest mean preservation of centering in the canal was found in the WaveOne Gold Glide and R-Pilot groups, respectively. At this level, there was no significant difference among the groups (P = 0.903). In the apical 1 mm, the lowest and highest mean preservation of centering in the canal was observed in the C-Pilot and R-Pilot groups, and the Hyflex EDM group, respectively. Meanwhile, no significant difference was observed among the groups in this respect (P = 0.566).
Table 1: Comparison of centering preservation in the canal in various sections

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Canal transportation

[Table 2] shows the mean, standard deviation, lowest and highest score of transportation, and Kruskal–Wallis test results in apical, middle, furcation, as well as 1- and 2-mm furcation sections in different groups. As observed, the lowest mean canal transportation in the furcation section was found in the groups of C-Pilot and WaveOne Gold Glider, whereas the highest mean was observed in the Hyflex EDM group. In this regard, the results were a little short of significance (P = 0.078). In the 1-mm furcation section, the lowest and highest mean transportation was observed in the Proglider and R-Pilot groups, respectively, and the results were a little short of significance (P = 0.076). In the 2-mm furcation section, the lowest and highest mean transportation was observed in the WaveOne Gold Glider and R-Pilot groups, respectively. Even though no significant difference was observed among the groups, the results were a little short of significance (P = 0.083). In the middle section, the lowest and highest mean transportation was detected in the C-Pilot and R-Pilot groups, respectively. Similarly, no significant difference was observed among the groups in terms of transportation (P = 0.891). In the apical section, the lowest and highest mean transportation were observed in the Hyflex EDM group, and R-Pilot and C-Pilot groups, respectively, showing no significant difference among the groups (P = 0.301).
Table 2: A comparison of canal transportation in apical, middle, furcation, and 1 and 2 mm furcation section

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[Table 3] shows the results related to canal transportation at each discussed section in various groups. As observed, the mean transportation was negative in coronal sections (i.e., furcation and 1- and 2-mm furcation) without considering the absolute value, which was indicative of transportation toward the distal end. The mean transportation was positive in the crest of curvature, demonstrating the occurrence of transportation toward the mesial canal in the middle section. Moreover, the mean transportation in the apical 1 mm section was positive in the groups, meaning that the transportation was toward the mesial in the apical section.
Table 3: Comparison of canal transportation in furcation, 1 and 2 mm furcation, as well as middle and apical sections

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  Discussion Top


The development of a Glide path is the crucial and primary step toward a more efficient and quicker preparation of the root canal while maintaining its anatomy, especially in narrow and curved canals.[24] Given that the preparation of curved canals has always been a challenge to dentists,[25] we focused on this canal by comparing different PathFiles in terms of canal transportation and centering ability to answer the question of: “which system can more safely and efficiently prepare the path in curved, calcified and narrow canals and can be selected as the best Glide Path system in clinic?”

In the design of the study and selection of PathFiles, attempts were made to use files with different functional techniques; in this regard, R-Pilot and WaveOne Gold Glider perform the Glide path process with reciprocal motions, whereas ProGlider and Hyflex EDM carry out the process with rotary motions with no file fracture. In addition, in each of the groups of reciprocal and rotary files, one file had a constant taper and the other had a progressive taper, which helped compare PathFile systems more accurately. Some studies, including research by Hartmann et al.[24] and Han et al.,[26] used root canal-simulating resin blocks. However, the use of extracted teeth was preferred due to the difference in the hardness of dentin and resin, and more similarity of extracted teeth to clinical conditions.[4]

In the present study, centering and transportation were assessed in five sections of roots. Based on a study on CBCT of 10 maxillary first molars to prepare the apical section, the closest point to the apical foramen that produces a clearer image of CBCT was 1 mm from the apex.[22] Therefore, similar to studies by Liu et al.[27] and Kabil et al.,[22] the 1-mm apical section represents the apical section in the transportation and centering assessment process. The root canal sections that are closer to the curvature are more exposed to changes and deviations from the main canal path.[22] Accordingly, similar to studies by Kabil et al.[22] and Česaitienė et al.,[28] the crest of curvature was considered as the middle section. The coronal section in the MB2 canal and its changes are also important due to the high slope of the canal when separated from the chamber pulp and the slight thickness of dentin in this section.[7] Therefore, three sections in furcation and 1- and 2-mm furcation areas were evaluated as representative of the coronal section in terms of transportation and centering.

Various methods exist to evaluate the efficiency of different PathFile systems regarding the preservation of root canal anatomy. In this regard, we can compare the root canal shape before and after preparation. Some of these methods include conventional two-dimensional radiography and root cutting, as well as computed tomography (CT) and CBCT techniques. CBCT systems offer three-dimensional imaging with an accurate detection ability by using lower doses, providing higher resolution, and allowing the assessment of sections without damaging the samples, which can be repeated.[29],[30],[31] Despite the advantages of CBCT, the micro-CT method is still used as the golden standard to assess various canal preparation methods with different files despite its time-consuming process and extremely high costs owing to its superimposition ability before and after preparation with high resolution.[18] Since there was no access to the micro-CT method in the present research, we applied CBCT before and after canal preparation, similar to studies conducted by Dhingra and Manchanda[32] and Arruda et al.[33]

Canal transportation is an error that reduces the efficiency of the preparation technique and disrupts the root canal cleaning process, which ultimately endangers apical sealing.[2],[34] In a study, Wu et al.[34] reported that apical transportation of more than 0.3 mm adversely affected the sealing ability of fillers. In the current research, we compared the amount of apical canal transportation in five sections. According to the results, the maximum mean apical transportation was related to the R-Pilot group at a distance of 1 mm from the apex with a value of 0.164 ± 0.117, which was lower than 0.3 mm, and it did not have a negative effect on sealing ability of fillers.[34]

Several studies have compared manual and rotary Glide path systems, some of which, including Pasqualini et al.[35] and Liu et al.[27] reported less transportation and better centering in rotary PathFile systems, compared to manual systems.

According to the results of the present study, all five PathFile systems are similar in terms of transportation and centering preservation, such that the primary anatomy of the canal was preserved favorably. It is worth noting that there was some transportation and deviation in all five systems. Moreover, the mean apical transportation was lower than 0.3 in all systems, which could clinically endanger apical sealing if it is larger than the mentioned value.[34]

One of the limitations of this study was the lack of access to micro-CT, which provides more accurate and higher-resolution images. Another limitation was the inaccuracy of the location of the reference point for measuring the desired variables, which was minimized by enlarging the image when preparing cross-sectional images. It is suggested to check how the amount of transportation and maintaining the centrality of the canal changes after completing canal preparation.


  Conclusions Top


All five PathFile systems carry out Glide path preparation similarly and appropriately in terms of canal transportation and centering ability, and it does not have a negative effect on the sealing ability of fillers.

Acknowledgments

This study was supported by a grant from the Vice Chancellor of the Research Council of Mashhad University of Medical Sciences, Iran. The results presented in this study have been taken from a student thesis at Mashhad University of Medical Sciences.

Financial support and sponsorship

The authors would like to appreciate the continued support of the Research Council of Mashhad University of Medical Sciences and the Student Research Committee of Mashhad University of Medical Sciences, Mashhad, Iran.

Conflicts of interest

There are no conflicts of interest.

 
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