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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 34  |  Issue : 2  |  Page : 121-126

Cone-beam computed tomography assessment of root canal transportation and evaluation of canal centering using Protaper Gold, XP Endoshaper, and Edgefile X7


1 Department of Conservative Dentistry and Endodontics, Guru Nanak Institute of Dental Sciences and Research, Kolkata, West Bengal, India
2 Former House Surgeon, R G Kar Medical College and Hospital, Kolkata, West Bengal, India

Date of Submission01-Aug-2021
Date of Decision25-Jan-2022
Date of Acceptance12-Mar-2022
Date of Web Publication01-Jul-2022

Correspondence Address:
Dr. Tushar Kanti Majumdar
Department of Conservative Dentistry and Endodontics, Guru Nanak Institute of Dental Sciences and Research, Kolkata - 700 114, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_146_21

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  Abstract 


Aim: This study aims to access and evaluate canal transportation and canal centering ability of Protaper Gold (PTG), XP EndoShaper (XPS) and EdgeFile X7 using cone-beam computed tomography (CBCT).
Materials and Methods: Sixty freshly extracted single-rooted premolars with mature apex and a canal curvature of 10°–20° were chosen and arbitrarily divided into three experimental groups (n = 20). After decoronation, the teeth measuring 16 mm were included in the study for standardization. According to the manufacturer's instructions, canals were shaped with PTG in Group 1, XPS in Group 2 and EdgeFile X7 in Group 3. For the evaluation of the root canal transportation at 2 mm, 4 mm, and 6 mm from the apex, canals were scanned before and after instrumentation using CBCT scanner. Independent t-tests and one-way ANOVA were used to analyze data and significance level was set at P < 0.05.
Results: XPS showed significantly lower canal transportation than PTG system. Moreover, the centering ability of the XPS significantly higher than EdgeFile X7 and PTG at all root levels (P < 0.05).
Conclusion: The XPS and EdgeFile X7 rotary file system showed the lowest transportation in both mesiodistal and buccolingual directions and also the highest centering ability. The PTG file showed the highest transportation and lowest centering ability.

Keywords: Canal centering ability, canal transportation, cone-beam computed tomography, Edgefile X7, Protaper Gold, XP Endoshaper


How to cite this article:
Majumdar TK, Chowdhury M, Mukherjee S, Mazumdar P. Cone-beam computed tomography assessment of root canal transportation and evaluation of canal centering using Protaper Gold, XP Endoshaper, and Edgefile X7. Endodontology 2022;34:121-6

How to cite this URL:
Majumdar TK, Chowdhury M, Mukherjee S, Mazumdar P. Cone-beam computed tomography assessment of root canal transportation and evaluation of canal centering using Protaper Gold, XP Endoshaper, and Edgefile X7. Endodontology [serial online] 2022 [cited 2022 Aug 8];34:121-6. Available from: https://www.endodontologyonweb.org/text.asp?2022/34/2/121/349572




  Introduction Top


The main objective of the biomechanical preparation in endodontic treatment is to remove infected pulpal remnants, destroy microorganisms, preserving the initial canal anatomy and adequately shape the root canal to achieve three-dimensional obturation. Endodontic biomechanical preparation becomes more challenging in curved canals as it may lead to deviation of original canal curvature anatomy of the tooth. Any deviation within the root curvature of the root canal considered to be a risk factor for procedural errors such as ledging, zipping, strip perforation, and canal transportation.[1]

During biomechanical preparation, canal transportation occurs due to the tendency of endodontic instruments to straighten within the root canal. According to Glossary of endodontic terms of the American Association of Endodontists defines canal transportation as “the removal of canal wall structure on the outside curve in the apical half of the canal due to the tendency of files to restore themselves to their original linear shape during canal preparation may lead to ledge formation and possible perforation.”[2]

In 1988 Walia et al. brought about the revolutionary modification in endodontic instrumentation systems that are replacing stainless steel with nickel–titanium (Ni-Ti) alloy.[3]

The inception of Ni-Ti instruments in endodontics is a paramount step in root canal shaping procedure as they maintain the original canal shape, reduced procedural errors particularly in narrow curved canals and also remain centered within the canal due to their superelasticity and shape memory properties.[4]

XP EndoShaper (XPS) (FKG Dentaire, Switzerland) is a single-file system which is a “Novel Adaptive core” rotary instrument operates in a clockwise continuous rotation motion with an apical diameter of 0.30 mm and fixed taper of 0.01. XPS is manufactured from MaxWire alloy. The martensite phase of the file at room temperature converts to austenite phase at body temperature and therefore the taper of 0.01 reaches to 0.04 assuming a “Snake” shape while preserving the initial canal anatomy and curvature.[4]

A classical multi-sequential rotary file system (ProTaper Gold [PTG]; Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) operates in a clockwise continuous rotation motion and is made of NiTi-alloy called M-wire with convex triangular cross-section and progressively tapered design. PTG has a 2-stage specific transformation behavior and high austenite finish (Af) temperatures.[5] Thereby PTG has the properties of shape memory, superelasticity along with increased cyclic fatigue resistance that is useful in curved canals.[6]

EdgeFile X7 (EdgeEndo, Albuquerque, USA) is a single-file system which is manufactured from “Heat Treated FireWire™ NiTi” alloy. EdgeFile X7 has a parabolic cross-section which according to the manufacturer increases flexural strength, enhancing durability and flexibility.[1]

Although several Ni-Ti endodontic files have been recently developed to the foremost effectiveness of our data, no study so far has compared the canal transportation and canal centering ability of these three single endodontic file systems. The purpose of this in vitro study was to assess and compare the canal transportation and canal centering ability of PTG compared with the XPS and EdgeFile X7 rotary file systems in a single-rooted teeth with curved canal. The null hypothesis tested was that there should be no significant differences in the canal transportation and canal centering ability, among the three experimental groups in single-rooted teeth with curved canal.


  Materials and Methods Top


Specimen selection

Ethical clearance for this in vitro study was attained from the institutional ethical committee (GNIDSR/IEC/19–36). Freshly extracted sixty human mandibular premolars teeth irrespective of the position in arch within the age group of 18–30 years for orthodontic reasons exhibiting only one canal, one apical foramen with the closed apex on buccal and proximal radiographic examinations, and having angles of root curvature within 10°–20° (assessed by Schneider's technique)[7] were chosen. Selected teeth were not having of any cracks, caries, calcifications, restoration, internal or external root resorption, and aberrant canal morphology.

The sample size was decided on the basis of a pilot study done with seven samples used per group using OpenEpi, Version 3 (Copyright (c) 2003, 2008 Andrew G. Dean and Kevin M. Sullivan, Atlanta, GA, USA). The samples utilized in the pilot study were discarded.

The teeth were cleaned of calculus and soft tissue remnants employing a hand curette and were disinfected using 5.25% sodium hypochlorite for 10 min and rinsed with distilled water as per Occupational Safety and Health Administration. The teeth were stored in normal saline at 4°C until use in a beaker.[8]

Sample preparation

All the samples were standardized to 16 mm length measured by vernier caliper, decoronation using a diamond disc by a single operator. The access cavity was prepared using Endo Access bur, 21 mm size 2 (Dentsply Maillefer, Switzerland) was used and initial canal patency to full working length (WL) was established with ISO 10K Flexofile (Dentsply Maillefer, Ballaigues, Switzerland), visible at the apex, and the WL was established 1 mm short of this length.

The teeth were randomly divided into three equal groups and embedded in modeling wax of 2.5 cm × 2.5 cm in mandibular arch form, Group 1 (n = 20)– PTG, Group 2 (n = 20)– XPS, and Group 3 (n = 20) – EdgeFile X7. Pre-instrumentation cone-beam computed tomography (CBCT) scan was done.

Root canal preparation

Group 1 (n = 20) root canals were instrumented using PTG upto F3 in 3-4 up and down strokes applying light apical pressure till WL was reached. Torque and speed values used for PTG in the Canal Pro 2 Endomotor were 2.5 Ncm and 500 rpm, respectively.

Group 2 (n = 20) root canals were instrumented using XPS (size 30/0.04 taper) single-file system with 3–4 up-and-down strokes applying light apical pressure till WL was reached. Torque and speed values used for XPS in the Canal Pro 2 Endomotor in the continuous rotation were 1 Ncm and 800 rpm, respectively.

Group 3 (n = 20) root canals were instrumented using EdgeFile X7 (size 30/0.04 taper) file system with 3–4 up-and-down strokes applying light apical pressure till WL was reached. Torque and speed values used for EdgeFile X7 in the Canal Pro 2 Endomotor in the continuous rotation were 2.5 Ncm and 500 rpm, respectively.

The final apical preparation was standardized at size 30 for all specimens. The root canals were irrigated with 2 ml 3% sodium hypochlorite at the change of each instrument. Final irrigation was performed by 2 ml 17% Ethylenediaminetetraacetic acid for 1 min followed by a final rinse of 2 ml normal saline. All root canals were irrigated using 30-gauge side-vented needles (Max-I-Probe; Dentsply Maillefer, Switzerland) and placed before the binding point with a distance of 3 mm from the WL.

Each instrument was used to prepare four canals, and then, the files were discarded. Experimental teeth were then again scanned under CBCT and data were analyzed.

Image analysis

All the teeth were scanned using CBCT (Orthophos XG3D, Dentsply Sirona) with the following setup: 90 kVp, 27 mA, 0.1 mm × 0.1 mm × 0.1 mm voxel size, and 0.1 mm axial thickness, to determine the root canal configuration before instrumentation. The first section was at 2 mm from the apical end of the root (apical level), the second section at middle third (mid-root level) 4 mm from the apex, while the third section at the coronal third, 6 mm from the apex was recorded. Image analysis was performed using On-Demand 3D App software (Yokohama, Japan) after the initial scan and root canals were instrumented.

Evaluation of canal transportation and centering ability

The following formula was used for the calculation of canal transportation mesiodistally and buccolingually at each level for the experimental groups using the subsequent formula, as described by Gambill, Alder:[9]

  • Mesiodistally = (a1-a2)-(b1-b2)
  • Buccolingually = (c1-c2)-(d1-d2)
  • Mesial (a1)/lingual (d1) is the least distance from the mesial/lingual edge of the root to the mesial/lingual edge of the uninstrumented canal
  • Distal (b1)/buccal (c1) is the least distance from the distal/buccal edge of the root to the distal/buccal edge of the uninstrumented canal
  • mesial (a2)/lingual (d2) is the least distance from the mesial/lingual edge of the root to the mesial/lingual edge of the instrumented canal
  • Distal (b2)/buccal (c2) is the least distance from the distal/buccal edge of the root to the distal/buccal edge of the instrumented canal.


On the basis of this formula, “0” indicates no canal transportation whereas other values mean that canal transportation has occurred.

Using the subsequent formula, the canal centering ratio at each root level was calculated.[10]

  • (a1-a2)/(b1-b2) or (b1-b2)/(a1-a2).


On the basis of this formula, 1 represents perfect canal centering, whereas other values show changes in the canal centering.

Statistical analysis

Statistical analysis was conducted using IBM SPSS Software version 20 (IBM SPSS Inc., Chicago, IL, USA). A one-way analysis of variance was used to compare canal transportation and canal centering among the three experimental groups at three root levels. Independent t-test was done for pairwise comparison between the experimental groups at 95% confidence level.


  Results Top


A significant difference was observed between canal apical transportation and centering ratio for PTG and XPS (P > 0.05), and between PTG and EdgeFile X7 at all root levels (P < 0.05). No statistical significance in canal apical transportation and centering ratio was found between XPS and EdgeFile X7 at all root levels (P > 0.05) [Table 1]. The overall canal apical transportation and centering ratio is more at 6 mm level as compared to the 2 mm level [Figure 1].
Figure 1: A1, A2 and A3-cone-beam computed tomography image of Protaper Gold file system at 2 mm, 4 mm and 6 mm apical (Pre-instrumentation) respectively. A4, A5 and A6-cone-beam computed tomography image of Protaper Gold file system at 2 mm, 4 mm and 6 mm apical (Post-instrumentation) respectively. B1, B2 and B3-cone-beam computed tomography image of XP EndoShaper file system at 2 mm, 4 mm and 6 mm apical (Pre-instrumentation) respectively. B4, B5 and B6-cone-beam computed tomography image of XP EndoShaper file system at 2 mm, 4 mm and 6 mm apical (Post-instrumentation) respectively. C1, C2 and C3-cone-beam computed tomography image of EdgeFile X7 file system at 2 mm, 4 mm and 6 mm apical (Pre-instrumentation) respectively. C4, C5 and C6-cone-beam computed tomography image of EdgeFile X7 file system at 2 mm, 4 mm and 6 mm apical (Post-instrumentation) respectively

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Table 1: The mean values of mesiodistal and buccolingual transportation and the canal centering ratio in three different rotary file systems

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  Discussion Top


In this in vitro study, the null hypothesis has been rejected. In 1974, Schilder suggested that root canal shaping is a paramount aspect of endodontic treatment because it influences the outcome of the subsequent phases of root canal irrigation, intracanal medicament placement, three-dimensional obturation, and the overall success of the treatment.[11] Ideally, during the root canal preparation, the instruments should always retain the original configuration of the canal to maximize the cleaning effectiveness and minimize unnecessary thinning of canal walls leading to vertical root fracture. During the preparation of curved root canals iatrogenic mishaps can lead to ledge formation, blockage, perforation, and apical transportation.[12]

Canal transportation is an iatrogenic error or change within the physiologic pathway of the root canal, mainly within the external surface of the canal. There are three different types of canal transportation can occur from Type I (mild form) to Type III (severe form). The only Type I transportation is often by nonsurgical endodontics.[13]

NiTi alloys exist in two crystallographic forms, i.e., austenite and martensite, phases which are interconvertible by heat and stress and thereby determine its mechanical properties. At higher temperature, Nitinol is in an austenitic phase which is stiff and possess superior superelastic (SE) properties. At the lower temperature, it is in martensitic phase which is soft, ductile, can be easily deformed and possess shape memory effect (SME).[14]

Therefore, manufacturers have been using complex procedures to modify alloy transformation temperatures such as austenite start, Af, martensite start, and martensite finish temperature and consequently improve its mechanical performance. Af temperature for most conventional NiTi files is at or below room temperature, exhibiting austenitic phase during clinical use, whereas the Af of thermally treated files is above the body temperature and is mainly in the martensite phase that possess typical characteristics of SE and SME.[15]

Hence, this study was conducted to evaluate shaping ability of three heat-treated file systems with variations in a cross-sectional design, taper, number of files, and sequence of instruments beside metallurgical processes, i.e., PTG, XPS and EdgeFile X7.

The mandibular premolars were chosen because they are flattened mesiodistally and have a greater buccolingual dimension, making biomechanical preparation of the canal walls challenging for endodontic instruments. Curved canals ranging from 10° to 20° were selected for this study because they present greater challenges to instrumentation.[16] In the current study, three root levels were chosen: 2, 4 and 6 mm which represent the apical, middle, and coronal thirds of the canals where root curvatures with high vulnerability to iatrogenic mishaps exist.[7] The apical preparation was standardized to size 30 so as to keep uniformity in the apical preparation of all the experimental samples.

To determine the efficacy of instruments and techniques developed for root canal preparation, numerous methods have been used. CBCT is a three-dimensional rendition, noninvasive, accurate, reproducible diagnostic method with low-dose radiation and allows the evaluation of precise images. It is useful in comparing the anatomy of root canal system before and after biomechanical preparation, allowing to evaluate the canal transportation and canal centering ability.[17]

Regarding canal transportation and centering ratio, at all root levels, XPS and EdgeFile X7 reported having a significant difference as compared to PTG. XPS and EdgeFile X7 have better canal transportation and centering ability compared to PTG. This is attributed to the metallurgy of XPS made from MaxWire alloy is characterized by superelasticity and shape memory which allows for increased resistance to cyclic fatigue and a better negotiation of curvatures. XPS has the booster tip along with expanding type of movement which ensures better centering of the instrument, and its shorter time for preparation minimizes chances of transportation.[18] Whereas EdgeFile X7 file has a parabolic cross-section and made from “Heat Treated FireWire™ NiTi” alloy.

According to the results of the present study, PTG was found to cause the highest transportation at all levels with significant differences at 2 mm, 4 mm, and 6 mm on comparison with XPS and EdgeFile X7. According to Gagliardi et al.[19] study, PTU showed increased cutting ability in the middle and coronal third of the root canal. PTG has a file design of convex triangular cross section with sharp cutting edges which is similar to ProTaper Universal but has different metallurgy due to heat treatment.[20] Thus, similar cutting ability of PTG can be expected at middle and coronal third area which could be responsible for increased transportation at 4 mm and 6 mm as in accordance with the findings of this study.

Singh et al.[21] stated that PTG had significantly higher canal transportation and canal centering ratio at all root levels of mesial roots of molars than 2S.

However, studies are suggesting that the greater taper of more than 0.06 should be avoided for apical enlargement especially within the curved canal as there is an increased tendency for canal transportation because the diameter of the files increases. In this study, all file systems showed canal transportation within the acceptable range at the apical level according to Wu et al.[22]

The limitation of this current study could be that it is an in vitro study performed on extracted teeth hence canal preparation will be different to the condition present in vivo, the angulation and inclination of the teeth present in the oral cavity might produce varying results in root canal preparation. Further studies are recommended to be performed evaluating different aspects of clinical performance of these endodontic rotary file system in multirooted teeth.


  Conclusion Top


Within the scope of this research, the subsequent conclusions are drawn:

  1. All file systems cause canal transportation to some extent and do not result in a completely centered preparation. In apical third, all examined file systems demonstrated canal transportation within the acceptable range, where PTG exhibited maximum values. In the middle third, PTG showed significantly more canal transportation than XPS and EdgeFile X7, while in the coronal third, XPS and EdgeFile X7 showed significantly less CT than PTG
  2. The most centered preparation at the apical level was shown by XPS and EdgeFile X7, at middle level by EdgeFile X7 and at coronal third by XPS, with no statistically significant differences among these groups. This indicates safety in the preparation of curved root canals with the new single-file system XPS and EdgeFile X7.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Hasheminia SM, Farhad A, Sheikhi M, Soltani P, Hendi SS, Ahmadi M. Cone-beam computed tomographic analysis of canal transportation and centering ability of single-file systems. J Endod 2018;44:1788-91.  Back to cited text no. 1
    
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Tambe VH, Nagmode PS, Abraham S, Patait M, Lahoti PV, Jaju N. Comparison of canal transportation and centering ability of rotary protaper, one shape system and wave one system using cone beam computed tomography: An in vitro study. J Conserv Dent 2014;17:561-5.  Back to cited text no. 8
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Gambill JM, Alder M, del Rio CE. Comparison of nickel-titanium and stainless steel hand-file instrumentation using computed tomography. J Endod 1996;22:369-75.  Back to cited text no. 9
    
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Schäfer E, Vlassis M. Comparative investigation of two rotary nickel-titanium instruments: ProTaper versus RaCe. Part 1. Shaping ability in simulated curved canals. Int Endod J 2004;37:229-38.  Back to cited text no. 10
    
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Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:269-96.  Back to cited text no. 11
    
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Carvalho LA, Bonetti I, Borges MA. A comparison of molar root canal preparation using stainless-steel and nickel-titanium instruments. J Endod 1999;25:807-10.  Back to cited text no. 12
    
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Gluskin AH, Peters CI, Wong RD, Ruddle CJ. Retreatment of non healing endodontic therapy and management of mishaps. In: Ingle's Endodontics 6. Lewiston, NY: BC Decker; 2008. p. 1088-161.  Back to cited text no. 13
    
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Zhou H, Peng B, Zheng YF. An overview of the mechanical properties of nickel-titanium endodontic instruments. Endod Topic 2013;29:42-54.  Back to cited text no. 14
    
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Zupanc J, Vahdat-Pajouh N, Schäfer E. New thermomechanically treated NiTi alloys – A review. Int Endod J 2018;51:1088-1103.  Back to cited text no. 15
    
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Zhao D, Shen Y, Peng B, Haapasalo M. Root canal preparation of mandibular molars with 3 nickel-titanium rotary instruments: A micro-computed tomographic study. J Endod 2014;40:1860-4.  Back to cited text no. 16
    
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Estrela C, Bueno MR, Sousa-Neto MD, Pécora JD. Method for determination of root curvature radius using cone-beam computed tomography images. Braz Dent J 2008;19:114-8.  Back to cited text no. 17
    
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Al Khazali YC, Shukri BMS. A comparative study to evaluate canal transportation and centering ability of simulated curved canals prepared by XP-Shaper, WaveOne Gold and ProTaper NEXT files. MDJ 2018;15:18-22.  Back to cited text no. 18
    
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Singh S, Gupta T, Pandey V, Singhania H, Pandey P, Gangavane S. Shaping ability of Two-shape and ProTaper Gold files by using cone-beam computed tomography. J Contemp Dent Pract 2019;20:330-4.  Back to cited text no. 21
    
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