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| Year : 2023 | Volume
: 26
| Issue : 3 | Page : 326-333 |
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| Comparative evaluation of canal transportation and canal centering ability in oval canals with newer nickel–titanium rotary single file systems – A cone-beam computed tomography study |
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Simar Kaur Manocha1, Suparna Ganguly Saha1, Rolly S Agarwal1, Neelam Vijaywargiya2, Mainak Kanti Saha3, Anjali Surana1
1 Department of Conservative Dentistry and Endodontics, Index Institute of Dental Sciences, Indore, Madhya Pradesh, India
2 Department of Conservative Dentistry and Endodontics, Government Dental College, Indore, Madhya Pradesh, India
3 Department of Prosthodontics, Crown and Bridge, Modern Dental College and Research Centre, Indore, Madhya Pradesh, India
Click here for correspondence address and email
| Date of Submission | 08-Feb-2023 |
| Date of Decision | 08-Mar-2023 |
| Date of Acceptance | 23-Mar-2023 |
| Date of Web Publication | 16-May-2023 |
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 Abstract | | |
Context: The purpose of this study was to evaluate and compare the centering ability and canal transportation of TruNatomy, OneCurve, and Jizai file systems to assess their performance in oval-shaped canals using cone-beam computed tomography imaging.
Materials and Methods: Forty-two fully formed single-rooted mandibular premolars were selected with a buccolingual canal size 2–2.5 times the mesiodistal size at 5 mm from the apex, with 0°–10° canal curvature with a 5–6 mm radius, at 5 mm from the apex. The teeth were divided into three groups (n = 14) and prepared with TruNatomy, OneCurve, and Jizai files based on the manufacturer's instructions. Cone-beam computed tomographic images were taken before and after instrumentation. The canal transportation and centering ability was calculated at 3, 6, and 9 mm from the apex in both mesiodistal and buccolingual directions.
Statistical Analysis: Intergroup comparison was done using Kolmogorov–Smirnov test. Intragroup comparison was done using Freidman test. A comparison of categorical variables was done using the Chi-square test.
Results: The results obtained did not present any statistically significant difference between the three groups, with TruNatomy and OneCurve showing relatively lesser canal transportation and better centering ratio when compared to the Jizai file system.
Conclusions: It can, therefore, be concluded that all three systems used in the study are capable of safely preparing root canals with minimal errors.
Keywords: Canal centering ability; canal configuration; canal curvature; canal transportation; cone-beam computed tomography; Jizai file system; OneCurve file system; TruNatomy file system
How to cite this article:
Manocha SK, Saha SG, Agarwal RS, Vijaywargiya N, Saha MK, Surana A. Comparative evaluation of canal transportation and canal centering ability in oval canals with newer nickel–titanium rotary single file systems – A cone-beam computed tomography study. J Conserv Dent 2023;26:326-33 |
How to cite this URL:
Manocha SK, Saha SG, Agarwal RS, Vijaywargiya N, Saha MK, Surana A. Comparative evaluation of canal transportation and canal centering ability in oval canals with newer nickel–titanium rotary single file systems – A cone-beam computed tomography study. J Conserv Dent [serial online] 2023 [cited 2023 Oct 2];26:326-33. Available from: https://www.jcd.org.in/text.asp?2023/26/3/326/376919 |
| Introduction | |  |
The main technical objective of root canal preparation is the development of a shape, tapering from the coronal to the apical part, while preserving the original anatomical configuration of the canal.[1] Canal shaping is a crucial aspect of endodontic treatment because it influences the outcome of subsequent phases of root canal irrigation, obturation, and hence, the overall success of the treatment itself.[2]
However, due to variations in the root canal anatomy, complete debridement of the root canal becomes difficult to achieve. An oval-shaped root canal, for instance, can pose a special challenge for adequate chemomechanical preparation resulting in uninstrumented recesses.[3],[4]
It has been estimated that oval-shaped root canals account for about 25% of human teeth, of which more than 50% are reported to be in the maxillary second premolars and the mandibular incisors, and 25%–30% in the distal root of the mandibular molars.[5]
The continuous advancement in the field of nickel–titanium (NiTi) rotary instruments has resulted in reliable and predictable canal shaping. Hence, there is a need for research, which is aimed at consolidating a safe instrumentation technique that promotes effective cleaning and shaping along with maintaining the original canal shape, without causing transportation, or loss of centricity.[6]
The introduction of various new systems in the market has created the importance for the equitable evaluation of these systems to select the best system available.
One such file system, TruNatomy claims to provide slim shaping instruments because of its geometry, regressive taper, and slim design.[6]
OneCurve is another file system made of heat-treated C-wire Ni-Ti material with the property of controlled memory (CM). The shape of the file can be flexibly modified before entering the canal to ensure easy access into the root canal.[7]
Jizai is a newly developed NiTi rotary file system made of proprietary heat-treated NiTi alloy where manufacturers claim that it generates low screw-in forces and provides wide spaces for debris removal.[8]
An ideal instrumentation system should remove an equal amount of dentin from the canal walls, offering effectiveness in cleaning and shaping while preventing undesired overpreparation of the canal lumen.[1] Evaluation of canal transportation and centering ratio are influential parameters used to analyze the quality of root canal preparation achieved with instruments and techniques.[3] Canal transportation is defined by the glossary of endodontic terms 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, whereas the centering ratio, on the other hand, is a measure of the ability of the instrument to stay centered in the canal.[6],[9] Smaller the ratio, the better the instrument will remain centered in the canal.[5],[10]
This study intends to compare the canal transportation and canal centering ability of TruNatomy, OneCurve, and Jizai file systems to assess their performance in oval-shaped canals using Cone-beam computed tomography (CBCT).
| Materials and Methods | | |
Forty-two extracted human mandibular premolars with fully developed roots were collected and stored in 10% buffered formalin solution.
The access cavity preparation and working length determination were carried out following a standard protocol. All the teeth were then randomly divided into three groups of 14 teeth each. The teeth were first mounted on modeling wax to facilitate positioning, and then preoperative CBCT scans were taken.
Only teeth with a buccolingual canal size of 2–2.5 times the mesiodistal canal dimension, as observed radiographically, at 5 mm from the apex, were selected. Moreover, the selected teeth had a similar length (14 ± 2 mm) with an angle of curvature ranging from 0° to 10° with a radius of curvature no <5–6 mm, measured, based on the Pruett method.[11]
Root canal preparation
A #15 K hand file was initially used to prepare all the root canals to the determined working length.
In Group A, samples (n = 14) were prepared with TruNatomy rotary file system (26/0.04) at 500 rpm and torque 1.5 Ncm with continuous rotation motion, using Endomatic Endomotor.
In Group B, samples (n = 14) were prepared with OneCurve rotary file system (25/0.06) at speed of 300 rpm and torque of 2.5 Ncm with continuous rotation motion, using Endomatic Endomotor.
In Group C, samples (n = 14) were prepared with Jizai rotary files (25/0.04) at speed of 500 rpm and torque of 3.0 Ncm, with continuous rotation motion, using Endomatic Endomotor.
Instrumentation was done using 5.25% sodium hypochlorite as an irrigant.
After root canal preparation, postoperative CBCT scans were obtained using the same parameters as those for the preoperative CBCT scans. Images of the cross-sectional planes at 3, 6, and 9 mm from the apical end of the root canal before and after instrumentation were then analyzed for canal transportation and centering ability.
Canal transportation and centering ability
Canal transportation was calculated by measuring the smallest distance from the margin of the uninstrumented samples to the border of the root and then comparing these dimensions with the parameters obtained from the instrumented sample scans.
According to Gambill et al.,[12] canal transportation in the mesiodistal and buccolingual direction can be measured based on the following formula.
- (a1 − a2) − (b1 − b2)
- (c1 − c2) − (d1 − d2) [Figure 1].
 | Figure 1: Diagram showing canal transportation and centering ability evaluation based on Gambill's formula
Click here to view |
According to this formula, 0 indicates that no transportation occurred in the canal, whereas positive and negative values show mesial or buccal and distal or lingual transportation, respectively.[2]
According to Gambill et al.,[12] the mean centering ratio indicates the ability of the instrument to stay centered in the canal. Therefore, each section was calculated using the following ratios:
- (a1 − a2)/(b1 − b2) or (b1 − b2)/(a1 − a2)
- (c1 − c2)/(d1 − d2) or (d1 − d2)/(c1 − c2).
In the formulas shown, the value of 1 indicates complete centering, whereas any other value denotes changes in the canal pathway.
Whereas a1, b1, c1, and d1 denote the shortest distances from the mesial, distal, buccal, and lingual edges of the root, respectively, to the related edges of the uninstrumented canal [Figure 1], a2, b2, c2, and d2 are the shortest distances from the mesial, distal, buccal and lingual edges of the root, respectively, to the related edges of the instrumented canal [Figure 1].
The mean and standard deviation were calculated for both groups separately in the mesiodistal and buccolingual directions and at 3 different levels from the apex (3, 6, and 9 mm).
Statistical analysis
The two parameters, canal transportation and centering ability, were obtained for each tooth based on CBCT scan measurements. Data were entered into the Excel sheet and analyzed using Statistical Package for Social Sciences, 21.0 version (IBM, Chicago, IL, USA). Data when analyzed for probability distribution using Kolmogorov–Smirnov test, and it was found that it was not normally distributed and thus nonparametric test of significance was applied. Intergroup comparison was done using Kolmogorov–Smirnov test. Intragroup comparison was done using Freidman test. Comparison of categorical variables was done using the Chi-square test. P < 0.05 was considered statistically significant.
| Results | | |
[Table 1] Median value and interquartile range of centering ability and canal transportation in mesiodistal and buccolingual direction at three different levels from the apex (3, 6, and 9 mm) for three different groups evaluated. | Table 1: Median value and interquartile range of centering ability and canal transportation in mesiodistal and buccolingual direction at three different levels from the apex (3, 6, and 9 mm) for three different groups evaluated
Click here to view |
Intergroup comparison of canal transportation and centering ability, both mesiodistally and buccolingually revealed that when compared at 3, 6, and 9 mm, all three file systems (TruNatomy, OneCurve, and Jizai) showed no statistically significant difference.
Intragroup comparison of canal transportation and centering ability, both mesiodistally and buccolingually, revealed that for each of the three file systems, when compared at 3, 6, and 9 mm, no statistically significant difference was observed.
[Table 2] Comparison of canal transportation in the mesial/buccal or distal/lingual direction at all 3 levels between different groups. | Table 2: Comparison of canal transportation at all three levels between different groups
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[Figure 2] Preoperative and postoperative images of the three file systems at the three levels. | Figure 2: Preoperative and Postoperative images of the three file systems at the three levels
Click here to view |
| Discussion | | |
Incompatibility between the original canal anatomy and the configuration, of the prepared canal due to canal transportation caused by the insufficient and unequal contact of the endodontic instruments along the entire perimeter of the root canal leads to compromised fracture resistance of the tooth.[2],[3] Therefore, a study was conducted to evaluate canal transportation and the centering ability of some recently introduced file systems. Oval canals are usually oriented in buccolingual direction, which is usually missed in two-dimensional radiographs. Teeth with long oval single canals were, therefore, evaluated using CBCT, to assess the ability of the tested files to circumvent the problem of unequal contact of the file with the root canal wall.[1],[13],[14]
In most of the published literature, canal transportation and centering ability have been evaluated in the mesiodistal direction only. However, the main goal of this study was to evaluate the measurements in multiple dimensions, both mesiodistal as well as buccolingual.[1]
Intergroup comparison of all the file systems showed comparable results while evaluating canal transportation and centering ability, both mesiodistally and buccolingually, when evaluated at all three levels. However, TruNatomy revealed numerically superior results, followed by OneCurve and Jizai.
The superior results obtained with TruNatomy could be because the file system is manufactured using a NiTi alloy which uses heat-treatment process designed to maximize the fatigue resistance and flexibility of this system. It has a regressive taper and an off-centered parallelogram cross-section.[15] The results of the present study are in agreement with studies conducted by Piţ et al.[16] and Kabil et al.[17] who stated that TruNatomy instruments safeguard the structural dentin and tooth integrity due to their off-centered parallelogram cross-section, regressive taper, slim design, along with special heat treatment of the NiTi alloy.[18]
The OneCurve instrument which presented minimum canal transportation in the apical and coronal third, when evaluated in the mesiodistal direction, is produced from a C-wire using proprietary heat treatment with CM property, and is in the martensitic phase at canal temperature.[6] According to Singla et al.,[19] OneCurve being a single file system with S-shaped cross-section, has a smaller core area, thus showing greater flexibility and minimum transportation. OneCurve was found to preserve the canal shape better because it possesses unique asymmetrical cutting profile, with improved snake-like movement, thereby causing minimum transportation, while preserving the original canal shape.[20] The results are in accordance with studies conducted by Ghoneim[20] and Tufenkci et al.[7] which concluded that one curve achieved satisfactory centering in the apical zone of the root canal.
According to Wu et al.,[21] apical transportation is only clinically relevant when it is >0.300 mm, which compromises the sealing ability of the root canal filling material. In the present study, none of the apical transportation values surpassed this limit,[19] thus making them suitable alternatives for the safe and effective preparation of oval root canals.[5]
In the present study, Jizai showed relatively higher canal transportation and lower centering ability; however, the results were not statistically significant. The comparable results obtained with this file system could be attributed to this fact. That this file system possesses a unique asymmetrical cross-sectional design resulting in an offset mass of rotation, characterized by radial lands at the shorter side of a modified rectangle.[22],[23]
Intragroup comparison of canal transportation and centering ability, both mesiodistally and buccolingually, when observed at 3, 6, and 9 mm, revealed that all the file systems were equally effective in maintaining the canal anatomy, at all levels.
Continuous research is, however, required to evaluate the metallurgy and rotational dynamics of various file systems, to ensure the safe and effective preparation of root canals.
| Conclusions | | |
Based on the results of the CBCT study, it may be concluded that all three file systems, TruNatomy, OneCurve, and Jizai, are capable of effective preparation of root canals while at the same time preserving the original canal configuration, i.e., their shape and curvature.
Acknowledgment
It is my genuine pleasure to express my deep sense of gratitude to my mentor and guide Dr. Suparna Ganguly Saha, Professor and Head, Department of Conservative Dentistry and Endodontics, Index Institute of Dental Sciences, Indore. Her dedication and keen interest to help her students was solely and mainly responsible for completing my study. Her timely advice, meticulous scrutiny, and scientific approach have helped me to a very great extent to accomplish this study. I owe a deep sense of gratitude to Dr. Rolly S. Agarwal, Professor, Department of Conservative Dentistry and Endodontics, Index Institute of Dental Sciences, Indore. Her prompt inspiration, timely suggestions, and enthusiasm has helped me to successfully complete my study.
I thank profusely all the staff of the Department of Conservative Dentistry and Endodontics, Index Institute of Dental Sciences, Indore, for their kind help and cooperation throughout our study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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Correspondence Address:
Dr. Simar Kaur Manocha
No. 26, Shankaracharya Marg, Kalalseri, Namakmandi, Ujjain, Madhya Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jcd.jcd_98_23
[Figure 1], [Figure 2]
[Table 1], [Table 2] |
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