ABSTRACT
Aim:
To assess the canal transportation and centering ability in the mandibular first molars’ curved mesiobuccal canals after instrumentation with file systems XP endo Shaper, self-adjusting File (SAF), Hyflex EDM, Pro Taper NEXT, WaveOne Gold, and K files with the help of Cone-Beam Computed Tomography (CBCT).
Materials and Methods:
Ninety recently extracted mandibular first molars with mesiobuccal roots that had a 25-30 degree canal curvature were assessed. Following preoperative CBCT scans, teeth were allocated randomly to six experimental groups of fifteen. After preparation with XP endo Shaper, SAF, Hyflex EDM, Pro Taper Next, WaveOne Gold, and K files, post-instrumentation scans were taken using same parameters as pre operative scans. At 3 mm, 6 mm, and 9 mm from the apex, samples were assessed for canal transportation and centering ratio.
Results:
Apical transportation was least for XP endo Shaper as compared to other groups except SAF and the results were statistically significant. K file showed the highest apical transportation toward the lateral wall of the root canal. XP endo Shaper was better in maintaining centering ability of middle and apical third of canal and SAF was better in maintaining centering ability of coronal third.
Conclusion:
In root canal preparation, least apical transportation and better centering ability with XP endo Shaper than other file systems compared. K file showed the highest transportation.
KEYWORDS: Centering ability, reciprocating motion, rotary files, transportation
INTRODUCTION
The goal of biomechanical preparation is to create a continuously tapered preparation while preserving the original canal anatomy and minimizing the size of the apical foramen. Such a goal is difficult to accomplish in case of curved canals, as the prepared canal tends to divert away from the original axis.[1]
Due to NiTi files two important features elasticity and shape memory, treatment is possible with fewer procedural errors. Numerous investigations have demonstrated NiTi files’ capacity to stay centered and preserve the original canal shape.[2]
Recently super-elastic Niti alloys with a special heat treatment are developed based on M-Wire, R-Phase, Controlled memory wire, and MAX (Martensite-Austenite-electropolished-file X) wire technology.[3] The different concepts of rotary mechanics are continuous rotation, reciprocation or discontinuous rotation, and continuous rotation with oscillatory motion.[4] Selection of file was done in a way that corresponded to each of the above mentioned concepts. As a result, we selected three file systems: WaveOne Gold (WOG), a RECIPROCATING FILE, and continuous ROTATION FILES XP endo Shaper, Hyflex-EDM, and Protaper Next (PTN). The Self Adjusting File’s (SAF) motion is an inside and outward trans-linear vibratory motion. Yet, no comparative studies are carried out comparing all of the above file systems.
Therefore, the goal of current study was carried out to evaluate the canal centering ability and canal transportation of curved mesiobuccal canals of mandibular first molar after instrumentation with file system XP endo Shaper, Self Adjusting File (SAF), Hyflex EDM, Protaper Next, wave-one gold, and K files.
MATERIALS AND METHODS
The current study was carried out after approval of the Institutional Ethics Committee (AMC/IEC/CONSPG49/18). 90 freshly extracted intact permanent caries free mandibular first molars were primarily included for this study; having 20-30 degree of canal curvature in mesiobuccal root as evaluated by Schnieder’s method were included.
The selected specimens were divided into six experimental groups, each with fifteen teeth randomly. All the teeth were mounted in a clear acrylic resin arch shaped jig prepared as per the dimensions of the CBCT platform and scanned using the before instrumentation, CBCT is used to measure the mesiodistal thickness of the root canal. The teeth were scanned with an axial slice thickness of 0.1 mm at 3 mm, 6 mm, and 9 mm from the canal’s apex. Access cavities in teeth of all groups were prepared and working length was established. These six groups are: group -I: XP endo Shaper, group -II: SAF, group -III: Hyflex EDM, group -IV Protaper Next, group -V: Wave One Gold, group -VI: K files.
For all the groups, each file was used as per manufacturer’s recommended sequence and torque and canal was irrigated using 2.5% Sodium Hypochlorite. After the shaping technique was finished, the canals were rinsed twice, once with 5 ml 17% EDTA and another time with 5 ml normal saline. Postoperative CBCT scan was done after instrumentation.
EVALUATION OF CANAL TRANSPORTATION: For both groups, transportation at each level was calculated using the formula below: {(A1-A2) - (B1-B2)}.
A1—Minimum distance from the mesial edge of the uninstrumented canal to the mesial edge of the curved root.
B1—Minimum distance from the distal edge of the uninstrumented canal to the distal edge of the curved root.
A2—Minimum distance from the mesial edge of the instrumented canal to the mesial edge of the curved root.
B2—Minimum distance from the distal edge of the uninstrumented canal to the distal edge of the curved root [Figure 1].[5]
Figure 1.
Schematic Representationof denominations for measuring Root canal Transportation and Centering ability
A value of “0” indicates that there was no canal transportation, according to this calculation.
If the answer is anything other than “0,” transportation has taken place in the canal.
2) EVALUATION OF CENTERING ABILITY: The instrument’s capacity to maintain its center in the canal is indicated by the term “mean centering ratio.”
This ratio was as:
(A1—A2)
(B1—B2)
Or
(B1—B2)
(A1—A2)
If these numbers are not equal, the lower figure is considered as the numerator of the ratio. According to this formula, a result of “1” indicates perfect centering.
RESULTS
After collection of data, the descriptive analysis was done for mean, standard deviation, and median using Statistical Package for Social Sciences version 22.
Intergroup comparison was done [Tables 1 and 2]. There were no variations in in the amount of transportation at 6 mm and 9 mm from the apex. However, at 3 mm all the groups showed significantly higher mean canal transportation (P < 0.05). Hence, pair wise comparison of canal transportation at 3 mm between groups was done using Mann Whitney test.
Table 1.
Descriptive Statistics of mean canal transportation values (Kruskal-Wallis test)
| Groups | 3 mm | 6 mm | 9 mm |
|---|---|---|---|
| I-XPES | 0.78±0.20 | 0.79±0.22 | 0.75±0.22 |
| II-SAF | 0.65±0.22 | 0.75±0.26 | 0.70±0.13 |
| III-Hyflex EDM | 0.70±0.22 | 0.65±0.26 | 0.78±0.19 |
| IV-ProTaper Next | 0.67±0.22 | 0.70±0.23 | 0.67±0.21 |
| V-WaveOne Gold | 0.62±0.26 | 0.67±0.26 | 0.65±0.25 |
| VI-K file | 0.4±0.32 | 0.47±0.40 | 0.50±0.29 |
| P | 0.19 | 0.36 | 0.68 |
Table 2.
Descriptive statistics of mean canal centering ability values (Kruskal-Wallis test)
| Groups | 3 mm | 6 mm | 9 mm |
|---|---|---|---|
| I-XPES | 0.01±0.05 | 0.03±0.07 | 0.02±0.14 |
| II-SAF | 0.1±0.15 | -0.03±0.15 | 0.01±0.12 |
| III-Hyflex EDM | 0.1±0.09 | 0.08±0.09 | -0.05±0.15 |
| IV-ProTaper Next | 0.11±0.07 | 0.1±0.07 | 0.02±0.16 |
| V-WaveOne Gold | 0.15±0.14 | -0.09±0.16 | 0.11±0.20 |
| VI-K file | 0.23±0.14 | 0.12±0.23 | 0.17±0.21 |
| P | <0.001* | 0.12 | 0.11 |
*Highly significant
Order of canal transportation:
3mm: XP endo Shaper <SAF = HFEDM <PTN <WOG <K File
6 mm: XP endo Shaper = SAF <HFEDM <WOG <PTN <K File
9 mm: SAF <XP endo Shaper = PTN <HFEDM <WOG <K File
Order of canal centering ability:
3 mm: XP endo Shaper >HFEDM >PTN >SAF >WOG >K File
6 mm: XP endo Shaper >SAF >PTN >WOG >HFEDM >K File
9 mm: HFEDM >XP endo Shaper >SAF >PTN >WOG >K File
DISCUSSION
One of the key requirements of root canal shaping is to maintain the canal’s original path, keep the foramen as narrow as feasible, and create a continuous tapering preparation from crown to apex. Any novel instrument must achieve the goals outlined by Schilder.[1]
Using stainless steel hand devices to accomplish this goal might be challenging, especially in curved canals. The likelihood of apical transportation has decreased due to the rotating nickel titanium (NiTi) devices. Some factors that influence the frequency of canal transportation and canal centering ability have been identified.[6,7] They are: degree and radius of curvature, file design, alloy, instrumentation technique, and movement.
Numerous studies on the factors that could influence the final shape of the root canal as well as the shaping capabilities of various brands of Ni-Ti files have been carried out. The goal of this study was to examine Canal Transportation and Centering Ratio made possible by these systems with Cone Beam Computed Tomography (CBCT) before and after canal instrumentation.[6]
The file systems used in the study varied tapered and varied in size. The canals were enlarged at least up to #25 since less than 0.25 mm of apical preparation is linked to poor and incomplete preparation as well as decreased irrigation frequency. The size of preparations was attempted to be as accurate as feasible despite the varying designs and tapers of the instruments.
XP endo Shaper (XPES) had the least amount of canal transportation when comparing the canal transportation at the apical third, and the results were statistically significant for all the other files except SAF. K files demonstrated maximum transportation. All file systems at the coronal and middle third levels maintained the original root canal structure, and the outcomes were insignificant.
Our findings are consistent with a 2017 study by Pier Venino et al.,[8] which compared the shaping capabilities of Hyflex EDM with ProTaper Next and found that Hyflex EDM files outperformed ProTaper Next between the middle and coronal thirds. The outcomes were consistent with the current investigation, which found that the HFEDM and PTN systems were both equally effective and safely prepared the root canals while maintaining the original anatomies of the patients. Similar work was carried out by Yusra et al.[9] in 2018. The findings were essentially identical to those of the current investigation, which found that XP endo Shaper had the best centering and least transportation capabilities across file systems.
The findings of our work are consistent with a previous study by Tutino et al.[10] that demonstrated that root canal instruments built of HFEDM can be more flexible and fatigue resistant than those constructed of standard Martensitic NiTi.
However, it is in contrast with other studies by Mathieu Goldberg et al. in 2012[11] and Dhingra et al. in 2015[12] which state that reciprocating instruments are greater in terms of preserving the canal anatomy.
Thus, within the limits of our study, in terms of canal centering and apical canal transportation, XP endo Shaper has proved to be best amongst the other files analyzed with significant results. Despite of the insignificant results in coronal and middle thirds, the file has stayed consistently better as long as the mean differences were taken in account.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
REFERENCES
- 1.Schilder H. Cleaning and shaping the root canal. Dent Clin North Am. 1974;18:269–96. [PubMed] [Google Scholar]
- 2.Glosson CR, Haller RH, Dove SB, del Rio CE. A comparison of root canal preparations using Ni-Ti hand, Ni-Ti engine-driven and K-Flex endodontic instruments. J Endod. 1995;21:146–51. doi: 10.1016/s0099-2399(06)80441-3. [DOI] [PubMed] [Google Scholar]
- 3.Al-Hadlaq SMS, AlJarbou FA, AlThumairy RI. Evaluation of cyclic flexural fatigue of M-wire nickel-titanium rotary instruments. J Endod. 2010;36:305–7. doi: 10.1016/j.joen.2009.10.032. [DOI] [PubMed] [Google Scholar]
- 4.Agarwal RS, Agarwal J, Jain P, Chandra A. Comparative analysis of canal centering ability of different single file systems using cone beam computed tomography- An in-vitro study. J Clin Diagn Res. 2015;9:ZC06–10. doi: 10.7860/JCDR/2015/12097.5863. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.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. doi: 10.1016/S0099-2399(96)80221-4. [DOI] [PubMed] [Google Scholar]
- 6.Garip Y, Günday M. The use of computed tomography when comparing nickel titanium and stainless steel files during preparation of simulated curved canals. Int. Endod J. 2001;36:452–7. doi: 10.1046/j.1365-2591.2001.00416.x. [DOI] [PubMed] [Google Scholar]
- 7.Gutmann JL. Problem solving in Endodontics. 3rd ed. Mosby Inc; 1997. p. 96. [Google Scholar]
- 8.Venino PM, Citterio CL, Pellegatta A, Ciccarelli M, Maddalone M. A micro-computed tomography evaluation of the shaping ability of two nickel-titanium instruments, HyFlex EDM and Pro Taper NEXT. J Endod. 2017;43:628–32. doi: 10.1016/j.joen.2016.11.022. [DOI] [PubMed] [Google Scholar]
- 9.Al Khaali YHC, Shukri BMS. A comparative study to evaluate canal transportation and centering ability of simulated curved canals prepared by XP Shaper, WaveOne Gold and Pro Taper NEXT files. Mustansiriya Dental Journal. 2018;15:18–24. [Google Scholar]
- 10.Tutino F, Alovisi M, Bernardi M, Carpegna G, Comba A, Pasqualini D, et al. Micro-CT evaluation of ProTaper next and WaveOne gold shaping in maxillary first molars curved canals:An in vitro study. Giornale Italiano di Endodonzia. 2019;33:65–9. [Google Scholar]
- 11.Goldberg M, Dahan S, Machtou P. Centering ability and influence of experience when using WaveOne single-file technique in simulated canals. Int J Dent. 2012;2012:206321. doi: 10.1155/2012/206321. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Dhingra A, Kochar R, Banerjee S, Srivastava P. Comparative evaluation of the canal curvature modifications after instrumentation with one shape rotary and WaveOne reciprocating files. J Conserv Dent. 2014;17:138–41. doi: 10.4103/0972-0707.128049. [DOI] [PMC free article] [PubMed] [Google Scholar]