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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 29  |  Issue : 2  |  Page : 120-124

Comparitive evaluation of canal shaping ability of three nickel titanium instrument systems using cone beam computed tomography: An in vitro study


Department of Conservative Dentistry and Endodontics, Government Dental College and Hospital, Vijayawada, Andhra Pradesh, India

Date of Web Publication6-Nov-2017

Correspondence Address:
Murali Mohan Thota
Department of Conservative Dentistry and Endodontics, Government Dental College and Hospital, Vijayawada, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_17_17

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  Abstract 


Aim: The aim of the study is to evaluate the canal transportation and canal centering ability of WaveOne, ProTaper, and F6 SkyTaper nickel-titanium instrument systems using cone beam computed tomography (CBCT).
Materials and Methods: A total of 45 mandibular first molars with a curvature angle ranging from 20° to 40° of the mesiobuccal canal were included and randomly divided into three groups with 15 specimens each according to the rotary systems used: in Group 1, specimens were prepared with WaveOne system, in Group 2, specimens were prepared with ProTaper rotary system, and in Group 3, specimens were prepared with F6 SkyTaper rotary system. CBCT was used as a diagnostic method to evaluate centering ratio and canal transportation at 1, 3, 5, 7 mm from apical foramen.
Statistical Analysis: To evaluate canal centering ratio and canal transportation between file systems, one-way analysis of variance and post hoc Tukey tests were used.
Results: Statistically, significant differences are well-established between the different files though all the files conserved the aboriginal canal curvature. WaveOne files exhibited lesser transportation and stayed better centered in the root canal system than F6 SkyTaper and Rotary ProTaper files.
Conclusions: WaveOne files showed slighter transportation and better centering ability than F6 SkyTaper and ProTaper.

Keywords: Canal shaping ability, cone beam computed tomography, F6 SkyTaper, WaveOne


How to cite this article:
Thota MM, Kakollu S, Duvvuri M, Garikapati RB. Comparitive evaluation of canal shaping ability of three nickel titanium instrument systems using cone beam computed tomography: An in vitro study. Endodontology 2017;29:120-4

How to cite this URL:
Thota MM, Kakollu S, Duvvuri M, Garikapati RB. Comparitive evaluation of canal shaping ability of three nickel titanium instrument systems using cone beam computed tomography: An in vitro study. Endodontology [serial online] 2017 [cited 2018 Sep 26];29:120-4. Available from: http://www.endodontologyonweb.org/text.asp?2017/29/2/120/217705




  Introduction Top


Overall success of the endodontic treatment largely depends on canal shaping as it influences the outcome of the subsequent phases of treatment such as canal irrigation and obturation.[1],[2],[3],[4],[5] Canal shaping can be considered as one of the aims of the root canal instrumentation, which creates a tapered shape with sufficient volume that allows effective irrigation and obturation (European Society of Endodontology, 1994).[6] Conventional stainless steel hand instruments however were not sufficient to fulfill these objectives (Kandaswamy 2009, Schäfer and Vlassis 2004, Dhingra 2014).[1],[6],[17] With the introduction of the nickel-titanium (NiTi) alloys, a revolution took place in the manufacture of endodontic instruments.[7],[8],[9] Super-elasticity of NiTi alloys made it possible to stand out when compared to hand instruments.[8] Super-elastic property of the alloy allows the files to be better centered [2],[4],[5],[8] and that can shape extremely curved canals with less transportation.[8],[10] With time, many NiTi instrument systems with different features have been introduced. One among them is ProTaper NiTi rotary instruments (Dentsply Maillefer, Switzerland), which has changing helical angle and pitch over the cutting blades and a noncutting, modified guiding tip.[2] WaveOne (Dentsply Maillefer, Switzerland) files are made of a NiTi alloy with a special technology, thermal treatment process called M-Wire,[11],[12] which is able to completely shape the root canals with a single instrument.[3] Recently, a new single file system has been introduced, i.e., F6 SkyTaper (Komet, Germany), single use NiTi system works on continuous rotation, distinguished by S-shaped cross-sectional model. For efficient root canal shaping, these are available in five different sizes (20–40) with a constant taper of 0.06.[13] To overcome the disadvantages of NiTi systems, new modernistic empirical search is more focusing on the advancements in instrumentation techniques. Several studies have established that the use of reciprocating approach to curtail the incidence of fracture. However, a mere information is available in literature regarding the shaping ability of such reciprocating and rotary single file preparation techniques.[4] Various methods have been proposed to compare the shaping ability of different NiTi rotary systems such as radiographic comparisons, including invasive methods that are scanning electron microscopy, sectioning of the tooth.[4],[7],[14],[15],[16] Cone beam computed tomography (CBCT) is a noninvasive procedure used to assess shaping ability of NiTi instruments before and after root canal instrumentation.[4] CBCT provides three-dimensional images that are superior in quality when compared to other techniques, and hence, it can be used as a valid diagnosis for assessing the shaping ability of root canal.[4],[14]

To our knowledge, till now, there are no studies comparing F6 SkyTaper regarding canal shaping ability with reciprocating WaveOne and rotary ProTaper systems. Hence, the purpose of this investigation is to compare the shaping ability and the canal transportation using the two new single-file systems, F6 SkyTaper and WaveOne, compared with the rotary ProTaper systems.


  Materials and Methods Top


Forty-five mesiobuccal root canals of extracted mandibular first molar teeth were used. Teeth were cleaned for tissue fragments and calcified debris and stored in formalin solution. Mesial roots with completely formed apices and separate foramina were selected. Angle of curvature ranged between 20° and 40° according to the criteria described by Nagaraja (2010).[7] Roots were sectioned to remove distal roots along with crowns and to standardize the length of the roots (16 mm). Estrela et al. proposed a method to determine the canal curvature angle of root canals, in which two straight lines of the same length were used. One line is drawn parallel to long axis of the root canal, and the second one passes through the foramen until it merges the first line at the beginning of curvature. After deciding the midpoint of two lines, radii of curvature had been determined and the canal curvature was expressed in degrees.[14]

The specimens were randomly divided into three groups (n = 15) based on the canal curvature angle and radius.[10] Teeth were accessed with a round bur, and working length (WL) had been determined by inserting size 10 K-type file till the root apex, and from this measurement, 1 mm was retracted. A glide path was performed with 15 K-file. RC-Prep (Premier) was used in all canal preparations. Irrigation was performed with 5.25% sodium hypochlorite.[10] The preparation sequences were as follows:

Group 1: Canals were shaped with ProTaper instruments (Dentsply Maillefer, Switzerland) with an endodontic handpiece which is torque-controlled X-Smart (Dentsply Maillefer, Switzerland). Specimens were prepared conferring to the manufacturer directions. The canals were finished up to F2 that reaches the WL (D1 diameter 0.25 mm).

Group 2: A WaveOne primary file size 25 and 0.08 taper was used in a reciprocating, slow in- and out-pecking motion according to the manufacturer's instructions till WL, which was operated in a reciprocating motion powered by a reciprocating motor X-Smart Plus (Dentsply Maillefer, Switzerland) used with the manufacturer configuration setup. After three pecking motions, the instrument was removed and cleaned, and the canal was irrigated.

Group 3: F6 SkyTaper was set into permanent rotation with X-Smart (Dentsply Maillefer, Switzerland). Teeth were prepared using the F6 SkyTaper system at a speed of 300 rpm and torque of 2.2 N/cm. The instrument (25/0.06) was used with quiet in-and-out motion till WL. For each root canal, a new file was used. After three in-and-out movements, flutes were cleaned of debris and were irrigated with NaOCl.

Cone beam computed tomographic measurements

Pre- and post-instrumentation measurements of mesiobuccal canals were achieved using the CS3D Imaging Software (Carestream Dental, Chicago, IL, USA) [Figure 1]. Canal transportation and centering ratio were calculated at four cross-section levels, i.e., 1, 3, 5, and 7 mm from the apical end of the root using the following criteria.
Figure 1: Analysis of image acquired by cone beam computed tomography using CS3D Imaging Software

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Evaluation of centric ability

The centering ratio, which means the ability of the instrument to endure in a central position within the canal, was determined for each cross-section from the values obtained. The ratio of (A1 − A2) to (B1 − B2)[11] as described by Gergi et al., where A1 is the distance between mesial edge of outer surface of the root and the mesial edge portions of the uninstrumented canal, A2 is the distance between mesial edge of outer surface of the root and the mesial edge of the instrumented canal, B1 is the distance between distal edge of the outer surface of the root and distal edge the uninstrumented canal, and B2 is the distance between distal edge of outer surface of the root and the distal edge of the instrumented canal, was measured.[4],[11] If these numbers are not equal, numerator of the ratio will be the smaller of the two. According to this formula, a result of “1” indicates perfect centering.[5]

Evaluation of canal transportation

Canal transportation, which means deviation of canal from its original anatomy, was calculated in millimeters using the formula ([A1 − A2] – [B1 − B2]). Comparison between pre- and post-operative measurements was to reveal the presence or absence of deviations from the canal anatomy and to establish the most affected region.[11] A value of “0” denotes that there is no canal transportation.[7]

The data were collected and tabulated accordingly and statistical analysis was implemented using one-way analysis of variance (ANOVA) and Tukey's honestly significant difference tests at a 95% level of significance (α < 0.05).


  Results Top


Mean centering ratio at 1, 3, 5, 7 levels in three groups under study is shown in [Table 1]. At all the levels, the maximal mean value was attained for WaveOne while minimal value was achieved for ProTaper [Graph 1]. Centering ratio was significantly more with WaveOne (P< 0.001). No significance difference was found between ProTaper and F6 SkyTaper (P > 0.05).
Table 1: Distribution of mean and standard deviation values of centering ability at 1, 3, 5, and 7 mm from the apex (P<0.05)

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Mean transportation at 1, 3, 5, 7 levels in three groups under study is shown in [Table 2]. At all the levels, maximal mean value was achieved for ProTaper while minimal value was attained for WaveOne. Transportation was significantly less with WaveOne (P > 0.05). No significance difference was found between ProTaper and F6 SkyTaper. File systems transport away from the furcation at the 1 and 3 mm levels and toward the furcation at the 5 and 7 mm levels [Graph 2].
Table 2: Distribution of mean and standard deviation values of canal transportation at 1, 3, 5, and 7 mm from the apex (P<0.05)

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ANOVA reveals a statistical significant intergroup difference at all the levels. Although there was no statistical significance between ProTaper and F6 SkyTaper file systems, latter had better centered than the former.


  Discussion Top


The preservation of apical root canal anatomy and prevention of apical transportation provide a well-sealed root filling with mere extrusion of debris and diminished postoperative discomfort. Various factors contribute to mechanical instrumentation outcomes are the design of instrument, sequence of instrumentation, rotational speed, experience of operator, and the use of irrigants.[17]

In the present study, root canal transportation was maximum at all the levels in Group 3 [Figure 2]. This can be attributed to the design of ProTaper which includes progressive taper along its surface; convex core mass causes reduction in instrument flexibility and increased tip stiffness of the file.[1],[6],[16],[18] The results obtained are in congruence with the study made by Maitin 2013 and Stern 2012, who found that apical transportation was more in instrumented with ProTaper in comparison to other instrument.[16],[19] To simplify the process of root canal shaping, WaveOne NiTi reciprocating system has been introduced in which a single file is sufficient to reach adequate root canal size and taper.[3] One of the major breakthroughs in endodontic instrumentation is developing metallurgy for an automated instrument is i.e., M-Wire technology that have gained popularity in recent times.[3],[20] It is because of its increased flexibility; WaveOne files could respect the true canal morphology reducing the chances of ledging and apical transportation. It has also got the higher resistance to cyclic fatigue cutting down the chances of file separation. These mechanical properties rendered WaveOne files to be superior when compared to conventional NiTi files.[4] The unique design of the WaveOne file with two different cross-sections along the length of active portion is one of the prime reasons for decreased core diameter leading to increased flexibility of the file. Active portion of the file also has changing pitch and helical angle which further helped in decreasing the core diameter. Increased canal centering ability is one of the characteristic features of reciprocating motion, which was proposed primarily to reduce the risk of root canal deformity. As theorized by Estrela et al., the balance force during root canal instrumentation by reciprocating motion is based on the law of action and equal opposite reaction. The use reciprocating motion in place of continuous rotation reduces the torsional stress, thereby minimizing the risk of instrument separation in WaveOne file.[14] Various studies showed that larger cross-sectional instruments have super-flexibility and torsional stiffness and consequently greater resistance to torsion and cyclic fatigue.[21] In the present study, F6 SkyTaper has stayed better centered than ProTaper as it is a deviceful rotary single file design with a combination of double-S cross-section and consistent taper for superior, judicious cutting, and the instrument's revolutionary thin core that provides much resilience to file. The exclusive design of the file aids in meticulous irrigation and cleaning all through the treatment and optimally conserves the anatomy of the canal.[13] Furthermore, CBCT images permit symmetrically explicit determination of variables such as surface areas, volume, and cross-sectional shape of the canal. The portion of prepared surface can be evaluated with software which does not hamper the prototypal configuration of the images, acknowledging the scrutiny of the precise location and direction of canal transportation. In this study, a weighable analysis was carried out through examination of differences between pre- and post-instrumentation images using CBCT.[4],[22] The occurrence of apical transportation of 0.15 mm has been considered admissible and should not be over 0.30 mm.[12],[18] In this study, all the three groups produced canal transportation in the apical region ranges from −0.031 mm to −0.083 mm, which is within the tolerable range. Overall in all the four sections, WaveOne system (Group 1) exhibited less canal transportation and superior centering ability followed by F6 SkyTaper (Group 2) and ProTaper (Group 3).
Figure 2: Postoperative images of WaveOne, F6 SkyTaper, and ProTaper at 3 mm from the apex

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  Conclusions Top


Within the limitations of this study, all the three groups showed significant difference. F6 SkyTaper is a safe instrument for root canal instrumentation. It was found that WaveOne single-file reciprocation has better-centering ability and lesser canal transportation than ProTaper and F6 SkyTaper.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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