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ORIGINAL ARTICLE
Year : 2020  |  Volume : 7  |  Issue : 3  |  Page : 58-60

A comparative evaluation of the efficacy of two instrumentation techniques in simulated root canals when using contemporary rotary files


Associate Professor, Department of Restorative Dental Sciences, College of Dentistry, King Khalid University, Abha, Saudi Arabia

Date of Submission29-Apr-2020
Date of Acceptance19-May-2020
Date of Web Publication24-Jul-2020

Correspondence Address:
Dr. Mohammed Al Qarni
Department of Restorative Dental Sciences, College of Dentistry, King Khalid University, Abha
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/INPC.INPC_11_20

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  Abstract 


Background: Over the past many years, rotary nickel–titanium (NiTi) instruments have become widely used in endodontics. These superelastic instruments offer benefits over hand instrumentation for preparing curved root canals, including less transportation of the canal and reduced operating time. The purpose of this in vitro study was to compare single length with crown-down methods' shaping ability using Mtwo NiTi files.
Subjects and Methods: One hundred extracted human first and second mandibular molars were divided into two experimental groups. In Group A, single length technique was used, and in Group B, root canals were prepared by the crown-down technique. Pre- and postpreparation canals were photographed in a standardized manner and were superimposed.
Results: Statistical analysis revealed that in Group A, the inner wall was predominantly removed (P < 0.01), whereas in Group B, dentine was equally removed within the canal coronal to the curvature.
Conclusion: There was no significant difference between the single length method and crown-down technique using Mtwo for the preparation f the apical and middle portion of canal curvature.

Keywords: Curvatures, instrumentation, Mtwo, nickel-titanium, root canal treatment


How to cite this article:
Al Qarni M. A comparative evaluation of the efficacy of two instrumentation techniques in simulated root canals when using contemporary rotary files. Int J Prev Clin Dent Res 2020;7:58-60

How to cite this URL:
Al Qarni M. A comparative evaluation of the efficacy of two instrumentation techniques in simulated root canals when using contemporary rotary files. Int J Prev Clin Dent Res [serial online] 2020 [cited 2020 Oct 21];7:58-60. Available from: https://www.ijpcdr.org/text.asp?2020/7/3/58/290694




  Introduction Top


Over the past many years, rotary nickel–titanium (NiTi) instruments have become widely used in endodontics. These superelastic instruments offer benefits over hand instrumentation for preparing curved root canals, including less transportation of the canal and reduced operating time. In contemporary clinical practice, most systems with rotary NiTi instruments follow a “crown-down” philosophy.[1],[2],[3] This reduces friction between instruments and root canal walls, minimizing the risk of instrument separation during use. While all of these instruments have shown overall good shaping quality in root canals, little is known about the performance and assessment of these different preparation techniques by inexperienced operators who have had no previous contact with such different root canal preparation strategies. In the last few years, a new instrument design has been introduced (Mtwo, VDW, Munich, Germany).

These instruments have an S-shaped cross-sectional design with a noncutting tip. The two cutting edges have a positive rake angle to cut dentine effectively. In addition, the pitch length increases from the tip to the shaft. This design is claimed to eliminate threading and binding in continuous rotation and to reduce the transportation of debris toward the apex.[4],[5] The basic series of Mtwo instruments includes eight instruments, with tapers ranging between 0.04 and 0.07 and sizes from ISO 10 to 40. The manufacturers claim that a crown-down instrumentation sequence is no longer required, since each instrument creates a glide path to the apex for the following instrument and is used to the full working length to shape the entire length of the canal. The purpose of thisin vitro study was to compare the shaping ability and cleaning effectiveness of the Mtwo in curved mesiobuccal canals in the human permanent molar teeth.[6]


  Subjects and Methods Top


One hundred extracted human first and second mandibular molars that were extracted because of periodontal problems were selected. Teeth were disinfected in sodium hypochlorite 5.25% for 30 min and then maintained in normal saline solution until use. Straight radiographs in mesiodistal and buccolingual directions were taken to determine the root canal anatomy. The teeth with mature apices, with no resorption, without restoration, with no cracks, and distinct mesial and distal roots with curvature within 15°–45° limit were selected. Canal curvature was determined using the Schneider method. Teeth with multiple, rapid apical curvature, or calcified canals were excluded from the study. The apical foramina were sealed with dental wax, and all teeth were then mounted in acrylic resin blocks of 10 cm diameter (preinstrumentation images were taken by cone-beam computed tomography [CBCT] machine, Alphard VEGA, Asahi Roentgen Ind., Kyoto, Japan) with the following settings: 80 kV, 4 mA, 51 mm × 51 field of view, and 0.1/voxel (mm) size. Access cavities were prepared using diamond burs, and apical patency was checked with stainless steel #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland). Each resin block was divided into two rows by a dental saw so that we could determine the working length by radiography. The working length was established with #15 K-file that was 1 mm shorter than the radiographic apex. Simulated canals were divided into two experimental groups as follows:

Group A

Coronal enlargement was done the orifice for 5 s. Then, Mtwo (VDW Co., Munich, Germany) #10 (0.04 taper), #15 (0.05 taper), #20 (0.06 taper), and #25 (0.06 taper) were used, respectively, to the full length of the canal; each file was rotated for 3 s in the canal until it reached the apical point.

Group B

Same as Group A, coronal enlargement was done the orifice for 5 s. Mtwo #25 (0.06 taper) was worked passively through the coronal third, then #20 (0.06 taper) passively enlarged the middle part, and #15 (0.05 taper) in the apical third of the canal. For final shaping of canals, Mtwo #25 (0.06 taper) was used to full working length; each file was rotated for 3 s. All files were used by the torque-controlled motor and rotational speed programmed in the file library of the Dentaport ZX (Morita Corp., USA). NiTi instruments were only used to prepare four canals; the preparation was carried out by a single operator. Pre- and postpreparation canals were photographed in a standardized manner (Mavo Zoom, ×50) and stored in a computer. In both experimental groups, as each instrument was changed, the canal was irrigated with 1 ml of 2.5% NaOCl. After canal preparation, the smear layer was removed by 3 ml of 17% ethylenediaminetetraacetic acid. The number of fractured and permanently deformed instruments during preparation was also recorded. If there was any file fracture, another tooth was replaced for preparation. After canal shaping, postinstrumentation CBCT scans were performed with similar values and position as preinstrumentation scans.


  Results Top


According to this study, Groups A and B have no statistically significant difference at α and β points [Table 1]. P values at α and β points are 0.85 and 0.42, respectively. Nevertheless, Student's t-test revealed that these two groups had a statistically significant difference at γ point; more resin was removed from the inner wall in Group A. In Group B, both sides of the canal were equally removed. This means that in Group B, the canals' internal shape remained more unchanged at the most coronal part of the curvature, even though these two groups had no difference at the other sections of the canal curvature (P < 0.01).
Table 1: Mean values and standard errors of resin removal in 25 different groups at three points of the canal wall

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  Discussion Top


This study was carried out with the aim of assessing the preparation of the rotary Mtwo NiTi instrument using the crown-down technique with single length technique. In the present study, one rotary file technique using an Mtwo for each tooth was offered. The most notable benefits of this technique are no excess cost and no need to buy new instruments or specific motors. Reduced preparation time and a previously experienced sense during canal preparation are the other benefits.[6],[7]

Several methods have been used to evaluate the quality of root canal preparations, such as serial sectioning and microscopic evaluation, simulated canals, radiographic evaluation, and CBCT.[6],[7],[8],[9] In the present study, CBCT was used to compare the centering ability of one rotary file technique with the established rotary Mtwo instruments in curved root canals (round or oval shape) of the extracted human mandibular molar teeth.[5]

The preparation time is dependent on the technique and the numbers of instruments used. In the present study, the preparation time included active instrumentation as well as the time required for changing instruments, cleaning the flutes of the instruments, and irrigation. Therefore, the preparation time significantly decreased in one rotary file technique because of no need to changing the files and more focus on canal preparation.

In our study, there was no significant difference between crown-down and single length techniques at three different points of acrylic-resin blocks with simulated canals. At α point, the apex anatomy was respected; this is consistent with Veltri et al., who reported keeping-centered preparations in the apical region using Mtwo instrument.[10] No fractured with Mtwo instruments occurred. This finding is in accordance with the previous researchers such as Schafer et al. and Veltri et al.[10] In a study done by Hamze F et al[11] Mtwo was used in single length technique, and they revealed no significant difference between this method and crown-down technique. The main cause of no Mtwo file fracture even after enlargement of four canals may be due to its increasing pitch length from the tip to the shaft of these instruments or less usage. Mandibular molars, such as most teeth, usually have significant curvature in both mesiodistal and buccolingual planes. Furthermore, they often have concavities on the mesial and distal surfaces of the root. These factors make the tooth susceptible to transportation and preparation errors such as perforations. There is limited information regarding transportation in buccolingual direction; however, in this study, centering ability was evaluated in both directions.

Mtwo instruments have good cutting efficiency, low cross-sectional area, and relatively low number of spirals in each length unit. Therefore, it can resist deformation, but it is more rigid too. This might explain the slightly higher incidence of canal aberrations observed in Mtwo system. Celik et al.[3] researches, previous studies concluded the lowest transported canals in Mtwo groups.


  Conclusion Top


According to the results of the present study, larger volumes of irrigant and additionally activation of the irrigant should be used to improve disinfection. Although Mtwo could be used in single length technique, our study revealed no significant difference between this method and crown-down technique using Mtwo for the preparation of apical and mid portion of the canal curvature. However, at the most coronal part of canal curvature, the crown-down technique better respected the canal anatomy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Machado ME, Sapia LA, Cai S, Martins GH, Nabeshima CK. Comparison of two rotary systems in root canal preparation regarding disinfection. J Endod 2010;36:1238-40.  Back to cited text no. 1
    
2.
Lin J, Shen Y, Haapasalo M. A comparative study of biofilm removal with hand, rotary nickel-titanium, and self-adjusting file instrumentation using a novelin vitro biofilm model. J Endod 2013;39:658-63.  Back to cited text no. 2
    
3.
Celik D, Taşdemir T, Er K. Comparative study of 6 rotary nickel-titanium systems and hand instrumentation for root canal preparation in severely curved root canals of extracted teeth. J Endod 2013;39:278-82.  Back to cited text no. 3
    
4.
Gekelman D, Ramamurthy R, Mirfarsi S, Paqué F, Peters OA. Rotary nickel-titanium GT and ProTaper files for root canal shaping by novice operators: A radiographic and micro-computed tomography evaluation. J Endod 2009;35:1584-8.  Back to cited text no. 4
    
5.
Aydin C, Inan U, Yasar S, Bulucu B, Tunca YM. Comparison of shaping ability of RaCe and Hero Shaper instruments in simulated curved canals. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e92-7.  Back to cited text no. 5
    
6.
Rangel S, Cremonese R, Bryant S, Dummer P. Shaping ability of RaCe rotary nickel-titanium instruments in simulated root canals. J Endod 2005;31:460-3.  Back to cited text no. 6
    
7.
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. 7
    
8.
Yang G, Yuan G, Yun X, Zhou X, Liu B, Wu H. Effects of two nickel-titanium instrument systems, Mtwo versus ProTaper universal, on root canal geometry assessed by micro-computed tomography. J Endod 2011;37:1412-6.  Back to cited text no. 8
    
9.
Schäfer E, Erler M, Dammaschke T. Comparative study on the shaping ability and cleaning efficiency of rotary Mtwo instruments. Part 1. Shaping ability in simulated curved canals. Int Endod J 2006;39:196-202.  Back to cited text no. 9
    
10.
Veltri M, Mollo A, Pini PP, Ghelli LF, Balleri P.In vitro comparison of shaping abilities of ProTaper and GT rotary files. J Endod 2004;30:163-6.  Back to cited text no. 10
    
11.
Hamze F, Honardar K, Nazarimoghadam K. Comparison of two canal preparation techniques using mtwo rotary instruments. Iran Endod J. 2011;6:150-4.  Back to cited text no. 11
    



 
 
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  In this article
   Abstract
  Introduction
  Subjects and Methods
  Results
  Discussion
  Conclusion
   References
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