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Year : 2016  |  Volume : 3  |  Issue : 1  |  Page : 60-64

In vitro comparison of K-file, Mtwo, and WaveOne in cleaning efficacy and instrumentation time in primary molars

Pathak Dental Care, Sector 12, Karnal, Haryana, India

Date of Web Publication22-Dec-2015

Correspondence Address:
Sidhant Pathak
Pathak Dental Care, Sector 12, Karnal, Haryana
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2348-3334.172407

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Aim: The aim of this study was to compare instrumentation time and cleaning efficacy of manual instrumentation and two rotary systems in the preparation of primary molar root canals. Materials and Methods: The teeth were randomly divided into three experimental groups, Group 1 K-file (n = 30), Group 2 Mtwo (n = 30), Group 3 WaveOne (n = 30), and one control group (n = 30). The root canals were prepared using one of the three file systems followed by clearing the teeth with different demineralizing solutions. The instrumentation time in each root canal was measured by a chronometer. The results were statistically evaluated using Kruskal–Wallis tests.Results: In the coronal third, WaveOne showed more ink removal and the difference found was highly significant (P < 0.0001). In the middle third of the root canal, WaveOne performed better than Mtwo and K-file (P < 0.005). At the apical level, there was no statistical difference between the three systems. WaveOne was found to take significantly (P < 0.0001) less time than Mtwo and K-file. Conclusion: WaveOne took less time and showed better cleaning efficacy when compared to other instrumentation techniques, especially in coronal and middle one-third.

Keywords: Chronometer, manual instrumentation, primary molars, rotary systems

How to cite this article:
Pathak S. In vitro comparison of K-file, Mtwo, and WaveOne in cleaning efficacy and instrumentation time in primary molars. CHRISMED J Health Res 2016;3:60-4

How to cite this URL:
Pathak S. In vitro comparison of K-file, Mtwo, and WaveOne in cleaning efficacy and instrumentation time in primary molars. CHRISMED J Health Res [serial online] 2016 [cited 2022 Jul 7];3:60-4. Available from: https://www.cjhr.org/text.asp?2016/3/1/60/172407

  Introduction Top

Endodontics is a difficult task in children due to the complex anatomy of the root canals in primary teeth.[1] Successful treatment depends on the technique of instrumentation, irrigation, disinfection, and obturation of the root canal.[2] Conventional endodontic treatment for primary teeth is time-consuming and often causes fatigue to the operator and child.[1],[3]

Pediatric Endodontics was bestowed with rotary instruments by Barr et al., in 2000.[4] It enhances the quality of obturation by providing conical shape to the root canal.[5] Nickel-titanium (NiTi) alloy instruments inherent flexibility that allows the files to preserve the original anatomy of curved canals, especially in primary teeth and reduce the chances of procedural errors.[6]

Mtwo system was developed and introduced in 2003. The standard Mtwo rotary set includes four instruments with variable tip sizes ranging from #10 to #25 and tapers ranging from 0.04 to 0.06–0.07. According to the manufacturer, the minimally invasive Mtwo NiTi instruments should be used in single-length techniques without early coronal enlargement.[7],[8],[9]

The new WaveOne NiTi single-file system was introduced by Dentsply Maillefer (Ballaigues, Switzerland) in 2011. The system is designed to be used with a dedicated reciprocating motion motor. It consists of three single-use files: Small (ISO 21 tip and 0.06 taper) for fine canals, primary (ISO 25 tip and 0.08 taper) for the majority of the canals, and large (ISO 40 and 0.08 tapers) for large canals. The files are manufactured with M-Wire (Dentsply Tulsa Dental Specialties) NiTi alloy.[10]

The aim of this study was to compare instrumentation time and cleaning efficacy of manual instrumentation and rotary systems in the preparation of primary molar root canals.

  Materials and Methods Top

After receiving the approval from Institutional Review Board, Eighty-four extracted primary teeth were collected without any prior treatment done on them. The exact reasons for tooth extraction were unknown to their searchers, but it was assumed that they were extracted because of caries, periodontal problems, and preventive orthodontic treatment. The inclusion criteria were extracted teeth with no external or internal pathological root resorption, absence of perforation in the internal or external furcation area, moderate root angulation, and two-thirds of intact root. The exclusion criteria were the presence of pathological root resorption, presence of perforation in the furcation area, severe root angulation, and root length less than two-third. One hundred and twenty root canals from 84 teeth were selected for the study.

All teeth were stored in distilled water at room temperature. They were then immersed in 3% sodium hypochlorite (Amdent, India) for 1 week for disinfection, and then stored in distilled water until they were used for the study. Digital radiographs were taken in a lab for selection of the root canals prior to the instrumentation of root canal. Standard coronal access was achieved with BR-31 diamond round bur (Mani, Japan) and Endo Z (Dentsply Maillefer, Ballaigues, Switzerland) at high speed, under cooling with distilled water. All specimens were then rinsed with saline. The root canals were filled with India ink using a 30 gauge needle syringe. The teeth were left in wet conditions at room temperature for 48 h.

Thirty root canals were randomly divided in three experimental groups and one control group. All root canals were prepared by the same operator.

Group 1 specimens were instrumented with stainless steel K-files (Dentsply Maillefer, Ballaigues, Switzerland). In Group 2, Mtwo files® (VDW, Munich, Germany) and in Group 3, WaveOne system (Dentsply Maillefer, Ballaigues, Switzerland) were used for instrumentation. In Group 4, (control group) no instrumentation was done. The actual root canal length was determined visually by inserting an ISO size 10 hand K-file (Dentsply Maillefer, Ballaigues, Switzerland) into the canal until the file tip could be seen at the apical foramen. The working length was calculated by subtracting 1 mm from actual root canal length. In Group 1, all the 30 root canals were instrumented manually with K-files with the step-back technique up to file ISO size 30.

In Group 2, all the 30 root canals were cleaned with 21 mm-long Mtwo NiTi rotary files driven with a torque-limited rotation Mtwo direct handpiece (Sirona, Bensheim, Germany) with torque control at a maximum speed of 280 rpm. All the files were used to the full length of the root canal, as for the single-length technique. Four Mtwo instruments (10/0.04, 15/0.05, 20/0.06 and 25/0.06) were used in primary teeth.

In Group 3, all the 30 root canals were prepared using WaveOne small file (6% taper) using the crown-down technique. The instrumentation time in each root canal was measured by a chronometer.

In all three experimental groups, the canals were flushed with 5 ml normal saline and dried with absorbent paper points. The pulp chamber was then filled with temporary cement (Coltosol, Coltene/Whaledent AG, Switzerland) and apical ends were sealed with sticky wax. The instrumented teeth were then stored in wet conditions.

For evaluation of cleaning efficacy, the teeth were placed separately in 7% hydrochloric acid and the acid solutions were changed daily until the tooth was completely decalcified. The teeth were then washed under running water and dehydrated in a series of ethyl alcohol concentrations: 70% alcohol for 16 h (changed after 8 h) followed by 80% alcohol for 8 h, 95% alcohol for 8 h, and 100% alcohol for 8 h. After dehydration, the teeth were cleared in methyl salicylate for 6 h.

The cleared teeth were examined under a stereo microscope (SMZ-143 series, Motic Company) at × 10 magnification. The scoring was done by an independent blinded examiner. They were scored according to the amount of India ink remaining in the coronal, middle, and apical thirds of the canal on a scale of 0–3.

  • 0 -Total clearing in which the whole canal was completely clean
  • 1 -Almost complete ink removal
  • 2 -Partial ink removal
  • 3 -No ink removal.

The scores, thus, obtained were tabulated and statistically analyzed by Kruskal–Wallis test using MedCalc Statistical Software, version 12.7.2 (MedCalc Software bvba, Ostend, Belgium). The significance of values of time taken for instrumentation with manual, reciprocation, and rotary techniques was done with Student's t-test.

  Results Top

Comparison between the control group and the three experimental groups revealed that files in the three experimental groups were able to remove the ink. The cleaning efficacy of both Mtwo and WaveOne was better than the K-file at the coronal third of the root canal. Among experimental groups, at the coronal level, WaveOne showed more ink removal and the difference found was highly significant (P < 0.0001).

In the middle third of the root canal, WaveOne performed better than Mtwo and K-file. The difference in their cleaning ability was found to be statistically significant (P < 0.005).

In the apical third of the root canal, K-file performed better than other file systems, but the difference was not found to be statistically significant (P = 0.059). When the composite score of all three levels were evaluated, WaveOne was better than the Mtwo and K-file [Table 1] and [Table 2].
Table 1: Cleaning efficacy of files in primary molars

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Table 2: Cleaning efficacy of files in primary molars

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The mean value of time spent for instrumentation of canal by the K-file was 6.22 min, Mtwo was 3.78 min, and WaveOne was 2.37 min. WaveOne was found to take significantly (P < 0.0001) less time than Mtwo and K-file [Table 3].
Table 3: Instrumentation time taken by three file system

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  Discussion Top

There are few studies that compare the cleaning ability of manual and rotary instrumentation in primary teeth. The current study compared the cleaning efficacy of manual instrument and two rotary systems in the preparation of primary molar root canals.

The ink penetration and clearing technique is useful for studying the cleaning ability of the instrumentation and the morphology of human teeth because it makes the teeth transparent so that the pulp cavity and root canal walls can be diagnosed.[1],[6]

Some studies have reported the advantages of manual instrumentation over rotary files regarding root canal wall preparation.[11],[12] However, other studies have reported better results with rotary NiTi systems.[13]

The new Mtwo files have an S-shaped cross section and a noncutting tip. Thus, their positive rake angle with two noncutting edges is responsible for effective dentine cutting and achieving symmetrical root canals.[14] The low fracture rate of Mtwo may be due to the increasing pitch length from tip to shaft, which reduces the tendency of the files to screw-in, thus minimizing the risk of instrument fracture.[8] In addition, the electric torque-limited handpiece used with Mtwo direct helps reduce file fractures. However, according to Bürklein and Schäfer, both the Endo IT motor and Mtwo direct handpiece control motors are equally safe and suitable for preparing curved canals.[15] Because of the particular design features of Mtwo instruments, file deformation may be significantly more frequent than with other instruments. Thus, the working parts of Mtwo files should be carefully examined after every use.[8]

The efficacy of Mtwo rotary systems has been compared to that of other rotary files. Foschi et al. reported that both the Mtwo and Pro Taper rotary systems produced a clean canal in the coronal and middle thirds, but were unable to produce dentine surfaces free from smear layer and debris in the apical third.[16] Schäfer and Oitzinger found that Mtwo and RaCe instruments had a greater cutting efficiency than the profile of Flexmaster and Alfafile rotary NiTi instruments.[17] Other studies evaluated the preparation of curved canals by comparing Mtwo files against other NiTi rotary devices. The results confirmed that Mtwo NiTi files preserved canal curvatures better than K3, RaCe,[8],[9] and Pro Taper [7] instruments. Other researchers reported fewer preparation errors with Mtwo files, a finding that may be related to the specific design of these instruments.[18]

With no literature available for the use of WaveOne file system in primary tooth, we followed the manufacturer's instructions for preparation of the root canal. Primary file (0.06 taper) was selected by considering primary molar root canal morphology. WaveOne showed best results which can be attributed to the reciprocating motion, reverse cutting action, modified convex triangular cross section at the tip end, and a convex triangular cross section at the coronal end.[19] This design improves the overall flexibility of the instrument. The tips are modified to follow canal curvature accurately. The variable pitch flutes along the length of the instrument improves safety considerably.[20]

The advantages of the reciprocating motion are based on the physics' law of action and reaction applied to root canal instrumentation, which results in a balanced force.[20] To overcome the root curvature, balanced forced technique was proposed by Roane et al.[21] The reciprocating movement minimizes torsional and flexural stresses, increases the canal centering ability, and reduces the taper lock within the number of instrument cycles within the root canal.[20]

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 of the canal.

According to studies, preparation time is dependent on the technique, operators experience, number and type of instruments used.[22],[23]

In this study, there was a significant difference in the mean preparation time between all three file systems (P < 0.0001). WaveOne required significantly less time (2.37 min) for preparation of root canals than preparation with Mtwo (3.78 min) and K-file (6.22 min).

  Conclusion Top

Mtwo and WaveOne systems showed significant difference in cleaning ability in the coronal and middle third of the primary molar root canal as compared to manual instrumentation (K-file).

While considering the coronal and middle third of the root canal, WaveOne's cleaning ability was the best among the three file systems.

All three file systems clean the apical third of the root canal effectively and efficiently yet there was not much difference between the files in cleaning efficacy at the apical third.

In addition, while evaluating the instrumentation time, WaveOne took less time than the other two file systems.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Silva LA, Leonardo MR, Nelson-Filho P, Tanomaru JM. Comparison of rotary and manual instrumentation techniques on cleaning capacity and instrumentation time in deciduous molars. J Dent Child (Chic) 2004;71:45-7.  Back to cited text no. 1
Guler C, Gurbuz T, Yilmaz Y. The clinical success of different root canal treatments in primary molars. Cumhuriyet Dent J 2013;16:31-9.  Back to cited text no. 2
Kuo CI, Wang YL, Chang HH, Huang GF. Application of Ni-Ti rotary files for pulpectomy in primary molars. J Dent Sci 2006;1:10-5.  Back to cited text no. 3
Barr ES, Kleier DJ, Barr NV. Use of nickel-titanium rotary files for root canal preparation in primary teeth. Pediatr Dent 2000;22:77-8.  Back to cited text no. 4
Kummer TR, Calvo MC, Cordeiro MM, de Sousa Vieira R, de Carvalho Rocha MJ. Ex vivo study of manual and rotary instrumentation techniques in human primary teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e84-92.  Back to cited text no. 5
Crespo S, Cortes O, Garcia C, Perez L. Comparison between rotary and manual instrumentation in primary teeth. J Clin Pediatr Dent 2008;32:295-8.  Back to cited text no. 6
Sonntag D, Ott M, Kook K, Stachniss V. Root canal preparation with the NiTi systems K3, Mtwo and ProTaper. Aust Endod J 2007;33:73-81.  Back to cited text no. 7
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. 8
Schäfer E, Erler M, Dammaschke T. Comparative study on the shaping ability and cleaning efficiency of rotary Mtwo instruments. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth. Int Endod J 2006;39:203-12.  Back to cited text no. 9
Johnson E, Lloyd A, Kuttler S, Namerow K. Comparison between a novel nickel-titanium alloy and 508 nitinol on the cyclic fatigue life of ProFile 25/.04 rotary instruments. J Endod 2008;34:1406-9.  Back to cited text no. 10
Barbizam JV, Fariniuk LF, Marchesan MA, Pecora JD, Sousa-Neto MD. Effectiveness of manual and rotary instrumentation techniques for cleaning flattened root canals. J Endod 2002;28:365-6.  Back to cited text no. 11
Schäfer E, Schlingemann R. Efficiency of rotary nickel-titanium K3 instruments compared with stainless steel hand K-Flexofile. Part 2. Cleaning effectiveness and shaping ability in severely curved root canals of extracted teeth. Int Endod J 2003;36:208-17.  Back to cited text no. 12
Guelzow A, Stamm O, Martus P, Kielbassa AM. Comparative study of six rotary nickel-titanium systems and hand instrumentation for root canal preparation. Int Endod J 2005;38:743-52.  Back to cited text no. 13
Veltri M, Mollo A, Mantovani L, Pini P, Balleri P, Grandini S. A comparative study of endoflare-hero shaper and Mtwo NiTi instruments in the preparation of curved root canals. Int Endod J 2005;38:610-6.  Back to cited text no. 14
Bürklein S, Schäfer E. The influence of various automated devices on the shaping ability of Mtwo rotary nickel-titanium instruments. Int Endod J 2006;39:945-51.  Back to cited text no. 15
Foschi F, Nucci C, Montebugnoli L, Marchionni S, Breschi L, Malagnino VA, et al. SEM evaluation of canal wall dentine following use of Mtwo and ProTaper NiTi rotary instruments. Int Endod J 2004;37:832-9.  Back to cited text no. 16
Schäfer E, Oitzinger M. Cutting efficiency of five different types of rotary nickel-titanium instruments. J Endod 2008;34:198-200.  Back to cited text no. 17
Giovannone T, Migliau G, Bedini R, Ferrari M, Gallottini L. Shaping outcomes using two Ni-Ti rotary instruments in simulated canals. Minerva Stomatol 2008;57:143-54.  Back to cited text no. 18
Webber J, Machtou P, Pertot W, Kuttler S, Ruddle C, West J. The WaveOne single-file reciprocating system. Roots 2011;1:28-33.  Back to cited text no. 19
Berutti E, Chiandussi G, Paolino DS, Scotti N, Cantatore G, Castellucci A, et al. Canal shaping with WaveOne Primary reciprocating files and ProTaper system: A comparative study. J Endod 2012;38:505-9.  Back to cited text no. 20
Roane JB, Sabala CL, Duncanson MG Jr. The “balanced force” concept for instrumentation of curved canals. J Endod 1985;11:203-11.  Back to cited text no. 21
Hülsmann M, Peters OA, Dummer PM. Mechanical preparation of root canals: Shaping goals, techniques and means. Endod Topics 2005;10:30-76.  Back to cited text no. 22
Bürklein S, Hinschitza K, Dammaschke T, Schäfer E. Shaping ability and cleaning effectiveness of two single-file systems in severely curved root canals of extracted teeth: Reciproc and WaveOne versus Mtwo and ProTaper. Int Endod J 2012;45:449-61.  Back to cited text no. 23


  [Table 1], [Table 2], [Table 3]

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