SciELO - Scientific Electronic Library Online

vol.34 número3Avaliação histomorfométrica de alvéolos dentários humanos pós-extração tratados com fibrina autóloga, aglutinado ósseo ou fosfato de cálcio bifásicoComparación entre índices para el diagnóstico y orientación del tratamiento de caries dental índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados




  • No hay articulos citadosCitado por SciELO

Links relacionados

  • No hay articulos similaresSimilares en SciELO


Acta Odontológica Latinoamericana

versión impresa ISSN 0326-4815versión On-line ISSN 1852-4834

Acta odontol. latinoam. vol.34 no.3 Buenos Aires dic. 2021  Epub 31-Dic-2021 


Shaping ability of reciprocating and rotary systems in oval-shaped root canals: a microcomputed tomography study

Capacidade de modelagem dos sistemas reciprocante e rotatório em canais radiculares ovais: um estudo de microtomografia computadorizada

Thamires C de Medeiros1 

Carolina O de Lima2 

Ana Flávia A Barbosa2 

Carla M Augusto2 

Adília Maria V Bruno1 

Ricardo T Lopes3 

Pablo A. Amoroso-Silva4 

Marília FV Marceliano-Alves4 

1Universidade Federal do Rio de Janeiro, Departamento de Endodontia, Rio de Janeiro, Brasil

2Universidade do Estado do Rio de Janeiro, Departamento de Endodontia, Rio de Janeiro, Brasil

3Universidade Federal do Rio de Janeiro, Programa de Engenharia Nuclear, Rio de Janeiro, Brasil

4Universidade Iguaçu, Departamento de Endodontia e Pesquisa Odontológica, Nova Iguaçu, Rio de Janeiro, Brasil


This study compared the shaping ability of single-file reciprocating (WaveOne Gold) and multifile rotary (Mtwo) systems on mandibular oval-shaped canine root canals, using microcomputed tomography (micro-CT). Thirty mandibular canines were scanned by micro-CT and assigned to one of two groups (n=15) according to the system used for root canal preparation: WaveOne Gold or Mtwo. After preparation, the teeth were rescanned, and the percentage of untouched canal area, apical transportation and centering ability were analyzed. The data was evaluated using Kruskal and Mann- Whitney tests (p<0.05). No difference was found in percentage of unprepared canal area between groups in the entire root canal or the apical third, or in centering ability (p>0.05). WaveOne gold had less canal transportation than MTwo at the 5 mm section (p<0.05). WOG and Mtwo systems presented similar shaping ability and centering ability in oval-shaped canals. However, WOG presented less transportation than Mtwo at 5 mm from the apex.

Keywords: anatomy; root canal preparation; tooth; x-ray microtomography


Este estudo comparou a capacidade de modelagem dos sistemas reciprocante de lima única (WaveOne Gold) e rotatórios com múltiplas limas (Mtwo) em caninos ovais inferiores, usando microtomografia computadorizada (micro-CT). Trinta caninos inferiores foram escaneados por micro-CT e divididos em dois grupos (n = 15) de acordo com o sistema usado durante o preparo do canal radicular: WaveOne Gold (WOG) e Mtwo. Os dentes foram reeescaneados e a porcentagem de área do canal não preparada, transporte apical e capacidade de centralização foram analisados. Os dados foram avaliados pelos testes de Kruskal Wallis e Mann-Whitney (p<0,05). Nenhuma diferença foi encontrada na porcentagem de área não preparada entre os grupos em todo o canal radicular e no terço apical e na capacidade de centralização (p>0,05). O sistema WOG promoveu menor transporte do canal do que o sistema Mtwo na região de 5mm aquém do ápice (p<0,05). Os sistemas WOG e Mtwo apresentaram capacidade de modelagem e capacidade de centralização semelhantes em canais ovais. No entanto, WOG promoveu menor transporte do que Mtwo a 5 mm do ápice.


Intracanal microbial reduction is the primary goal of root canal treatment, and is accomplished through irrigation, chemical debridement, and mechanical action of instruments 1 , allowing periradicular tissue healing. However, these steps can be difficult to complete due to the complexity of root canal anatomy 2 .

The internal canal configuration of mandibular canines has a high incidence of oval-shaped root canals 3 . Several rotary and reciprocating systems are used to promote complete cleaning of oval-shaped canals 4 , but leave unprepared areas after root canal instrumentaron 4-6 . Furthermore, anatomical complexities can also make it difficult to control infection during instrumentation, allowing accumulation of hard tissue debris, with microorganisms remaining in areas that instruments are unable to reach 4-6 . Remaining microorganisms might have the potential to perpetuate periapical inflammation and compromise the success of endodontic treatment 7 . Therefore, endodontic instruments with different kinematics and heat treatments have been developed to deal with root canals with complex anatomy, such as oval-shaped root canals 8 .

The WaveOne Gold system (Dentsply-Sirona, Ballaigues, Switzerland) is a reciprocating single-file made of a heat-treated gold metal alloy (M-wire) 9 , 10 . It has a triangular convex cross-sectional design with two cutting edges, resulting in one or two points of contact between the cutting edges and the dentin walls 9 , which can increase the flexibility and improve cyclic fatigue resistance when compared to conventional NiTi alloys 11 , 12 .

Mtwo is a well-known NiTi superelastic (SE) rotary system (VDW, Munich, Germany), with an “S”-shaped cross-sectional design, a positive rake angle with 2 cutting edges, and low radial contact to increase flexibility and improve performance during root canal prepararion 13 , 14 . Its shape enables dentin to be cut effectively and greater root canal residue removal 15 .

Therefore, the aim of this ex vivo study was to evaluate the shaping ability of single-file reciprocating (WaveOne Gold) and multifile rotary (Mtwo) systems on mandibular oval-shaped canine root canals, using microcomputed tomography (micro-CT). The null hypothesis tested was that there would be no difference between WaveOne Gold and Mtwo in (i) shaping ability or in (ii) apical transportaron and centering ability of mandibular oval-shaped canine root canals.


This study was approved by the Iguaqu University Ethics Committee, Rio de Janeiro, Brazil (n.2.435.836).

Sample size calculation

A power calculation was performed based on data from a previous study 16 , with G*Power 3.1 software (Heinrich Heine University, Dusseldorf, Germany) using a power P = 95% and a = 5% as inputs into an independent samples test from the t tests family. The ideal sample size for each group was a minimum of 10 teeth. Five additional specimens per group were added to compensate for possible sample loss.

Specimen selection

Thirty mandibular canines with moderately curved mesial roots (10° to 20°) 17 were selected from a pool of 300 teeth from the Bank of Human Permanent Teeth of Iguaqu University. Teeth had been extracted for reasons unrelated to this study, Consent was secured prior to tooth donation. The teeth evaluated in this study were from patients of the metropolitan region of Rio de Janeiro city.

The remaining attached tissue was removed, and the teeth were stored in distilled water until the time they were to be used. All samples were scanned by micro-CT (SkyScan 1173, Bruker, Kontich, Belgium) operated at 50 kV and 160 mA, with a 1-mm-thick aluminum filter, 320-millisecond exposure time, 12.1 pm pixel size, 0.8 rotation step, and 360° rotation along the vertical axis. The files were then reconstructed into a three-dimensional dataset with the software NRecon v1.6.1.0 (Bruker micro-CT). Reconstruction parameters included a 50% beam hardening correction, ring artifact correction of 10, and fixed contrast limits (0 - 0.05) for all image stacks. The volume of interest extended from the cementoenamel junction to the apex of the root, resulting in the acquisition of 600 to 700 axial cross sections per sample.

Then, CTAn (v. 1.14.4, Bruker Micro-CT) and CTVol (v.2.2.1, Bruker Micro-CT) software were used to evaluate root canal morphological and 3D configuration. After that, the teeth were matched according to anatomical similarities of preoperative canal volume, canal surface area, and 3D configuration and randomly assigned to one of two groups (n-15) according to the instrument to be used during root canal preparation: Mtwo (VDW GmbH, Munich, German) or WaveOne Gold (Dentsply-Sirona, Ballaigues, Switzerland).

Root canal procedures

Endodontic accesses were performed with high-speed diamond (1014 HL; KG Sorensen, Sao Paulo, Brazil) and Endo Z burs (Dentsply-Sirona,

Ballaigues, Switzerland). A 10 K file (Dentsply-Sirona, Ballaigues, Switzerland) was used to determine apical patency, and the working length (WL) was considered 1 mm short of the apical foramen. A glide path was accomplished with a 15 K file (Dentsply Sirona) up to the WL.

The WaveOne Gold (Dentsply-Sirona) and Mtwo rotary (VDW GmbH) systems were activated with a VDW Silver motor (VDW GmbH, Munich, Germany), according to manufacturer’s instructions.

WaveOne Gold system

The WaveOne (WOG) primary (25/.07) was used in a reciprocating movement with an in-and-out pecking motion and an amplitude of 3 mm with light apical pressure until the WL was reached. After three movements, the instrument was removed from the canal and cleaned with a wet sterile gaze.

Mtwo system

The root canals were prepared using the sequence 10/.04, 15/.05, 20/.06, 25/.06 at 250 rpm with pecking motion, and small brushing movement with light apical pressure until the WL was reached.

An irrigation protocol was used for both groups. Root canal irrigation was performed with 2 mL of 2.5% sodium hypochlorite (NaOCl) with a 30-G Endo-Eze needle (Ultradent Products Inc; South Jordan, UT, USA) inserted until it was 2 mm from the WL. Final irrigation was performed with 2 mL of 2.5% NaOCl, 2 mL of17% EDTA (Mil Fórmulas, Rio de Janeiro, RJ, Brazil) for 1 min and 2 mL of 2.5% NaOCl. The root canals were dried with paper points, after which the teeth were scanned for a second time using the same parameters as mentioned above. A single experienced operator performed all procedures.

Micro-CT Evaluation

The teeth were submitted to a second micro-CT scan and reconstructed (NRecon) using the same parameters as described previously. The postoperative stacks of the root canals after preparation were registered with their respective preoperative stacks with an affine algorithm of the 3D Slicer software. The software ImageJ 1.50d (National Institutes of Health, Bethesda, MD, USA) was used to evaluate the initial and final volume (mm3), surface area (mm2), percentage of unprepared area, canal transportation and centering ability. The unprepared canal area was determined by calculating the number of static voxels (voxels present in the same position on the canal surface before and after instrumentation) divided by the total number of voxels present on the root canal surface 6 , according to the following formula:

number of static voxels×100total number of surface voxels

Canal transportation and centering ratio were calculated at 3 cross-sectional levels (3-, 5-, and 7-mm distance from the apical foramen) using the following equations 18 :

Degree of canal transportation = (m 1 - m2) - (d 1 - d 2 ) Canal centering ratio = (m 1 - m2) - (d 1 - d 2 ) or (d 1 -

d 2 ) - (m 2 - m2),

where m1 is the shortest distance from the mesial of root canal to the mesial of the non-prepared canal, m2 is the shortest distance from the mesial of root canal to the mesial of the prepared canal, d1 is the shortest distance from the distal of root canal to the distal of the non-prepared canal, and d2 is the shortest distance from the distal of root canal to the distal of the prepared canal 18 .

Statistical analysis

The degree of homogeneity between the groups at baseline was confirmed through the analysis of initial volume and initial surface area of the root canals (p>0.05). Data distribution was verified for normality with the Shapiro-Wilk test. Due to the lack of normality, a Kruskal-Wallis test was used to compare intragroup transportation and centering ability parameters. The Mann-Whitney T test was used to compare canal transportation and centering ability between the same canal sections in different groups. The data were processed with Prism 7.0 (GraphPad Software, Inc., La Jolla, CA, USA) and expressed as the median, minimum and maximum values. The significance level was set at 5%.


The degree of homogeneity of the matched teeth regarding canal volume and surface area before root canal preparation was confirmed (p>0.05). No significant difference was found regarding the percentage of unprepared root canal areas between groups for the entire root canal or in the apical third (p>0.05). There was an increase in volume and surface area after root canal preparation compared to the initial sample in the groups tested. These results are described in Table 1 and Fig. 1.

No significant difference was observed in centering ability between the experimental groups (p>0.05). Canal transportation showed no statistically

significant differences in the intragroup comparison at the evaluated sections in either group (p>0.05). When each section was analyzed separately, WaveOne gold had less transportation than the MTwo file only at the 5 mm section (p<0.05). No statistical difference was found in centering ability at any of evaluated levels between groups (p>0.05). The total analyzed values are shown in Table 2.

Table 1 Median, mínimum and máximum values of volume, surface area and percentage of unprepared canal area in root canal and apical third, after the different root canal preparations in WaveOne Gold and Mtwo Groups 

Fig. 1 Representative 3D micro-CT images before (green) and after (red) root canal preparation of experimental groups: a) Wa-veOne Gold and b) MTwo. Representative transverse section of canals before (green) and after (red) root preparation at coronal (C), middle (M), and apical (A) thirds. 

Table 2 Canal transportation and centering ability (mm) in the root canals sections after preparation for the two instrumentation systems 

Different lowercase letters in each column indícate statistically significant differences within the same group between all evaluated sections. Different uppercase letters in each column indicate statistically significant differences between groups for each evaluated canal section.


The development of nickel-titanium (NiTi) rotary systems led to progress in root canal instrumentation 19 . However, failures may occur in oval and flattened canals because the instruments generally provide a rounded cross-section preparation, presenting a challenge to prepare all root canal walls. The instrumentation of these cases is more difficult due to the greater amount of dentin that must be removed to accomplish the ideal root canal shape 3 , 20 . The unprepared areas may harbor remnants of tissue and bacterial byproducts that could cause persistent infection and affect the success of endodontic treatment 21 .

Neither of the systems evaluated in this study was able to completely prepare the root canal, which agrees with previous studies 22-24 . Also, no significant difference was found for unprepared areas between WOG and Mtwo instruments, either in the entire root canal or in the apical third. Thus, the first hypothesis was accepted. These results can be attributed to the standardization of the apical third by the diameter of the instruments tested 25 , 26 .

NiTi instruments have led to significant progress in root canal preparation 27 . Centering ability was evaluated as described by Gambill et al. 18 , who defines centering ability as the ability of the endodontic instrument to remain on the central axis of the root canal. In the present study, no significant difference was observed in centering ability between experimental groups, which is in line with other studies 12 , 28 . Although our study showed similar shaping ability in general results, when each section was analyzed separately, WOG file had less transportation than the MTwo instrument at the 5 mm section from the apex, which partially rejects the second hypothesis. This result can be explained by the fact that WOG is a gold wire heat-treated instrument, while Mtwo is a NiTi SE instrument which does not have controlled memory. The thermally treated NiTi alloys present a higher percentage of martensitic phase, which is more flexible than conventional NiTi files, and may explain why there is less canal transportation of WOG at the 5 mm section from the apex 29 . The present study selected only long oval-shaped canals because they are considered a significant clinical challenge 30 . Moreover, the sample was selected through micro-CT analysis, which provides excellent pairing of teeth, reducing the anatomical bias related to heterogeneity of root canal morphology 4 . The micro-CT technique affords reliable results in the evaluation of data on 2D and 3D parameters of root canal preparation because it is a trustworthy, precise method for this kind of analysis 5 .

Based on our results, WaveOne Gold and Mtwo systems presented similar shaping ability and centering ability during oval-shaped root canal preparation. However, WOG presented less transportation than MTwo at the 5 mm section from the apex.


1 Çapar ID, Arslan H. A review of instrumentation kinematics of engine-driven nickel- titanium instruments. Int Endod J 2016;49:119-135. [ Links ]

2 Nascimento EHL, Nascimento MCC, Gaêta-Araujo H, Fontenele RC, et al. Root canal configuration and its relation with endodontic technical errors in premolar teeth: a CBCT analysis. Int Endod J 2019;52:1410-1416. [ Links ]

3 Wu MK, R’oris A, Barkis D, Wesselink PR. Prevalence and extent of long oval canals in the apical third. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:739-743. [ Links ]

4 Versiani MA, Pécora JD, Sousa-Neto MD. Microcomputed tomography analysis of the root canal morphology of singlerooted mandibular canines. Int Endod J 2013;46:800-807. [ Links ]

5 Peters OA, Laib A, Göhring TN, Barbakow F. Changes in root canal geometry after preparation assessed by highresolution computed tomography. J Endod 2001;27:1-6. [ Links ]

6 De-Deus G, Belladonna FG, Silva EJ, Marins JR, et al. Micro-CT Evaluation of non-instrumented canal areas with different enlargements performed by NiTi systems. Braz Dent J 2015;26:624-629. [ Links ]

7 Versiani MA, Alves FRF, Andrade-Junior CV, Marceliano- Alves MF, et al. Micro-CT evaluation of the efficacy of hard-tissue removal from the root canal and isthmus area by positive and negative pressure irrigation systems. Int Endod J 2016;49:1079-1087. [ Links ]

8 Lacerda MFLS, Marceliano-Alves MF, Pérez AR, Provenzano JC, et al. Cleaning and shaping oval canals with 3 instrumentation systems: a correlative micro-computed tomographic and histologic study. J Endod. 2017;43:1878- 1884. [ Links ]

9 Webber J. Shaping canals with confidence: WaveOne Gold single-file. Roots 2015;1:34-40. [ Links ]

10 Özyürek T. Cyclic fatigue resistance of Reciproc, WaveOne, and WaveOne Gold nickel-titanium instruments. J Endod 2016;42:1536-1539. [ Links ]

11 Bürklein S, Poschmann T, Schäfer E. Shaping ability of different nickel-titanium systems in simulated S-shaped canals with and without glide path. J Endod 2014;40:1231- 1234. [ Links ]

12 Poly A, AlMalki F, Marques F, Karabucak B. Canal transportation and centering ratio after preparation in severely curved canals: analysis by micro-computed tomography and double-digital radiography. Clin Oral Investig 2019;23:4255-4262. [ Links ]

13 Yang G, Yuan G, Yun X, Zhou X, et al. Effects of two nickel-titanium instrument systems, Mtwo versus ProTaper universal, on root canal geometry assessed by microcomputed tomography. J Endod 2011;37:1412-1416. [ Links ]

14 Mokhtari H, Niknami M, Sohrabi A, Habibivand E, et al. Cone-beam computed tomography comparison of canal transportation after preparation with BioRaCe and Mtwo rotary instruments and hand K-Flexofiles. Iran Endod J 2014;9:180-184. [ Links ]

15 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. [ Links ]

16 Elnaghy AM, Al-Dharrab AA, Abbas HM, Elsaka SE. Evaluation of root canal transportation, centering ratio, and remaining dentin thickness of TRUShape and ProTaper Next systems in curved root canals using micro-computed tomography. Quintessence Int 2017;48:27-32. [ Links ]

17 Schneider SW. A comparison of canal preparations in straight and curved root. Oral Surg, Oral Med, Oral Pathol 1971;32:271-275. [ Links ]

18 Gambill JM, Alder M, del Rio CE. Comparison of nickeltitanium and stainless steel hand-file instrumentation using computed tomography. J Endod 1996;22:369-375. [ Links ]

19 Peters OA. Current challenges and concepts in the preparation of root canal systems: a review. J Endod 2004;30:559-567. [ Links ]

20 Silva EJ, Muniz BL, Pires F, Belladonna FG, et al. Comparison of canal transportation in simulated curved canals prepared with ProTaper Universal and ProTaper Gold systems. Restor Dent Endod 2016;41:1-5. [ Links ]

21 Marceliano-Alves MF, de Lima CO, Augusto CM, Almeida Barbosa AF, et al. The internal root canal morphology of single-rooted mandibular canines revealed by microcomputed tomography. J Conserv Dent 2018;21:588-591. [ Links ]

22 Zuolo ML, Zaia AA, Belladonna FG, Silva EJNL, et al. Micro-CT assessment of the shaping ability of four root canal instrumentation systems in oval-shaped canals. Int Endod J 2018;51:564-571. [ Links ]

23 Siqueira JF Jr, Pérez AR, Marceliano-Alves MF, Provenzano JC, et al. What happens to unprepared root canal walls: a correlative analysis using micro-computed tomography and histology/scanning electron microscopy. Int Endod J 2018;51:501-508. [ Links ]

24 De-Deus G, Simões-Carvalho M, Belladonna FG, Cavalcante DM, et al. Arrowhead design ultrasonic tip as a supplementary tool for canal debridement. Int Endod J 2020;53:410-420. [ Links ]

25 Duque JA, Vivan RR, Duarte MAH, Alcalde MP, et al. Effect of larger apical size on the quality of preparation in curved canals using reciprocating instruments with different heat thermal treatments. Int Endod J 2019;52:1652-1659. [ Links ]

26 Jardine AP, da Rosa RA, Santini MF, Zaccara IM, et al. Shaping ability of rotatory or reciprocating instruments in curved canals: a micro-computed tomographic study. Braz Oral Res 2016;30:S1806-83242016000100271. [ Links ]

27 Bürklein S, Benten S, Schäfer E. Shaping ability of different single-file systems in severely curved root canals of extracted teeth. Int Endod J 2013;46:590-597. [ Links ]

28 Saberi E, Farhad-Mollashahi N, Bijari S, Daryaeian M. Comparative evaluation of root canal transportation by three NiTi single-file systems in curved canals: a cone beam computed tomography study. Int J Dent 2018:4151692. [ Links ]

29 Klymus ME, Alcalde MP, Vivan RR, Só MVR, et al. Effect of temperature on the cyclic fatigue resistance of thermally treated reciprocating instruments. Clin Oral Investig 2019;23:3047-3052. [ Links ]

30 Paqué F, Peters OA. Micro-computed tomography evaluation of the preparation of long oval root canals in mandibular molars with the self-adjusting file. J Endod 2011;37:517-521. [ Links ]

FUNDING This study was supported by Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)

Received: August 2021; Accepted: December 2021

CORRESPONDENCE Dr. Marília F. Marceliano-Alves Departamento de Pesquisa Odontológica e em Endodontia Av. Abílio Augusto Távora, 2134 Nova Iguaçu – RJ, Brazil 26260-045

DECLARATION OF CONFLICTING INTERESTS The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Creative Commons License This is an article published in open access under a Creative Commons license