• Users Online: 54
  • Home
  • Print this page
  • Email this page
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 

 Table of Contents  
Year : 2019  |  Volume : 16  |  Issue : 2  |  Page : 68-72

Effect of heat treatment on the centering ability and dentin removal of a nickel–titanium single file rotary system

Department of Endodontics, Faculty of Dentistry, Tanta University, Tanta, Egypt

Date of Submission31-Dec-2018
Date of Acceptance25-Feb-2019
Date of Web Publication23-Sep-2019

Correspondence Address:
Walaa M Ghoneim
Department of Endodontics, Faculty of Dentistry, Tanta University, Tanta
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tdj.tdj_47_18

Rights and Permissions

The aim of this study was to investigate the effect of heat treatment on the centering ability and amount of dentin removal of OneShape single file rotary system (OS) by cone beam computed tomography.
Materials and methods
Twenty human premolars with single root canals were allocated into two equal groups (n = 10) according to the used rotary system: group 1: OS system, group 2: One Curve which is heat-treated OS single file rotary system. Preinstrumentation and postinstrumentation images were obtained at 3, 6, and 9 mm from the apex and assessed to determine canal centering ability. Amount of removed dentin was estimated by difference between preinstrumentation and postinstrumentation root canal volumes. Data were analyzed using t-test and significance level was set at P value less than or equal to 0.05.
The results showed that One Curve file has higher mean centering ratio and more dentin removal than OS file with no statistically significant difference between them (P > 0.05).
It was concluded that heat treatment did not have significant effect as both files could maintain the original canal path without significant differences in centering ability and amount of removed dentin.

Keywords: centering ability, cone beam computed tomography, dentin removal, One Curve, OneShape

How to cite this article:
Ghoneim WM. Effect of heat treatment on the centering ability and dentin removal of a nickel–titanium single file rotary system. Tanta Dent J 2019;16:68-72

How to cite this URL:
Ghoneim WM. Effect of heat treatment on the centering ability and dentin removal of a nickel–titanium single file rotary system. Tanta Dent J [serial online] 2019 [cited 2020 Mar 28];16:68-72. Available from: http://www.tmj.eg.net/text.asp?2019/16/2/68/267568

  Introduction Top

One of the most important principles of shaping the root canal system is maintaining the original canal anatomy by uniformly preparing all surfaces of the canal to prevent procedural errors such as zipping, ledging, perforations, and apical transportation [1]. However, prevention of these undesirable consequences is a great challenge, especially in severely curved canals [2].

Centering ability is an essential feature of instruments to obtain uniform preparation. It is influenced by instruments characteristics; as alloy [3], cross-section [4], tapering, tip design [5], manufacturing method [6], type of movement [7], and rotation angle [8] in addition to root canal anatomy such as the presence of curvatures [9].

Conservation of radicular dentin, especially in areas of risk such as developmental depressions, concavities and grooves, is mandatory as excessive dentin removal in a single direction within the canal causes canal transportation that may lead to ledge formation, strip perforation and vertical root fractures [10].

Although different nickel–titanium (NiTi) systems have been developed [11], single file systems use was recommended to reduce instrument fatigue and possible cross-contamination [12]. OneShape system (OS), composed of a 55-NiTi alloy, is a single instrument that features continuous rotation for performing a complete root canal preparation. The instrument has size 25 initial diameter and 0.06 mm taper and presents variable cross-sections across the length of its active portion [13].

Many manufacturers have been seeking ways to alter the presently available root canal instrument designs, with a focus on altering the surface of the alloy or altering the alloy microstructure with postmachining or post-twisting heat treatment [14]. One Curve single file system (OC) is heat-treated OS NiTi file, made of C. Wire which is a technique designed, developed and applied by Micro-Mega Company. It is claimed by the manufacturer to be hyperflexible, cyclic fatigue resistant, and without sucking effect [15].

Cone beam computed tomography (CBCT) has been suggested for assessing the tomography of canal walls as it is a nondestructive technique which provides three-dimensional reproduction of the tooth and allows better preoperative and postoperative evaluation of morphological changes in the root canal trajectory [16] for better assessment of root curvatures and canal transportation [1].

Although OS file centering ability is well studied and compared with different rotary and reciprocating systems, no published data is found comparing its centering ability and amount of dentin removal in comparison to OC file. Therefore, this study was designed to evaluate centering ability and amount of removed dentin of OS and OC files in curved root canals to evaluate the effect of heat treatment.

  Materials and Methods Top

Sample selection and preparation

Twenty freshly extracted, fully developed human premolars with single root canals with similar range of canal curvature (21°–39°) according to Schneider's method [17] extracted for orthodontic or periodontal reasons were collected. Approval of this research was obtained from Research Ethics Committee, Faculty of Dentistry, Tanta University. The purpose of this study was explained to the patients and informed consents were obtained to use their extracted teeth on the research. Teeth were thoroughly cleaned, polished, rinsed under running water and stored in sterile saline solution at 4°C until use [18].

All teeth were decoronated using water cooled low speed diamond disc (Dica; Dendia, USA) leaving 13 ± 1 mm long roots. Canals diameters were standardized by selecting roots fitting initial apical file #15 K-type (Dentsuply/Maillefer, Ballaigues, Switzerland) and working length (WL) of each canal was determined by measuring the length of K-type file size #10 at the apical foramen minus 1 mm.

Roots were coded and randomly divided into two equal experimental groups (n = 10) according to instrumentation system and fixed in one acrylic block with a small ball of gutta-percha fixed in one corner of the block as a fixed landmark helping in repositioning during further scanning of the specimens using CBCT.

Preinstrumentation cone beam computed tomography scanning

Preinstrumentation scanning was achieved through adjusting the position of acrylic block by the aid of four laser beams of CBCT machine (Scanora 3D Soredex; Orion Corporation, Helsinki, Finland).

Root canal preparation

In group 1; after glide path creation using #15 K-file, root canals were prepared using OS single rotary file (#25/0.06) (Micro-Mega, Besancon, France) using X-Smart Plus endodontic electromotor (Dentsuply/Maillefer) at a constant speed of 400 rpm and 2.5 N × cm torque following the manufacturer's instructions. OS instrument was coated with Glyde File Prep lubricant agent (Dentsuply/Maillefer) and taken down to two-third of the WL using an in-and-out passive movement while performing an upward circumferential filing movement, then the file was withdrawn and cleaned. Canal was then irrigated and checked for patency.

Then, OS file was inserted 3 mm from WL in a passive movement. This was continued until OS instrument reached the full WL without pressure in one or more passages depending on the complexity of the canal anatomy.

In group 2; glide path was created using #15 K-file and canals were prepared by OC single rotary file (Micro-Mega) using X-Smart Plus endodontic electromotor at a constant speed of 300 rpm and 2.5 N × cm torque in a crown down manner until reaching full WL following manufacturer's instructions.

All root canals were irrigated with 10 ml of 2.5% sodium hypochlorite (Clorox Co., 10th of Ramadan City, Egypt) solution throughout instrumentation using a plastic disposable syringe with a 30-G closed-end needle (NaviTip; Ultradent Products Inc., South Jordan, Utah, USA) positioned 2 mm short of the WL.

Postinstrumentation cone beam computed tomography scanning

After instrumentation, the specimens were scanned using the same standers as preinstrumentation scanning. Preinstrumentation image was fused to the postinstrumentation using a software (Ondemand 3D; Cybermed Inc., Seoul, South Korea) allowing the best possible accuracy.

From fused image, preinstrumentation and postinstrumentation images can be obtained to record the measurement of preinstrumentation and postinstrumentation on the same plane direction and cut to ensure standardization. Cut lines at 3, 6, and 9 mm from the apical end of each root in each group, representing mid-apical, mid-middle and mid-coronal root thirds respectively, were determined on axial view of the fused CBCT image.

Evaluation of centering ability

Centering ability was calculated for each section using centering ratio [19]:

where Y 1 is the shortest distance from the mesial aspect of the root to the periphery of the uninstrumented canal. Y′1 is the shortest distance from the mesial aspect of the root to the periphery of the prepared canal. Y 2 is the shortest distance from the distal aspect of the root to the periphery of the uninstrumented canal. Y′2 is the shortest distance from the distal aspect of the root to the periphery of the prepared canal.

According to this formula, the ratio equal to 1 indicates a perfect centering ability; the closer the result is to 0, the worse is the ability of the instrument to remain centered 213. If these numbers were unequal, the numerator for this formula was the smallest of the two numbers (Y 1 − Y′1) or (Y 2 − Y′2) [20].

Evaluation of amount of removed dentin

The preinstrumented and postinstrumented root canal volume of each root was measured with 3D software (Cybermed Inc.) and volume of dentin removed during instrumentation was determined for each canal by subtracting the preinstrumented canal volume from the instrumented one. The volume of each root canal was determined in cubic millimeters.

Statistical analysis

Mean ± SD values of centering ratio and amount of dentin removal of the two tested root canal preparation systems were calculated and statistically analyzed by t-test using SPSS statistical software (version 20; SPSS Inc., Chicago, Illinois, USA); P values less than or equal to 0.05 were considered to be statistically significant.

  Results Top

Centering ability

Mean ± SD values of centering ratio of the two tested root canal preparation systems were represented and compared at different root canal levels as shown in [Table 1]. Centering ratio mean values were higher in group 2 using OC file system than group 1 using OS file without significant difference between both systems at all root canal levels (P > 0.05).
Table 1: Mean±SD and statistical analysis using t-test for comparison between centering ratio of both groups

Click here to view

Amount of dentin removal

Mean ± SD values of amount of removed dentin for each group was calculated and it was found that OC system recorded higher amount of dentin removal (4.07 ± 0.80) than OS system (3.27 ± 0.38). Comparison between both systems using t-test revealed nonsignificant difference (P = 0.17).

  Discussion Top

Endodontic instruments should remain centered in the root canal throughout the preparation [21] otherwise, canal transportation may occurs and leads to inappropriate dentine removal, with a high risk of straightening the original canal curvature and forming ledges in the dentine wall [22],[23]. Therefore, centering ability is an important feature to be tested in instruments.

Although no consensus on the amount of dentin that should be removed during instrumentation, overinstrumentation of the root canal could result in excessive thinning of the root [7]. Therefore, canal volume was measured preinstrumentation and postinstrumentation in this study to analyze the effect of canal instrumentation on amount of dentine removal [24],[25].

CBCT image technology was used in this study to evaluate centering ability and the canals volume before and after root canal preparation as it provides a precise, reproducible, three-dimensional assessment of alterations in dentine thickness and root canal volume without destructive sectioning of the specimens or loss of the root material during sectioning [26].

Both instruments maintained the original canal curvature well. These results might be explained by similar design of both single files systems used in this study as both files have unique asymmetrical cutting profile, which improves its snake-like movement into the canal and therefore may cause less transportation and preserves the original canal shape [27],[28]. In addition to safety tip of size 25, continuous taper of 0.06 and variable pitch which reduces instrument screwing effects [27],[29].

The results of this study were supported by Rashid and Saleh [30], who reported that all tested single file systems (F360, OS, Reciproc, and WO) maintained root canal curvature well without significant differences and were safe to use. In addition, Santa-Rosa et al. [31] concluded that WO and OS single file systems were able to shape curved root canals producing minor changes in the canal curvature. Moreover, Saleh et al. [32] showed that OS maintained the anatomy of the canals better than WO and Reciproc systems.

Regarding the amount of dentin removal, the unique design of OS, OC instruments which incorporates a variety of different cross-sections along the active length of the file offers an improved cutting action in the root canal. Although the difference between both OS and OC systems was statistically nonsignificant, higher mean centering ratio and more amount of dentin removal recorded in OC group may be because of its heat treatment [33], C-wire technology which increased instrument flexibility and decreased screwing effects [15].

  Conclusion Top

  1. None of the tested instruments remained perfectly centralized within the root canals.
  2. Both tested single file systems (OS and OC) could maintain the original canal path without significant differences between them in centering ability and amount of removed dentin.
  3. Heat treatment in OC file improved its centering ability and amount of dentin removal than OS file but without significant effect.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Elsherief SM, Zayet MK, Hamouda IM. Cone-beam computed tomography analysis of curved root canals after mechanical preparation with three nickel–titanium rotary instruments. J Biomed Res 2013; 27:326–335.  Back to cited text no. 1
Mitra G, Sharma V, Sachdeva J, Singla M, Taneja K, Bhatnagar A. To evaluate and compare canal transportation, canal-centering ability, and vertical root fracture resistance of teeth prepared with three different rotary file systems: an in vitro study. Endodontology 2017; 29:53–59.  Back to cited text no. 2
  [Full text]  
Thompson M, Sidow SJ, Lindsey K, Chuang A, McPherson JC. Evaluation of a new filing system's ability to maintain canal morphology. J Endod 2014; 40:867–870.  Back to cited text no. 3
Nagaraja S, Sreenivasa Murthy BV. CT evaluation of canal preparation using rotary and hand NI-TI instruments: an in vitro study. J Conserv Dent 2010; 13:16–22.  Back to cited text no. 4
[PUBMED]  [Full text]  
Lim YJ, Park SJ, Kim HC, Min KS. Comparison of the centering ability of WaveOne and Reciproc nickel–titanium instruments in simulated curved canals. Restor Dent Endod 2013; 38:21–25.  Back to cited text no. 5
Arora A, Taneja S, Kumar M. Comparative evaluation of shaping ability of different rotary NiTi instruments in curved canals using CBCT. J Conserv Dent 2014; 17:35–39.  Back to cited text no. 6
[PUBMED]  [Full text]  
Stern S, Patel S, Foschi F, Sherriff M, Mannocci F. Changes in centering and shaping ability using three nickel–titanium instrumentation techniques analysed by micro-computed tomography (μCT). Int Endod J 2012; 45:514–523.  Back to cited text no. 7
Saber Sel D, Abu El Sadat SM. Effect of altering the reciprocation range on the fatigue life and the shaping ability of WaveOne nickel–titanium instruments. J Endod 2013; 39:685–688.  Back to cited text no. 8
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; 2012:1–7.  Back to cited text no. 9
Tabrizizadeh M, Reuben J, Khalesi M, Mousavinasab M, Ezabadi MG. Evaluation of radicular dentin thickness of danger zone in mandibular first molars. J Dent (Tehran) 2010; 7:196–199.  Back to cited text no. 10
Saber SE, Nagy MM, Schafer E. Comparative evaluation of the shaping ability of ProTaper Next, iRaCe and Hyflex CM rotary NiTi files in severely curved root canals. Int Endod J 2015; 48:131–136.  Back to cited text no. 11
Sharma N, Sarfi S, Sharma A, Grewal MS. Evaluation of canal preparation with rotary and hand NiTi files in curved root canals using cone beam computed tomography: an in vitro study. Int Arch Integ Med 2017; 4:45–55.  Back to cited text no. 12
Dhingra A, Ruhal N, Miglani A. Evaluation of single file systems Reciproc, Oneshape, and WaveOne using cone beam computed tomography – an in vitro study. J Clin Diagn Res 2015; 9:30–34.  Back to cited text no. 13
Gutmann JL, Gao Y. Alteration in the inherent metallic and surface properties of nickel–titanium root canal instruments to enhance performance, durability and safety: a focused review. Int Endod J 2012; 45:113–128.  Back to cited text no. 14
Micro-Mega. Brochure One Curve; Besançon Cedex, France. Available at: http://www.micro-mega.com. [Accessed 30 December 2018].  Back to cited text no. 15
Oget D, Braux J, Compas C, Guigand M. Comparative analysis of root canal changes after preparation with three systems using cone-beam computed tomography. G Ital Endod 2017; 31:83–88.  Back to cited text no. 16
Schneider SW. A comparison of canal preparations in straight and curved root canals. Oral Surg Oral Med Oral Pathol1971; 32:271–275.  Back to cited text no. 17
Carvalho AS, Camargo CHR, Valera MC, Camargo SEA, Mancini MNG. Smear layer removal by auxiliary chemical substances in biomechanical preparation: a scanning electron microscope study. J Endod 2008; 34:1396–1400.  Back to cited text no. 18
Aguiar CM, Donida FA, Câmara AC, Frazão M. Changes in root canal anatomy using three nickel–titanium rotary system: a cone beam computed tomography analysis. Braz J Oral Sci 2013; 12:307–312.  Back to cited text no. 19
Gandhi A, Gandhi T. Comparison of canal transportation and centering ability of hand Protaper files and rotary Protaper files by using micro computed tomography. Rev Sul Bras Odontol 2011; 8:375–380.  Back to cited text no. 20
El Ayouti A, Dima E, Judenhofer MS, Löst C, Pichler BJ. Increased apical enlargement contributes to excessive dentin removal in curved root canals: a stepwise microcomputed tomography study. J Endod 2011; 37:1580–1584.  Back to cited text no. 21
Jafarzadeh H, Abbott PV. Ledge formation: review of a great challenge in endodontics. J Endod 2007; 33:1155–1162.  Back to cited text no. 22
Loizides A, Eliopoulos D, Kontakiotis E. Root canal transportation with a Ni-Ti rotary file system and stainless steel hand files in simulated root canals. Quintessence Int 2006; 37:3–7.  Back to cited text no. 23
Bergmans L, van Cleynenbreugel J, Wevers M, Lambrechts P. A methodology for quantitative evaluation of root canal instrumentation using microcomputed tomography. Int Endod J 2001; 34:390–398.  Back to cited text no. 24
Peters OA, Schönenberger K, Laib A. Effects of four Ni–Ti preparation techniques on root canal geometry assessed by micro computed tomography. Int Endod J 2001; 34:221–230.  Back to cited text no. 25
Mamede-Neto I, Borges AH, Guedes OA, de Oliveira D, Pedro FLM, Estrela C. Root canal transportation and centering ability of nickel–titanium rotary instruments in mandibular premolars assessed using cone-beam computed tomography. Open Dent J 2017; 11:71–76.  Back to cited text no. 26
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.  Back to cited text no. 27
Alrahabi M, Alkady A. Comparison of the shaping ability of various nickel–titanium file systems in simulated curved canals. Saudi Endod J 2017; 7:97–101.  Back to cited text no. 28
  [Full text]  
Bürklein S, Benten S, Schäfer E. Quantitative evaluation of apically extruded debris with different single-file systems: Reciproc, F360 and OneShape versus Mtwo. Int Endod J 2014; 47:405–409.  Back to cited text no. 29
Rashid A, Saleh AR. Shaping ability of different endodontic single-file systems using simulated resin blocks. Int J Multidiscip Dent 2016; 6:61–67.  Back to cited text no. 30
Santa-Rosa J, de Sousa-Neto MD, Versiani MA, Nevares G, Xavier F, Romeiro K, et al. Shaping ability of single-file systems with different movements: a micro-computed tomographic study. Iran Endod J 2016; 11:228–233.  Back to cited text no. 31
Saleh AM, Gilani PV, Tavanafar S, Schäfer E. Shaping ability of 4 different single-file systems in simulated S-shaped canals. J Endod 2015; 41:548–552.  Back to cited text no. 32
Kuhn G, Jordan L. Fatigue and mechanical properties of nickel–titanium endodontic instruments. J Endod 2002; 28:716–720.  Back to cited text no. 33


  [Table 1]


Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Materials and Me...
Article Tables

 Article Access Statistics
    PDF Downloaded94    
    Comments [Add]    

Recommend this journal