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DRJ Dent Res J Dental Research Journal Dental Research Journal 1735-3327 2008-0255 Medknow Publications Pvt Ltd India DRJ-12-534 10.4103/1735-3327.170570 Original Article Influence of the glide path on various parameters of root canal prepared with WaveOne reciprocating file using cone beam computed tomography Dhingra Anil Nagar Nidhi Sapra Vipul Department of Conservative Dentistry and Endodontics, D.J. College of Dental Sciences and Research, Modinagar, Uttar Pradesh, India Department of Conservative Dentistry and Endodontics, D.J. College of Dental Sciences and Research, Modinagar, Uttar Pradesh, India Department of Conservative Dentistry and Endodontics, D.J. College of Dental Sciences and Research, Modinagar, Uttar Pradesh, India Address for correspondence:Nidhi Nagar, Department of Conservative Dentistry and Endodontics, D.J. College of Dental Sciences and Research, Modinagar, Uttar Pradesh, India drnidhinagar21@gmail.com Nov–Dec 2015 12 6 534 540 Copyright: © Dental Research Journal 2015

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 Background:

Nickel-titanium (NiTi) rotary instrumentation carries a risk of fracture, mainly as a result of flexural (fatigue fracture) and torsional (shear failure) stresses. This risk might be reduced by creating a glide path before NiTi rotary instrumentation. The aim of this study was to compare various root canal parameters with the new WaveOne single-file reciprocating system in mesial canals of mandibular molars with and without glide path using cone beam computed tomography (CBCT).

 Materials and Methods:

One hundred mandibular molar teeth with canal curvature between 20° and 30° were divided into two groups of 50 teeth each. In Group 1, no glide path was created, whereas in Group 2, a glide path was created with PathFiles at working length (WL). In both groups, canals were shaped with WaveOne primary reciprocating files to the WL. Canals were scanned in a CBCT unit before and after instrumentation. Postinstrumentation changes in canal curvature, cross-sectional area, centric ability, residual dentin thickness, and the extent of canal transportation were calculated using image analysis software and subjected to statistical analysis. Data were analyzed using Student′s t-test and Mann-Whitney U-test (P < 0.05).

 Results:

The mean difference of root canal curvature, cross-sectional area, centric ability, and residual dentin thickness increased, whereas it reduced significantly for canal transportation in Group 2.

 Conclusion:

WaveOne NiTi files appeared to maintain the original canal anatomy and the presence of a glide path further improves their performance and was found to be beneficial for all the parameters tested in this study.

 Cone beam computed tomography glide path reciprocating motion WaveOne files </sec> <sec> <title>Introduction

The goals of endodontic treatment are thorough cleaning and shaping of the root canal system by removing all the infected pulp tissue, bacteria, and their by-products. 1 , 2 Nickel-titanium (NiTi) rotary instruments are commonly used for shaping with an increased possibility to produce a more rounded and tapered funnel-shaped canal and a reduced incidence of procedural accidents such as transportation and ledge formation. 3 , 4 Despite these advantages, NiTi instruments appear to have a high risk of separation. 5 , 6 Canal curvature is considered as one of the major risk factors for instrument failure caused by bending cyclic fatigue; 7 stresses due to bending cannot be significantly influenced by the clinician. In 2008, a new preparation technique with only one ProTaper F2 instrument in a reciprocating motion was proposed by Yared. 8

A reciprocating motion was introduced to decrease the impact of cyclic fatigue on NiTi rotary instruments, compared with a rotational motion. 9 , 10 This reciprocating movement is believed to ultimately increase the lifespan of the instrument. 10 , 11 The WaveOne NiTi single file system (DentsplyMaillefer, Ballaigues, Switzerland) is designed to be used with a reciprocating motion motor. The manufacturer claims that the reciprocal motion would reduce the torsional stress by periodically reversing the rotation (170° counter-clockwise, then 50° clockwise rotations) of the file. It consists of three single-use files: Small (International Organization for Standardization [ISO] 21 tip and 6% taper) for fine canals; primary (ISO 25 tip and 8% taper) for the majority of canals; and large (ISO 40 and 8% taper) for large canals. The files are manufactured with M-Wire NiTi alloy. 12 The clinical protocol does not advocate the preliminary creation of a glide path before use. WaveOne small is suggested when a #10 K-file is very resistant to the movement when reaching full working length (WL); WaveOne primary is indicated when a #10 K-file moves to WL easily, and WaveOne large when a #20 K-file or larger easily goes to WL. 13

Cone beam computed tomography (CBCT) provides a higher resolution image in a three-dimensional pixel (voxel). As these voxels are isotropic, the object is accurately measured in different directions. This enables the rendering of geometrically undistorted images of the maxillofacial skeletal structure and allows viewing at different angles. 14 High resolution CBCT instruments might help in the reliable visualization of the root canal, improving the outcome of the endodontic treatment.

Therefore, the aim of this ex vivo study was to compare the various root canal parameters (root canal curvature, cross-sectional area, centric ability, residual dentin thickness, and extent of canal transportation) with the new WaveOne single-file reciprocating system in mesial canals of mandibular first molars with and without glide path using CBCT.

 Materials and Methods

One hundred mandibular first molars extracted due to periodontal disease were used under a protocol approved by the local ethical committee. All the samples were cleaned by scaling and soaking in 2.5% sodium hypochlorite for 24 h. Inclusion criteria were stipulated that the tooth had a curved mesial root with two separate canals and apices, with the curvature angles ranging within 20-30°. The curvature of each canal was measured using the method described by Schneider. 15 Teeth with curvature less or more than this were excluded from the study. The samples were stored in saline at 4°C until use. The teeth were embedded into autopolymerizing acrylic resin, endodontic access was gained, the mesial canals were located and explored with a size 10 K-type file (DentsplyMaillefer, Ballaigues, Switzerland), which was passively advanced into the canals until the tip of the instrument penetrated and adjusted to the apical foramen. The root canal length was recorded, and the WL was calculated by subtracting 1 mm from this measurement using an Endodontic Ruler (DentsplyMaillefer, Ballaigues, Switzerland). Preinstrumentation CBCT images using software CS9300 (Carestream Healthcare, Uttar Pradesh, India) were obtained. Teeth were assigned into two separate groups (n = 50).

In Group 1, glide path was not created. Each canal was shaped with WaveOne primary reciprocating files (DentsplyMaillefer, Ballaigues, Switzerland), with a pecking motion until it reached the full WL using Glyde (DentsplyMaillefer, Ballaigues, Switzerland) as lubricating agent. After instrumentation, all specimens in each group were repositioned in the slot.

In Group 2, the mechanical glide path was made using Glyde (DentsplyMaillefer, Ballaigues, Switzerland) as a lubricating agent, with NiTi rotary instruments PathFile (PF) (DentsplyMaillefer, Ballaigues, Switzerland). The system consists of three instruments with 21-, 25-, and 31-mm length and 0.02 taper; with a square cross-section. PF #1 (purple) has an ISO 13 tip size; PF #2 (white) an ISO 16 tip size; and PF #3 (yellow) has an ISO 19 tip size. PF #1 was used immediately after a size #10 hand K-file (DentsplyMaillefer, Ballaigues, Switzerland) had been used to prepare the root canal to full WL. An endodontic engine (X-Smart; DentsplyMaillefer, Ballaigues, Switzerland) at 300 rpm and 5 N/cm torque, was used with all reciprocating files. After the first PF #1 was used to WL, PF #2 and PF #3 were used sequentially.

Irrigation in both the groups was performed with a 30-G needle syringe 10 ml 2.5% NaOCl after each instrument. The files were discarded after preparation of each canal.

Superimposition and image evaluation

Following instrumentation, the pre- Figure 1a and d and post-operative images Figure 1b and e were measured using the CBCT scan software CS9300 equipment (Carestream Healthcare, Uttar Pradesh, India) in the high resolution dental mode (i.e., 90 μ resolution). Axial and coronal sections corresponding to distances 0, 1, 2, 3, 5, and 7 mm from the anatomic apex were selected and distances between the edges of uninstrumented canals and the root edges were measured in mesial and distal directions. After instrumentation, the same reference points were adopted for the acquisition of postoperative measurements. Then the pre- and post-instrumentation CBCT images were superimposed using OnDemand3D software version 1.0 (Cyber Med. Seoul, Korea). The postinstrumented image was outlined in red, and it was superimposed over the initial image (grey outline) Figure 1c and f.

(a and b) Pre- and post-instrumented images at 7 mm in axial section. (c) Superimposed image. (d and e) Preand post-instrumented images at 7 mm in coronal section. (f) Superimposed image.

Figure 1

Changes in root canal curvature

To calculate the root canal curvature the angle of maximum curvature of the root canal from the anatomic apex in coronal and transverse section was measured. After superimposition of the pre- and post-instrumentation CBCT images the difference between the angles of curvature were measured.

Cross-sectional area

To calculate the postoperative changes in cross-sectional area and to detect the root canal wall differences, the pre- and post-instrumentation CBCT images were superimposed using the OnDemand3D software (Cyber Med Inc.Korea version 1.0)

Evaluation of centric ability

The centring ratio, which measures the ability of the instrument to remain in a central position within the canal, was calculated for each cross-section using the values obtained in the assessment of root canal transportation. The ratio of (X1 − X2) to (Y1 − Y2) as described by Gambill et al., 16 where X1 is the distance between the mesial portions of the root and the uninstrumented canal, X2 is the distance between the mesial portions of the root and the instrumented canal, Y1 is the distance between the distal portions of the root and the uninstrumented canal, and Y2 is the distance between the distal portions of the root and the instrumented canal, were measured.

Whenever the numbers were not equal, the lower figure was considered to be the numerator of the ratio. According to this formula, the result of 1 indicates the optimal centring ability.

Residual dentin thickness

For both the groups, the shortest distance from the canal outline to the closest adjacent root surface was measured at each level.

Evaluation of canal transportation

Canal transportation was calculated in millimeters with the formula [(X1 − X2) − (Y1 − Y2)]. 11 Pre- and post-operative measurements were compared to reveal the presence or absence of deviations in canal anatomy and to identify the most affected region.

Statistical analysis

All statistical analyses were performed using the software package SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). The level of significance was set at P < 0.05.

Within each group, pre- and post-instrumentation changes in root canal curvature, cross-sectional area, and residual dentin thickness were analyzed statistically using Student′s t-test at (P < 0.05). Mann-Whitney U-test was applied to test-centric ability and extent of canal transportation.

 Results

Changes in root canal curvature

In Group 1 (1.3540 ± 0.84520) and Group 2 (3.1700 ± 1.61400), a significant mean difference was found indicating that the root canal curvature increases more significantly in Group 2 Figure 2a (P < 0.05) Table 1.

(a) Graphical representation of mean difference in root canal curvature between the two groups. (b) Cross-sectional area at different levels. (c) Mean difference in centric ability, (d) Mean difference in canal transportation. (e) Residual dentin thickness at different levels.

Figure 2 {Table 1}

Changes in cross-sectional root canal area

The mean difference was significant between groups at all levels except at 2 mm (P > 0.05) Figure 2b.

Centric ability and canal transportation

The centric ability increased Figure 2c and the extent of canal transportation decreased significantly in Group 2 Figure 2d, Figure 3a and b, Table 2.

(a) Line diagram represents mean difference in centric ability. (b) Line diagram represents mean difference in canal transportation.

Figure 3 {Table 2}

Residual dentin thickness

The residual dentin thickness was significantly more in Group 2 Figure 2e (P < 0.05).

 Discussion

The WaveOne NiTi reciprocating system has been introduced to simplify canal shaping. 13 Only a single file is suggested to reach adequate root canal size and taper. Single use, reciprocating motion, and M-Wire alloy manufacturing are the main characteristics of these instruments M-Wire NiTi technology raises performance to unprecedented heights by offering significantly more of the benefits endodontists care about most, including flexibility and the resistance to cyclic fatigue - the leading cause of file separation. 17

Reciprocating motion was proposed to increase the canal centring ability as well as to reduce the risk of root canal deformity. 18 , 19 , 20 This statement supports the results founded in the present study, where both the experimental groups (Group 1 and Group 2) produced centric preparation, but increase in centric ability was seen in Group 2 (with previous glide path preparation).

Coronal enlargement 21 and preliminary creation of a glide path are fundamental for safer use of NiTi rotary instrumentation. 22 , 23 The use of a small-size hand K-file followed by a more flexible and less tapered NiTi rotary PF might be a less invasive and safer method to provide a glide path that better maintains the original canal anatomy, compared with manual preflaring performed with stainless steel K-file. 24 Similarly, in this study, a glide path was prepared using PF that significantly improved the shaping ability of the WaveOne file in curved root canals.

The literature suggests that the modification in canal curvature after instrumentation is a reliable method to evaluate the tendency of a shaping technique to maintain the original canal anatomy or to straighten the curves. 25 The methods commonly used for evaluating canal shaping are radiographs, 20 tooth sections, 26 and plastic blocks. 27 The newest techniques for evaluation of shaping ability of rotary instrumentation are microtomography, 28 , 29 high-resolution CT, 30 , 31 and CBCT, 32 which are nondestructive and show more details. 33 Furthermore, CBCT images permit metrically exact analyses of variables such as volume, surface areas, cross-sectional shape, and taper. The fraction of prepared surface can be analyzed with software which does not interfere in the original format of the images, allowing the analysis of the exact position and direction of canal transportation. 34 In this study, a quantitative analysis was performed through observation of changes between pre- and post-instrumentation images by using CBCT.

Several studies have surveyed shaping ability of WaveOne file. 35 , 36 These studies have yielded that canal modifications are reduced with WaveOne file as compared with other rotary systems.

Another recommendation for improving the performance of WaveOne file is by preparing a glide path. Similarly, in this study, a glide path was prepared based on the findings of Berutti et al. 37 who reported that canal modifications seem to be significantly reduced when previous glide path is performed using the new WaveOne NiTi single-file system.

In the present study, establishment of a glide-path increased the ability of WaveOne file to remain centered in prepared canals and produced less canal transportation, consistent with the results reported by Lim et al. 38 and Saber et al. 35

It can, therefore, be summarized that the root canal curvature, cross-sectional area, centric ability, and residual dentin thickness increased significantly, whereas the canal transportation significantly decreased in the presence of a previous glide path.

 Conclusion

WaveOne NiTi files appear to maintain the original canal anatomy and the presence of a glide path further improves their performance and was found to be beneficial for all the parameters tested in this study.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or non-financial in this article.

 Schilder H Cleaning and shaping the root canal Dent Clin North Am 1974 18 269 96 Chugal NM Clive JM Spångberg LS Endodontic infection: Some biologic and treatment factors associated with outcome Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003 96 81 90 Short JA Morgan LA Baumgartner JC A comparison of canal centering ability of four instrumentation techniques J Endod 1997 23 503 7 Glossen CR Haller RH Dove SB del Rio CE A comparison of root canal preparations using Ni-Ti hand, Ni-Ti engine-driven, and K-Flex endodontic instruments J Endod 1995 21 146 51 Arens FC Hoen MM Steiman HR Dietz GC Jr Evaluation of single-use rotary nickel-titanium instruments J Endod 2003 29 664 6 Sattapan B Nervo GJ Palamara JE Messer HH Defects in rotary nickel-titanium files after clinical use J Endod 2000 26 161 5 Peters OA Current challenges and concepts in the preparation of root canal systems: a review J Endod 2004 30 559 67 Yared G Canal preparation using only one Ni-Ti rotary instrument: Preliminary observations Int Endod J 2008 41 339 44 You SY Bae KS Baek SH Kum KY Shon WJ Lee W Lifespan of one nickel-titanium rotary file with reciprocating motion in curved root canals J Endod 2010 36 1991 4 Varela-Patiño P Ibañez-Párraga A Rivas-Mundiña B Cantatore G Otero XL Martin-Biedma B Alternating versus continuous rotation: a comparative study of the effect on instrument life J Endod 2010 36 157 9 De-Deus G Moreira EJ Lopes HP Elias CN Extended cyclic fatigue life of F2 ProTaper instruments used in reciprocating movement Int Endod J 2010 43 1063 8 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 Webber J Machtou P Pertot W Kuttler S Ruddle C West J The WaveOne single-file reciprocating system Roots 2011 1 28 33 Leung SF Cone beam computed tomography in endodontics Dent Bull ;;- 9 Cone beam computed tomography in endodontics Dent Bull 2010;15;16-9 Schneider SW A comparison of canal preparations in straight and curved root canals Oral Surg Oral Med Oral Pathol 1971 32 271 5 Gambill JM Alder M del Rio CE Comparison of nickel-titanium and stainless steel hand-file instrumentation using computed tomography J Endod 1996 22 369 75 Shen Y Cheung GS Bian Z Peng B Comparison of defects in ProFile and ProTaper systems after clinical use J Endod 2006 32 61 5 Roane JB Sabala CL Duncanson MG Jr The "balanced force" concept for instrumentation of curved canals J Endod 1985 11 203 11 Roane JB Sabala C Clockwise or counterclockwise J Endod 1984 10 349 53 Southard DW Oswald RJ Natkin E Instrumentation of curved molar root canals with the Roane technique J Endod 1987 13 479 89 Roland DD Andelin WE Browning DF Hsu GH Torabinejad M The effect of preflaring on the rates of separation for 0.04 taper nickel titanium rotary instruments J Endod 2002 28 543 5 Patiño PV Biedma BM Liébana CR Cantatore G Bahillo JG The influence of a manual glide path on the separation rate of NiTi rotary instruments J Endod 2005 31 114 6 Berutti E Negro AR Lendini M Pasqualini D Influence of manual preflaring and torque on the failure rate of ProTaper rotary instruments J Endod 2004 30 228 30 Berutti E Cantatore G Castellucci A Chiandussi G Pera F Migliaretti G Use of nickel-titanium rotary PathFile to create the glide path: Comparison with manual preflaring in simulated root canals J Endod 2009 35 408 12 Merrett SJ Bryant ST Dummer PM Comparison of the shaping ability of RaCe and FlexMaster rotary nickel-titanium systems in simulated canals J Endod 2006 32 960 2 Bramante CM Berbert A Borges RP A methodology for evaluation of root canal instrumentation J Endod 1987 13 243 5 Weine FS Kelly RF Lio PJ The effect of preparation procedures on original canal shape and on apical foramen shape J Endod 1975 1 255 62 Sattapan B Palamara JE Messer HH Torque during canal instrumentation using rotary nickel-titanium files J Endod 2000 26 156 60 Boessler C Peters OA Zehnder M Impact of lubricant parameters on rotary instrument torque and force J Endod 2007 33 280 3 Estrela C Bueno MR Sousa-Neto MD Pécora JD Method for determination of root curvature radius using cone-beam computed tomography images Braz Dent J 2008 19 114 8 da Silva FM Kobayashi C Suda H Analysis of forces developed during mechanical preparation of extracted teeth using RaCe rotary instruments and ProFiles Int Endod J 2005 38 17 21 Paqué F Al-Jadaa A Kfir A Hard-tissue debris accumulation created by conventional rotary versus self-adjusting file instrumentation in mesial root canal systems of mandibular molars Int Endod J 2012 45 413 8 Peters OA Peters CI Schönenberger K Barbakow F ProTaper rotary root canal preparation: Assessment of torque and force in relation to canal anatomy Int Endod J 2003 36 93 9 Paqué F Ganahl D Peters OA Effects of root canal preparation on apical geometry assessed by micro-computed tomography J Endod 2009 35 1056 9 Saber SE Nagy MM Schäfer E Comparative evaluation of the shaping ability of WaveOne, Reciproc and OneShape single-file systems in severely curved root canals of extracted teeth Int Endod J 4 Comparative evaluation of the shaping ability of WaveOne, Reciproc and OneShape single-file systems in severely curved root canals of extracted teeth Int Endod J 2014 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 Berutti E Paolino DS Chiandussi G Alovisi M Cantatore G Castellucci A Root canal anatomy preservation of WaveOne reciprocating files with or without glide path J Endod 2012 38 101 4 Lim YJ Park SJ Kim HC Min KS Comparison of the centering ability of Wave·One and Reciproc nickel-titanium instruments in simulated curved canals Restor Dent Endod 2013 38 21 5