SIGNIFICANCE

Micro-CT analysis of canalgeometry before and afterinstrumentation revealed thatWaveOne Gold, TRUShape,EdgeCoil, and XP-3D Shaperall had similar abilities to shapesingle, oval-shaped canals.

From the *University of Detroit MercySchool of Dentistry–GraduateEndodontics, Detroit and †University ofMichigan School of Dentistry–MicroCTCore, Ann Arbor, Michigan

Address requests for reprints to Dr SusanPaurazas, 2700 Martin Luther King JrBoulevard, Room 317, Detroit, MI 48208.E-mail address: paurazsb@udmercy.edu0099-2399/$ - see front matter

Copyright © 2019 American Associationof Endodontists.https://doi.org/10.1016/j.joen.2019.11.001

James P. Thomas, DDS,*

Michelle Lynch, BA,†

Susan Paurazas, DDS, MS,MPH,* and Mazin Askar, BDS,

MS*

244 Thomas et al.

BASIC RESEARCH – TECHNOLOGY

Micro–computed TomographicEvaluation of the ShapingAbility of WaveOne Gold,TRUShape, EdgeCoil, andXP-3D Shaper EndodonticFiles in Single, Oval-shapedCanals: An In Vitro Study

ABSTRACT

Introduction: This study evaluated and compared the shaping ability of the WaveOne Gold(Dentsply/Tulsa Dental Specialties, Tulsa, OK), TRUShape 3D Conforming File (Dentsply/Tulsa Dental Specialties), EdgeCoil (EdgeEndo, Albuquerque, NM), and XP-3D Shaper(Brasseler USA, Savannah, GA) endodontic file systems on oval-shaped canals using micro–computed tomographic (micro-CT) technology. Methods: Thirty-two oval-shaped, single-canal extracted human teeth were decoronated 1mm coronal to the cementoenamel junctionand scanned via a micro-CT scanner (mCT100; Scanco Medical, Bassersdorf, Switzerland).Teeth were divided into 4 groups (n 5 8) and instrumented according to the manufacturer’sinstructions. Coregistered images, before and after root canal preparation, were evaluated formorphometric measurements of the surface area, volume, structure model index (SMI),conicity, and percent of walls untouched using the manufacturer’s evaluation software (IPLRegister, Scanco Medical). Data were statistically compared between groups using 1-wayanalysis of variance and within groups using a paired sample t test. Results: Instrumentationwith all file types increased the surface area, volume, and conicity between and within groups.There was no statistically significant difference between the groups for any of the rotaryinstruments used (P , .05). Conclusions: Instrumentation of oval-shaped canals withWaveOne Gold, TRUShape, EdgeCoil, and XP-3D Shaper rotary endodontic instrumentssimilarly increase the volume, surface area, and conicity. None of the file systems werecapable of contacting all of the surface area in any canal. (J Endod 2020;46:244–251.)

KEY WORDS

3-dimensional analysis; EdgeCoil; micro–computed tomography; TRUShape 3D; WaveOne;XP-3D Shaper

One of the primary goals of effective root canal instrumentation is to maintain the original shape of thecanal configuration1. Currently, nickel-titanium (NiTi) rotary file systems are able to act mechanically on thecentral body of the canal space. Oval-shaped canals pose a unique challenge during cleaning andshaping procedures. The majority of micro–computed tomographic (micro-CT) studies found that59.6%–79.9% of the dentinal walls remain untouched during root canal preparation of oval-shapedcanals2–5. Metallurgic advancements in NiTi rotary files over the last 2 decades have led to endodonticpreparations that may be accomplished more predictably and with reduced iatrogenic risk6. However, alimitation remains when using round cross-sectional–shaped rotary files to prepare oval-shaped canals inmeeting 2 primary objectives: removing adequate circumferential dentin from all areas of the root canaland avoiding overpreparation of root canal dentin. Attempting to overcome these limitations may lead tomultiple instrumentation errors, including the risk of weakening the tooth structure by

JOE � Volume 46, Number 2, February 2020

overinstrumentation, perforation, and canaltransportation7. These procedural errors havebeen shown to decrease treatment outcome8.

Instrumentation of oval-shaped canalsoften results in uninstrumented recesses9. It isnoteworthy that recent endodontic trendsfocus on preservation of the tooth structurewith increased emphasis on chemicaldisinfection despite numerous studiessupporting mechanical debridement of thecanal system as being paramount in biofilmremoval10–12. Untouched portions of the canalspace may harbor microbial biofilms that serveas a persistent source of infection13,14. Biofilmsare widely recognized to cause an increasedantigenic host response and have decreasedsusceptibility to the immune system andchemotherapeutics15. Novel file designs aim toprovide greater contact to canal walls andimprove apical cleaning while preserving theoriginal root canal shape and cervical dentin16.Recently, using heat treatment technology,several manufacturers have produced rotaryfile shapes with corkscrew-like or S-shapedgeometry as well as reciprocating action toaccomplish these objectives17–20.

Potential advantages of using files with aflexible and expandable profile are

1. improved adaptation to irregular canalgeometries,

2. a reduced risk of overenlarging narrowportions of the root canal, and

3. improved cyclic fatigue resistance throughmodified file geometries andmetallurgies21–23. NiTi endodontic filescurrently on the market that implement aprofile-based geometry, as opposed to apredefined fixed shape, include theTRUShape (Dentsply/Tulsa DentalSpecialties), EdgeCoil (EdgeEndo,Albuquerque, NM), and XP-3D Shaper(Brasseler USA, Savannah, GA).

Evaluation of the instrumented canalwall surface contacted by rotary files can beaccurately measured using micro-CT 3-dimensional scanning. Micro-CT analysis iscurrently considered the gold standard, whichpermits noninvasive analysis of changes incanal morphology, surface area, and volumeand identification of unprepared areas4,24–26. Amorphometric parameter of canal geometricconvexity can be measured through astructure model index (SMI) with valuesranging from 0–4. This 3-dimensional (3D)scoring system assigns a plate a score of 0, acylinder a score of 3, and a sphere a score of427. The SMI represents surface convexity of a3D structure evaluated with Scanco evaluationsoftware (Scanco Medical, Bassersdorf,Switzerland) evaluation software. The goals ofthis study were to use micro-CT scanning and

JOE � Volume 46, Number 2, February 2020

software analysis to evaluate and compare thepercent of untreated surface area and thevolumetric and geometric change ofinstrumented oval-shaped canals of the 4selected rotary systems. The null hypothesiswas that no significant difference exists inmorphometric parameters of the instrumentedoval-shaped canals using WaveOne Gold(Dentsply Tulsa Dental Specialties, Tulsa, OK),TRUShape, EdgeCoil, and XP-3D Shaper files.

A pilot study was conducted to validatethe methodology of Scanco evaluationsoftware (Scanco Medical, IPL Register l). Ascanning mounting jig was printed fromstereolithography (.stl) files provided by theUniversity of Michigan School of DentistryMicroCT Core (mCT100, Scanco Medical) tosecure specimens within the micro-CT unit.Each jig held 5 teeth, whereas the Scancomicro-CT scanner is able to accommodateseveral jigs per scan. Five oval-shapedpremolar teeth were collected, mounted in thescanning jig using Aquasil VPS bite registrationmaterial (Dentsply Caulk, Milford, DE), andscanned at the University of Michigan Schoolof Dentistry MicroCT Core laboratory. Teethwere then instrumented with ProTaper S2rotary files (Dentsply/Tulsa Dental Specialties)irrigated with tap water, and rescanned.Scanco evaluation software was used foranalysis of morphometric changes viasuperimposition of the preinstrumented andpostinstrumented root canals. The use ofmicro-CT scans before and afterinstrumentation allowed superimposition withScanco evaluation software. The analysis wasable to provide the volumetric and geometricchange, SMI values, and color renderings pre-and postinstrumentation.

MATERIALS AND METHODS

After approval of the Institutional Review Boardat the University of Detroit Mercy School ofDentistry, deidentified straight single-rootedmaxillary and mandibular human premolarteeth were selected from a pool of extractedteeth. Extracted teeth were stored in saline at25�C and evaluated using 2-dimensionalSchick CMOS digital radiography (DentsplySirona, York, PA) in both a buccolingual andmesiodistal dimension to identify single-rootedteeth with oval canals. Teeth that hadbuccolingual dimension 2 times greater thanthe mesiodistal dimension were consideredoval canals9 (Supplemental Fig. S1 is availableonline at www.jendodon.com). The exclusioncriteria were teeth with 2 or more root canals,nonoval canals, gross caries, severe rootcurvatures, and immature apices.

Thirty-two teeth passed the inclusion/exclusion criteria and were randomly assigned to

1 of 4 (n 5 8) experimental groups: WaveOne,TRUShape, EdgeCoil, and XP-3D Shaper. Teethwere sectioned 1 mm coronal to thecementoenamel junction, washed with runningtap water, air-dried at room temperature, andscanned on a custom mounting attachment in amicro-CT scanner (mCT100) (Supplemental Fig.S2B is available online at www.jendodon.com).

Specimens were placed in a 48-mmdiameter specimen holder and scanned overthe entire length of the tooth using the Scancomicro-CT system. The scan settings were asfollows: voxel size of 25 mm, 90 kVp, 155 mA,0.1-mm Cu filter, and integration time of 500milliseconds. Scans were performed bothbefore and after instrumentation. The volumeof interest was defined as an 8-mm-longregion ending 1 mm from the root apex(D1–D9). Analysis was performed using themanufacturer’s evaluation software (IPLRegister) to calculate root superimpositionafter instrumentation, enabling the visualizationand 3D quantification of uninstrumented areas.

Images of each specimen werereconstructed (Scanco manufacturer’s micro-CT software) to provide axial cross sections oftheir canal structure, and each canal wasevaluated over the predetermined volume ofinterest (8-mm canal length) withapproximately 600–800 slices/specimen.Scanco micro-CT software was used for 3Dvolume, surface area, and SMI evaluation.

Decoronated teeth were stored in sterilephysiologic saline before instrumentation andinstrumented in a heated water bathmaintained at body temperature (37�C) tohydrate dentin and perform instrumentation atbody temperature. Teeth were individuallymounted in a tooth securing device (Panavise,Sparks, NV), and all hand and rotary fileinstrumentation was performed under surgicaloperating microscopes (Global SurgicalCorporation, St Louis, MO) (Supplemental Fig.S2A is available online at www.jendodon.com).Root canals were negotiated with size #10 and#15 K-files (Dentsply Tulsa Dental Specialties)to establish a glide path. The working lengthwas determined by inserting a size #10 K-fileuntil it was visible at the tip and subtracting 1mm from the patency length. After lengthdetermination, each rotary systemwas used tothe manufacturer’s guidelines to the fullworking length. A single operator withexperience in all systems performed all canalpreparations and was blinded to the virtual 3Dmodels of the teeth before preparation of theroot canals to prevent bias. Theinstrumentation groups were as follows:

1. WaveOne Gold: instrumentation wasperformed with light pecking and outstrokebrushing motions according to the

Shaping Ability of Endodontic Files 245

FIGURE 1 – Reconstructed micro-CT images of the (A ) axial views at the midroot level and (B ) lateral views ofsuperimposed canals before instrumentation (green ) and after instrumentation (red ) with the WaveOne Gold rotary filesystem.

FIGURE 2 – Reconstructed micro-CT images of the (A ) axial views at the midroot level and (B ) lateral views ofsuperimposed canals before instrumentation (green ) and after instrumentation (red ) with the TRUShape rotary filesystem.

manufacturer’s directions for use. Canalswere instrumented using a single-filetechnique with reverse reciprocatingmotion to size 25/07. WaveOne Gold ismarketed as a “single-file system” and isavailable in the following sizes/tapers: 20/07, 25/07, 35/06, and 45/05. WaveOneGold files have an offset rectangular shape,have a variable taper, and aremanufactured with “gold” thermaltreatment used in a reverse reciprocatingmotion that is aimed to be fatigue resistantand maximize cutting efficiency.

2. TRUShape: canals were instrumentedusing size 25/06 at 300 rpm and 3 Ncmtorque with a light pecking and brushingmotion against the buccal and lingualcanal walls until the working length wasreached. The TRUShape Conforming Fileis available in the following sizes/tapers:20/06, 25/06, 30/06, and 40/06; the .06taper occurs in the apical 2 mm, and theremainder of the instrument shaft has avariable taper so that the maximum shaftwidth is no more than .80 mm. The file hasa symmetric triangular cross section and isoperated at 300 rpm and 3 Ncm torque.The manufacturer claims that this filepromotes greater dentin preservation thanclassic rotary files.

3. EdgeCoil: Canals were instrumented usinga single-file technique with reversereciprocating motion and short-amplitudeinward-outward motions. EdgeCoil wasused with a brushing motion on theoutstroke with 1 or more passes to reachthe working length. EdgeCoil is a heat-treated FireWire NiTi single-file shapingprotocol stated to be capable of negotiating90� curves. It has a reverse-reciprocatingrectangular cross section that can expandand contract from 20/04 to 50/06 becauseof its flexible profile.

4. XP-3D Shaper: canals were instrumentedusing a single-file technique at 800–1000rpm at 1 Ncm torque. Long gentle strokeswere used until the file reached the fullworking length. XP-3D Shaper is anadaptive core design that is able to cleanfrom a #30 to a size #90 apical size andcan range from a .02 to .08 taper. This ismade possible by MaxWire (BrasselerUSA) technology, providing a superelastic,cyclic fatigue resistance alloy. MaxWire ispredominantly in a martensitic phase at68�F (20�C) and transforms to anaustenitic phase at 95�F (35�C). TheBooster Tip (Brasseler USA) is designed tohave a #15 size tip that transitions to a#30 within 1 mm, which facilitatessimultaneous scouting and canalpreparation.

246 Thomas et al.

Canals were instrumented with ampleirrigation using the same irrigation protocol forall instrumentation groups. Canals wereirrigated with 3 mm 6% sodium hypochlorite

using a 30-G ProRinse needle (Dentsply TulsaDental Specialties) inserted 1 mm less than thebinding. Teeth were subsequently rinsed with1 mL 17% EDTA followed by 1 mL 6% sodium

JOE � Volume 46, Number 2, February 2020

hypochlorite for 1 minute each. A final 1-mLsterile water rinse was used, and the canalswere dried with sterile paper points. Teethwere allowed to dry at room temperature, andpostinstrumentation micro-CT scanning wascompleted.

A comparison was made before andafter instrumentation to measure changes insurface area, volume, unprepared canalsurface area, and SMI. Scanco software alsoallowed for computation of conicity, which isthe average best-fit line slope of divergencewithin the canal after instrumentation. Twoexaminers blinded to preparation protocolsperformed micro-CT scanning and statisticalanalysis, respectively. Micro-CT images wereconstructed with preinstrumentation (green)and postinstrumentation (pink) geometry.Figures 1 through 4 show mesiodistal andbuccolingual views as well as a single axialsection 5 mm from the apex. Changes ingeometric parameters were compared withpreoperative values using analysis of variance(P, .05) between groups and a paired samplet test within groups (a 5 .05).

FIGURE 3 – Reconstructed micro-CT images of the (A ) axial views at the midroot level and (B) lateral views ofsuperimposed canals before instrumentation (green ) and after instrumentation (red ) with the EdgeCoil rotary file system.

FIGURE 4 – Reconstructed micro-CT images of the (A ) axial views at the midroot level and (B ) lateral views ofsuperimposed canals before instrumentation (green ) and after instrumentation (red ) with the XP-3D Shaper rotary filesystem.

RESULTS

Visual analysis of registration alignmentidentified internal or external cracks in 7 of 32teeth, which were excluded from the study.The remaining 25 teeth resulted in the following4 experimental groups: WaveOne (n 5 4),TRUShape (n 5 6), EdgeCoil (n 5 7), and XP-3D Shaper (n 5 8). The results showed nosignificant difference between all experimentalgroups in volumetric, surface area, conicity,and percent of untreated voxels (P, .05). Thenull hypothesis was accepted because allinstrument groups had similar shapingtendencies (Table 1). Although not significant,instrumented canals in the EdgeCoil groupresulted in the least percent of untreatedvoxels (39.09%) and the greatest increase involume (62.4%) and surface area (24.3%).Canals in the XP-3D group exhibited thegreatest increase in conicity (101%) comparedwith the other file systems, indicating that thedegree of taper within the canal increasedcompared with preoperative canal geometry.In contrast, canals in the TRUShape groupshowed very little increase in conicity (1.6%).Within the experimental groups, all file typessignificantly increased the surface area (a 5

.05) (Table 2). Additionally, TRUShape,EdgeCoil, and XP-3D Shaper files had asignificant effect on volume change. TheWaveOne file group was nearly significant at aP value of .060. No file system by itself showeda significant increase of conicity. However, theoverall pooled data showed a significantincrease in conicity.

JOE � Volume 46, Number 2, February 2020 Shaping Ability of Endodontic Files 247

TABLE 1 - 1-way Analysis of Variance Comparisons of 4 File Types

Measurement

Overall WaveOne TrueShaped EdgeCoil XP-3D Shaper1-wayANOVA

n Mean (SD) n Mean (SD) n Mean (SD) n Mean (SD) n Mean (SD) P value

% Untreated voxelsrelative to before

25 49.08 6 24.75 4 50.90 6 37.75 6 55.26 6 19.94 7 39.09 6 25.61 8 52.28 6 22.31 .671

Conicity before 25 .0653 6 .0318 4 .0500 6 .0155 6 .0728 6 .0225 7 .0677 6 .0497 8 .0653 6 .0264 .755Conicity after 25 .0789 6 .0165 4 .0655 6 .0110 6 .0718 6 .0179 7 .0819 6 .0114 8 .0884 6 .0168 .072Conicitychange (b – a)

25 .0136 6 .0313 4 .0154 6 .0137 6 2.0009 6 .0089 7 .0142 6 0.0498 8 .0231 6 .0284 .589

% Change conicity 25 57.7 6 130.9 4 41.6 6 53.6 6 1.6 6 14.2 7 63.4 6 85.4 8 101.0 6 214.6 .587Surface area before 25 19.60 6 5.86 4 14.57 6 3.54 6 19.92 6 5.68 7 18.33 6 5.66 8 22.99 6 5.70 .105Surface area after 25 22.70 6 5.98 4 17.12 6 2.45 6 22.77 6 7.12 7 21.97 6 4.56 8 26.07 6 5.89 .096Surface areachange (b 2 a)

25 3.10 6 1.72 4 2.55 6 1.32 6 2.85 6 1.76 7 3.64 6 2.52 8 3.09 6 1.11 .772

% Changesurface area

25 17.9 6 14.7 4 19.6 6 13.4 6 14.0 6 6.1 7 24.3 6 24.4 8 14.2 6 7.2 .535

Voxels before 25 3.66 6 1.81 4 2.29 6 1.01 6 3.57 6 1.35 7 3.27 6 1.80 8 4.76 6 2.03 .129Voxels after 25 4.79 6 1.93 4 3.05 6 0.72 6 4.65 6 2.15 7 4.64 6 1.66 8 5.89 6 1.92 .105Voxelschange (b 2 a)

25 1.13 6 0.74 4 0.75 6 0.51 6 1.08 6 0.97 7 1.37 6 0.79 8 1.13 6 0.64 .642

% change voxels 25 40.5 6 42.4 4 40.7 6 30.6 6 28.8 6 16.3 7 62.4 6 70.2 8 30.0 6 25.4 .446SMI before 25 3.12 6 0.39 4 3.19 6 0.21 6 3.06 6 0.42 7 3.05 6 0.24 8 3.19 6 0.56 .871SMI after 25 3.19 6 0.32 4 3.22 6 0.10 6 3.13 6 0.33 7 3.16 6 0.15 8 3.24 6 0.48 .933SMIchange (b 2 a)

25 0.07 6 0.19 4 0.02 6 0.18 6 0.08 6 0.16 7 0.11 6 0.15 8 0.05 6 0.26 .876

% change SMI 25 2.8 6 6.6 4 0.9 6 6.0 6 3.1 6 6.2 7 4.1 6 5.2 8 2.5 6 8.8 .904

ANOVA, analysis of variance; SD, standard deviation; SMI, structure model index.

DISCUSSION

It is important to assess the shaping ability ofnew file designs to determine its impact on theability to meet the objectives of

TABLE 2 - t Test Analysis Comparing Instrumentation withi

Measurement

Overall

N Mean ± SD

Conicity before 25 .0653 6 .03Conicity after 25 .0789 6 .01Conicity change (a 2 b) 25 .0136 6 .03% Change conicity 25 57.67 6 130P value (before vs after) .040Surface area before 25 19.60 6 5.8Surface area after 25 22.70 6 5.9Surface area change (a 2 b) 25 3.10 6 1.7% Change surface area 25 17.88 6 14.P value (before vs after) ,.001Volume before 25 3.66 6 1.8Volume after 25 4.79 6 1.9Volume change (a 2 b) 25 1.13 6 0.7% Change volume 25 21.63 6 15.P value (before vs after) ,.001SMI before 25 3.12 6 0.3SMI after 25 3.19 6 0.3SMI change (a 2 b) 25 0.07 6 0.1% Change SMI 25 2.82 6 6.5P value (before vs after) .073

SD, standard deviation; SMI, structure model index.Instrumentation significantly increased surface area, volume, anWaveOne increased the surface area only. No statistically sign

248 Thomas et al.

instrumentation. The operator must considerbiologic factors weighed againstcharacteristics of the instrument to ensure safepreparation of the root canal and facilitatechemical disinfection28. This study used micro-

n Groups and Overall

WaveOne TrueShaped

n Mean ± SD n Mean ± SD

18 4 .0500 6 .0155 6 .0728 6 .022565 4 .0655 6 .0110 6 .0718 6 .017913 4 .0154 6 .0137 6 2.0009 6 .0089.9 4 41.65 6 53.61 6 1.65 6 14.24

.110 .8056 4 14.57 6 3.54 6 19.92 6 5.688 4 17.12 6 2.45 6 22.77 6 7.122 4 2.55 6 1.32 6 2.85 6 1.7668 4 19.65 6 13.43 6 14.05 6 6.06

.031 .0111 4 2.29 6 1.01 6 3.57 6 1.353 4 3.05 6 0.72 6 4.65 6 2.154 4 0.75 6 0.51 6 1.08 6 0.9762 4 22.44 6 12.92 6 19.69 6 7.56

.060 .0419 4 3.19 6 0.21 6 3.06 6 0.422 4 3.22 6 0.10 6 3.13 6 0.339 4 0.02 6 0.18 6 0.08 6 0.167 4 0.91 6 5.95 6 3.13 6 6.25

.830 .287

d conicity overall. TRUShape, EdgeCoil, and XP-3D Shaper incrificant difference was observed in SMI after instrumentation for

CT technology to assess the effect of 4endodontic file systems in altering canalmorphology. To date, no article has beenpublished on the shaping ability of theEdgeCoil file system in oval-shaped canals

EdgeCoil XP-3D Shaper

n Mean ± SD n Mean ± SD

7 .0677 6 .0497 8 .0653 6 .02647 .0819 6 .0114 8 .0884 6 .01687 .0142 6 0.0498 8 .0231 6 .02847 65.37 6 85.40 8 100.98 6 214.58

.481 .0557 18.33 6 5.66 8 22.99 6 5.707 21.97 6 4.56 8 26.07 6 5.897 3.64 6 2.52 8 3.09 6 1.117 24.34 6 24.44 8 14.23 6 7.21

.009 ,.0017 3.27 6 1.80 8 4.76 6 2.037 4.64 6 1.66 8 5.89 6 1.927 1.37 6 0.79 8 1.13 6 0.647 27.31 6 26.57 8 17.71 6 8.11

.004 .0027 3.05 6 0.24 8 3.19 6 0.567 3.16 6 0.15 8 3.24 6 0.487 0.11 6 0.15 8 0.05 6 0.267 4.06 6 5.24 8 2.48 6 8.80

.083 .592

eased the surface area and volume within groups, whereasany group or overall.

JOE � Volume 46, Number 2, February 2020

using the Scanco software technology. Thecurrent research showed no significantdifference of morphometric measurementsbetween the experimental groups.

No file system tested was capable ofcompletely preparing the oval shaped canals,leaving areas of untouched canal walls. This isin agreement with other studies that evaluatedother rotary systems29–32. The statisticalanalysis did not show a significant difference insurface area and volume increase between theevaluated file systems. Although statisticallynot significant, the EdgeCoil did show a greaterpercent increase in surface area (24.3%) andvolume (62.4%) compared to the other filesystems tested. In addition, the EdgeCoil alsoresulted in the least untouched voxels(39.09%) in oval-shaped canals, indicatingmore surface area was contacted by this newlyintroduced rotary file system.

The current findings also showed nosignificant difference in conicity, surface area,and SMI between WaveOne and EdgeCoilreciprocating files compared with TRUShapeand XP-3D continuous rotary motion files. Thisis in agreement with other studies32 that foundno significance difference between root canalvolume, surface area, and SMI betweenWaveOne, ProTaper Universal, and ProTaperNext file systems (Densply/Tulsa DentalSpecialties) and no difference in terms ofshaping ability when evaluating reciprocatingand continuous rotating motion of the Mtwo filecompared with Reciproc reciprocating filesystems (VDW, Munich, Germany).33

The XP-3D Shaper had a nearlysignificant conicity (P 5 .055) in the t test,suggesting the XP-3D rotary system effectively

JOE � Volume 46, Number 2, February 2020

produced an increased canal taper. Thisfinding is in agreement with Versiani et al27,who found that the XP-endo Shaper (FKGDentaire SA, La Chaux-de-Fonds, Switzerland)significantly altered the overall geometry of theroot canal to a more conical shape. TheEdgeCoil had the least untreated voxels whileonly having moderate increases in conicity.This may suggest that the EdgeCoil is moreefficient in contacting more surface area inoval-shaped canals. Clinically, this maytranslate into more complete instrumentationwithout increasing the coronal shape of thecanal as exhibited by the XP-3D Shaper.Further studies with larger sample sizes areneeded to confirm such effectiveness.

Statistical t test results comparinginstrumentation within groups are significantfor volume, with the exception of the WaveOneGold (P 5 .060). The nonsignificant value maybe attributed to a reduced sample size of thisgroup resulting from an unexpected crackingcomplication, perhaps caused by desiccationof the teeth, which affected coregistration andanalysis. The analysis of variance test showednone of the file systems tested resulted insignificant conicity change. However, theoverall pooled data represented a statisticallysignificant increase in conicity. This finding maysimilarly be attributed to the lack of the samplesize of certain groups caused by the previouslymentioned technical difficulties. Further studieswith increased sample sizes are suggested toconfirm the current findings and take intoconsideration homogeneity of tooth anatomy.An alternative suggestion to control some ofthese limitations is to use 3D-printed teeth withsimilar canal anatomy and dentinlike hardness.

CONCLUSION

Within the limitations of this study, it can beconcluded that the WaveOne Gold,TRUShape, Edge Coil, and XP-3D Shaper filesystems increase volume, surface area, andconicity of instrumented root canals. No filesystem was capable of contacting all of thesurface area in any canal, but EdgeCoilattained the greatest increase in volume andsurface area as well as the least amount ofuntreated voxels among all of the file systemstested.

ACKNOWLEDGMENTS

The authors thank Dentsply for supplyingWaveOne Gold and TRUShape 3D conformingFiles, EdgeEndo for supplying EdgeCoil files,and Brasseler for supplying XP-3D Shaperfiles.

Supported in part by a research grantfrom the American Association ofEndodontists Foundation and in part by theUniversity of Detroit Mercy School of DentistryResearch Fund. The University of MichiganSchool of Dentistry MicroCT Core was fundedin part by NIH/NCRR S10RR026475-01.

The authors deny any conflicts ofinterest related to this study.

SUPPLEMENTARY MATERIAL

Supplementary material associated with thisarticle can be found in the online version at www.jendodon.com (https://doi.org/10.1016/j.joen.2019.11.001).

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SUPPLEMENTAL FIGURE S1 – Radiographic identification of oval-shaped single-rooted teeth during screening evaluation in a (A ) buccolingual and (B ) proximal view.

SUPPLEMENTAL FIGURE S2 – The experimental setup for teeth and micro-CT preparation. (A ) Mounted teeth in the experimental instrumentation setup held at 37�C within asecured device under a surgical operating microscope. (B ) A close-up of teeth secured in a micro-CT mounting jig.

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