In vitro evaluation of root canal transportation after use of BT-Race files

w w w . e l s e v i e r . p t / s p e m d

Revista

Portuguesa

de

Estomatologia,

Medicina

Dentária

e

Cirurgia

Maxilofacial

Original

research

In

vitro

evaluation

of

root

canal

transportation

after

use

of

BT-Race

files

Ranya

Faraj

Elemam

_,

_Jose

_Antonio

_Capelas

_,

_Mário

_Vaz

_,

_Nuno

_Viriato

_,

Maria

de

Lurdes

Ferreira

Lobo

Pereira

_,

_Álvaro

_Azevedo

a_{FacultyofDentalMedicine,UniversityofPorto,Porto,Portugal}

b_{DepartmentofMechanicalEngineering,FacultyofEngineering,UniversityofPorto,Porto,Portugal} c_{INEGI–InstituteofMechanicalEngineeringandIndustrialManagement,Porto,Portugal}

d_{EPIUnit,InstituteofPublicHealth,UniversityofPorto,Porto,Portugal}

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Articlehistory:

Received4November2015 Accepted18February2016 Availableonline26March2016

Keywords: Endodontics Instrumentation Reuse

Shapingability NITIrotaryinstruments

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b

s

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t

Objective:ToevaluatetheeffectofrepeateduseontheshapingabilityoftheBT-Race instru-ment.

Methods:Thirty-sixcanalsinresinblockswereallocatedintosixgroups.Glidepathswere floodedwithalcoholwhilecanalswerepreparedusingacrown-downtechniquetoafinal apicalsizeof35/.04.Pre-andpost-instrumentationimagesweretakenusingmacroscopic magnifier,layeredbyPaintShopPro9software,andcanaltransportationwasmeasuredusing SolidworkCAD2014inapical,middleandcoronallevels.DatawereanalyzedusingaGeneral LinearModelwitha0.05significancelevel.

Results:Whenthenumberofusesonlywasconsidered,therewerenostatisticallysignificant differencesintransportation(F=0.453;p=0.808).Nostatisticallysignificantdifferenceswere foundintransportationintheinterdependenceinfluenceofthelocationsandthenumber ofusesofthefiles(F=0.746;p=0.691).Therewerestatisticallysignificantdifferencesinthis measurebetweenthelocationswhenallgroupsaboutnumberofuses(F=22.358;p<0.0005) wereconsidered.Thelargestmeasureswereseenatfiveandsevenmillimetersfromthe apexandtheshortestonesintheapicalarea.Thedirectionoftransportationwastoward theoutersideofthecurvatureintheapicallevelandtowardtheinnersideinthemiddle andcoronalparts.

Conclusion: BT-Racefilerespectsthecanalmorphologywellandwassafetouserepeatedly withfewincidencesoftransportation.

©2016SociedadePortuguesadeEstomatologiaeMedicinaDentária.Publishedby ElsevierEspaña,S.L.U.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense (http://creativecommons.org/licenses/by-nc-nd/4.0/).

∗ _{Correspondingauthor.}

E-mailaddresses:[email protected],[email protected](R.F.Elemam). http://dx.doi.org/10.1016/j.rpemd.2016.02.003

1646-2890/©2016SociedadePortuguesadeEstomatologiaeMedicinaDentária.PublishedbyElsevierEspaña,S.L.U.Thisisanopenaccess articleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Avaliac¸ão

in

vitro

do

transporte

de

canais

radiculares

após

utilizac¸ão

das

limas

BT-Race

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u

m

o

Objetivo: Avaliaroefeitodo usorepetidodos instrumentosBT-Racenacapacidade de conformac¸ãodecanais.

Métodos:Trintaeseisblocosderesinacomcanaissimuladosforamdivididosem6grupos.A permeabilidadefoimantidaenquantooscanaisforampreparados,irrigando-oscomálcool eusandoumatécnicacrown-downatéumcalibrefinalde35/0,04.Foramobtidasimagens préepós-instrumentac¸ão,usandoumalupamacroscópica,esobrepostascomauxíliodo softwarePaintShopPro9.Otransportedoscanaisfoideterminadoanívelapical,médioe coronalutilizandoosoftwareSolidworkCAD2014.Osdadosforamanalisadosutilizandoum modelogerallinearcomumníveldesignificânciade0,05.

Resultados: Considerandoapenasonúmerodeutilizac¸ões,nãoseobservaramdiferenc¸as estatisticamentesignificativasnotransportedoscanais(F=0,453;p=0,808).Tambémnão seobservaramdiferenc¸ascomsignificadoestatísticonotransportenainfluência interde-pendentedaslocalizac¸õesenúmerodeutilizac¸õesdaslimas(F=0,746;p=0,691).Existem diferenc¸asestatisticamentesignificativasnasmedidasentrelocalizac¸õesdiferentesquando sãoconsideradostodososgruposemrelac¸ãoaonúmerodeutilizac¸ões(F=22,358;p<0,0005). Asmaioresmedidasobtiveram-sea5e7milímetrosdoápexeasmenoresnazonaapical. Anívelapicaladirec¸ãodetransporteverificou-separaoladoexteriordacurvaturaenas porc¸õesmédiasecoronalemdirec¸ãoaoladointerior.

ConclusãoAslimasBT-Racerespeitamamorfologiadoscanais,podendoserusadas repeti-damentedeformaseguraprovocandopoucotransportedoscanais.

©2016SociedadePortuguesadeEstomatologiaeMedicinaDentária.Publicadopor ElsevierEspaña,S.L.U.EsteéumartigoOpenAccesssobalicençadeCCBY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Rootcanal’sinstrumentationisanessentialstepofrootcanal treatmentprocedure sinceit determinesthe efficacy ofall subsequentprocedures.1_{Thistreatmentphaseisassociated}

withrootcanaldisinfectionandcanaltaperingshape,with maintenance of the foramen position without any devia-tions from the original path of the canal.2 _{These shaping}

goals have been set asmajor objectives by various prepa-ration techniques, and instruments that were introduced for canal instrumentation3 _{of this concept is difficult to}

reachincurvedcanalwhereproceduralerrorsarevery com-montotakeplace.4 _{Stainlesssteelfilesinducegreatlateral}

forces in curved canals due to its stiffness that lead to alter the canalmorphology.5 _{Flexible NITI endodontic files}

did improve the root canal preparation by their ability to shape the narrow and curvedroot canalswithout produc-ing any aberrations6 _{besidescreating more centered canal}

preparationsthanstainlesssteelhandfiles.7 Evaluatingthe performanceof endodontics files was alwayscorrelated to theirabilitytoshapethecurvedrootcanalsandtheir capa-bilitytopreservetheoriginalanatomyofthem.8–10_Although

many evaluating parameters were reported in the litera-turewhenshapingabilityofinstrumentwasevaluated, yet transportationisthemostfrequentlyused.Suchevaluations are important to clinicians and researchers; their consid-eration is valued in the selection of a particular rotary NiTiinstrument.11

BT-Race(FKG,LaChaux-de-Fonds,Switzerland)isanewly introducedendodonticfilesystem.Itmainlyconsistsofthree sequencesoffiles.BT1(10/.06),BT2(35/.00),andBT3(35/.04),but BT4(40/.04)andBT5(50/.04)arealsoavailable.BT-Raceis ster-ileandforasingleuse,toavoidpatientcross-contamination, reducebothcyclicalfatigueandtorsionstressoninstruments and,reducethepossibilityofbreakage.12_{Singleusedfilesare}

frequentlyusedtopreparemultiplecanalsinasinglefurcated tooth;thesefilesperformasignificantamountofwork.

Literaturehaslimitedinformationabouttheshaping abil-ity ofBT-Raceinstruments;onlyonestudywas available,13

whichrevealedthatBT-Racehasarespectableabilityto main-tainrootcanalcurvature.13

Theaimofthisinvitrostudyistoevaluaterepeateduse ofBT-Racefiletoresemblemulti-rootedcanals;forthis,the researchquestionsraisedare:Doesthenewrotaryfiles sys-temsBT-Raceinducerootcanaltransportationandhowdoes repetitiveuse1–6_{affecttheabilityofBT-Racefiletoinduceroot}

canaltransportation?

Material

and

methods

Atotalofthirty-sixcurvedrootcanalsinclearresinblocks (Dentsply-Maillefer) were used for this study. Each was mountedwithanangle ofapical curvatureof60◦ and was of16-mmcanallength.Theblocksweregivennumbersfrom onetothirty-six(B1–B36)andthenassembledintosixgroups (G1–G6). Eachgroup consistedofsix blocks.Six kits ofthe

Table1–Meanandstandarddeviationoftransportationofthecanalcenterat4locations.

Locationmm Once(n=6) Twice(n=6) Threetimes(n=6) Fourtimes(n=6) Fivetimes(n=5) Sixtimes(n=6) Total(n=35)

1 0.022±0.019 0.029±0.015 0.027±0.022 0.037±0.029 0.036±0.022 0.041±0.014 0.032±0.021

3 0.040±0.035 0.027±0.022 0.048±0.024 0.036±0.016 0.040±0.023 0.035±0.005 0.038±0.023

5 0.088±0.044 0.083±0.028 0.098±0.039 0.087±0.046 0.089±0.045 0.059±0.028 0.085±0.039

7 0.078±0.032 0.049±0.023 0.057±0.040 0.064±0.051 0.042±0.020 0.051±0.022 0.057±0.034

Fig.1–ModeltransferredontotheSolidworksoftware (SolidWorks2014×64Edition).

BT-Racefilesystemwerealsogivennumbersfromonetosix (F.S.1.–F.S.6).Eachkitwasusedtopreparethecorresponding numberoftheblock’sgroupwhereeachfilewasusedsixtimes each,onetimeineachblockwithineachgroup.

Inallcanals,workinglength(WL)wassetuptothelevelof theapicalforamenusinga#10handK-file(Dentsply Maille-fer,Ballaigues,Switzerland)andglidepath wasestablished usinga#10handK-file(DentsplyMaillefer,Ballaigues, Switzer-land). Thecanalswere then instrumentedbyBT-Racefiles usingcrown-downtechnique,drivenbytheRooterEndodontic motor(FKG,La-ChauxDeFonds,Switzerland);therotational speedwassetattherecommendedrotationof800rpmand 1.5N/cmtorque.Preparationwasperformedbythesame oper-ator,usingthefilesinagentlein-and-outmotionuntilthefull workinglengthwasreached.Theinstrumentationsequence wasasfollows:BT1(size10,0.06taper);BT2(size35,0.00taper); andBT3(size35,0.04taper).Betweentheusesofeachrotary instrumentinordertokeeptheglide pathopen,all canals werefrequentlyirrigatedwith99%ethylalcoholusinga 30-Gside-ventedneedleandrepeatedlyrecapitulatedwithK-file ISO10.

All blockswere photographed before and after prepara-tionusingmacroscopicmagnifier(LeicaMicrosystems)with atotalof6×magnificationwithanimageanalysisprogram (LeicaApplicationSuite© _{2008LeicaMicrosystems,}

Switzer-land.Ltd.).Thenbothimagesforeachblockwereoverlapped accuratelyusingPaintShopPro9(JascSoftware®_U.S.A.).They

werethentransferredasoneimagetotheSolidWorks pro-gram(SolidWorks2014×64Edition)andadrawingmodelwas generated(Fig.1).

Thepossibilityofcanaltransportationwasassessedatfour locationsalongthecanalwallsonbothsidesofthesimulated canal(outerandinner);thosesiteswereselectedtosignifythe apical,middle,andcoronallevels.Themeasurementsof1mm

Table2–Thedirectionsofthemeansoftransportation

ofthecanalcenterat4locations.

Blocks 1mm 3mm 5mm 7mm

35Blocks −0.032 −0.037 +0.085 +0.058

and3mmwereusedtodemonstratetheapicallevel,5mm indicated themiddle level, and7mmspecifiedthe coronal level.

Transportation of the canal’scenter was determined by subtracting the amountofresin removedatthe outerwall (convex)fromthatremovedattheinnerwall(concave)divided bytwo. Apositive resultmeans that transportation occurs mainly on the inner surface of the canal curvature and negativevalueindicatesthattransportationoccursmainlyon theoutersurfaceofthecanalcurvature.

SPSSsoftwareV.22wasusedfordataanalysis,and mul-tivariate statistical analysis (GLM – General Linear Model) wasappliedtocomparethetransportationbetweenthesix groups when time of uses and the transportation in the fourlocationsinthecanalswereconsidered.Thestatistical Greenhouse–Geisserwasconsideredtowardtherejectionof covariancehomogeneity afterapplicationofMauchly’stest. TheBonferronicorrectionwasusedformultiplecomparisons analysiswithasignificancelevelof0.05.

Results

Onefilefractured;BT2number4wasbrokenduringthesixth timeattemptingtoprepareblocknumberthirty-four.

Means and standard deviations of canal center trans-portationsare shown in(Table1).When all locationswere considered,therewerenostatisticallysignificantdifferences in transportation betweenthe six groupsof files(F=0.453; p=0.808). BT-Race rotary NiTi instruments showed trans-portation in both canal sides. However, there was more transportationtowardtheinsideofthecurveinthecoronal andmiddle levels(−values),ratherthanfurthertowardthe outsideofthecurveattheapicallevel(+values)(Table2).

Ontheotherhandtherewerestatisticallysignificant differ-encesinthismeasurebetweenthelocationswhenallgroups aboutnumberofuses(F=22.358;p<0.0005)–wereconsidered (Table1).

Nostatisticallysignificantdifferenceswerefoundin trans-portationintheinteractiveinfluenceofthelocationsandthe numberofusesofthefiles(F=0.746,p=0.691)–(Fig.2).

In average, the transportation was greater and statisti-callysignificantat5mmfromtheapexthanotherlocations (p<0.05).Themajormean difference oftransportation was found between 5mmfrom the apex and 1mm (0.052mm; p<0.0005).The second largest transportationwas foundat

Table3–Pairwisecomparisonsbasedonestimatedmarginalmeansoftransportation(mm)betweenlocations.

(I)Location (J)Location Meandifference(I-J) Std.error Sig.a _{95%Confidenceintervalfordifference}a

Lowerbound Upperbound

1mm 3mm −0.005 0.006 1.000 −0.023 0.013 5mm −0.052 0.009 0.000 −0.078 −0.026 7mm −0.025 0.008 0.029 −0.047 −0.002 3mm 1mm 0.005 0.006 1.000 −0.013 0.023 5mm −0.046 0.005 0.000 −0.061 −0.031 7mm −0.019 0.006 0.026 −0.037 −0.002 5mm 1mm 0.052 0.009 0.000 0.026 0.078 3mm 0.046 0.005 0.000 0.031 0.061 7mm 0.027 0.006 0.001 0.009 0.045 7mm 1mm 0.025 0.008 0.029 0.002 0.047 3mm 0.019 0.006 0.026 0.002 0.037 5mm −0.027 0.006 0.001 −0.045 −0.009

a _{Adjustmentformultiplecomparisons:Bonferronicorrection.}

.1000 Number of_uses Once Twice Three times Four times Five times Six times .0800 .0600 .0400 .0200 3 1 Locations (mm)

Estimated marginal means of location

Estimated marginal means

7 5

Fig.2–MeasuresoftransportationinducedbyBTfiles consideringlocationsandnumberofusage.

7mmfromtheapex.Inthiscase,thelargestmeandifference occurredwhencomparedthelocationat1mmfromtheapex (0.025mm;p<0.03)–(Table3).

Discussion

Thepurposeofthisstudywastodeterminetheshaping abil-ity ofBT-Raceendodontic file systemsby measuringcanal transportationinsimulatedrootcanalsinresinblocks.The reliabilityofresinblocksasanexperimentalmodelfor assess-ment ofinstrumentsand preparationtechniques hasbeen established.14,15_{Althoughliteraturehasreportedthatcaution}

shouldbetakeninjustificationoftheresults,sincethereare differencesbetweenresinanddentinmaterials,16_clinical

rel-evancecanbetransmittedasresultoftheiroutcomes.17,18

Inthisstudy,transportationofthecanalattheapicallevel ofthesimulatedcanalswasanalyzedinatwo-dimensional planusingSolidworksoftware.Apreviousstudyfoundthat

highestacceptableamountofcanaltransportationoccurred apically; this measurement is reachedup to 0.15mm and shouldnotbegreaterthan0.30mm.1_{Measurementsoutside}

ofthisrangeareresponsiblefornumberofadverseeffectson the apicalseal.19 _{Ourstudy demonstratedthatthe amount}

ofthecanaltransportationinducedbyBT-Racewaslessthan bothfiguresmentioned(Table1;Fig.2).

Tilldate,onlyonestudy byBurkleinetal.evaluatedthe shapingabilityofBT-Race.13_{Theinspectedlocations,aswell}

as the methodologies, are different. Burklein et al. study, showed that the transportation at0.5mm was 0.12±0.08; ourstudyshowedthatat1mm,itwas0.032±0.020.Burklein etal.studycomparedtheBT-RacewithMtwo,PTU,andPTN systems, andshowednosignificantdifferencesbetweenall fourinstrumentsregardingcanaltransportation.Oursshowed nostatisticallysignificantdifferencebetweenthefiles them-selves.

DuetothelackofstudiesconductedontheBT-Race,results were comparedwiththepublisheddataofthe predecessor systems.Despitethefactthatdifferentmethodologieswere used, the outcomes were similar. Saber et al.20 _measured

the transportation induced by iRaCe (FKG, La Chaux-de-Fonds, Switzerland)attheapicalregion,and foundit tobe (0.06±0.01); this study’s data showed (0.032±0.020)as the value ofthetransportation atthe centerofthe canal.The otherRacestudyshowedtransportationatapicallevelof3mm (0.10±0.10)andatmiddlelevel of6mm(0.15±0.13)21_{; this}

study’sresultsarewellwithintherangesshownbyBT-Race filesat3mm(0.038±0.022)andat5mm(0.085±0.038),and almost equaltoNabavizadehetal.22 _{that revealed0.034at}

1mm,and0.010at5mmforBioRace.

In this study’s results, the amount ofcanal transporta-tions wasgenerallysmall;thereasonforthesmallamount oftransportationinducedbyBT-Racecanbeexplainedbythe fileflexibility.Previousstudiesfoundthatalesseramountof transportation takesplacewithmoreflexiblefiles.23 _Itwas

also specifiedthat thecentered canalpreparationdepends on the file design, its flexibility, or the instrumentation technique.24 _{Thefile sequences and BTtip ofthe BT-Race}

BT1 010 6% at 800 [rpm] and 1 [mm/s] 8 Torque +Force –Force 7 6 5 4 [NCM] [N] 3 2 1 0 0 5 Advance [mm] 10 15 20

Total machining-time = 20.5 [sec] X - appr. = 0.3 [mm] 04.04.2014 15:51:02

Line-thickness = 2

Torque-max. = 0.77 [Ncm] + Force-max. = 0.61 [N] – Force-max. = 0.19 [N]

Fig.3–Effectoftorque.PositiveandnegativeforcesonB1.

BT2 035 at 800 [rpm] and 1 [mm/s] 8 Torque +Force –Force 7 6 5 4 [NCM] [N] 3 2 1 0 0 5 Advance [mm] 10 15 20

Total machining-time = 20.5 [sec] X - appr. = 0.3 [mm]

04.04.2014 15:55:13 Torque-max. = 0.20 [Ncm] + Force-max. = 2.16 [N] – Force-max. = 0.17 [N] Line-thickness = 2

Fig.4–Effectoftorque.PositiveandnegativeforcesonB2.

thattheoriginalcanalshapeismaintained,andkeepthefiles centered inthe canal.12,25 _{These reasons could beanother}

causeofthesmallamountofobservedtransportation. Thisstudy’sdatashowedalsothatthedirectionof trans-portationwasintheapicalareatowardtheoutsidecurvature, afindingsupportedbythepreviousreports,whichalso con-firmedthesameinclination;this wasexplainedasaresult offile’ssuperelasticity,whichwasallowingtheinstrumentto followthecanalcurvature.9,26,27

Evaluatingthechangesoftheamountofrootcanal trans-portationuponreusingthefilesixtimeswaschosentomimic theclinicalsituationoftreatingoneortwomolarswithinthe samepatient.SinglepatientNiTiuseistheworld’s endodon-ticgoldenstandard,specificallyforthecross-contamination reason and breakage of instruments as a result of metal fatigue.Itiscrucialtostudyinstrumentsinnon-clinicalreuse

circumstances todecide theirmostextremecapacities and performance. Our result exhibited no statistical difference betweenamount ofcanaltransportationwhenthe filewas usedsixtimes. Uptothepresent time,nostudy evaluated howseveralclinicalusesofBT-Raceinstrumentswouldeffect rootcanaltransportation;however,onestudyexaminedthe effectsofmultipleclinicalusesofProtaperuniversalfileonthe incidenceofrootcanaltransportation.28_{Thisstudyreported}

significantdiversityintheamountoftransportationbetween thenumbersoffileuses.Thevariancesbetweenthe instru-ments’designmadethecomparisonimpossible.

BT-Racefilesystemhasa“non-screw-indesign”that intro-ducesthemintotherootcanalwithlowmagnitudeofpositive forceandtorque,andallowsthemtoberemovedsmoothly from the canal with low magnitude ofnegative force and torque,Thiscouldbeseenin(Figs.3–5)asprovidedfromthe

BT3 035 4% at 800 [rpm] and 1 [mm/s] 8

Torque

+Force

-Force

[NCM] [N]

Total machining-time = 20.5 [sec] X - appr. = 0.3 [mm]

04.04.2014 15:59:46 Torque-max. = 0.50 [Ncm] + Force-max. = 0.61 [N] – Force-max. = 0.73 [N] Line-thickness = 2

Fig.5–Effectoftorque.PositiveandnegativeforcesonB3.

FKGbasedonourrequest.Thisabilitycanbeaddedtothe rea-sonwhyBT-Raceinstrumentscanbeusedfrequentlywithout significantchangesinamountoftransportation.

Itisimportanttonotethattheinstrumentsdomaintain their cutting efficiency throughout the experiment; trans-portationdecreaseswerenotduetodecreasesinbladecutting ability.Ourstudyshowedthatthefileswereabletomaintain theircuttingefficiencyevenafter6timesusage,sincethey couldremovetheresinmaterialsonboththeinnerandouter sidesofthetestedsimulatedcanals.

Thesingle use BT-Racefile is idealforuse inone case only;themanufactureclaimsthatitisidealformolarswith 4/5 canals.12 _{In our study, a fracture happened after the}

instrument was used six times; this could be due to sig-nificant amount of work done above the recommendation bythe manufacturer(more than 5).In addition, the inher-ent resistanceofthe resinmaterialused inthe blockmay causeunwindingoftheinstrumentflutesand,consequently, fractureofthefiles.29–31 _{Burklinetal.alsoreportedone}

BT-Racefilefractured(BT2)13_{anddeducedthattothecylindrical}

designoftheinstrumentthatmakesitpronetofracture.The electro-polishedsurfacefeatureofthefileisresponsiblefor decreasingtheeffectsoftorsionalandcyclicfatigue,25_which

couldexplainitsresistancetofracture.Despitethelimitations ofthisstudy,asmallamountoftransportationwasinduced byBT-Racefile;repetitiveuse1–6 _{didnotaffecttheabilityof}

BT-Racetomaintaintheshapingabilityofcurvedrootcanal astherewerenostatisticallydifferencebetweentheamount oftransportationandthenumberofuses.Astandard proto-colfortestingtheshapingabilityofNiTirotaryinstrumentsis requiredtoconfirmconsistencyofmethodologyandtoobtain comparableresultswhenassessingthetransportationofnew instrumentsandtechniques.

Conclusion

Undertheconditionofthisstudy,BT-Racefiles(FKG,La Chaux-de-Fonds,Switzerland) respecttheoriginal canalcurvature

well.Itcanbeusedtopreparemulti-rootedteethwithminimal amountoftransportation.

Ethical

disclosures

Protection of human and animal subjects.The authors declarethatnoexperimentswereperformedonhumansor animalsforthisstudy.

Confidentiality ofdata.Theauthors declarethatnopatient dataappearinthisarticle.

Righttoprivacyandinformedconsent.Theauthorsdeclare thatnopatientdataappearinthisarticle.

Conflicts

of

interest

Theauthorshavenoconflictsofinteresttodeclare.

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