ARTICOLO
ORIGINALE
Debridement
effectiveness
of
two
different
techniques
using
negative
pressure
irrigation
system
Efficacia
nella
detersione
di
due
differenti
tecniche
d’irrigazione
a
pressione
negativa
Flavio
Palazzi
a,*
,
Luciano
Giardino
b,
Zahed
Mohammadi
c,
Sandro
Rengo
a,
Francesco
Riccitiello
aa
DepartmentofOdontostomatologicalandMaxillofacialSciences,FedericoIIUniversityofNaples,Italy
bFacultyofDentistry,UniversityofTorino,Italy c
DepartmentofEndodontics,HamedanUniversityofMedicalSciences,Hamedan,Iran Received24April2012;accepted3September2012
Availableonline6October2012
KEYWORDS
Closedsystemmodel; EndoVac; Needleirrigation; Negativepressure irrigation; Smearlayer. PAROLECHIAVE
Sistemacanalarechiuso; EndoVac;
Irrigazioneconsiringa; Irrigazioneapressione negativa;
Fangodentinale.
Summary
Objectives: Toevaluatethecleaningefficacyoftwoapicalnegativepressureirrigation tech-niquescomparedtoneedleirrigation.
MaterialsandMethods: Eightyextractedhumansinglecanalteethwereshapedandassignedto 3experimentalgroups(n=20)accordingtotheirrigationtechniqueperformedandtwonegative control groups (n=10) as follows: 1) NI (Max-I-Probe side-vented needle irrigation); 2) EV (EndoVacsystem);3)EVM(EndoVac-modifiedtechnique);4)EV-C(EndoVac-negativecontrol); 5)NI-C(needle irrigation-negativecontrol). A scanning electron microscopicevaluationwas performed.Thepresenceofdebrisandsmearlayeratalllevels(coronal,middle,apical)was evaluated.
Resultsand conclusions: A newirrigation protocol,usingEndoVacSystemresulted inbetter removalofthesmearlayeratalllevels.
ß2012Societa` ItalianadiEndodonzia.PublishedbyElsevierSrl.Allrightsreserved. Riassunto
Obiettivi: Valutarel’efficaciadiduetecniched’irrigazioneapressioneapicalenegativa para-gonandoleaquellatradizionaleconsiringa.
Materiali e metodi: Ottanta denti umani monocanalari, assegnati a 3 gruppi sperimentali (n=20)in accordo allatecnica d’irrigazioneutilizzata eduegruppicontrollo(n=10). 1) NI
* Correspondingauthor.ViaPansini,5-80131Napoli,Italy. E-mail:flaviopalazzi@gmail.com(F.Palazzi).
Availableonlineatwww.sciencedirect.com
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1121-4171/$—seefrontmatterß2012Societa` ItalianadiEndodonzia.PublishedbyElsevierSrl.Allrightsreserved.
Introduction
Theidealoutcomeofrootcanaltreatmentistheeffective destructionandremovalofbacterial biofilmsandtheir by-productsfromtherootcanalsystem(RCS),oratleasttheir significantreductiontolevelscompatiblewithperiradicular tissuehealing[1].Duetoitsanatomicalcomplexities,suchas isthmi,fins,deltas,andaccessorycanals,complete debride-mentoftheRCSisalaboriouschallenge[2].
Current instrumentation techniques are ineffective in shapingand cleaning all surfaces andirregularities of the rootcanalspace[3—6].Additionally,accumulationofdebris and producing smear layer are potential side effects of mechanicalinstrumentation[7],whichmayimpede disinfec-tion of the RCS in cases with apical periodontitis [8,9], harbour microorganismsand disrupt theseal betweenthe root filling material and canal walls, possibly leading to treatmentfailure [10,11].Therefore,irrigation using anti-microbialandtissue-dissolvingirrigantsiscomplementaryto instrumentationinfacilitating theremovalofbacteriaand disinfectionoftheRCS,flushingdebrisandnecrotictissue, andremovingsmearlayer[12,13],especiallyfromareasthat areroutinelyleft uninstrumentedfollowingrootcanal pre-paration,e.g.isthmuses,ovalextensionsandapicaldeltas
[4,14].
Because of its broad spectrum antimicrobial efficacy
[15,16]aswellasitsuniqueabilitytodissolveorganicdebris
[17,18],sodiumhypochlorite(NaOCl)isrecommendedasthe mainirrigantduringendodontictherapy[19].However,itis not ableto dissolve the inorganic components of dentine debris[20].Seventeenpercentethylenediaminetetraacetic acid(17%EDTA)isachelatingagentthatisoftenusedasthe active final rinse to remove the inorganic component of thesmearlayer.
It isbestused incombination,butnotcoincident, with NaOCl [19,21]. It was statedthat removal ofdebris relies mostlyontheflushingactionoftheirrigant[22,23]. There-fore,asufficientvolume,ahighflowrateandanunrestricted flow of the irrigant along the canal walls are crucial for thorough debridement of the RCS [24—26]. Conventional manualirrigationwithasyringeandneedleremainswidely accepted[4],althoughitsflushingactionisnotsufficientin removingdebrisfromrootcanalirregularities[13,14,27,28]. Theflushingactionandtheextentofirrigantreplacementof syringeirrigationisdependentonmanyfactorssuchasthe insertiondepthanddiameteroftheneedle[25,26,29].The optimalneedledepthmaybealsoinfluencedbythepresence ofacurvatureandbythefinalsizeandtaperoftheprepared root canal [22,30,31]. Moreover, gas entrapment could prevent optimal irrigant delivery and flow 0-2mm from
the end-point of canals [32]. Several studies have shown thatcurrentirrigationmethodsareeffectiveincleaningroot canals coronally but less are effective apically [33—35]. Huang et al.[31] and Sedgley etal. [36] reported that a thoroughcleaningwasattainablewiththetipofthesyringe locatedapically.
Differenttechniquesanddeviceshavebeenproposedto improve the flow and distribution of irrigating solutions within the RCS [27]. EndoVac (Discus Dental, Culver City, CA)isacommerciallyavailablenegativepressureirrigation systemthatisdesigned todeliverirrigatingsolutiontothe apical end of the canal system and remove debris via a negativepressuremechanism.Thissystemcombinesa mas-ter delivery/suctiontip (MDT) (fig. 1)that simultaneously deliversand evacuatesirrigantsto/from theaccess cavity whiledrawingirrigantsintothecanalspacebyusing macro-(fig.2) andmicro-cannulas(fig.3).The EndoVac hasbeen shown to introduce a higher flow of irrigant andproduce betterdebridementat 1mmfromtheworkinglength(WL) whencomparedwithpositivepressureneedleirrigation[37]. Nonetheless,nodifferenceswereobservedforthecanalarea 3mmshortoftheWL,inagreementwiththefindingsofSiu and Baumgartner [38]. However, their comparisons are biased.Syringeirrigationwasperformedat2mmawayfrom WLorevenmore,whileEndovacwasinsertedtofullWL.To beeffective,endodonticirrigantsshouldideallybedelivered closetoWL.IrrigantreplacementreachedtheWLonlywhen theside-ventedneedlewasplacedwithin1mmfromtheWL
[39]. Usingan ex vivo open-end canalmodel, Abarajithan et al. [40] showed that both Endovac and conventional irrigation were ineffective in complete removal of smear layer from the apicalthird of root canalinstrumented up toamasterapicalfile(MAF)ISOsize60.Additionally,Susin
(Irrigazioneconsiringa);2)EV(EndoVac);3)EVM(EndoVac-tecnicamodificata);4)EV-C (Endo-Vac-controllonegativo);5)NI-C(Irrigazioneconsiringa-controllonegativo).Dopodetersionee sagomatura icampionisono stati valutatiattraversola microscopiaelettronica ascansione. Irisultatisonostatianalizzatistatisticamentemedianteanalisinonparametricadellavarianza (p<0.05).
Risultatieconclusioni: Unnuovoprotocollod’irrigazioneconilsistemaendovacsie` dimostrato significativamentepiu` efficacenellarimozionedelfangodentinaleatuttiilivelli.
ß2012Societa` ItalianadiEndodonzia.PubblicatodaElsevierSrl.Tuttiidirittiriservati.
et al. [41] studied canal and isthmus debris debridement efficacies of apical negative pressure (ANP) technique in comparison with manual dynamic irrigation [42], using an ex vivo closed-end canal model. The ANP technique was unabletocompletelyremovedebrisfromthenarrowisthmi presentbetweenthecanalsinthemesialrootofmandibular molars, because ofthedifficulty in getting irrigating solu-tions to reach the isthmus and to create a strong enough currenttoflowthroughtheisthmus.
Thus, the purpose of the present ex vivo study was to examine the canal debridement and smear layer removal efficacyoftwoirrigantdeliveryANPtechniqueswithEndoVac system versus positive pressure needle irrigation, using a closedcanaldesign.Thenull hypotheseswas thatthere is no difference between the canal debridement and smear removalbyusingtwodifferentANPirrigantdelivery techni-ques and needle irrigation, at different levels from the anatomicalapex,inasimulatedclosedcanalsystem.
Materials
and
Methods
Toothselectionandpreparation
Eightyfreshly extractedhumanpermanentanterior single-rootedteethwithstraightrootcanal(maxillarylateral inci-sorsandmandibular incisors)werecollected andstoredin sterile saline before the investigation. The age of the patients from whom these teeth were extracted was less than (40%)and over (60%) 30. The inclusion criteria were small restorations, intact pulp chamber, andintact closed apices, whereas the exclusion criteria were previous root canal treatment, extensive restorations, root caries, root fractures,teeth with anirregular rootcanalanatomy,and rootlengthlessthan16mm.
ThestudywasapprovedbytheEthicsCommitteof Fed-erico II Naples University. After preparation of the access cavity, rootcanal was negotiatedusing a size10 stainless steelK-file,insertedintotherootcanaluntilthetipofthe instrumentwasjustvisibleattheapicalforamen.TheWLwas determined by subtracting 1mm from this length. Each toothwasradiographedinbuccolingualandmesiodistal pro-jectionstodetectanypossibleobstruction,toevaluatethe shapeoftherootcanalandtodeterminethedegreeofroot canalcurvature[43].Teethwithnosinglecanalsystem,canal
curvature angles of more than 20 degrees, calcified root canals,orrootcanalsallowingintroductionofaninstrument exceedingISOsize30totheapicalforamenwereexcluded. Theincisal edgewas adjusted,so that thelengthof each toothwas21mmfromtheapicalforamen.Tosimulateinvivo conditions,eachroothadtheirapicalforaminacoveredand sealedbyhotflexibleglueexpressedfromahotgluegun.This set-up permitted recapitulation of canalpatency but pre-ventedfluidextrusionfromtheapicalforamenduringcanal preparation.Thenthecementum,totallyfromapextothe cemento-enameljunctionandsetgluewerecoatedwithtray adhesive(Dentsply Caulk,Milford,DE, USA).Accesscavity finishing andpulp canalorifice expansion wereperformed withsizes5and3ultrasonictipsStart-X(Dentsply,Maillefer, Baillagues,Switzerland).Thecervicalbulgeofdentinewas removedbyusingX-Gatesbur(CavityAccessSet;Dentsply, Maillefer,Baillagues,Switzerland).Aglidepathwas estab-lishedby mechanical instrumentationupto an apical dia-meterof 0.19mm at the WLwith sizes #13/.02,#16/.02, #19/.02 nickel-titanium (NiTi) rotary Pathfiles (Dentsply, Maillefer,Baillagues,Switzerland).Briefly,thecoronaltwo thirdsoftherootcanalswereenlargedbyusingProtaperS1 NiTirotaryinstrument(Dentsply,Maillefer,Baillagues, Swit-zerland)attheWL.Rootcanalsweretheninstrumentedto finalsize#40/.04taperNiTirotaryGTSeriesXfile(Dentsply, Maillefer,Baillagues,Switzerland)inacrown-downapproach to a standardized WL of 21mm. Apical patency was con-firmedwith asmallfile(stainless steelhandk-filesize10) throughouttheproceduresaftereachlargerfilesize.Before instrumentation,theteethweredividedintothree experi-mental groups, according to the irrigation technique per-formedof20teetheachandtwonegativecontrolgroupsfor negativeandpositivepressureirrigation,of10teetheach, balancingthe5groupswithregardtoageoftheteeth,root curvature and number of round-shaped and oval-shaped canals.
Experimentalgroups
For all experimental groups, irrigation with 5.25% NaOCl (Niclor 5; Ogna Laboratori Farmaceutici,Muggio`,Italy) at 378C and with 17% EDTA (Ogna Laboratori Farmaceutici, Muggio`, Italy) began before the use of the X-Gates drill. Thecanalswerekeptfloodedwith5.25%NaOClthroughout
theinstrumentationprocedure.Finally,thecanalwasflushed with17%EDTAfollowedby5.25%NaOCl[44].Eachtoothin eachgroupreceivedanequalamountoftimeforirrigation andthesamevolume ofirrigants.Altogether, 35mL5.25% NaOClwasused:threemillilitersduringaccesscavity finish-ing and pulp canal orifice expansion, 16mL during rotary instrumentation,10mLduringmacro-irrigationand6mLfor micro-irrigation(thefirstcycleandthefinalflushafterEDTA application).Furthermore,3mL17%EDTAwasusedforeach tooth.
a)EVgroup(n=20):EndoVacsystem
For the EV group, irrigation began during the use of the X-Gatesdrill.Theirrigantwasdeliveredintothepulp cham-berbyusingMDTconnectedtotheNaOClsyringeandplaced abovetheaccessopening.
Suction tubing attached to the syringe tip through an aluminumadapter(fig.4)removedanyexcessirrigant.This allowedthecanalandpulpchambertobefullofirrigantatall times.Duringallinstrumentation,thechamberwasflooded with 2mL 5.25% NaOCl replenished with 2mL after each instrument.Onceinstrumentationwascomplete,whenthe MAF (#40/.04)reachedWL, thecanal was macro-irrigated andmicro-irrigatedaccordingtothemanufacturer’s instruc-tions. Thirty seconds of macroirrigation (active irrigation) with5.25%NaOClwereaccomplishedasfollows:10mLwere delivered coronally by the MDT while macro-cannulus insertedintothecanalwasconstantlymovedupanddown, from a point up to apically binding point (4mm short of
theWL)toapointjustbelowthecanalorifice.TheNaOClwas suctioned throughthetipofthemacro-cannuluswhilethe NaOClwasconstantlybeingreplenishedviathesyringetip. The irrigant was then left undisturbed for 60seconds in a totally filled canal to allow further chemical reactions between fresh NaOCl and residual organic debris. Then 3 cycles of micro-irrigation wereaccomplished. During each cycle,pulpchamberwasmaintainedfullofirrigantdelivered by metalneedle of MDTover 30seconds while the micro-cannuluswasplacedinsequence,atWLfor6seconds,2mm shortoftheWL(6seconds)andbacktotheWLfor6seconds: this alternating movementbetween these positions lasted 30seconds,allowing18secondsofactiveirrigationdirectly atWL.Themicro-cannuluswasat lastwithdrawnfromthe canalinthepresenceofafullirrigantpulpchamber,ensuring a totally filled canal for a 60seconds passive wait. This completed 1 cycle of micro-irrigation. NaOCl (5.25%) was used inthefirst cycle.EDTA(17%)was usedin thesecond cycle andNaOCl (5.25%)was used once again inthe third cycle.After3cyclessequenceand60secondspassivewait, NaOClwasaspiratedusingthemicro-cannulusatWL. b)EVMgroup(n=20):EndoVacsystem-modified technique
For the EVM group, macro-irrigation began during rotary instrumentationasfollows: 2mLof5.25%NaOClbetween eachinstrumentchangebyusingatthesametimeMDTon pulpchamberandmacro-cannulusintotherootcanalplaced uptotheapicallybindingpointwithout‘‘up-down’’motion. The NaOCl was suctioned through the tip of the macro-cannuluswhiletheNaOClwasconstantlybeingreplenished viathesyringetip.OncetheMAFreachedWL,the micro-cannulusreplacedmacro-cannulusanda3cyclessequence ofmicro-irrigationstartedat WL.Themicro-cannuluswas constantly left at WL without ‘‘up-down’’ movements. NaOCl(5.25%)wasusedinthefirstcycle.EDTA(17%)was usedinthesecondcycle.NaOCl(5.25%)wasusedonceagain in the third cycle. After each cycle of micro-irrigation (30seconds) a 60seconds passive wait (pulp chamber and root canal full of fresh irrigant) followed. After micro-irrigationcompletionNaOClwasaspiratedusingthe micro-cannulusatWL.
c)NI-group(n=20):Needleirrigationgroup
Fortheneedle irrigationgroup,irrigationbeganduringthe useoftheX-Gatesdrill.Thepulpchamberandcanalwere irrigatedbyusingaconventionalsyringeand30-gaugeHawe Max-i-Probeside-ventedneedle(DentsplyRinn).Atwo milli-litersflush of5.25%NaOCl over 30seconds wasused after each instrument,leavingthe canalfilled withirrigant and undisturbedfor60secondsbeforeusingthenextfile.During irrigation, the needle was inserted in the canal as deep apically aspossiblewithoutbindingandto fullWL.During irrigation the needle was constantly moved up and down (simulating macro-cannulus)from apicallybindingpointon dentinal wall to a point just below root canal orifice to properly improve apical irrigant replacement [44]. Once the MAF reached WL, the canal received irrigation with 10mL of 5.25% NaOCl over 30seconds. The irrigant was then left undisturbed for 60seconds. After a 60seconds passivewait,threeadditionalcyclesofirrigationwereused
(simulatingmicro-irrigationcycles).Eachcycleinvolved irri-gationwiththeneedleconstantlymovingin2mmamplitudes (simulating micro-cannulus): this alternating ‘‘up-down’’ movementevery6secondsbetweenfullWLand2mmshort oftheWL lasted30seconds,allowing18seconds ofactive irrigation directly at WL followedby a 60seconds passive waitduringwhatirrigantwasleftundisturbed.NaOCl(5.25%) wasusedinthefirstcycle.EDTA(17%)wasusedinthesecond cycle.NaOCl(5.25%)wasusedinthethirdcycle.Theirrigant wasaspiratedfromthecanalbyusinga30-gaugeopen-ended needle (NaviTip Ultradent, South Jordan, UT) that was placedatWL.
Controlgroups
a)EV-Cgroup(n=10):EndoVac-negativecontrol Inthisgroup,thesameprotocolforirrigationwasfollowedas inEVgroup,butonlysalinesolutionwasusedasanirrigant. b)NI-Cgroup(n=10):Needleirrigation-negative control
Inthisgroup,thesameprotocolforirrigationwasfollowedas inNIgroup,butonlysalinesolutionwasusedasanirrigant.
RootSectioningandScanningElectron
Microscope Examination
Uponcompletionof therespectiveirrigation protocol,the rootcanalswererinsedwith2.5mLofsterilesalinesolution percanaltodilutetheNaOClsolutionanddriedwithmultiple paperpoints.Additionally,shallow horizontalgrooveswere placedat5mmintervalsfromtheapicalforamenmarking theapicalthird,middlethirdandcoronalthirdofeachroot. Subsequently,therootsweresplitlongitudinallyina bucco-lingualdirection,resultingin20and40samplespercontrol and experimental groups respectively. Two longitudinal grooves,whichdidnotpenetrateintothecanal,were pre-pared along the buccaland lingual external root surface, using a narrow, pointed, high-speed tungsten carbide bur undercopiouswatercoolingto facilitatelongitudinal split-tingoftherootandtoexposetheinstrumentedcanal.Gentle tappingofanewrazorbladeplacedinoneofthegrooves, withtherootsecuredwithtwofingers,causedthesplittingof therootintotwolongitudinalhalves.
Bothhalveswerefixedin2%glutaraldehyde,dehydrated by using a graded series of ethanol solutions, mounted in aluminiumstubs,gold-sputteredandexaminedunder scan-ning electron microscope (SEM) (Autoscan Siemens, Erlan-gen,Germany)operatingat15kV.
SEMEvaluation
Micrographs for assessingthe efficacyof debris andsmear layerremovalweretakenat200Xand1,000Xmagnifications respectively,inthecoronal,middleandapicalpartsofthe canalwallsaccordingtoascaledevelopedbyHu¨lsmannetal.
[45].Thisfivestagescaleincludedadetailedverbal descrip-tionandavisualexample(i.e.aSEMphotograph)foreach gradation(1-5).Debriswasdefined asdentinechips, rem-nants of necrotic pulp tissue, and particleslying looseon thecanalwall.Thefive-level scoringsystememployedfor
assessingtheefficacyofdebrisremovalwas: 1,cleanroot canal wall, only very few debris particles; 2, few small conglomerationsofdebris;3,manyconglomerationsof deb-riscoveringlessthan50%oftherootcanalwall;4,morethan 50%ofthecanalwallcoveredwithconglomerationsofdebris; 5,completeornearlycompletecoverofthecanalwallwith conglomerations.Thesmearlayerwasdefinedasasurface filmof debris retainedon dentineor other surfaces after instrumentationwitheitherrotaryinstrumentsor endodon-ticfiles.Thefive-levelscoringsystememployedforassessing theefficacyofsmearlayer removalwas:1,smearlayeris completelyabsent.Mosttubulesarepatentanddebris-free (coronalthirdandmiddlethird)oroccludedwithsclerotic casts(apicalthird);2,smearlayercoveringlessthan25%of thecanalwall.Dentinaltubuleorifices,whenidentified,may be reduced in dimensions owing to partial or complete occlusion by debris; 3, homogenous smear layer covering the root canal wall and evident in 25%—50% of the canal surface.Onlyafewdentinaltubulesopen.Dentinaltubule orifices, when identified, may be reduced in dimensions owingtopartialorcompleteocclusionbydebris;4, homo-geneussmearlayerevidentin50%—75%ofthecanalsurface andtubules;no open dentinal tubules;5,heavy, homoge-neoussmearlayercovering75%—100%ofthecanalsurface andtubules.Asthelast2mmoftheapicalthirdofmostcanal wallswashighlyscleroticandthetubuleswereoccludedby scleroticcasts,scoringcouldnotbeconductedbasedonthe presenceorabsenceofpatentdentinaltubuleorificesonly.In thoseregions,assessment wasmadebased onwhetherthe scleroticdentinewascoveredbythesmearlayer.Theformer, even in the complete absence of dentinal tubules, still retainedtheanatomyofscleroticdentine.Thelattercould alwaysbediscernedbythepresenceofaflat surfacethat containsevidenceofinstrumentation.Foreachroothalf,10 images for debridement effectiveness and 10 images for smearlayer retention were takenfrom the coronal third, the middle third and the apical third (i.e. experimental groups:20imagesat200Xmagnificationthreelocations 60roots=3600images/20imagesat1000Xmagnification threelocations60roots=3600images).
The images were selected by an independent blinded operatorinarandomwalkmannerthroughthedefined sec-tions.Thereafter,theselected imageswere photographed, codedandrandomlymixed.Separateblindevaluationswere undertakenbyfourtrainedobserverswhowereblindedand wellversedintheinterpretationofSEMmorphology.
Separate evaluations were undertaken at each canal level.Whenagreement independentlyoccurredon ascore amongthefourexaminers,agreedscorewasrecorded.When discrepanciesexistduringthecourseofevaluation,a‘‘forced agreement’’betweenthefourexaminerswasused,sothat allexaminersagreedonthescoresforeachimagetakenfrom eachcanallevel. Intra-examinerandinter-examiner relia-bility and reproducibility for SEM assessment was verified using Kappa statistics to data, with a significance of 0.5. Statistical analysis of differences between groups with respecttodebrisandsmearscoreswasperformedbyusing theKruskal Wallisnonparametric analysis ofvariance, fol-lowedbyDunn’sranksumtestforpair-wisecomparisons.The Friedman’stest wasused toanalyze theresultsfromeach thirdofthesamegroup.Thelevelofsignificancewassetat p<0.05.
Results
TheCohen’skstatisticwasused toanalyzeintra-examiner andinter-examineragreementamongtheevaluators:kappa testresults,showedgoodtoexcellentreliabilityand repro-ducibilityamongthefourobservers,withallk-values0.9 forthedifferentgroupsandthedifferencebetweenmatched gradesneverexceeded1score.Debrisandsmearscoresof thethreeexperimentalgroupsandthetwocontrolgroupsat coronal,middleandapicallevelsare expressedas percen-tagedistributioninthefig.5(graphs5aand5brespectively). Examination of the surface of the rootcanal walls in the
EV-control andNI-control groups revealed its complete or nearlycompletecoverwithconglomerationsofdebrisanda heavyhomogeneussmearlayer(fig.6).
Examinationofthesurfaceoftherootcanalwallsinthe EVMgrouprevealedcleanrootcanalwallwithonlyveryfew debrisparticlesandfewsmallconglomerationsofdebrisand therewasnosmearlayeratall(fig.6).
Comparativeevaluationofdebrisandsmearlayerscores between groups at each level has been demonstrated in
Tables 1 and 2. The Kruskal-Wallis statistic showed that thesmearlayerandthedebrisscoresforalltheexperimental groups weresignificantly different from those for thetwo control groups (p<0.001). The Dunn’s rank sum test showed nosignificantdifferences(p>0.05)amongallthe experimentalgroupsattheapicalthirdwithrespecttothe debrisscores.Nonetheless,significantlybetterresultswere obtainedforthecoronal(p<0.001)andmiddle(p<0.01) areasinEVMgroupthaninEVgroup.Furthermore,therewas no statistically significant differencebetween NI andEVM groups (p>0.05) at the coronal and middle levels, but significantly more debris were removed from the coronal (p<0.001)andmiddle(p<0.001)areasin NIgroupthan in EVgroup.EVMtechnique performedsignificantly better thanEVtechnique(p<0.001)atalllevelswithrespectto removalofthesmearlayer.Moreover,EVMprotocolresulted insignificantlymoresmearlayerremovalthanneedle irriga-tionatthecoronal(p<0.05),middle(p<0.001)andapical (p<0.001)levels.Forthecoronalregion,significantly bet-terresults(p<0.001)weredetectedinNIgroupthaninEV groupwithrespecttosmearscore;nosignificantdifference (p>0.05)betweenNI andEVgroups wasobservedat the middlelevel.
Significantly more residual smear layer than in the EV group(p<0.001),withscoresof3-5,wasobservedatthe apical level in the NI group. The differences among all thirds of the same group, analyzed statistically by using theFriedman’stestareillustratedinTable3.
Discussion
Inthepresentstudycleansinganddebridementefficacyof three different irrigationregimens, inthecoronal, middle andapicalthirdsofrootcanalwallswereinvestigatedusing SEMmicrographs,separatelyfordebrisandsmearlayer,and the scoring system proposed [45]. The use of an ex vivo closed-endcanal modelmore accuratelysimulates in vivo situations, inwhichthetooth’sforamenandoutersurface are sealed by the periodontal ligament and further embeddedinalveolarbone[5,34].
A new protocol for ANP irrigation (EVM) with EndoVac system(DiscusDental,CulverCity,CA,USA)wasevaluated in comparison with EndoVac according to manufacturer’s instructions and needle irrigation. For the EVM group macro-irrigation began during rotary instrumentation, betweeneachinstrumentchangebyusingatthesametime MDT on pulp chamber and macro-cannulus into the root canal, placed up to the apically binding point without ‘‘up-down’’motion;oncetheMAF,reachedWL,the micro-cannulusreplacedmacro-cannulusanda3cyclessequenceof micro-irrigation started at WL; the micro-cannulus was constantly left at WL without ‘‘up-down’’ movements.
Figure 5 Percentage distribution of debris scores (a) and smearscores (b)at coronal(A,D,G,J,M), middle (B,E,H,K,N) andapical(C,F,I,L,O)levelsinNIgroup(Needleirrigation/ 30G-Max-I-Probeside-ventedneedle)(A-C),EVgroup(EndoVac Sys-tem) (D-F),EVM group(EndoVac /modified technique) (G-I), EV-Cgroup(EndoVac-negativecontrol)(J-L),NI-Cgroup (Nee-dleirrigation-negativecontrol)(M-O).
An isolated observation of the coronal and middle thirds displayedthattheEndoVacsystem(EV)wassignificantlyless effectivethanneedleirrigationindebrisremovalwithonly 8.33%and38.33%ofthecoronalimagesand6.67%and56.67% ofthemiddlemicrographsshowingscores1and2 respecti-vely.Theintroductiondepthofcannulastipsandthedistance to thedentinal wallseemtoplayan importantroleinthe removal of debris, reinforcing the benefit of the physical flushing action [29]. Boutsioukis et al. [46] found that increasing theapicalpreparation sizeortaper of theroot canalfurtherthanacertainvaluemightinfactdecreasethe debridementefficacyofneedleirrigation,becausethe aver-age velocity andthe wall shearstress decrease. A similar finding has been reported in a previous study simulating
irrigantflowinrootcanalswith differentapicalsizes[47]. The larger distance of the cannulas and their tips to the dentinalwallsinthecoronalandmiddlethirdsmighthavean effectonthemechanicaldebridementinthesesectionsof theRCS.Thecloserdistanceofthecannulasandneedle,and their tips to the dentine walls in the apical third might explaindebrisscoresinthissectionoftheRCS.The Fried-man’s statistic confirmedsignificantly better performance (p<0.001)oftheEndoVac system(EV)at theapicalthird thanatthecoronalandmiddlethirdswithrespecttodebris score.Whenmacro-irrigationbeganearlyduring instrumen-tation(EVM protocol),itprovided significantlymore effec-tivedebris removalinthecoronalandmiddleregionsthan in EV group, with 100% and 90% (respectively) of SEM
Figure 6 Scanning electron microscopy (SEM) images of the cleaned and shaped canal walls (Scale=20mm;Mag=1.00K X; EHT=15.00kV)takenfromcoronal(A,D,G,J,M),middle(B,E,H,K,N)andapical(C,F,I,L,O)thirdsforNIgroup(Needleirrigation) (A-C),EVgroup(EndoVacSystem)(D-F),EVMgroup(EndoVac-modifiedtechnique)(G-I),EV-Cgroup(EndoVac-negativecontrol)(J-L), NI-Cgroup(Needleirrigation-negativecontrol)(M-O).
micrographsshowing score 1 andno significantdifference betweenmiddleandapicalthirds.Susinetal.[41]suggested thatthedifficultyingettingirrigatingsolutionstoreachthe isthmusandtocreateastrongenoughcurrenttoflowthrough theisthmusbetweencanalscouldexplainwhyANPirrigation didnotcompletelyremovedebrisfromtheisthmusregionsin aclosedcanalsystem.Itshouldbenotedthatdebrisremoval iscertainlymuchmoredifficultinthenarrowisthmusregions
than in the instrumented canals, since this complicated morphology renders it extremely difficult for the delivery ofalargevolumeofirrigantwithahighflowrateevenwith theuseoftheANPtechnique. Itispossibletoassumethat ANP irrigation performed following EVM protocol could improve debridement efficacy into uninstrumented areas ofRCS.
No significant differences were detected in debris removal amongNI apical, EVapical,and EVMapical sub-groupswithmostoftheSEMimagesshowingscore1(19.2%, 23.33%,20% respectively)and 2(77.5%,70%,80% respec-tively).Itispossibletoassumethatapicalsizeandtaperof therootcanalresultsinasufficientincreaseinthe cross-sectionalareaoftheannulusbetweentheneedleor cannu-lasandtherootcanalwalltosupplyadequateirrigantflow rate totheWL withoutblockingthe backflow. Itmust be emphasized that the disruption or detachment of debris cannot ensure their removal unless there is a favorable irrigantflowtocarrythemtowardthecanalorifice(reverse flow)[47].Althoughnoconsensusexistsregardingthe mini-mumapical preparation sizeor taper, instrumentationto size ISO #35 or #40 resultsin clinically adequateirrigant volume amounts for both positive and negative pressure systems [48]. Followingthe manufacturer’s recommenda-tions,anISO#35wasconsideredtobethesmallestapical sizetoeffectivelyallow irriganttopasscircumferentially aroundthe0.32mmmicro-cannulus.Anincreaseinsizefrom ISO#35toISO#40resultedinapercentagegainof approxi-mately44%inmeanirrigantvolume[48].Astheapicalsize increasestoasizeofISO#40,thereisadecreasedchanceof suction holes, along the side of the last 0.70mm of the micro-cannulus,contactingtherootcanalwalland becom-ingblocked.Also,theconcomitantandmorepotentcoronal aspirationwiththeMDTcompeteswiththemicro-cannulus forfluidevacuation.
For the EV group, the micro-cannulus was placed in sequence at WL for 6seconds, 2mm short of the WL and backtotheWLandsoon:thisalternatingmovementallows fortheremovalofmicro-bubblesofammoniumandcarbon
Table1 Dunn’sranksumtestformultiplepair-wise com-parisonsofdebris scoresfor needleirrigation(NI)and ANP irrigationwithEndoVacsystemaccordingtomanufacturer’s instructions(EV)andtoanewprotocol(EVM).
Subgroups*
pvalue (NICoronal)a versus (EVCoronal)b p<0.001
(EVMCoronal)a (EV-CCoronal)c
(NI-CCoronal)c (NIMiddle)d versus (EVMiddle)e
(EVMMiddle)d (EV-CMiddle)f
(NI-CMiddle)f (NIApical)g versus (EVApical)g
(EVMApical)g
(EV-CApical)h (NI-CApical)h
Significancelevelofa=0.05;*Subgroupswithsamesuperscript are not statistically significant (p>0.05); EV-C: EndoVac-negative control; NI-C: Needle irrigation-negative control; ANP:apicalnegativepressure.
Table2 Dunn’sranksumtestformultiplepair-wise com-parisonsof smearscoresforneedle irrigation(NI)and ANP irrigationwithEndoVacsystemaccordingtomanufacturer’s instructions(EV)andtoanewprotocol(EVM).
Subgroups*
pvalue (NCoronal)a versus (EVCoronal)b p<0.001
(EVMCoronal)c (EV-CCoronal)d (NI-CCoronal)e
(NIMiddle)f versus (EVMiddle)f
(EVMMiddle)g (EV-CMiddle)h
(NI-CMiddle)h (NIApical)l versus (EVApical)j
(EVMApical)k (EV-CApical)l
(NI-CApical)l
Significancelevelofa=0.05;*Subgroupswithsamesuperscript are not statistically significant (p>0.05); EV-C: EndoVac-negative control; NI-C: Needle irrigation-negative control; ANP:apicalnegativepressure.
Table3 Statisticalanalysisofdifferencesamongallthirds ofthesamegroup(Friedman’stest).
Groups CvsM CvsA MvsA NI debrisscores *** *** * smearscores *** *** *** EV debrisscores ** *** *** smearscores ns ns *
EVM debrisscores *** *** ns
smearscores ns * ns
EV-C debrisscores ns ns ns
smearscores *** *** ***
NI-C debrisscores *** *** us
smearscores *** *** ***
C: coronalthird;M:middle third;A: apicalthird;significance levelofa=0.05; *:p<0.05; **:p<0.01; ***: p<0.001;ns: p>0.05.
dioxideresultingfromthehydrolysisoforganictissue.Inthe apicalthirdthesemicro-bubblescouldisolateresidualtissue from further contact with hypochlorite, adhering to the dentinal walls, the micro-cannulus and tissue remnants. AstheapicalsizeincreasestoasizeofISO#40,thelarger area surrounding the micro-cannulus also allows for increasedvolumeofirriganttothemicro-cannulustipand increased wall shear stress [48]: ‘‘up-down’’ movements becomeunnecessary.
Concerningcoronallevel,theneedleirrigationachieved significantlymoresmearlayerfreecanalwallsthanEndoVac System (EV) with 60% and 40% (versus 8.3% and 40%) of micrographsshowingsmearscore1and2respectively,with a trend toward better smear layer removal in the middle thirdtoo(19.17%and55%versus10%and50%oftheimages showingscore1and2respectively).Itmightbespeculated thatthecoronal andmiddlethirds are flushedmoreoften withNaOClduringtheclinicalprocedure,resultinginbetter debridementandsmearremovalcoronally.IntheEVgroup, onlyafterreachingWLwiththeMAF,macro-irrigationwith the EndoVac was accomplished. Sodium hypochlorite was thenusedtoreplenishtheirrigantonlyinthepulpchamber after each rotary NiTi instrument, injecting fresh NaOCl down the canal, since fresh NaOCl was dynamically exchanged throughout instrumentation. When the instru-mentisremovedcoronally,accordingtoArchimedean prin-cipleoffluiddisplacement,theNaOClfromthepulpchamber shouldreplaceit[49].Thisconstantexchangewouldnegate the need for injecting fresh NaOCl down the canal. It is possibletoassume thatuponcompletionofallrotary pre-parations,therootcanalscouldbeclean,butnotenoughto alloweffectivedebrisandsmearremovalattheendofroot canal treatment. The micro-hurricane of NaOCl created insidetheRCSbyusingthemacro-cannulus,couldcreatea pressure-washing effect alongthe dentinal wallsnot suffi-cient to ensure effective flushing action of irrigants and macrodebrisevacuation.
Abarajithan et al. [40] showed that ANP irrigation and conventionalirrigation wereequally effective in removing smearlayerfromthecoronalandmiddlethirdsoftheroot canals, while in the apical third the Endovac system per-formed significantly better than needle irrigation. Their results are questionable because apical size preparation wasin theirstudystandardizedtoISO size#60 toimprove theirrigantflowintoopen-endrootcanals.Thedifferencein smear layer removal at all levels between EVM and EV protocolswasstatisticallysignificant(p<0.001),andboth techniquesperformedsignificantlybetterthanneedle irriga-tionintheapicalregion(p<0.001).Apossibleexplanation ofthisfindingisthatpositivepressureirrigationmightfailto avoidvaporlockeffectinaclosedcanalsystem,thatmore accuratelysimulateinvivoapplicationofirrigants,withless effectivecontacttimebetweenirrigantsanddentineinthe apical third. Vapor lock that results in trapped air in the apical third of root canals might hinder the exchange of irrigantsandaffecttheirdebridementefficacy[32].
Parenteetal.[50]reportedthatANPirrigationcan over-comethefluiddynamicschallengesinherentinclosedcanal systems,producingcleandentinalsurfacesinclosed-endroot canals instrumented to size #40/.06 taper. The EndoVac system’seffectivenessinproducingcleandentinalsurfaces may beattributed to its ANPapproach. Placement of the
macro-cannulusatmiddle-apicalthirdofthecanalfollowed bytheplacementofthemicro-cannulusdirectlyattheapical endenablesanirriganttobesuctionedinsufficientvolume andflowto displacedebrisandremovesmearlayer. Addi-tionally,theorificesofthemicro-cannulusprovideaportalof exitforcanaldebrisinclosed-endcanalsystems.Inourstudy, rootcanalpreparationtofinalsize#40/.04taperwas esti-mated[48]torepresentagoodbalance oftoothstructure preservationandadequatevolumeofirrigationattheapical thirdwhenusingtheANPirrigationsystem,sinceanincrease inpreparationtaperfromsize#40/.04tapertosize#40/.06 taperresultedinvolumepercentagegainofonly5.4%[48]. ThenegativepressureirrigationaccordingtoEVMtechnique performedsignificantlybetterthanEndoVacsystem(EV)also attheapicallevel(p<0.001):thisfindingmightbe attrib-utedto30secondsofactiveirrigationfor‘‘microcycle’’with micro-cannulus constantly placed at full WL, providing a supportiveeffect on smearlayerremoval. The Friedman’s test confirmed almost uniform high effectiveness for EVM protocolthroughoutrootcanalswithrespecttosmearscore, with no significant difference between middle and apical thirds (p>0.05) and between coronal and middle thirds (p>0.05). The resultsobtained from this study rejected thenullhypothesis.Underlaboratoryconditionsboth nega-tiveandpositivepressureirrigationswithNaOClandEDTAas irrigants, showed no statistically significant difference in antimicrobialefficacyagainstE.faecalis[51,52],confirming that deep disinfection depends on penetration ability of irrigantsintodentinaltubules.
Negative pressure irrigation may improve irrigants volumes,intimacyandtimeofcontactwithrootcanalwalls, especiallyintouninstrumentedareasoftheRCS,enhancing surfacedebridementanddisinfection:itwouldbeofinterest tooptimizeexposuretimeandvolumeforrootcanalirrigants balancingdebridement anddisinfectioneffectiveness with respect of the structural and mechanical properties of dentine.
Conclusions
Under the conditions of the present study, ANP irrigation showedsignificantlybetterperformanceinremovingsmear layercomparedwithneedleirrigationintheapicalthirdof RCS. A new irrigation protocol by using EndoVac System resultedinbetterremovalofthesmearlayerthanEndoVac systemusedaccordingtothemanufacturer’sinstructionsand needleirrigation,at alllevels,inasimulated closedcanal system.Furtherresearchisneededtoconfirmourresultsin curvedcanalsandto determinewhetherthisdifferencein remainingcanaldebrisaffectsclinicalsuccess.
Clinicalrelevance:Althoughinstrumentsremovemostof thecanal contents in the main rootcanal area, irrigation playsanindispensableroleinallareasoftheRCSinaccessible forinstrumentation.Oneofthemostfavorablefeaturesof irrigantsistheirflushingaction.Anewirrigationprotocolby usingEndoVacSystemcouldensureapressure-washingeffect alongthedentinalwallssufficienttoalloweffectiveflushing actionofirrigantsatalllevels.Moreoveritcouldproducea strongenoughcurrenttoflowthroughtheisthmusbetween canalsdeliveringlargevolumeofirrigantswithahighflow rateandallowingeffectivemacrodebrisevacuation.
Conflict
of
interest
The authors deny any conflicts of interest related to this study.
Appendix
A.
Supplementary
data
Supplementary dataassociated with thisarticle can be found,intheonlineversion,athttp://dx.doi.org/10.1016/ j.gien.2012.09.001.
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