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1 ROOTCANALTREATMENT:ACLINICALGUIDEFORDENTALSTUDENTS, GENERALDENTISTSWHOLIKEDOINGRCTSANDGENERALDENTISTSWHOHATEDOINGRCTS©2016 GregY.Kim,DDS Diplomate,AmericanBoardofEndodontics Thisdocumentisintendedasaneasy-to-readguidefordentalstudentsandgeneralpractitionersofdifferent clinicalcapacitywhoseektoimprovetheirrootcanaltreatmentskillsandobtainamoreconsistentlypredictable outcomeintheireverydaypractice.Doingarootcanaltreatment(RCT),forthemostpart,isnotacomplicated taskandtheprocedureshouldbecomeeasierandmoresystematicasthecliniciangainsmoreexperience.There are,however,differentcomponentsofdevelopmentinbecomingamoreskilledclinician,andbecoming technicallygoodisonlyoneaspectofit.Inordertobetrulyproficientinthisfield,aclinicianmustalsoimprove his/herdiagnosticskillsandunderstandingofitsbiologicalprinciples.Thisguideisdividedintodifferenttopicsand subtopicswhicharedeemedimportantforunderstandingofthosefundamentalendodonticprinciples. DIAGNOSIS Gooddiagnosticskillsareundeniablyimportantforbettermanagementofendodonticcases.Dayinanddayout, weseeawholeslewoferrorsassociatedpoordiagnosis,whetheritbeprescribingwrongmedicationsor treatment-planningforawrongprocedure.Theimportanceofthisfirststepoftreatmentcan’tbestressed enough.Startingoutwithagooddiagnosisattheonsetcanreallysparethedentistofunnecessaryheadaches duringfollow-upphase.Forthepurposeofthisguide,differentpulpalandperiapicaldiagnosesarenotgoingtobe discussedcomprehensively,butsomeofthemostcommonerrorsassociatedwitheitherdoinganerroneous diagnosisorNOdiagnosisdeserveadiscussionhere. o PrescribingAntibioticsforPulpitis Pulpitisbydefinitionisaninflammationofthepulptissueandcouldbeexceedinglypainfulunderacute inflammatoryconditions.Forpainrelief,eitherthisinflamedpulptissueneedstoberemovedorthe toothneedstoberemoved.Whenthepulpisstillvitalandinflamed(note:blooduponaccessopening), takingantibioticsactuallydoesnothingforpainreliefandonlyaddsthehassleofhavingtotake medicationsformultipledaysforanalreadydistressedpatient.Forantibioticstobeeffectiveatreducing symptoms,thepulphastobenecroticandinfectedforthemostpart(note:absenceofbloodupon enteringpulpspace).Now,ithastobenotedthatpercussionsensitivitycouldpresentwithbothvitaland nonvitalpulp.But,ingeneral,thecaseswhereantibioticscanworkforpainreliefdonotrespondto thermalstimuli(endoice,hotcoffee,etc.)butinsteaddisplaymarkedpercussionsensitivitythatcanbe localizedbythepatient.Tendernessofsofttissueinthevestibuleneartheapicesoftheassociatedtooth maybepresentaswell.Ontheotherhand,ifapatient’schiefcomplaintishavingseverepainupon drinkingsomethingcoldorhot,donotgivethatpatientantibioticsforthepurposeofaddressingthat 2 chiefcomplaint.Atleastdoapulpotomyifyouhavetime,orfindanendodontistwhocanprovidean emergencytreatmentforyou.Besuretodoathoroughdiagnosisasmanypatientswillpresentwitha tooththatisnecroticandinfectedbutwillalsocomplainofthermalsensitivityfromadjacentteethas well.Thekeyistoaddressthetooththatisthemaincauseofacutesymptoms. o NotInstrumentingtheCanalsforaNecroticToothwithInfectedRootCanals Thisisanothercommonerrorcommonlyencountered.Whenpulpalinflammationprogressesandthe pulpbecomesnecrotic,fullinstrumentationofthecanalsisrequiredtoeliminatetheinfectionandreduce symptoms.Anecrotictoothhasinfectioninthecanals,themostcommoncauseofwhichisbacterial insultfromcaries.Thesepatientscanpresentwithswollengumsand/orface.Instrumentingtoatleast size30/04withagoodamountofsodiumhypochloriteirrigationisrecommended.Otherwise,givethe patientantibiotics(oryoucandoboth)andthepatientwilltypicallyseereliefofsymptomswithinaday ortwo. Diagnosisdictatestreatments:A8-year-oldboypresentedwithanexposureof#9fromtrauma.Patient’shistoryofchiefcomplaint anddiagnostictestsindicatedthatthepulpwasstillinareversiblestateofinflammation.Thetoothstructureimmediatelyadjacent tothesiteofexposurewascleanedoutwithasmallroundburanddisinfectedwithsodiumhypochlorite.Thisareawascappedwith aBioceramicPuttymaterialandthepatientwasreferredbacktothegeneraldentistforacompositerestoration.A9-monthfollowupshowed(despiteforeshorteninginthefirsttwox-rays)thatthetoothmaintaineditsvitalityandcontinueditsnormal development.IfRCThadbeendonewithoutproperlydiagnosingthestateofthepulpandtheperiapex,thetoothwouldhave st nd stoppeditsnormaldevelopmentandwouldhaveresultedinaclinicallymorecomplicatedsituation.(1 x-ray:Preop,2 x-ray: rd ImmediatePostop,3 x-ray:9MonthFollow-Up) ANTIBIOTICS o Thego-tomedicationforanodontogenicinfectionisPenVK500mg(bactericidal,narrowerspectrumof actionthanamoxicillin,taken4timesperday).Forpatientswithamoxicillin/penicillinallergy, Clindamycinshouldfirstbeconsidered. o Forpatientswithalarge,noticeableswelling:Refertoanoralsurgeonifnottotallycomfortabledealing withthesituation.Ifyougive2differentantibioticstogether,themosteffectivecombinationwouldbe2 bactericidalantibiotics,suchasPenVKandmetronidazole.Acombinationofbactericidaland bacteriostaticantibiotics(suchaspenicillinwithclindamycin)maycounteracttheeffectivenessofeach otherandmaynotbeashelpful. 3 THETREATMENT:STEPBYSTEP Beforeinitiatinganytreatment,takealong,closelookatthex-rays.Mostoftheworstexperiencesassociated withrootcanalprocedures,byyouandbythepatient,canbeavoidedbychoosingNOTtodothemost complicatedcases.Olderpatientshaveahigherlikelihoodofpresentingwithcalcifiedcanalsandmaynotbeable totoleratelongertreatmentsessionsatthesametime.Ifyouhavedifficultydiscerningthecanalsdueto calcification,itmaybeadvisabletorefertoaspecialist.Lookingatbitewingx-raysaswellasperiapicalscanalso giveyouadditionalinformationastowhatkindofdifficultyleveltoexpect. o Access Agoodaccesscanfacilitatetherestoftheprocedure.Apooraccess,bythesametoken,canmakethe proceduremoredifficultthanneeded.Studythebitewingx-raybeforepickingupahigh-speedhandpiece togaugehowmuchyouhavetogodowntobeinthepulpchamber.Itshouldalwaysberemembered thatthepulpchamberdepthislargestontopofthebiggercanals,meaningthatitwouldbeeasierto exposethispartofthechamberfirstandthenpeelawayfromhere.Forexample,foruppermolars,it’s easiesttoexposethepalatalcanalfirstbecauseit’sthelargestcanalwiththemostamountofcoronal chamberspaceontopofit.Asyoupeelawaytheroofofthepulpchamber,adarkpulpalfloorreveals itselfandtheothercanalsarefoundattheouteredgesofthisdarkerfloor.Italsohelpstoremember thatthepulpchamberiscenteredandconcentricwiththetoothoutlineattheleveloftheCEJ.Makea habitoflookingattheCEJoutlineandenvisioningthepulpchamberatthecenterofthiscrosssection. Doingthisoccasionallywhileaccess-preppingcanhelpyougetreorientedifyouaredrillinginawrong direction.Caution:ThisinformationregardingtheCEJmaybedistortedincrownedteeth. o MeasuringWorkingLength Theveryfirstfilesplacedinacanalmustalwaysbepre-curvedwiththesmallestpossibleradius.That is,all10andK15fileshavetobecurved(thereareinstrumentsspecificallyusedforthispurposebutifyou don’thavethose,acollegeplierwilldo)atthetipinordertonegotiatearoundthecurvatureofthecanal andtopreservethatnaturalcurvaturewiththeleastamountoftransportation.Thiscurvingofthetipof asmallfileisutterlyimportant.Oncethetipofasmallfileiscurved,itisplacedinthecanalandgently workedwithacircumferentialwatch-windingmotionuntilitisabletoreachtheapex.Itisimportantto rememberthat,inyourendeavortogettotheapex,thecircumferentialwatch-windingmotionmay provetobemuchmoreeffectivethanastraightup-and-downfilingmotion.Fornarrowercanals,you maynotbeabletoreachtheapeximmediately.Thegoalistoworkyourselfdownincrementally withoutdistortingthecanalanatomy.Whenyouaresuccessfullyworkingyourselfdowntoreachthe apex,thecanalfeelsstickyandthisisagoodindicationthatyoucancontinuetocarefullyworkyourself 4 downtoestablishthelength.Acanalthatnolongerfeelsstickybutfeelslikeahardwallindicatesthat youcouldbetransportingthecanaloutofitsnaturalcurvature(orafilehadseparated).Ifyounolonger feelthestickinessofthecanal,backstepforonesecond,takeadeepbreath,anddothefollowingthree things:openupthecoronalpartofthecanal,irrigatecopiously,andpickupthesmallestfilethatyouhave available(K6orK8)andagaingiveitasmallcurveatthetip.Placethesmallfileinthecanalwhilekeeping aneyeonitasK6andK8filesareverydelicateandwillcrimpleeasilyifyouhitanyotherhardsurface whiletryingtoplacetheminthecanal.Onceitisinthecanal,gentlykeeprotatingthembackandforth toseeifyoucanfindthestickyspotagain.Virtuallynoapicalpressureisneededwhiledoingthis.Oncea stickyspotisfound,youmayhavetokeepworkinginthesamemannerwhilefrequentlyirrigating.Again, thesmallfilescanseparateeasilyinanarrowcanalifhandledcarelessly,anditmaybewisetoinspect themfrequentlyandtogothroughafewoftheminsteadofusingoneuntilitseparates. AK15filecurvedwithasmallradiusofcurveatthetip (left-useful)andwithalargeradiusofcurveatthetip (right-notasuseful).ALLsmallfiles(6,8,10,15)mustbe pre-curvedwithasmallradiuscurveatthetip.Afile shouldnotbebentwithalargeradiuscurveliketheone shownontherightbecausecurvingafilethiswayhas onlylimitedbenefits. o Coronal/OrificeWidening Howweachievethiscoronalwideningofthecanalhaschangedsomewhatovertheyears.First,the rationaleforcoronalcanalwidening:Insmallercanals,openingupthecoronalportionofthecanal allowsyoutoreachtheapexmoreeasily,againwithlesstransportationinthecriticalapical1/3ofthe canal.Inotherwords,youaremorelikelytopreservethenaturalcanalanatomywhenthecoronal portionofthecanalhasbeenopenedupfirst.Inlargercanalswhereyouareabletoreachtheapex easily,orifice/coronalcanalwideningisactuallynotthatsignificant.Itmustbepointedoutthatthegates gliddenisnolongerroutinelyusedforthispurpose,atleastbytoday’seducators’standards.Therearea numberofstudiesintheliteraturethatshowedremovingexcessivetoothstructurefromthecoronalpart ofthecanalcanreducetheresistancetofracture.Obviously,thereisnogoodreasontoremovemore toothstructurethannecessaryespeciallywhenit’smorelikelytoleadtoamoreadverseoutcome. Personally,Iseldomusethegatesglidden,andIonlyuse04taperrotaryfiles,evenforcoronalflaring. 5 • AdvancedTip:Incorporatingsomedegreeof“crown-down”techniquemaygiveyoubetterresultsin manycases.Iusuallypickupabiggerrotaryfile,suchasa40/04ora35/04file,toinitiatecrown downformostofmycases.ThisisactuallydoneevenbeforeImeasuremyworkinglength.Knowing thatthemajorityofrootcanalworkinglengthsfallunder19mm-22mmrange,Iwillusetherotaryina crown-downfashion,startingwitha40/04andthenusinga35/04anda30/04toabout15-16mms downthecanal.Imeasuremylengthatthispoint,hand-filealittlebitandthenbegintherotary instrumentationatfullworkinglength.Thisislistedasanadvancedtipbecauseyouhavetobefully proficientatdoingRCTsbeforeyoucaneffectivelytakeadvantageofthistechnique.Choosingthe rightsizerotaryfiletoinitiateyourcrown-downisajudgmentcallasyourinitialfilesizemaybe differentforeachcase.Youhavetohavebuiltsomespeedintoyourtreatmentsandalsohavetobe abletoperceivewhentochangetherotaryfiletoasmalleronewhilegoingdownapicallywhenthe rightamountofresistanceismet. #19is26mmslong.Workinglengthwasmeasuredaftercoronalhalfofthecanalshavebeenopenedupwithrotaryfiles. Managementofcurveintheapical1/3wouldhavebeenmuchmoredifficultwithoutfirstinstrumentingthecoronalhalfofthe canals. #19and#3RCTcasesondifferentpatients.Notepreservationoftoothstructureandnaturalcanalanatomy.Apreviouslydone#18 showsextensivewideningofthecoronalportionofthecanalswithgatesgliddenandstraighteningofthecanals.#3isaheavily calcifiedcase.Instrumentationwasdoneusingthecrowndowntechniquealongwithcarefulnegotiatingwithsmallcurvedfiles. o Instrumentation Thegeneralruleistohand-instrumenttosizeK15beforeswitchingtorotaryfiles.Oneofthemost disturbingexperiencesapractitionerdoingaRCTcanhaveistohaveaseparationofafile.Toprevent thismishapandotheriatrogenicerrors,itisimportanttorememberafewthings.First,alwayshavesome formoflubricationsuchassodiumhypochloriteorRCPrepinsidethecanal.Continuousinstrumentation insideadebris-filleddrycanalcanbeamaincauseofallsortsoftroubles.Second,justlikethehandfiles, 6 ifyouarenotgettingtothemeasuredlengthinoneattemptwitharotaryfile,thenthelengthshouldbe attainedincrementally.Thismeansremovingthefilewhenresistanceismet,irrigating,andwipingthe fileswithanalcohol-soakedgauzetoremovethedebrisstuckintheflutesofthefile.Sometimes irrationalitycouldtakeoverandwecanpushalittletoohard(It’sFridayafternoon,4:30PMandyouhad alatestartwiththelastcaseofday)inanattempttoreachtheworkinglengthquickly,butdoingsocan inevitablyresultinaseparatedfileatsomepoint. • Oneofthegreatbutlesstalkedaboutbenefitsofamodernendodonticrotaryinstrumentisthat itremovesdebrisfromthecanalasitrotatesclockwise.Observethefiletoseeifitis accumulatingtoomuchdebrisintheflutesandwipethemofftopreventgeneratingexcessive torqueandstress. • Theeffectofalarge-taperinstrumentisnotawellunderstoodconcept.Wetypicallyassociate increasedstiffnessanddecreasedflexibilityofarotaryfilewiththeincreaseintipsizeonly.That is,wesaythatsize30isstifferandlessflexiblethansize25becauseitisbigger,andsize40isless flexiblethansize35,andsoon.Butincreasingthetaperoftheinstrumentcanalsohavea dramaticnegativeeffectontheoverallflexibilityoftheinstrument.Thus,an06taperfileis muchstifferandlessflexiblethanan04taperfile,andbecauseofthatinflexibilityitmaynotbe abletogetintosomecanalsthatan04taperfileofthesametipsizecan. • OnEfficientInstrumentation,RPM,andContactTime:Anargumentcouldbemadethatusinga rotaryfileatahighRPM(>500)isdangerousforlessexperiencedclinicians.Anargumentcould bemadethatusingarotaryfileatalowRPM(<300)isalsodangerousforlessexperienced clinicians(whichprobablyindicatesthatwhat’sdangerousistheperson).Itisoftenoverlooked howusingahigherRPMcandramaticallyincreasethecontacttimeoftheinstrumentwiththe wallsofthecanal,butthisisanotherimportantconcepttounderstand.Astraightfileinserted intothecanalwantstostraightenitselfinsideacanal.Thisishowtransportationofthecanal occurs.Therefore,inordertominimizetransportation,afile’scontacttimewiththewallsof thecanalshouldbekeptasminimalaspracticallypossible.Thus,whenafilehasdoneitsjobof reachingtheapex,thecanalshouldbeirrigatedtoremovedebris,andthenextlargerfilesize mustbeused.Thereisatendencyforlessexperiencedclinicianstorepeatedlyinstrumentthe canals,overandover.Thishabitisespeciallydeadlywhentherepeatedinstrumentationisdone underahighRPM,asthemostcommonundesirableoutcomewouldbeeitheraseverely transportedcanalorablown-outapex. 7 o InstrumentationSize Thisisanareaoffiercecontroversyandtherearevaryingopinionsabouthowbigacanalneedstobe instrumentedto(IoncehadarepfromthelargestdentalproductcompanyintheUSaskmewhyI instrumentthecanalstocertainsizes).Onethingthatmostendodontistsdoagreeon,however,isthat theirrigantmustbeabletoreachtheapextoremovedebrisanddisinfectthecanals.Asmallcanal (instrumentedtosize25/04orsmaller)maynothavetheirrigantreachthecriticalapical1/3ofthecanal andalsomaybedifficulttofillproperlyinsomecases.Conversely,inaheavilyinfectedrootcanalsystem itmaybenecessarytoinstrumentthecanalstoabiggersizethanwhenthepulpisstillvital(vitalmeans sterile).Thefollowingisalistofmyusualinstrumentationsizesasofthiswriting: • UpperCentrals:45/04or50/04 • UpperLaterals:35/04or40/04(Thistoothhasanapicaldistolingualcurvethatisoftentimes mismanaged,leadingtomanyfailedtreatments.) • LowerIncisors:30/04,35/04,or40/04(Consideredthemostdifficulttoothbysomespecialists) • AllCanines:40/04or45/04 • SingleCanalPremolars:Atleastsize40 • TwoCanalPremolars:30/04or35/04 • MesialCanalsofLowerMolars:30/04or35/04 • DistalCanalsofLowerMolars:40/04or45/04 • MBandDBofUpperMolars:30/04or35/04 • PalatalofUpperMolars:40/04or45/04 • Thisis,ofcourse,alooseguideline.Afinaldecisiononthesizeofinstrumentationismadewhile thecanalsarebeinginstrumented.Insomerarecases,averylargecanalwithalongstanding infectionandaresorbedrootendmayhavetobeinstrumentedtoevenhigherthansize50. Somecanalswithwickedcurvesmaynotbeabletobeinstrumentedtoanythingbiggerthansize 25.Atanyrate,itisimportanttorememberthatthediscussionofapicalsizeshouldbecarried outalongwithaconsiderationfortheinstrument’staper.Afilewithasize25tipand08taper wouldbemoreaggressiveinremovingrootdentinthanafilewithasize35tipand04taper.It mustbenotedthatlargetaperinstruments(06orgreater)removemoredentinfromthecoronal halfoftheroot,whichunnecessarilyweakenstheroot. 8 Anupperlateralincisorwithalongstandinginfection.Thebluntedroottipindicatesrootresorptionandlackofanatural constrictionattheapex.Size45/04guttaperchashowsthatitmaynotcreateanadequateapicalseal.Thecanalwastakento size70usingaLightSpeedsystem(0taper,parallelinstrument)andfilledwithamatchingSimpliFillguttaperchaobturator. Alternatively,theapical1/3ofthecanalcouldhavebeenfilledwithMTA. o RootFilling/Obturation Verticalcompactionofguttaperchausingaheatedpluggerandbackfillingwiththermoplasticgutta perchahasbecomemoreorlessthestandardobturationtechniqueovertheyears.Thebasicpremiseof thistechniqueisbasedoncreatinga“smallapex”andacontinuouslytapered,flaringcanalusingalarge taperedinstrument.Thosetwoprinciplesaboutcreatinganapexassmallaspossibleandinstrumenting thecanalwithacontinuouslytaperedinstrumentrepresentthe“inborn”characteristicsofthisvertical compactiontechniqueatitsorigin.However,inpastandpresent,thisparticularobturationtechniquehas hadasomewhatunfortunateinfluenceontheoveralldesignofrotaryinstruments(smalltip, larger/progressivetaper)inthemarket.Itmustbepointedoutthatthisisprobablytheoppositeofwhat weshouldbethinking,becauseourfirstpriorityindoingarootcanaltreatmentshouldbeproper debridinganddisinfectionofthecanals,notfillingtherootsaccordingtothemandatesofaspecific obturationtechnique.Obturationtechniqueswillevolveandgetmodifiedovertime.Moreover,some cliniciansmaytakeastandthatitisnotpossibletocreatea“continuouslytaperingfunnel”inallthe canals.Asstatedbefore,thesizeofinstrumentationremainsanareaofopendiscussion,butwhat everybodyagreesonisthefactthatbyinstrumentingthecanalswemustcreateastoporaboxjustshort oftheapicalconstriction.Let’slookatsomeofthetechniquesthatmayfacilitatetherootfillingprocess. • Overuseofthesealercanmakethingsmoredifficult.Itshouldberememberedthatexcess sealerjustcomesbackoutduringbackfillingwithguttapercha,makingthingsmessier,especially whenalargeamountofsealerisallmuddledupwiththermoplasticguttapercha. • Thesealercanalsobeplacedinthecanalbeforeconeplacementeitherwithafileorwitha smallersizeguttapercha,butthisisnotmandatory.Then,asmallamountofsealercouldbe placedonthe3-4mmtipoftheguttaperchaconeandplacedinthecanal. • Anypastetypematerial,suchasthesealerorcalciumhydroxidepasteusedasinter-appointment medicament,canbeplacedinthecanalbyrotatingafileinacounterclockwisemotion. 9 Rememberthatthedefaultclockwiserotationofarotaryfileremovesdebrisupandoutofthe canal. • Treattheguttaperchaconewithcarewhileplacingitinthecanalwithacollegepliertomake surethatthetipdoesn’tgetfoldedover.Keepaneyeonthetipuntilitdisappearsintothe orifice.Then,usingyourfingers,gentlyrotatetheconebackandforthuntilitadvancesallthe waytoworkinglength.Strictlyusingaverticallydirectedmotionwithoutanyrotationmay preventtheguttaperchaconefromseatingallthewayinsomecanals. • Twocanalsthatjoin:Separatelyplacingaguttaperchaconeineachcanalwillallowittoadvance toworkinglength,butwhenplacedtogether,thefirstconewillpreventthesecondconefrom gettingtolength.Thishappensfrequentlyinthetwomesiobuccalsofmaxillarymolars,thetwo mesialsofthemandibularsecondmolars,upperpremolars,andlowerincisors.Youmayalsoget ahintofthisparticularanatomyifyouarelookingattheorificeswithahigh-powered magnificationwhiledryingthecanals,asyoumaybeabletonoticethefluctuationofirrigantin nd st the2 canalwhilethe1 canalisbeingdriedwithapaperpoint.Placethefirstconeinthecanal thatisassumedtobelargerorstraighter(e.g.,inMB1beforeMB2inuppermolars,inthepalatal beforethebuccalinupperpremolars,inthemesiolingualbeforethemesiobuccalinmandibular nd st molars).Now,searoffthe2 conethatisnotreachingtheapexfirst,thenburnoffthe1 cone st thatwasinitiallyplacedtolength.Insummary,thestepsareasfollows:Placethe1 coneto nd nd st length,placethe2 conetojoininglevel,burnoffthe2 cone,thenburnoffthe1 cone. • Oneofthemorefrequentlyaskedquestionsinregardtoobturationisaboutfillingthecanals thatbranchinto2ormorecanalsfurtherapically.Forallintentsandpurposes,stronglyconsider referringthesecasestoaspecialist.Thelevelofdifficultyisexceedinglyhighinsomecases, especiallywhenonecanalbranchesoutatasharpangle,andpropermanagementmayonlybe possibleundertheuseofamicroscope. • Help!Myguttaperchadoesn’tgotomyworkinglength!Sometimeswerealizethatdespite havingfullycompletedtheinstrumentation,theguttaperchaconedoesn’tfitallthewayto workinglength.Thereareanumberofpossibleexplanationsforthis,butwhateveryoudo,resist thetemptationtofillit3mmsshortandmaketheall-too-commondefensivestatement—Well, myapexlocatortoldmethatthatwastheworkinglength.Itneedstobepointedoutthatthe canalconstrictionisshortoftheradiographicapexandinsomecasestherootfillingcouldlooka littleshort.Yet,iftheapexlocatorinitiallyindicatedthattheworkinglengthwas20mms,andifI filleditto18mms,thenthemachinemostcertainlydidnottellmethat18mmswasthelength. What’sresponsibleforthatdiscrepancyisthehumanerrorinproperexecution.Let’slookat someofthereasonswhyaguttaperchaconemaynotgofullytoworkinglength: 10 o Debrisinthecanal:Afilemaystillgotoworkinglengthinpresenceofsomedebris becauseitismetal,butasoftguttaperchaconemaynot.Hittheapexonemoretime withthelargestrotaryfileyouused(wipethefilecleanbeforeyoudothis)andthen irrigatethecanalonemoretime. o Discrepancyinmanufacturing:Ifyoutook5differentbrandsofguttaperchaand comparedtheexacttipsizeusingagauge,thenitwouldshowusthatsomebrandsof guttaperchaarebiggerorsmallerthantheothers.Now,ifyouopenedupapacketof guttaperchafromonebrandandthencomparedtheguttaperchaconesinthatpacket, youarestilllikelytogetsomediscrepancyinsizedespitetheconesbeingmadebythe samemanufacturer.Atanyrate,ifoneconedoesnotfittoyourdesiredlength,try anotheroneofthesamesizeorasmallersize(whichmayhavetobemodified). o Usingastrictlyverticalmotiontoplacethecone:Asexplainedbefore,incorporatea rotatingmotionwhenplacingtheguttapercha. Ifyourgoalwastoinstrumentacanaltoacertainsize,andiftheguttaperchaconestopsalittle short,thenyoucanalsotryinstrumentingthatcanalwithafileonesizelargertoabout0.5mm1mmshortoftheworkinglength.Iactuallydothisroutinelywithsmallercanals.Forexample,if Iintendedtofillthemesialcanalsofalowermolarwithsize30/04guttaperchaconesandthe workinglengthis20mms,thenIwouldinstrumentthecanalswithasize30/04rotarytolength andthenwithasize35/04toabout19or19.5mms.Usingthistechnique,theconewilladvance righttotheworkinglengthandstillgiveyouasolidtugbackmostofthetime. AFINALWORD BackinthedayswhenIwasadentalstudent,arespectableperiodontistwhowastheheadoftheperiodontics departmenthadsaidsomethingthatIremembertothisday—thathedidn’tlearntoSRPuntil2yearsafterhe becameaperiodontist.ThisstatementwassostrikingtomethatIstillrememberthetoneoftheprofessor’s voicewhenhesaidit.Not2yearsafterhegraduateddentalschool,but2yearsafterhebecameaspecialist. Myperspectiveabouttheendodonticspecialtyissimilar.AndIsaythisnottomakeitseemlikelearning aboutrootcanalsisadauntingtask,butasareminderthatcontinuouslylearningtoimproveyourselfand puttingintheeffortcanresultinalevelofproficiencythataddslayersofsatisfactiontoyourpracticeof dentistry.IfyoucontinuetodoRCTsinyourpractice,youareboundtohavedifficultandfrustratingcasesat somepoint.Butgettingbetteratanythingworthwhileisahumblingexperiencebecauseitgoeshandinhand withfailure.Itisonlyhumantobediscouragedbytheseexperiences,butthemostimportantthingistosee whatcouldbelearnedfromthesechallengingcases.Standup,dustyourselfoff,anddon’tstopdoingyour carefullyselectedcases.Iwishyouthebestofluck!