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ROOTCANALTREATMENT:ACLINICALGUIDEFORDENTALSTUDENTS,

GENERALDENTISTSWHOLIKEDOINGRCTSANDGENERALDENTISTSWHOHATEDOINGRCTS©2016

GregY.Kim,DDSDiplomate,AmericanBoardofEndodontics

Thisdocumentisintendedtobeaneasy-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.Inmyoffice,Ihaveseenapatientgiven

antibioticsforpulpitis,andwhensymptomsdidnotimprove,shewasadministeredtotheERandgiven

evenhigherdosageofIVantibiotics.Thiswouldbeahard-to-defendcaseifshedecidedtoseeyouatthe

court.Forantibioticstobeeffectiveatreducingsymptoms,thepulpmustbenecroticandinfectedfor

themostpart(note:absenceofblooduponenteringpulpspace).Now,itshouldbenotedthat

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percussionsensitivitycouldpresentwithbothvitalandnon-vitalpulp.But,ingeneral,thecaseswhere

antibioticscanworkforpainreliefdonotrespondtothermalstimuli(endoice,hotcoffee,etc.)but

insteaddisplaymarkedpercussionsensitivitythatcanbelocalizedwellbythepatient.Tendernessofsoft

tissueinthevestibuleneartheapicesoftheassociatedtoothmaybepresentaswell.Ontheotherhand,

ifapatient’schiefcomplaintisexperiencingseverepainupondrinkingsomethingcoldorhot,donotgive

thatpatientantibioticsforthepurposeofaddressingthatchiefcomplaint.Atleastdoapulpotomyifyou

havetime,orfindanendodontistwhocanprovideanemergencytreatmentforyou.Anotherkey

indicationofpulpitis,otherthanpainonthermalstimulus,isatypeofpainthatseemstojumparound

andcannotbelocalizedwellbythepatient.Pulpitiscannotbelocalizedwellbythepatientbecause

therearenosignificantproprioceptivenervefibersinthepulp.Besuretodoathoroughdiagnosisas

manypatientswillpresentwithatooththatisnecroticandinfectedbutwillalsocomplainofthermal

sensitivityfromadjacentvitalteethaswell.Thekeyistoaddressthetooththatisthemaincauseof

acutesymptoms(targetingthechiefcomplaint).

o NotInstrumentingtheCanalsforaNecroticToothwithInfectedRootCanals

Thisisanothererrorcommonlyencountered.Whenpulpalinflammationprogressesandthepulp

becomesnecrotic,fullinstrumentationofthecanalsisrequiredtoeliminatetheinfectionandreduce

symptoms.Anecrotictoothhasinfectioninthecanals,themostcommoncauseofwhichisbacterial

insultfromcaries.Thesepatientscanpresentwithswollengumsand/orface.Instrumentingtoatleast

size30/04withagoodamountofsodiumhypochloriteirrigationisrecommended.Otherwise,givethe

patientantibiotics(oryoucandoboth)andthepatientwilltypicallyseereliefofsymptomswithinaday

ortwo.

Beforeinitiatingthistreatment,Iaskedmyselfthefollowingquestions—whyistherealesiononmid-distalpartoftheroot?Istherearootfracture?Istherealocalizeddeepprobingdepthinthisarea?Ifarootcanalprocedureiscarriedout,thenwillithelpresolvethispathology?Thepost-opPAshowsthatthereisalateralcanalinthispartoftheroot,confirmingtheendodonticoriginofthelesion.

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DIAGNOSISDICTATESTREATMENT.An8-year-oldboypresentedwithapinpointexposureof#9fromtrauma.Patient’shistoryofchiefcomplaintanddiagnostictestsindicatedthatthepulpwasstillinareversiblestateofinflammation.Thetoothstructureimmediatelyadjacenttothesiteofexposurewascleanedoutwithasmallroundburanddisinfectedwithsodiumhypochlorite.ThisareawascappedwithBioceramicPuttymaterialandthepatientwasreferredbacktothegeneraldentistforacompositerestoration.A9-monthfollow-upshowed(despiteforeshorteninginthefirsttwox-rays)thatthetoothmaintaineditsvitalityandcontinueditsnormaldevelopment.IfRCThadbeendonewithoutproperlydiagnosingthestateofthepulpandtheperiapex,thetoothwouldhavestoppeditsnormaldevelopmentandwouldhaveresultedinaclinicallymorecomplicatedsituation.(1stPA:Pre-op,2ndPA:ImmediatePost-op,3rdPA:9-MonthFollow-Up)

ANTIBIOTICS

o Thego-tomedicationforanodontogenicinfectionisPenVK500mg(bactericidal,narrowerspectrumof

actionthanamoxicillin,taken4timesperday).Forpatientswithamoxicillin/penicillinallergy,

Clindamycinshouldfirstbeconsidered.

o Forpatientswithalarge,noticeableswelling:Refertoanoralsurgeonifyouarenottotallycomfortable

dealingwiththesituation.Ifyougive2differentantibioticstogether,themosteffectivecombinationmay

be2bactericidalantibiotics,suchasPenVKandmetronidazole.Acombinationofbactericidaland

bacteriostaticantibiotics(suchaspenicillinwithclindamycin)mightpotentiallycounteractthe

effectivenessofeachotherandmaynotbeashelpful.

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-speedmotorto

gaugehowmuchyouneedtogodowntobeinthepulpchamber.Itshouldalwaysberememberedthat

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thecoronalpulptissuevolumeislargestontopofthebiggercanals,meaningthatitwouldbeeasierto

exposethispartofthechamberfirstandthenpeelawayfromhere(Note:Thisisnotnecessarilythe

highestpointofthepulpchamber.Mandibularmolarshavehighmesialpulphornsbutthemesial

canalsaresmallerthandistalcanals).Foruppermolars,it’seasiesttoexposethepalatalcanalfirst

becauseit’sthelargestcanalwiththemostamountofcoronalpulpchamberspaceontopofit.Thisis

especiallyhelpfultorememberifyouareworkingonacalcifiedtoothwithareducedpulpspace.Asyou

peelawaytheroofofthepulpchamber,adarkpulpalfloorrevealsitselfandtheothercanalsarefoundat

theouteredgesofthisdarkerfloor.Italsohelpstorememberthatthepulpchamberiscenteredand

concentricwiththetoothoutlineattheleveloftheCEJ.MakeahabitoflookingattheCEJoutlineand

envisioningthepulpchamberatthecenterofthiscrosssection.Doingthisoccasionallywhileaccess-

preppingcanhelpyougetreorientedifyouaredrillinginawrongdirection.Caution:Thisinformation

regardingtheCEJanditsrelationtopulpchambermaybedistortedincrownedteeth.

o MeasuringWorkingLength

Theveryfirstfilesplacedinacanalmustalwaysbepre-curvedwiththesmallestpossibleradius.That

is,allK10andK15fileshavetobecurved(thereareinstrumentsspecificallyusedforthispurposebutif

youdon’thavethose,acollegeplierwilldo)atthetipinordertonegotiatearoundthecurvatureofthe

canalandtopreservethatnaturalcurvaturewiththeleastamountoftransportation.Thiscurvingofthe

tipofasmallfileisutterly,criticallyimportant.Oncethetipofasmallfileiscurved,itisplacedinthe

canalandgentlyworkedwithacircumferentialwatch-windingmotionuntilitisabletoreachtheapex.It

isimportanttorememberthat,inyourendeavortogettotheapex,thecircumferentialwatch-winding

motionmayprovetobemuchmoreeffectivethanastraightup-and-downfilingmotion.Fornarrower

canals,youmaynotbeabletoreachtheapeximmediately.Thegoalistoworkyourselfdown

incrementallywithoutdistortingthecanalanatomy.Whenyouaresuccessfullyworkingyourselfdown

toreachtheapex,thecanalfeelsstickyandthisisagoodindicationthatyoucancontinuetocarefully

workyourselfdowntoestablishthelength.Acanalthatnolongerfeelsstickybutfeelslikeahardwall

indicatesthatyoucouldbetransportingthecanaloutofitsnaturalanatomy.Thismeansthatyouare

makingyourowncanal,andsuccessratetypicallynosedivesinthosecaseswithaman-made-canal.Ifyou

nolongerfeelthestickinessofthecanal,backstepforonesecond,takeadeepbreath,anddothe

followingthreethings:openupthecoronalpartofthecanal(moreonthislater),irrigatecopiously,and

pickupthesmallestfilethatyouhaveavailable(K6orK8)andagaingiveitasmallcurveatthetip.Place

thesmallfileinthecanalwhilekeepinganeyeonitasK6andK8filesareverydelicateandwillcrimple

easilyifyouhitanyotherhardsurfacewhiletryingtoplacetheminthecanal.Onceitisinthecanal,

gentlykeeprotatingthembackandforthtoseeifyoucanfindthestickyspotagain.Virtuallynoapical

pressureisneededwhiledoingthis.Onceastickyspotisfound,youmayhavetokeepworkinginthe

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samemannerwhilefrequentlyirrigating.Again,thesmallfilescanseparateeasilyinanarrowcanalif

handledcarelessly,anditmaybewisetoinspectthemfrequentlyandtogothroughafewofthem

insteadofusingoneuntilitseparates.

AK15filecurvedwithasmallradiusofcurveatthetipandwithalargeradiusofcurveatthetip.ALLsmallfiles(6,8,10,15)mustbepre-curvedwithasmallradiuscurveatthetip.Afileshouldnotbebentwithalargeradiuscurveliketheoneshownontherightbecausecurvingafilethiswayhasonlylimitedbenefits.

o Coronal/OrificeWidening

Howweachievethiscoronalwideningofthecanalhaschangedsomewhatovertheyears.First,the

rationaleforcoronalcanalwidening:Insmallercanals,openingupthecoronalportionofthecanal

allowsyoutoreachtheapexmoreeasily,againwithlesstransportationinthecriticalapical1/3ofthe

canal.Inotherwords,youaremorelikelytopreservethenaturalcanalanatomywhenthecoronal

portionofthecanalhasbeenopenedupfirst.Inlargercanalswhereyouareabletoreachtheapex

easily,orifice/coronalcanalwideningisactuallynotthatimportant.Itmustbepointedoutthatthegates

gliddenisnolongerroutinelyusedforthispurpose,atleastbytoday’seducators’standards.Therearea

fewstudiesintheliteraturethatshowedremovingexcessivetoothstructurefromthecoronalpartofthe

canalcanreducetheresistanceofthetoothtorootfracture.Obviously,thereisnogoodreasonto

removemoretoothstructurethannecessaryespeciallywhenit’smorelikelytoleadtoamoreadverse

outcome.Personally,Iseldomusethegatesglidden,andIonlyuse04taperrotaryfiles,evenforcoronal

flaring.

• AdvancedTip:Incorporatingsomedegreeof“crown-down”techniquemaygiveyoubetterresultsin

manycases.Iusuallypickupabiggerrotaryfile,suchasa40/04ora35/04file,toinitiatecrown

downformostofmycases.ThisisactuallydoneevenbeforeImeasuremyworkinglength.Knowing

thatthemajorityofrootcanalworkinglengthsfallunder19mms–22mmsrange,Iwillusetherotary

inacrown-downfashion,startingwitha40/04andthenusinga35/04anda30/04toabout14mms–

16mms.Imeasuremylengthatthispoint,hand-filealittlebitandthenbegintherotary

instrumentationatfullworkinglength.Thisislistedasanadvancedtipbecauseyouhavetobe

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proficientatdoingRCTsbeforeyoucaneffectivelytakeadvantageofthistechnique.Choosingthe

rightsizerotaryfiletoinitiateyourcrown-downisajudgmentcallasyourinitialfilesizemaybe

differentfordifferentcases.Youmusthavebuiltsomespeedintoyourtreatments,andyoualso

mustbeabletoperceivewhentochangetherotaryfiletoasmalleronewhilegoingdownapically

whencertainamountofresistanceismet.

#19WITHSEVERELYCALCIFIEDMESIALCANALS.Thesecasescantake2-3timeslongerthanastraightforwardcase,andpatientsshouldbeinformedofthatbeforeinitiationoftreatment.

#19WITHLONGROOTS.Workinglength(26mms)wasmeasuredafteratleastcoronalhalfofthecanalshavebeenopenedupwithrotaryfiles.Managementofcurveintheapical1/3wouldhavebeenmuchmoredifficultwithoutfirstinstrumentingthecoronalportionsofthecanals.

o Instrumentation

Thegeneralruleistohand-instrumenttosizeK15beforeswitchingtorotaryfiles.Oneofthemost

disturbingexperiencesapractitionerdoingaRCTcanhaveistohaveafileseparation.Topreventthis

mishapandotheriatrogenicerrors,itisimportanttorememberafewthings.First,alwayshavesome

formoflubricationsuchassodiumhypochloriteorRCPrepinsidethecanal.Continuousinstrumentation

insideadebris-filleddrycanalcanbeamaincauseofallsortsoftroubles.Second,justlikethehandfiles,

ifyouarenotgettingtothemeasuredlengthinoneattemptwitharotaryfile,thenthelengthshouldbe

attainedincrementally.Thismeansremovingthefilewhenresistanceismet,irrigating,andwipingthe

fileswithanalcohol-soakedgauzetoremovethedebrisstuckintheflutesofthefile.Sometimes

irrationalitycouldtakeoverandwecanpushalittletoohard(It’sFridayafternoon,4:30PMandyouhad

alatestartwiththelastcaseofday)inanattempttoreachtheworkinglengthquickly,butdoingsocan

inevitablyresultinaseparatedfileatsomepoint.

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• Oneofthesignificantbutlesstalkedaboutbenefitsofamodernendodonticrotaryinstrumentis

thatitremovesdebrisfromthecanalasitrotatesclockwise.Observethefiletoseeifitis

accumulatingtoomuchdebrisintheflutesandwipethemofftopreventgeneratingexcessive

torqueandstress.

• Theeffectofalarge-taperinstrumentisnotawellunderstoodconcept.Wetypicallyassociate

increasedstiffnessanddecreasedflexibilityofarotaryfilewiththeincreaseintipsizeonly.That

is,wesaythatsize30isstifferandlessflexiblethansize25becauseitisbigger,andsize40isless

flexiblethansize35,andsoon.Butincreasingthetaperoftheinstrumentcanalsohavea

dramaticnegativeeffectontheoverallflexibilityoftheinstrument.Thus,an06-taperfileis

muchstifferandlessflexiblethanan04-taperfile,andbecauseofthatinflexibilityitmaynotbe

abletobypassacurvedpartofthecanalthatan04-taperfileofthesametipsizecan.

CHALLENGINGINSTRUMENTATION.ForMBandDcanals,workinglengthcouldnotbereachedwithapre-curvedK10handfile.Instrumentationwasdoneusingthefollowingsequence:40/04toopenuptheverycoronalportionofthecanal,then35/04,30/04,and25/04toresistance(advancingfurtherapicallyusingincrementallysmallerrotaryfiles),thenK8,andthenC6handfilestomeasurelength.Then,incrementallybiggerinstrumentswereusedatworkinglengthforcompleteinstrumentation:K8again,K10,15/04,20/04,25/04,30/04,andfinally35/04.ItmayhavebeenimpossibletoinstrumenttheMBcanaltothesametipsize35usinganytaperlargerthan04.

• 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

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canals,overandover.Thishabitisespeciallydeadlywhentherepeatedinstrumentationisdone

underahighRPM,asthemostcommonundesirableoutcomewouldbeeitheraseverely

transportedcanalorablown-outapex.

o InstrumentationSize

Thisisanareaoffiercecontroversyandtherearevaryingopinionsabouthowbigacanalneedstobe

instrumentedto(IoncehadarepfromthelargestdentalproductcompanyintheUSaskmewhyI

instrumentthecanalstocertainsizes).Onethingthatmostendodontistsdoagreeon,however,isthat

theirrigatingsolutionmustbeabletoreachtheapextoremovedebrisanddisinfectthecanals.Asmall

canal(instrumentedtosize25/04orsmaller)maynothavetheirrigatingsolutionreachthecriticalapical

1/3ofthecanalandalsomaybedifficulttofillproperlyinsomecases.Conversely,inaheavilyinfected

rootcanalsystemitmaybenecessarytoinstrumentthecanalstoabiggersizethanwhenthepulpisstill

vital(vitalmeanssterile).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

mustagainbenotedthatlargetaperinstruments(06orgreater)removemoredentinfromthe

coronalhalfoftheroot,whichunnecessarilyweakenstheroot.

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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.

• Indiscriminatelyusingalargequantityofthesealercanmakethingsmoredifficult.Itshouldbe

rememberedthatexcesssealerjustcomesbackoutduringbackfillingwithguttapercha,making

thingsmessier,especiallywhenlargeamountofthesealerisallmuddledupwiththermoplastic

guttapercha.

• Thesealercanalsobeplacedinthecanalbeforeconeplacementeitherwithafileorwitha

smallersizeguttapercha,butthisisnotmandatory.Then,asmallamountofsealercouldbe

placedonthe3-4mmtipoftheguttaperchaconeandplacedinthecanal.

• Anypastetypematerial,suchasthesealerorcalciumhydroxidepasteusedasinter-appointment

medicament,canbeplacedinthecanalbyrotatingafileinacounterclockwisemotion.

Rememberthatthedefaultclockwiserotationofarotaryfileremovesdebrisupandoutofthe

canal.

• Treattheguttaperchaconewithcarewhileplacingitinthecanalwithacollegepliertomake

surethatthetipdoesn’tgetfoldedover.Keepaneyeonthetipuntilitdisappearsintothe

orifice.Then,usingyourfingers,gentlyrotatetheconebackandforthuntilitadvancesallthe

waytoworkinglength.Strictlyusingaverticallydirectedmotionwithoutanyrotationmay

preventtheguttaperchaconefromseatingallthewayinsomecanals.

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• Twocanalsthatjoin:Inthismorphology,separatelyplacingaguttaperchaconeineachcanal

willallowittoadvancetoworkinglength,butwhenplacedtogether,thefirstconewillprevent

thesecondconefromgettingtolength.Thishappensfrequentlyinthetwomesiobuccalsof

maxillarymolars,thetwomesialsofthemandibularsecondmolars,upperpremolars,andlower

incisors.Youmayalsogetahintofthisparticularanatomyifyouarelookingattheorificeswith

ahigh-poweredmagnificationwhiledryingthecanals,asyoumaybeabletonoticethe

fluctuationofirrigantinthe2ndcanalwhilethe1stcanalisbeingdriedwithapaperpoint.Place

thefirstconeinthecanalthatisassumedtobelargerorstraighter(e.g.,inMB1beforeMB2in

uppermolars,inthepalatalbeforethebuccalinupperpremolars,inthemesiolingualbeforethe

mesiobuccalinmandibularmolars),andthenplacethe2ndguttaperchaconetothepointof

joining.Now,searoffthe2ndconethatisnotreachingtheapexattheorificelevel,thenburnoff

the1stconethatwasinitiallyplacedtolength.Insummary,thestepsareasfollows:Placethe1st

conetolength,placethe2ndconetojoininglevel,burnoffthe2ndcone,thenburnoffthe1st

cone.

• Oneofthemorefrequentlyaskedquestionsregardingobturationtechniqueisaboutfillingthe

canalsthatbranchinto2ormorecanalsfurtherapically.Forallintentsandpurposes,strongly

considerreferringthesecasestoaspecialist.Thelevelofdifficultyisexceedinglyhighinsome

cases,especiallywhenonecanalbranchesoutatasharpangle,andpropermanagementmay

onlybepossiblewiththeuseofamicroscope.

MANDIBULARPREMOLARSWITHTHREECANALS.Thesecasesaretypicallymuchmoredifficultthanmaxillarypremolarswiththreecanals.Propermanagementofatri-furcatingmandibularpremolarmayrequiretheuseofamicroscope.Eachguttaperchaconeneedstobesearedoffatthelevelofbranching,andthiscanonlybedoneifthereisclearvisualizationofallthreeorifices.(1stPA:Pre-op,2ndPA:2guttaperchaconeshavebeensearedoffanda3rdconehasbeenplacedtolength,3rdPA:Post-op)

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• 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:

o Debrisinthecanal:Afilemaystillgotoworkinglengthinpresenceofsomedebris

becauseitismetal,butasoftguttaperchaconemaynot.Hittheapexonemoretime

withthelargestrotaryfileyouused(wipethefilecleanbeforeyoudothis)andthen

irrigatethecanalonemoretime.

o Discrepancyinmanufacturing:Ifyoutook5differentbrandsofguttaperchaand

comparedtheexacttipsizeusingagauge,thenitwouldshowusthatsomebrandsof

guttaperchaarebiggerorsmallerthantheothers.Now,ifyouopenedupapacketof

guttaperchafromonebrandandthencomparedtheguttaperchaconesinthatpacket,

youarestilllikelytogetsomediscrepancyinsizedespitetheconesbeingmadebythe

samemanufacturer.Atanyrate,ifoneconedoesnotfittoyourdesiredlength,try

anotheroneofthesameorsmallersize(whichmayhavetobemodifiedtocreatetug-

back).

o Usingastrictlyverticalmotiontoplacethecone:Asexplainedbefore,incorporatea

rotatingmotionwhenplacingtheguttaperchatomoreeasilygetitdowntotheapexof

acurvedcanal.

FINALTHOUGHTS

BackinthedayswhenIwasadentalstudent,arespectableperiodontistwhowastheheadoftheperiodontics

departmenthadsaidsomethingthatIremembertothisday—thathedidn’tlearntoSRPuntil2yearsafterhe

becameaperiodontist.ThisstatementwassostrikingtomethatIstillrememberthetoneoftheprofessor’s

voicewhenhesaidit.Not2yearsafterhegraduateddentalschool,but2yearsafterhebecameaspecialist.

Myperspectiveabouttheendodonticspecialtyissimilar.AndIsaythisnottomakeitseemlikelearning

aboutrootcanalsisadauntingtask,butasareminderthatcontinuouslylearningtoimproveyourselfand

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puttingintheeffortcanresultinalevelofproficiencythataddslayersofsatisfactiontoyourpracticeof

dentistry.IfyoucontinuetodoRCTsinyourpractice,youareboundtohavedifficultandfrustratingcasesat

somepoint.Butgettingbetteratanythingworthwhileisahumblingexperiencebecauseitgoeshandinhand

withfailure.Itisonlyhumantobediscouragedbytheseexperiences,butthemostimportantthingistosee

whatcouldbelearnedfromthesechallengingcases.Standup,dustyourselfoff,anddon’tstopdoingyour

carefullyselectedcases.Iwishyouthebestofluck!