ISBN 978-2-912550-59-0 - 1 File Download...endodontic retreatment and its myriad complications including perforations, blockages, fractured ... failure rate (that is, cases where clinical

$Page 1: ISBN 978-2-912550-59-0 - 1 File Download...endodontic retreatment and its myriad complications including perforations, blockages, fractured ... failure rate (that is, cases where clinical$

ClinicalSuccess

in

Endodontic

Retreatment

StéphaneSimon,DCDFormerStaffPhysicianDepartmentofDentalSurgeryUniversityofParis7Paris,France

Wilhelm-JosephPertot,DCDFormerAssistantProfessorLecturerDepartmentofDentalSurgeryUniversityoftheMediterraneanAix-MarseilleIIMarseille,France

ForewordJean-PierreProust

Paris,Berlin,Chicago,Tokyo,London,Milan,Barcelona,Istanbul,SãoPaulo,Mumbai,Moscow,Prague,andWarsaw

https://t.me/DentalBooksWorld

FirstpublishedinFrenchin2007byQuintessenceInternationalParisLareprisedutraitementendodontique

ISBN978-2-912550-59-0

©2009QuintessenceInternational

QuintessenceInternational11bis,rued’Aguesseau75008ParisFrance

Allrightsreserved.Thisbookoranypartthereofmaynotbereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,electronic,mechanical,photocopying,orotherwise,withoutpriorwrittenpermissionofthepublisher.

Design:STDI,Lassay-les-Châteaux,FrancePrintingandBinding:EMD,Lassay-les-Châteaux,FrancePrintedinFrance


TableofContents

Cover

TableofContents

Foreword

1 EndodonticFailuresandIndicationsforRetreatment

WhentoRetreat?PreoperativeConsiderations:ToRetreatorNottoRetreat?PriortoStartingRetreatmentTakingaHistoryRadiographicExaminationConventionalRetreatmentoraSurgicalApproach?

2 RemovalofExistingRestorations

ShouldExistingRestorationsBeRemovedRoutinely?RemovalofCoronalRestorationsRemovalofRestorativeMaterialandPosts

3 Access,RemovalofObturationMaterials,andNegotiationofCanalsImprovingAccessCanalAnatomyandClinicalImplicationsRemovalofObturationMaterialManagementofFracturedInstruments

4 ManagementofPerforations

FactorsInfluencingPrognosisandTypeofTreatmentMaterialsUsedforPerforationRepairPerforationsintheCoronalThirdFurcationorStripPerforationsPerforationsofthePulpChamberFloorPerforationsoftheMiddleandApicalThirdsoftheCanal

5 TreatmentofTeethwithOpenApices

ImmatureTeethTreatmentbyApexogenesisTreatmentbyApexificationManagementofOtherCaseswithOpenApicesAlternativeTreatmentOptions

6 PrognosisandRetreatment

EndodonticDiseaseandItsManagementAssessmentofPeriodontalHealthPrognosisofEndodonticTreatmentandRetreatmentFactorsthatCanInterferewithHealingEndodonticSurgery:AnAdjuncttoTreatment


Bibliography


Foreword

ItisagreathonortobeaskedbyWilhelmPertotandStéphaneSimontowritetheforewordforthisbook.Ilikethefactthatthisbookisclinicallyrelevantandaddressesthechallengesthatwe,asdentists,faceonadailybasis—indications formore retreatments thanpulpectomies,difficultiesofmanaging thesequelaeoftrauma,andtheproblemsassociatedwithfracturedinstruments.

ThepracticalfocusofthisbookmakesitaworthyadditiontotheClinicalSuccessseriespublishedundertheguidanceofJean-MarieKorbendau.Havingbeenhisstudentin1963to1964,Irememberwithgratitudetherigorouspracticalandtheoreticeducationheprovided.Eachweekheaskedustopresentawrittenaccountofourclinicalexperiences,andheplacedasmuchimportanceonthestyleasonthecontent.Unlessclearlyexpressed,eventhemostimportantideasbecomeunintelligible.

Thisnewbookisdevotedtothemosttime-consumingphaseofendodontics—retreatment.Thestep-by-stepguideshowstheclinicianhowtoovercomeobstaclessuchasblockages,perforations,andimmatureapices.In addition it details how to successfully prepare and fill canals to prevent bacterial proliferation, therebyavoidingasubsequentbacteremiawith itspotential complications.Thepersistenceofbacteria in the rootcanalsystem—awayfromthebloodvesselsthatconstitutethepoliceforceofourimmunesystem—makesitnecessaryforustoplacerootfillingsthatwalloffthebacteriaandpreventfurtherspreadofinfection.

Everyday,IapplythesametechniquesoutlinedinthisbookasdiligentlyasIcan.Infollow-upassessmentwithpatientstreated6monthspreviously,Ifindtheyhavebeencuredofunilateralsinusitisandheadaches.Cardiacpatientswhoneedtreatmentforadevitalizedtoothbutarescheduledforimmediatesurgerycannotaffordtowait6monthstocheckifthelesionishealing;Iamnowconvincedthatrootcanaltreatmentforadevitalized toothpresentsnogreater risk thanextraction,provided that the treatment is conducted in linewiththerecommendationspresentedinthisbookandwiththebestpossibledisinfectionproceduresinplace.

Thisbookiscompleteyetconciseandeasytoconsultbeforeappointmentswhenyourealizeanalternativetreatmentoptionmightbesimpler(eg,extraction, implant).Theauthorsguidetheclinicianthroughroutineendodontic retreatment and its myriad complications including perforations, blockages, fracturedinstruments,andpulpalnecrosisinimmatureteeth.

Whetheryouareapracticingclinicianorastudent,thisbookwillaidinprofessionaldevelopment.Itoffersawealthofinformationaccumulatedbytwopractitionerswhohaveacquiredenormouspracticalexperienceinthe field of endodontics. They have an extensive knowledge of the literature as well as a thoroughunderstandingofthematerialsinvolved.

I amgrateful for this opportunity to thank them for the invaluable contribution theyhavemade in helpingpractitioners overcome the difficulties that are, alas, all too frequently encountered in endodonticretreatment.

Jean-PierreProust,PU-PH


EndodonticFailures

IndicationsforRetreatment


Endodontictreatmentshouldfulfillavarietyofobjectives(Schilder,1967and1974):•Createacontinuouslytaperingpreparationfromthecrowntotheapices•Maintainthepositionoftheapicalforamenontherootsurface•Maintaintheshapeoftheoriginalcanalasmuchaspossible•Keeptheapicalforamenassmallaspossible•Usecopiousirrigationtoensuretherootcanalsystemisthoroughlycleanedanddisinfected•Obturateandsealtherootcanalsystem.Although theprocedures forendodontic treatmentofavitalornecroticpulpwere firstdescribeddecadesago, thenumberofunsatisfactoryendodonticresultsremainsratherhigh.Epidemiologicstudiespublishedoverthepast20yearsshowthatthenumberofinadequatetreatmentsvariesbetween60%and79%,withafailurerate(thatis,caseswhereclinicalsymptomsorperiapicallesionsexist)of22%to63%(Boucheretal,2002).

Endodonticretreatmentcanbedefinedasfurthertreatmentperformedbecausetheinitialtreatmentwasinadequateorthelesionfailedtoheal.

Fromaclinicalstandpoint,thefourcausesoffailureareinherentwithineachstageofendodontictreatment(Ruddle,2004):•Inadequateaccesscavityduetofailuretoappreciatetheanatomyofthetooth;thishampersvisibility,whichinturnresultsinthefollowing:–Failuretodetectaccessorycanals–Difficultyincorrectlypreparingthecanalbecauseofinstrumentsfurtherrestrictingvisibilityordifficultyinvisualizingtheentirecanalsystem

–Perforationsinthecoronalthirdofthetoothorinthepulpchamberfloor•Insufficientirrigationduringcanalpreparation•Improperuseofinstrumentsduringpreparation,whichmayresultinthefollowing:–Alterationofthecanaltrajectory,whichcancauseobstructionsandeventualperforations–Blockagesandsubsequentlossofworkinglength(obstructionbydebrisorafracturedinstrument);thispreventsirrigationofthewholerootcanalsystem

–Wideningoftheapicalforamen,makingcontrolledobturationimpossible•Anerrorinfittingthegutta-perchacone,resultinginmoisturecontamination,afaultfrequentlyassociatedwithinadequatepreparationoftheapex;however,obturationmaterialextrudedthroughtheapexisnotinitselfanindicationforeitherorthogradeorretrograderetreatment.

From a biologic standpoint, endodontic failure can result from improper preparation, disinfection, orobturationoftherootcanalnetwork.Reinfectionofthecanalsystemresultingfromapoorcoronalsealcouldalsoleadtoendodonticfailure.

Irrespectiveofthetechnicalinadequaciesorerrors,allendodonticfailuresaredirectlyassociatedwiththepresenceofbacteriaandtheirtoxinsintherootcanalsystem;theseirritantsmigrateintotheperiodontaltissuesbyanyroutepossible(eg,apicalforamen,lateralcanals,accessorycanals).

Thegoals of endodontic retreatment remain the sameas the goals of the initial treatment: elimination ofbacteriaandpreventionoffurtherbacterialcontaminationbymeansofawell-obturatedcanalandacoronalseal. Achieving these goals ensures long-term success with little chance of relapse or reappearance ofpathology(Figs1-1aand1-1b).

1-1aPreoperativeperiapicalradiographofamandibularmolarrequiringendodonticretreatmentpriortoplacementofanewcrown.


1-1bPeriapicalradiographtaken9yearspostoperatively.Goodpreparationandirrigationofthecanalinconjunctionwithagoodcoronalsealensuresthelongevityofthetreatment.

Manyendodonticfailurescanbeattributedtoinadequatetrainingoftheclinicianandalackofunderstandingof modern endodontic concepts and how to implement them. Resistance to change prevents manyexperiencedpractitionersfromadoptingnewtechniques,newinstruments,andnewmaterials;this,coupledwiththemisuseofunfamiliarequipment,contributestoanumberofendodonticfailures.Endodontictreatment,whenperformedcorrectly,ispredictableandenjoysasuccessrateabove95%.Thesamecannotbesaidforretreatment,inwhichaccesstocanalscanprovedifficult,evendangerous,andinwhichnegotiationofcanalscanbehamperedbythefollowing:–Coronalrestorationswithlargeintracanaldowels–Variouscanalfillingmaterialssuchashardandsoftpastes,gutta-percha,orsilverpoints–Calcificationoftheapicalportionofthecanalasaresultofinadequatepreparationduringinitialtreatment–Iatrogeniccausesincludingblockages,shoulders,ledges,perforations,andfracturedinstrumentsRetreatmentthereforenecessitatestheuseofspecifictechniquesandoftenprovescomplexanddifficult.

WhentoRetreat?Anumberofstudieshaveshown that thedecision toundertakeendodontic retreatment issubject tobothinter- and intrapractitioner variation.Agreement betweenpractitioners onwhether or not to retreat is rare(Aryanpouretal,2000).Thedecisionisoftenbasedontheindividualpractitioner’spersonalcriteriaratherthanonasetofuniversallyrecognized,objectivecriteria(Pagonisetal,2000;KvistandReit,2002).Althoughitwouldbeverydifficulttoproduceuniversalguidelinestoidentifycasesthatshouldberetreated,aconsensusdoesexistregardingcertainsituationsthatrequireendodonticretreatment(Friedman,2002).Afterrigorousclinicalexaminationtoeliminateanypossiblecausesoffailurethatarenonendodonticinorigin(eg, cracks or fractures, food packing, occlusal trauma, sinusitis, trigeminal neuralgia), endodonticretreatmentshouldbeundertakeninthefollowingcases.

ClinicalsymptomsRetreatmentisindicatedwhenclinicalsymptomspersistafterinitialtreatment.Patientsgenerallycomplainofspontaneouspainofvariableintensitythatisexacerbatedbyocclusalproblemsorduringmastication.Theremaybesignsofswelling,anabscess,orafistula.Radiographicevidenceofalesionisnotalwayspresent(Figs1-2aand1-2b).Ataclinicallevel,thefollowingapply:–Immediatepostoperativepainthatsubsideswithindaysisnotnecessarilyanindicationthatthetreatmentwillfailinthelongterm.Periodontalinflammationafterendodontictreatmentorretreatmentisacommonoccurrenceandisnotacauseforconcernunlessitpersists.

–Sensitivityinocclusiondoesnotnecessarilyimplyendodonticfailurebutmaysimplyindicateahighspot;ifthatisthecase,symptomswilldisappearoncethehighspothasbeenreduced.

–Complaintsofpaininatreatedtoothbroughtonbychangesintemperature(particularlycold)shouldmakethe operator first suspect the pain is referred from an adjacent tooth or elsewhere. If this possibility iseliminated, other potential causes should be investigated; there may be untreated canals or contactbetweenmetallicelementsandvitaltissue,suchasasilverpointprojectingthroughtheapex,whichcanleadtopain.

–Painorsensitivityonchewingcouldberelatedtoacrackedtoothorrootfracture.Toavoidunnecessaryendodontic treatment on such a tooth, the differential diagnosis must be considered after taking athoroughpainhistory,performingperiodontalprobing,assessing theocclusion,and takinga radiograph(PertotandSimon,2003).


1-2aPeriapicalradiographofamandibularmolarthatispainfulinocclusion;thereisnoradiographicevidenceofalesion.

1-2bPostoperativeradiograph.Thepainsubsidedafterendodonticretreatment.

RadiographicevidenceIn the absence of clinical symptoms,many practitioners prefer not to retreat a tooth even if a periapicallesionisevidentradiographically(Hulsmann,1994).Thedevelopmentorpersistenceofaperiapical lesionafteramonitoringperiodofseveralmonthssignalsendodonticfailureandisanindicationforretreatment.Aperiapicallesionresultsfrombacterialinfectionandthereforeneedstobetreated(Figs1-3ato1-3c).The practitioner must first determine how much time has passed since the initial treatment and then, ifpossible, should compareprevious radiographs to check if the lesion is in facthealing; this isparticularlyimportantifboththerootfillingandthecoronalrestorationappeartobeadequate.Althoughthefirststagesof healing can be seen radiographically 3months postoperatively with the formation of bony trabeculae,completehealingoflargelesionsmaytakeseveralyears.


1-3aPreoperativeradiographofamandibularmolarwithperiapicallesionsandsevereresorptionofthemesialroot.

1-3bImmediatepostoperativeperiapicalradiograph.

1-3cClearevidenceofhealing,1yearpostoperatively.

CaseswherenewcoronalrestorationsareplannedWhenanewcoronalrestorationisplanned,radiographicexaminationisnecessarytoassessanypreviousendodontictreatmentonthetooth;ifdeemedtechnicallyinadequate,therootfillingshouldberedoneasapreventivemeasure(Machtou,1993)(Figs1-4ato1-4c).Theabsenceofa radiographic lesionona toothwithaninadequaterootfillingdoesnotindicatetheabsenceofbacteriainthecanalnetwork.Teethwhosecanalshavebeencontaminatedbybacteriacanremainasymptomaticaslongasthebalancebetweenthebody’s defense system and the virulence of the bacteria is not altered. Disturbing this balance by


instrumentationandcrownpreparation(impressions,postspacepreparation)cancausealesiontodevelopwherepreviouslyonedidnotexist(Figs1-5aand1-5b).The objective of endodontic treatment or retreatment is to control the source of bacterial contamination,thereby tipping the balance in favor of the body’s defense system. In retreatment caseswhere the canalcannotbenegotiatedtotheapex,theuseofrubberdam,correcttaperingofthecanal,andcopiousirrigationareusuallysufficienttostimulatehealing.Itisthereforeimportanttoretreatteethwithapparentlyinadequateroot fillings even in the absence of clinical or radiographic signs of failure, in cases where new coronalrestorationsareplanned.

Ifnonewrestorationisplanned,however,andifthereisahealthyperiodontium,agoodcoronalseal,andabsenceofclinicalorradiographicsymptoms,practitionersshouldrefrainfromretreatingandshouldonlymonitor the tooth, even if the root filling is clearly unsatisfactory (unless medical reasons dictateotherwise).

1-4aPreoperativeradiographofamaxillaryincisor.Anewcrownisneeded,butpreviousendodontictreatmentisunsatisfactory.Retreatmentisindicatedevenintheabsenceofanypathology.

1-4bImmediatepostoperativeradiograph.


1-4cRadiographtaken3yearspostoperatively.

1-5aPreoperativeradiographofamandibularmolar.Anewcrownisrequired,butpreviousendodontictreatmentisunsatisfactory.Retreatmentwasnotcompletedbecausetherewerenoclinicalorradiographicsignsofpathology.

1-5bRadiographtaken6monthsafterthecrownwasplaced.Aperiapicallesionhasappearedeventhoughtherootfillingwasundisturbedduringcrownpreparation.

CaseswherethecoronalsealisdeficientRetreatmentisindicatedforanytoothwheretheaccesscavityhasbeeninadequatelysealedandhasbeenopen to the oral environment for a considerable period of time, even if the root filling seems adequate


radiographically. Numerous studies over the past 10 years have demonstrated that if the coronal seal isdeficient,bacteriacaninfiltrateandmigratedowntotheapexevenwhenrootcanalsareadequatelyfilled.Althoughthereported timefor thismigrationofbacteriavaries fromstudy tostudy,authorsagreethat thecoronal seal is an important factor in the long-termsuccessof root canal treatment. In vivo studieshaveshown that the first signs of periapical pathology can appear 4 months after treatment. These findingsconfirm the need to retreat all teeth where contamination has occurred and highlight the importance ofrestoringthetoothimmediatelyaftercompletionofendodontictreatmenttoensurethebestpossiblecoronalseal.Forthesamereasons,incomplexcaseswheremultipleteetharepreparedoverseveralweeks,agoodsealon temporary restorations is essential. After each root canal treatment, a definitive restoration must beplaced as soon as possible. A provisional crown does not provide a good seal; bacterial contaminationthroughthecoronalaspectisinevitableuntiladefinitiverestorationisplaced.

PreoperativeConsiderations:ToRetreatorNottoRetreat?Technologic advances in instruments and materials (eg, ultrasonic instruments for endodontic use),combinedwithmagnificationdevices(loupesandmicroscopes),allowthecliniciantoachieveoptimalresultswithretreatment.Nevertheless,exceptincaseswheretheneedforretreatmentisclear,manyotherfactorsmust be taken into consideration before making the decision to retreat a given tooth or to consideralternativetreatmentoptions.

Isthetoothstrategicallyimportantandwhatarethealternatives?Oncea root filling isdeemed tohave failed, theclinicianshouldevaluate the importanceof the toothandassessalternativetreatmentoptions,exploringtheadvantagesanddisadvantagesofeachwiththepatient.Endodonticretreatmentisnotanendinitself.Withthematerialsnowavailable,experiencedclinicianscanexpecttoobtaingoodresultsintheretreatmentofmostteeth;itis,however,essentialtoconsiderthevalueofthetoothintheoveralltreatmentplan.Thus,beforemakingadecisiononretreatment,theclinicianshouldassess thestrategic importanceof the tooth, theperiodontalcondition, theocclusion,andanyassociatedpathology (eg, perforation, resorption), and should evaluate the likelihood of a successful long-termrestoration(Figs1-6ato1-6c).

1-6aPreoperativeradiographofamaxillarypremolarwithafracturedinstrumentpassingthroughtheapex.


1-6bImmediatepostoperativeradiograph.

1-6cRadiographtaken6monthslatershowsarootfracture.Usingthealready-weakenedpremolarasanabutmenttoothforafixedpartialdenturewasarguablynotthebestcourseoftreatmentinthiscase.

PeriodontalassessmentAny factors that may influence the long-term viability of the tooth should be ascertained by periodontalprobing, assessment of toothmobility, evaluation of the crown-root relationship, and identification of anybonyresorption.Carefulperiodontalprobingisnecessarytoevaluatethequalityoftheepithelialattachment,especially in cases with furcation lesions. A lesion of endodontic origin with no fistula has a favorableprognosisevenwhenthelesionislarge(Figs1-7aand1-7b).Conversely,alesionthatcommunicateswiththe oral cavity via a fistula, following destruction of the epithelial attachment, has a far less favorableprognosis(Figs1-8aand1-8b).


1-7aPreoperativeradiographofamandibularmolarwithafurcationlesion.Periodontalprobingrevealedahealthyperiodontiumandnofistula.

1-7bRadiograph1yearpostoperatively.

1-8aPreoperativeradiographofamandibularmolarwithafurcationlesion.Periodontalprobingdemonstratedattachmentlossandcommunicationwiththeoralcavityviaasinustract.


1-8bAfterdiscussionoftreatmentoptionsandprognosis,thetoothwasextractedandreplacedwithanimplant.

Periodontal probing, combined with an occlusal assessment and often a radiograph, is essential whenconsideringadifferentialdiagnosisofrootfracture.Manyretreatmentprocedures(bothcoronalandsurgical)areperformedunnecessarilybecauseanundetectedrootfracturewastheactualcauseoftheproblems.Afairlyconsistentpocketdeptharoundthetoothsuggeststheproblemislikelytobeofperiodontalorigin;anincreaseinpocketdepthataparticularpointsuggestsafracturehasoccurred(Figs1-9ato1-9c).

1-9aPreoperativeradiographofamaxillarypremolarthatwastenderonocclusion.Previousendodontictreatmentappearsinadequate.Theinitialplanwastoretreatthistoothsurgically.

1-9bPeriodontalprobingrevealedanareawithlossofepithelialattachment.Consideredincombinationwiththetendernessinocclusion,thissuggestsarootfracture.


1-9cRaisingagingivalflapconfirmedthepresenceofafracture.

RestorabilityofthetoothTheobjectiveintreatingatoothendodonticallyistoallowittoremainasafunctionalunitinthearch.Atooththathasextensivecariesor thathasbrokendownandhas little functionorvalue in theoverall treatmentplanshouldnotbe restored.A toothwithacaries lesion thatextendssubgingivallymayneedperiodontalinterventionfirsttorestorethebiologicwidth.Wherepossible,crownlengtheningshouldbecompletedpriortoretreatment;thiscreatesmorefavorableconditionsforeachstageoftreatment.Fortheendodontist,thecrownlengtheningmakesiteasiertoplacearubberdamclampandallowsthetoothtoberestoredbeforetreatment; in thisway the four-walledaccesscavitycreatesa reservoir for the irrigant.Crown lengtheningalso enables placement of a stable temporary dressing that is capable of resisting occlusal forces andpreventing bacterial leakage. In the phase following endodontic treatment, the visibility gained by crownlengthening simplifies the placement of the final restoration. This helps to ensure long-term periodontalhealthand,aboveall,makesagoodcoronalsealpossible.

Surgerytimerequiredandcost-benefitratioThese factors must always be taken into consideration, irrespective of the treatment planned. This isparticularly true for retreatment caseswhere duration of treatmentmay be long and the outcome is lesspredictablethanwithinitialtreatment.Unfortunatelythetechnicaldifficultiesofretreatmentoftenmeanthatpractitionersprefer toextract thetoothandreplace itwithan implantorafixedpartialdenturerather thanattempttomaintaintheoriginaltooth.

PatientdemandsEndodonticretreatmentcanbetimeconsuming,withalowerchanceofsuccessthaninitialtreatment.It istherefore important to gain the cooperation of the patient, who should be fully informed about the entireprocedure, thepossibleneed foranadjunctivesurgicalprocedure,and the riskof failureandsubsequentextraction.

OperatorskillandexperienceInlightofthefactorsdiscussedandthepossiblecomplicationsofretreatment,itmaybeappropriatetoreferthose patients in need of retreatment to endodontic specialists who have the expertise and equipmentnecessarytodealwithcomplexcases.Itisimportant,thoughsometimesdifficult,togaugethecomplexityofthetreatment,toknowone’slimits,andtoknowwhentorefer.

PriortoStartingRetreatmentAfter considering treatment options and the indications for retreatment, the practitioner must investigatefurtherbeforeembarkingon theclinicalstagesof retreatment.Theresultingobservationswillhelp identifythecauseoffailure,bringto lightanyanticipateddifficulties,andallowatreatmentplantobecreatedthataims toovercome theseobstacles. It isnotalwaysobvious fromasimple radiographwhatproblemsmayoccur;anapparentlyeasycasecanquicklybecomecomplicatedandtimeconsuming.

TakingaHistoryA thorough history from the patient provides useful information about the original clinical signs and


symptoms(pain,edema,swelling,drainage)andabouttheprevioustreatment.Ifpreviousradiographsareavailable, they can be compared to recent films to assess changes in periapical pathology and helpdetermineifanyhealinghastakenplace.

RadiographicExaminationRadiographscanprovideonlyafractionoftheinformationneeded;nevertheless,goodqualityfilmscanbevery valuable. Prior to starting endodontic retreatment, the clinician should have at least a conventionalperiapicalfilmandanangledimagetakenusingtheparallaxprinciple.Insomecasesasecondangledfilm,takenfromthedistalaspect,allowsanuntreatedcanaltobeidentifiedorafracturedinstrumenttobelocated(Figs1-10aand1-10b).Numerousretreatmentfailureshaveresultedfrominadequateexaminationofradiographs,andthereforeanunderestimationof thedifficultiesof thecase,beforetreatment isbegun.Preoperativeradiographsenablethecliniciantoaccomplishthefollowing:–Assessrootanatomy,lookforthecauseoffailure,anddetermineif itcanberectified.Certainteethwithcomplexrootcanalconfigurations(eg,curvedroots,C-shapedcanals)canprovedifficulttoretreat.Thesecases can be further complicated by iatrogenic damage from the initial treatment (eg, fracturedinstruments,perforations).

– Examine the periapical area to identify any radiolucencies, detect any foreign bodies (eg, obturationmaterial,fracturedinstruments),andassesstheextentofanyresorption.

–Assessthecoronalrestorationandevaluatetheriskofdamagingthetoothwhenremovingthecrown.–Visualize thequalityof thecanalpreparationandobturationandsometimesdetermine thenatureof theobturationmaterial.Forexample,acurvedcanalthathasbeenobturatedtooshortoftheapexindicatesapossibleblockageand/oracalcifiedcanal.

–Identifyanyfracturedinstrumentsandthenassessthepossibilityoftheirremoval.Finally, itmustbe remembered that inaddition toproviding information, the radiographsplayanessentialrole in establishing a medicolegal record. A preoperative radiograph of the tooth should be kept in thepatient’sfilestodemonstrate,shouldtheneedarise,theconditionofthetoothbeforetreatment.Withoutthisitcouldbedifficultaftertreatmenttoconvinceapatientthatafracturedinstrumentorperforationwaspresentbeforetheretreatmentwasconducted.

1-10aAperiapicalradiographofamandibularmolarshowspersistentperiapicallesions,despiteanapparentlygoodrootfilling.


1-10bAnangledradiographrevealsafracturedinstrumentinthemesialroot.Theradiographshowstheinstrumentlyinginthemesiobuccalroot;theremayinfactbetwoseparateapicalforamina.

ConventionalRetreatmentoraSurgicalApproach?When planning endodontic retreatment, the option of a surgical approach must be considered. Newtechnology and materials have been developed over the past decade that make surgical endodontictreatmentmorepredictable.Nevertheless,exceptincaseswhereaccessisgoodandrootcanalanatomyissimple,retrogradetreatmentdealsonlywiththeapicalportionofthecanal,leavingtheremainderunirrigatedand unobturated. This technique could therefore prove to be ineffective at preventing further bacterialmigration into the periapical tissues and eventually lead to failure of the retreatment. Thus, even whensurgeryisplanned,orthogradetreatmentshouldbeperformedwherepossible,toensuregoodirrigationandobturationofthecoronalpartofthecanal.Asurgicalapproachisindicatedincaseswhereiatrogenicdamagehasoccurredintheapicalthird,therebypreventing repairof thedefectbyaconventionalapproach (tearingof theapical foramen,withorwithoutextrusionofobturationmaterial) (Figs1-11a to1-11d). In thesecases, evenwhena surgical approach isindicated,conventionalretreatmentshouldbeconductedfirst,wheneverpossible,todecontaminatetherootcanalsystem.Extrusionofmaterial through theapex isnot in itselfan indication forsurgicalendodonticsunless it is associated with marked widening of the apical foramen. Treatment failures resulting frominadequatecanalpreparationandpoorcontrolofobturationmaterialshouldberetreatedfirstfromacoronalapproach(Figs1-12ato1-12c).

1-11aPreoperativeradiographofamaxillarylateralincisorthatservesasanabutmentforafixedpartialdenture.Alargepostisinplaceandtheapicalforamenhasbeenwidenedexcessively.


1-11bRetrogradeobturationwithProRootMTA(Dentsply).Notetheoutlineofthecavity;theovalshapewascreatedduringthepreparationstageoftheinitialtreatment.

1-11cImmediatepostoperativeradiograph.

1-11dRadiographtaken3yearspostoperatively.


Nevertheless, surgical intervention may be necessary whenmaterial has been extruded in the followingcases:–Whenremovalofthepostandcoreislikelytoresultinrootfractureorperforation–Followingfailureofconventionalretreatmentandonlywhenaperiodofmonitoringhastakenplaceoverseveralmonths

Indicationsforsurgicalendodontictreatmentarebasedonthetechnicallimitationsorfailuresofconventionalretreatment.Thus,otherthaninexceptionalcases,aconventionalapproach,thoughmoretimeconsuming,ispreferredoversurgicalretreatmentinthefirstinstance.

1-12aPreoperativeperiapicalradiographoffirstandsecondmaxillarymolarswithperiapicallesionsandmaterialextrudedthroughtheapex.

1-12bPostoperativeradiographfollowingretreatment.

1-12cPeriapicalradiographtaken2yearspostoperatively.Goodpreparation,irrigation,andobturationofthecanalshasallowedhealingdespitethepresenceoftheextrudedmaterial.


Thegoalsofendodonticretreatmentaretoimprovetheexistingsituationandtotransformacasethathadbeen deemed a failure into one that can be described as a success. All the factors discussed in thischapterneedtobeconsideredwhenplanningretreatment.Thepractitionercanthendecidetoundertakeretreatment,chooseanalternativetreatmentoption,orreferthepatienttoaspecialist.


RemovalofExisting

Restorations


The firststep inendodontic treatment isgainingaccess to the rootcanals.Gainingaccess in retreatmentproceduresmightbecomplicatedbyavarietyoffactors:–Presenceofadirectorindirectcoronalrestoration–Lossofthepulpchamber–Complicationscreatedduringtheinitialtreatment(eg,pooraccesscavities,perforations)–Presenceofcrownsor fixedpartialdentures that, forestheticor functional reasons,havebeenmadeto

modifytheocclusalmorphologyand/orthenaturalaxisofthetooth–PresenceofapostOvercomingornegotiatingtheseobstaclesisessentialpriortoanyattemptstogainaccesstotherootcanalsystem. Preoperative radiographs and a thorough clinical examination can provide important information(Boxes2-1and2-2).Additional informationcanbegathered from thepatientnotesand, if possible, fromcommunicationwiththeclinicianwhoperformedtheprevioustreatment(Box2-3).Atreatmentplancanthenbedrawnup.

Box2-1Informationderivedfromradiographs

Longaxisofthetooth

Crown-rootrelationship

Presenceofandtypeofpost(eg,passive,threaded,nonmetallic)

Angulation,size,andshapeofaccesscavity

Typeofobturationmaterial

Thicknessofremainingpulpalfloor

Presenceofperforations

Numberofcanalstreated

Box2-2Informationderivedfromclinicalexamination

Periodontalstatus

Furcationinvolvement

Typeofcoronalrestoration(ie,crown,amalgam,composite)

Relationship of adjacent teeth (passing floss interdentally helps determine if crowns are single units orattachedtoadjacentteeth)

Restorativecomponentsused,thecolorofthematerial,anditstoughness

Box2-3Informationobtainedfromthepatientorpreviousclinician

Differentiation between an integrated post-retained crown and a tooth that has been restored with aseparatepostandcrown.Onlysplitpinpostsaredefinitiveevidencethattherestorationisnotasingleunit.

Typeoflutingcementused.

Typeofmetalusedforthepost.

Nature of nonmetallic posts. Carbon fiber posts, glass fiber posts, and ceramic posts are oftenradiolucent,anditisverydifficulttodistinguishbetweenthem.Nevertheless,ifpossible,itisimportanttoascertain the post material, which determines the method of removal. Even after a thorough clinicalexamination,somethingswillremainunclearuntil theretreatment isactuallybegun.It isessentialthatthe clinician has the necessary instruments and equipment available to dealwith the different clinicalscenariosthatmayariseastreatmentprogresses.


Shouldexistingrestorationsberemovedroutinely?It is strongly advisable to remove existing coronal restorations, since theymay complicate access to thecanalsystemandcancauseerrorstobemade.Theshapeoftherestoredtoothoftenbearsnoresemblanceto the original tooth morphology, and the coronal axis of the tooth also may have been masked by therestoration.Whengainingaccessthroughacrown,itisverydifficulttousethenormalanatomiclandmarksasaguide.Removingthecrownbeforestartingretreatmentmayrevealimportantinformation,suchasthetypeofmaterialusedfortheunderlyingcore.Allcorematerialshouldberemovedforproperassessmentofthe remaining tooth structure and detection of hidden cracks or fractures (Fig2-1). Some argue that thecrown should be kept and considered simply as a separate restoration placed prior to the endodontictreatment.Itisneverthelesspreferabletoremovetheexistingcrownwhilepreservingasmuchtoothtissueaspossible.Afterremovingtheexistingcrownandalltheunderlyingcorematerial,thepractitionercanusethiscrownasaprovisionalrestoration, liningitwitheithera lutingcementorglass-ionomercement.Thus,removing the crown not only reveals necessary information for proper assessment of the tooth, but alsoprovidesagoodprovisional restoration. Inexceptionalcaseswhereaccesshas tobegained through thecrown,thecoronalaccesscavityshouldbepreparedlargerthaninnaturalteethtoallowbettervisualization.

Toguaranteeagoodcoronalsealandpreventrecontaminationoftherootcanals,adefinitiverestorationmustbeplacedsoonaftertreatment.Theexistingcrownmustnotbeusedasthefinalrestorationbut,ifnecessary,shouldonlybeusedasaprovisionalrestorationduringthemonitoringperiodwhilewaitingforhealingtooccur.

2-1Removingthecrownandunderlyingcorematerialallowedapreviouslyunseenfracturetobeidentified.

RemovalofCoronalRestorations

DirectrestorationsDirect restorations caneasily be removedby cutting thematerial out. If an amalgam restoration is beingremoved, precautions must be taken to prevent fragments of amalgam from entering the root canals. Asimplewayofremovingtherestorationistorunaburalongthecavitywall,aroundtheedgeoftheamalgam;usingthistechnique,therestorationisoftenremovedinonepiece.Goodirrigationandsuctionareessential.Itisalsoadvisabletoplacerubberdamtoprotectthepatientfrommercuryvaporandaerosoldroplets.Compositerestorationscanberemovedinasimilarwaywithahigh-speedhandpieceandcopiousamountsofwater. It canbedifficult todistinguishbetween the restorationand the tooth ifagoodcolormatchhasbeenachieved.Topreserveasmuchtoothtissueaspossible,sonicorultrasonicinstrumentscanbeused;theseallowmoreprecisemovementsandmaintainaclearfieldofvision.

IntactcrownsIndividualcrownscanberemovedintactbydecementation,ortheycanberemovedinsections.Toremoveacrownintactor“decement”it,thecementsealbetweenthecrownandtheunderlyingtoothorcorematerialmustbebroken;thecrownitselfremainsintact.Whilethistechniqueisthemethodofchoiceforprovisionalcrowns,itisrarelyusedfordefinitiverestorations.Decementationoccursonlywhensufficientforce isappliedtobreakthecementseal.Fuhrerpliersareadvisedfor theremovalofprovisionalcrowns;thesespecializedplierswithadiamond-coatedsurfaceprovideextragrip.Theuseofconventionalcrownremovers(Fig2-2a)totakeoffdefinitivecrownsisstronglydiscouragedbecauseofthetransmittedforcetothe crown along one side of the tooth. The force is delivered along the axis of the crown remover andproducesatippingmotionthatdoesnotcorrespondtothecrown’spathofremoval.Thus,thereisahighriskof fracturing the underlying tooth (Fig 2-2b). If the tooth contains a post, this tipping motion will betransmittedtotherootandcouldcauserootfracture(Fig2-2c).


2-2aCrownremoverandtwodifferenttips.

2-2bTheforcetransmittedbythecrownremovercandamageorfracturetheunderlyingtooth.


2-2cCrownremoversshouldnotbeusedforpost-retainedcrowns,asthereisahighriskofrootfracture.

Crown removers powered by electric motors and compressed air are available (Fig 2-3). They deliverrepetitive shockwaves (up to 20 per second) to attempt breaking the cement seal; the force and thefrequency of these shockwaves are controlled by the operator. These devices, though effective,must behandled with care, especially when rigid tips are used. To remove fixed partial dentures, the parachutetechniquedescribedbelowisfarsaferandlesstraumatic.

2-3SafeRelax(Anthogyr)electriccrownremover.Therigidtipsmustbeusedwithcautiontoavoidfracturingtheunderlyingtooth;themetalcablesallowthecrownremovertobeusedsafelyandefficientlyintheparachutetechnique.Thepowerand

frequencyoftheshocksdeliveredbySafeRelaxcanbeadjustedbytheoperator.

TheMetalift(Metalift)crownremovalsystemisausefulinstrumentbasedontheprincipleofaself-threadingscrew(Fig2-4a).Asmallholeiscreatedintheocclusalsurfaceofthecrown(Fig2-4b)toexposethemetalsubstructure in porcelain-fused-to-metal crowns.A drill that corresponds to the diameter of theMetalift isusedtopenetratethroughthemetal(Fig2-4c).TheMetaliftcrownremoveristhenplacedintothepreparedchannelandscrewedin,threadingintothemetalasitisturned.Itcomestorestontheocclusalsurfaceoftheunderlying tooth.With continued turning, theMetalift pushesagainst thedentin/core, exerting a forcealongthelongaxisofthetoothandeventuallybreakingthecementsealanddecementingthecrown(Fig2-4d).Forporcelain-fused-to-metalcrowns itmaybeprudent to removetheporcelain first toprevent it fromfragmenting.CrownsremovedwiththeMetaliftsystemtendtoshowonlyminimaldamage,sotheycanbelinedwithalutingagentandusedasprovisionalrestorations.


2-4aMetaliftkit.

2-4bPorcelainontheocclusalsurfaceofthecrownisremovedwithadiamondbur.


2-4cAtungstencarbidedrillcorrespondingtothediameteroftheMetaliftisusedtoprepareachannelthroughthemetal.

2-4dTheMetaliftissetinthepreparedchannelandscrewedin;asitpushesagainsttheunderlyingtooth,thecementsealbreaks.

Theuseofacrownremoveris,however,dependentonwhetherornotthechannelthroughthecrownhasbeenpreparednodeeperthanthemetalsubstructure.Thiscanbedifficult togauge,asit is impossibletodeterminethethicknessofthemetalbeforestartingtheprocedure.TheWAMkey(WAM) iscurrently the instrumentofchoice for removingcrownsandevenshort-span fixedpartialdenturesintact(Figs2-5aand2-5b).Availableinthreesizes,theinstrumentisplacedontheocclusalsurface of the tooth and a rotatingmotion is used, allowing the crown to be lifted off. The design of theWAMkeytippreventsleverageforcesfrombeingappliedwhenitisused.AwindowispreparedonthelateralaspectofthecrownandtheheadoftheWAMkeyisinsertedbetweenthecrownandtheocclusalsurfaceofthetooth;theinstrumentisthenturnedgentlyinaclockwisedirection.


2-5aTheWAMkeyisavailableinthreesizes.

2-5bEachofthethreeWAmkeysfeaturesthedistinctivelyshapedtip,characteristicoftheproduct.

UseoftheWAMkeyonaporcelain-fused-to-metalcrown

1.Arounddiamond018burisusedwithplentyofwaterspraytoremoveporcelainfromthebuccalaspectofthecrown(Fig2-6a),creatingawindowintheporcelain.Thewindowshouldbesituated2.0mmto2.5mmbelowthebuccalgrooveandextenddepthwiseuntilthemetalsubstructureofthecrownisjustvisible.Itisimportanttousethebuccalgrooveandnotabuccalcuspasareferencepoint.

2.Thewindowisthendeepenedandextendedwitha012transmetalburtocreateahorizontalgrooveinthecrown(Figs2-6band2-6c).

3. The WAMkey #1 is inserted parallel to the occlusal surface and must penetrate through the fullthicknessofthecrown(Fig2-6d).

4.The instrument is rotatedaquarterofa turnwithout forcing it andwithoutapplyingany leverage. IfWAMkey #1 spins with no effect, WAMkey #2 and then #3 are tried. Because of the instrument’sshapedtip,rotationoftheWAMkeygentlyliftsthecrownanddecementationiseasilyachieved(Fig2-6e).


2-6aPorcelainisremovedwitharounddiamondburuntilthemetalsubstructureofthecrownisvisible.

2-6bThemarginsofthecavityarebevelled(blackarrow).Thecavityisextendedtocreateahorizontalgrooveinthecrownthatisparalleltotheocclusalsurfaceofthetooth.Itisdeepenedtoextendhalfwayintothetoothbuccolingually.


2-6cNotethefollowingfeatures:(1)porcelain;(2)metalsubstructureofthecrown;(3)amalgamcore;(4)goldpost.

2-6dTheWAMkeyisinsertedintothegrooveinthecrownandpositionedparalleltotheocclusalsurfaceofthetooth.


2-6eTheinstrumentisgentlyrotatedaquarterofaturnandthecrownliftsoffeasily.

UseoftheWAMkeyonametalcrown

The technique for removal of metal crowns is the same as that for porcelain-fused-to-metal (PFM)crowns,butgainingaccess isslightlydifferent.Ametalcrown isnotas thickasaPFMcrown,so theaccessgrooveinthemetalcrownispreparedjust1mmbelowthebuccalgroovewithatransmetalbur.

TheWAMkeyissuitableforremovingposteriorcrownsinthemajorityofcases,whereaccesscanbegainedfromthepalatalaspect,butitisnotappropriateforuseonanteriorteeth.One of the limitations of the WAMkey system is that it cannot be used for resin-bonded crowns thatdemonstrategoodretention;thesemustbecutoff.Itisimpossibletodetermineclinicallyifacrownhasbeencementedorbondedintoplace.IfthecrownprovesimpossibletoremovewithagentleturnoftheWAMkey,itshouldthenberemovedbysectioning.PersistingwiththeWAMkeyinsuchcasesmayresultinfractureofthe instrument.TheWAMkey is simple,quick,andeasy touse.Since littledamage isdone to thecrownduring removal, it canbe reusedasaprovisional restorationduringendodontic treatment.Althoughothersystems for crown removal are described in the literature (eg,modified enamel chisel, large burs), thesetechniques rely on a rocking movement and create leverage forces, which may fracture the tooth. ThedistinctivelyshapedtipoftheWAMkeyallowscrownstoberemovedatraumaticallyalongthelongaxisofthetooth.

SectioningcrownsSectioningacrowninvolvessacrificingthecrowntopreserveasmuchoftheunderlyingtoothstructureaspossible.1.Usinganappropriatebur(capableofcuttingthroughbothmetalandceramic,ifnecessary),theclinician

makesaverticalcutinthebuccalwallofthecrownandextendsittotheocclusalsurface.Thisgroovemustgothroughthefullthicknessofthecrownsothatthecementlayerisvisible(Fig2-7a).

2.Aflat-edgedinstrumentisinsertedintothegrooveinthecrownsothatthetwopartsofthecrownareseparated;itisessentialthatnoleverageforcesareapplied(Fig2-7b).

3.Anultrasonicinstrumentplacedbetweenthecrownandtheunderlyingtoothbreaksupthecementlayer.4.Withanexcavatorplacedatthemargin,thecrownisdelicatelyremoved.Ifmechanicalretentionfeatureshavebeenused(slots,grooves),sectioningthecrowninthiswaywillnotbesufficient.Theadditionalretentionfeatureswilldeterminethepathofremovalofthecrown.Incaseswherelittlemovementcanbegained, it isbetter tosectionthecrownintomultiplepiecesratherthantocontinueputtingforceonthetooth.

Regardless of the technique used, the clinician should never attempt to remove a crown by applyingleverage forces,especiallywhen thecrown ispost-retained.Removalmustalwaysbedonegentlyandshouldbealongthepathofinsertion.Useofexcessiveforcerisksfractureoftheunderlyingtooth.


2-7aThecrownissectionedonthebuccalandocclusalsurfaces.

2-7bAflat-edgedinstrumentisusedtoseparatethetwopartsofthecrown.

FixedpartialdenturesRemovingafixedpartialdenture(FPD)ismorecomplicatedthanremovinganindividualcrownbecauseofthe multiple abutment teeth. The path of removal can be difficult to identify, particularly in terms ofbuccolingualangulation.Onlyshort-spanFPDs(3or4units)canbesafelyremovedintact.

UseofacrownremoverwiththeparachutetechniqueIn theparachute technique, thecable ispassedunder theFPDandcrossedback theotherway towraparoundthepontic(Fig2-8a).OncetheelectriccrownremoverisactivatedandtheflexiblecablealignsitselfalongthepathofremovaloftheFPD,thedevicecanbeusedtosafelyremovetheFPDintact(Fig2-8b).Thistechniqueisuncomfortableforthepatient,particularlywhenusedinthemaxillaryposteriorregion;thismaybeduetoresonanceinthemaxillarysinus.

UseoftheWAMkeyEachFPDretaineristreatedasanindividualcrown.Ahorizontalgrooveiscutinthebuccalaspectofeachretainer,andtheWAMkeyisusedoneachinturn,breakingthecementsealandlooseningtheFPD.Onceeachoftheretainershasbeendecemented,theFPDcanthenbeliftedoffinonepiece(Figs2-9aand2-9b).

Long-spanfixedpartialdenturesLong-spanFPDsshouldbesectionedbetween theabutment teeth,andeachpart shouldbe removedasthoughitwereashort-spanFPDoranindividualcrown.


2-8aTheparachutetechniqueistheonlymethodofFPDremovalthatensuresthatforcesaretransmitteddownthelongaxisoftheteeth.

2-8bPassingthecablearoundtheponticallowsshort-spanFPDstobesafelyremoved.

2-9aShort-spanFPDscanberemovedwiththeWAMkey.Eachretaineristreatedasanindividualcrown.


2-9bSinceitisremovedintact,theFPDcanbeusedasaprovisionalrestorationuntiladefinitiverestorationisplaced.

Thedecisionofwhichcrown/FPDremovaltechniquetouseforaparticularcasemustbemadewiththeaimofpreservingasmuchof theunderlyingtoothstructureaspossible. If there isanydoubtaboutthetypeofrestorationorthenatureoftheunderlyingcore,thecrown/FPDshouldbesectionedandremovedinpieces;attemptstoremoveitintactmayharmtheremainingtoothstructure.Regardlessoftheremovalmethod, theold restorationshouldneverbe refittedasadefinitive restoration. If it is removed intact, itmaybeusedtemporarilyasaprovisionalrestoration.

RemovalofRestorativeMaterialandPostsAtooththathasbeenrestoredwithapost-retainedcrownmusthavethepostremovedbeforeconventionalrootcanalretreatmentcanbeundertaken.Postsarenotvisibleonclinicalexamination;onlyapreoperativeradiograph will provide the necessary information about the type and shape of post used. Specifictechniques for removal of eachof the followingwill bediscussed: passiveposts, threadedposts, indirectposts,splitpinposts,carbonfiberposts,glassfiberposts,andceramicposts.

PassivepostsPassivepostsaresometimesknownassmooth-sidedposts. In reality, theyare rarely totally smoothandtend to have slight irregularities,which the luting agent flows into, thus improving the retention.Althoughgenerallymadeofstainlesssteel,theycanalsobemadefromtitanium.Thepostscanbeparallel,tapered,oracombinationofboth.Becauseoftheparallelismofthetooth’swalls,aparallelpostishardertoremovethanataperedone.Oncethecrownhasbeenremoved,thepostmustbegentlyloosenedwithultrasonicvibration.Postremovalreliesonbreakingthecementseal;theeasiestandquickestwayofdoingthisiswithultrasonicinstruments.Alargeultrasonictip(InsertETPR,Acteon)oraball-endedtip(ProUltrano.1,Dentsply)shouldbeusedatmaximum power and placed on the coronal aspect of the post. The vibrations are transmitted down thelength of the post and cause the cement seal to break. The instrument is usedwithoutwater spray anddirectedupanddownthevisiblepartofthepost.Itmustnotremainstationaryonthepost.Whenthepostloosens,itiscarefullyremovedwithtweezers.Withpassiveposts,evenslightmovementofthe post indicates that the cement seal has been broken and that there is no need for further ultrasonicinstrumentation.Becauseultrasonicvibrationscreateheatandtheinstrumentisusedwithoutwaterspray,itisimportanttocheckthehandpieceregularlyduringtheproceduretoensureitisnotheatingup.Instrumentsthatoverheatcaninducebonynecrosisandperiodontalcomplications.

ThreadedpostsThese canusually beeasily identifiedon radiographs.Themost common type is theScrewPost (HenrySchein), butotherbrandssuchasFlexi-Post (EssentialDentalSystems)arealsowidelyused.Postsarerarelyscrewedor threadedintodentinbecauseof theriskofmicrocrackformation.Thethreadof thepostoffersaformofsecondaryretention:thelutingagentlocksintothethreadsandprovidesgoodmechanicalretention.Beforeathreadedpostisremoved,itisimpossibletodeterminewhetherithasbeenscrewedintothecanalorsimplycementedin;thetechniqueforremovalisthesameinbothcases.Thesepostsmustbeunscrewedtoberemoved.Asimpleelevationforcerisksfracturingthepostortheroot.Thecementshouldbecarefullyclearedawaytorevealthecoronalpartofthepost(Figs2-10ato2-10c).Theultrasonicinstrument(ProUltrano.1)issettomaximumpowerandplacedagainstthetopofthepost.Keepingtheinstrumentincontactwith


thepost, theoperatormoves theultrasonic tip inacounterclockwisedirection tounscrewthepost (Fig2-10d).Manualscrewdriversforremovingthreadedpostsarealsoavailable(Fig2-11).Screwdriverscanbedifficulttouse if thepost isdamaged,andgreatcaremustbetakenwhenclearingaroundthecoronalpartof thepost.Atrephinewithaknowndiametercanbeusedtomodifythediameterofthepost.Acalibratedtubulartapcanthenbethreadedontothepostinacounterclockwisedirection,thusunscrewingthepost.Ifapostfracturesduringremoval,theProUltrano.2andno.3ultrasonictipscanbeusedtocreateatrencharoundthefracturedpost(Figs2-12aand2-12b).Aball-endedultrasonictipistheninsertedinthistroughandusedatmaximumpower inacounterclockwisedirection tounscrew the fragment (Figs2-12cand2-12d).Thistechniqueaimstopreserveasmuchtoothtissueaspossible.

2-10aand2-10bThecoronalpartofthepostiscarefullyrevealed.

2-10cAnultrasonicinstrument(ProUltrano.2orno.3)iscarefullyusedtocompletelyfreethetopofthepostwithoutdamagingit.


2-10dTheProUltrano.1ultrasonictipisusedatmaximumpowerandrotatedinacounterclockwisedirectionaroundtheposttounscrewit.

2-11Thisscrewpostextractionkit(FFDM-Pneumat)offersfourscrewdriversofdifferentsizes.

2-12aPreoperativeradiographofamaxillarycaninewithafracturedpost.


2-12bAnultrasonictipisusedtocreateatrougharoundthefracturedpost(ProUltrano.2orno.3).

2-12cTheball-endedProUltrano.1tipisinsertedinthetroughandusedinacounterclockwisedirectiontounscrewthefragment.


2-12dOncethefracturedpostisremoved,theretreatmentcanbecompleted.

IndirectcastedpostsIndirectpostsarecasttofittherootcanalperfectly.Theyarehighlyretentiveandthereforecanprovedifficulttoremove.Thegreaterthelengthandthediameterofthepost,thegreaterthesurfaceareaforcementation.Anendodonticallypreparedtoothwithonlythinresidualwallsisparticularlyfragile.Along,wide,parallelpostwillbemoredifficulttoremovethanashort,narrow,taperedpost.Castedpostsareoftenplacedforapost-retainedcrownoraspartof a split pinpost restoration.Removalof castedposts is similar to removalofdirectposts:thefirststepistofreethecoronalpartofthepost.Thedifficultyandspeedwithwhichthis isdonedependson the typeof coronal restoration in place.This stage is done using awater-cooled high-speedhandpiece.Severalburchangesmaybenecessarytoreplacebursbluntedbythemetal.Thisactiontransforms thepost-retainedcrown intoasimplepost.Thevibrationsof theultrasonic instrumentsshouldthenbesufficienttodislodgetheremainingrestoration;noattemptsshouldbemadetoremovethepostbyapplyinglateralforce,astheriskofrootfractureishigh.

UniversalPostRemoverTheGononpostremoverwasintroducedmorethan40yearsago.Itwasrecentlymodifiedto includefourstainlesssteeltubulartapsthatworkinacounterclockwisedirection,whichmeansthesystemcannowalsobeusedfortheremovalofactivethreadedposts.Acolor-codedsystemhasbeenincorporatedtofacilitatetheuseoftheUniversalPostRemover(Fig2-13).Thedeviceexertstractiononthepostwhileapplyingadownwardforceonthetoothitself.Thedesignoftheextractorwithitsmetalandrubberwashersensuresthattheextractionforceisalwaysappliedalongthepathofinsertion(Machtou,1993).Whenusedcorrectly,theuniversalpostremoverisverysuccessful:99.4%ofpassivepostscanberemovedwithouttheriskofrootfracture(Abbott,2002).


2-13Therearefewerinstrumentsinthisupdatedversionoftheuniversalpostremoverkit(FFDM-Pneumat).Thenewtubulartapsareusedinacounterclockwisedirection,contrarytotheoriginalversion.

Technique

1.Thepostandcoreorpost-retainedcrownmustbetransformedintoasimplepostandmodifiedtomatchthecylindershapeofthetubulartap(Figs2-14ato2-14c).

2.Thetopofthepostisroundedoffwithadiamondbur.3.Thediameterofthepostisgauged,andtheappropriatetubulartapwiththesamediameterisselected.4.Thepostismodifiedanditsdiametercalibrated(Fig2-14d)usingthetrephinethatcorrespondstothe

selectedtubulartap.5.Thetubulartapincludesabrasswasher,aconvexsteelwasher(iftheedgesoftherootareirregular),and

arubberwasherthatliesagainstthetooth.6.Thetubulartapisthengentlyscrewedontothepostinacounterclockwisedirection;inthiswaythedevice

threadsintothemetalofthepost(Figs2-14eand2-14f).7.Anultrasonictipisplacedonthetubulartaptovibratethepost.8.Theuniversalextractorispositionedandthewheelisturnedslowlyandevenlyinaclockwisedirection.

Therotationofthewheelcausesthejawsoftheextractortoopen;thelowerjawrestsonthetoothwhiletheupperjawexertstractiononthetubulartapandthereforeindirectlyonthepostalongitslongaxis(Fig2-14g).

9.Thepostisremovedeasily,andtheendodontictreatmentcanbegin(Figs2-14hand2-14i).

Necessaryprecautions–Theaxisofthepostmustnotbemodifiedduringthepreparationstages;iftheangleweretobealtered,the

tractionforcewouldnotbeexertedcorrectlyalongthelongaxisofthepost.–Thelargestpossibletubulartapshouldbeselected.–Adropofoilcanbeplacedontheinsideofthetubulartaptomakeiteasiertothreaditontothepost.


2-14aPreoperativeradiographofamaxillarylateralincisorrestoredwithapostandcore.

2-14bThecrownisremovedfirst.


2-14cThepostismodifiedtomatchthecylindershapeofthetubulartap.Thetopofthepostisroundedoffwithadiamondbur.

2-14dThestumpiscalibratedwithasize4trephine.


2-14eThesize4tubulartapisscrewedontothepostinaclockwisedirectionandtheensembleisvibratedwithanultrasonictip.

2-14fThewashersareplacedonthetubulartapinthefollowingorder:rubberwasher,convexsteelwasher,brasswasher.


2-14gThejawsoftheextractorarepositioned.Therotationofthewheelallowstheextractortoopen;thelowerjawrestsonthewashersandthetooth,andtheupperjawexertstractiononthetubulartap.

2-14hThepostisremovedalongthepathofinsertionwithoutharmingtheroot.


2-14iThecanalisnowaccessibleandreadyforretreatment.

WAMXTheWAMX (WAM) is a post removal system consisting of a set of forceps and three pairs of prongedattachments.Theattachmentscanbemountedon the forcepsand freely rotated inanydirectionon theiraxis (Figs 2-15a to 2-15c). The clinician cuts horizontal grooves mesially and distally through the fullthickness of the crown, allowing the forcepswith its prongs to be positioned. The force produced by theforceps is enough to break the cement seal. The rotation of the attachments directs the force along thecorrectaxisandthuslimitstheriskofrootfracture.Although attractive in principle and effective in practice, the WAM X is difficult to operate. The WAM Xsystem ismost commonlyused for removingpost-retainedcrowns,as it avoids the laboriouspreparationstageneededtousetheuniversaldevice.Thegroovesthatarecutintothesidesofthecrownexposetherootfaceonwhichoneoftheattachmentswillrest(Figs2-15dto2-15h).However,aspost-retainedcrownstendtohavealedgeatthegingivalor justsubgingival level,thismaneuvercanberiskyforboththetoothandtheinterproximalgingiva.

2-15aand2-15bTheWAMXsystemconsistsofasetofforcepsandthreepairsofprongedattachments.


2-15cThefreerotationoftheprongsdirectstheforcealongthecorrectaxiswithoutriskinganyharmtotheroot.

2-15dand2-15eThepost-retainedcrownonthemaxillaryleftsecondpremolarneedstoberemovedsoendodonticretreatmentcanbeperformed.


2-15fHorizontalgroovesarecutinthesidesofthecrownandshouldextendthefulldepthofthecrown.Therootfacemustbelaidbaresotheattachmentscanbepositionedonthesurface.

2-15gThegroovesmustbelargeenoughtoallowtwooftheprongedattachmentstobepositionedontopofeachother.


2-15hWhenremovingacrowninthisway,theclinicianmustplaceafingerontheocclusalsurfaceofthetoothduringtheprocedure.Astheforcepsareclosed,thetipsspreadapartandthecementsealbreaks.

SplitpinpostsSplitpinpostsmustbesectionedintoasmanyfragmentsastherearepostsinordertoberemoved(Figs2-16ato2-16h).Thedifficultyliesinsectioningthecoronalaspect.Atrans-metalburshouldbeusedinahigh-speedhandpiece;alow-speedhandpieceisnotsuitable.Greatcaremustbetakenwhensectioningasplitpinposttoensurethepulpchamberfloorisnotdamagedorperforated.


2-16(a)Thismolarwasreconstructedwiththeuseofasplitpinpost.(b)Toberemoved,thesplitpinposthadtobesectionedintothreepieceswithatransmetalbur.(ctoe)Eachsectionisremovedwiththeuseofanultrasonictipat

maximumpower.(fandg)Withthesplitpinpostremoved,(h)retreatmentcanbeundertaken.

Bitewingradiographscanbeausefulguideastothethicknessoftheremainingmaterial(Figs2-17ato2-17c).Onceseparated,eachsectionisthentreatedasasimplepostandultrasonicvibrationisusedtobreakthecementseal.


2-17a,2-17band2-17cPeriapicalradiographstakenduringtheremovalofasplitpinpostallowtheproceduretobeassessedmidtreatment.Theyalsohelpensurethepulpalfloorisnotdamaged.Thistechniqueisnotapplicabletothe

maxillarymolars.

FiberpostsInrecentyearsnonmetallicpostshavebeenusedmoreandmorefrequently torestore teethwithbondedpost-retainedcrowns.Thesepostsaremadeupofcarbonfibers(blackposts)orglassfibers(whiteposts)embedded in a resin matrix. Because these posts are not radiopaque, the canal appears empty onradiographic examination. After they are bonded into the prepared canals, these posts cannot be simplydislodgedbutmustbedrilledout(Figs2-18aand2-18b).

Techniqueforremoval

1.Thecoronalrestorationisremovedandthepulpchamberisthoroughlycleaned.Contrarytometalposts,fiberpostsaresectionedattheorificeofthecanal,andthetopofthepostisremoved(Fig2-18c).

2.Asmallholeismadeinthecenterofthefiberpostwithasmallrounddiamondbur(Fig2-18d).3.Thelengthofthepostisassessedfrompreoperativeradiographsandismarkedwitharubberstopona

size1GatesGliddendrill(Dentsply-Maillefer).4.Thetipofthedrillisplacedinthepreparedhole,anditisrotatedat800rpm(Fig2-18e).5.ThepathwayisthenenlargedwithGatesGliddendrillssize2,3,and4(Fig2-18f),andtheremainderof

thepostisremoved(Figs2-18gand2-18h).Someauthorsrecommendtheuseofultrasonicinstrumentstoremovefiberposts.However,thisisatime-consumingprocessand,ifusedforcarbonfiberposts,generatesacloudofblackdust.

2-18aand2-18bThecarbonfiberpostinthedistalrootofthismandibularmolarcouldnotbedetectedradiographically.


2-18cThecoronalrestorationisremoved,andthepostissectionedatthepointwhereitentersthepulpchamber.

2-18dAsmallholeismadeinthepostwitharounddiamondbur.


2-18eAGatesGliddendrillsize1isusedat800rpmtopenetratebetweenthefibersofthepost.

2-18fByenlargingthepathwaywithGatesGliddendrillsofincreasingsize(2,3,and4),thepostisremovedlittlebylittle.


2-18gOncetheposthasbeenremoved,afilecanbeusedtonegotiatethecanaltotheapex.

2-18hEndodonticretreatmentcannowbecompleted.

CeramicpostsCeramic posts are bonded into the root canal, and removing them is difficult. They cannot be merely“debonded.”Thestrengthofthematerialmakesitimpossibletovibratethemoutwithultrasonics,simplygripthem,orthreadapostremoverontothem.Theonlywaytoremovethemistodrillthemout(Figs2-19ato2-19f).Thisisadelicateprocedurethatmustbedoneundermagnification—ideallyamicroscope.Perforationscanbepreventedbystudyingthepreoperativeradiographstodeterminetheangulationofthepost.Diamondor tungsten carbide burs can be used but will need to be replaced regularly. The procedure must beperformed with copious water spray to avoid overheating the ceramic and endangering the periodontaltissues.


2-19aand2-19bPreoperativeclinicalandradiographicviewsofalateralincisorwithafracturedceramicpost.

2-19cThepostiscarefullydrilledaway.Atungstencarbideburisusedinahigh-speedhandpiece,withlotsofwaterspray.

2-19dRadiographscanbetakenatregularintervalstoverifytheangulationofthedrill.


2-19eLittlebylittle,thepostiscompletelyremoved,andtheobturationmaterialintheapicalpartofthecanalbecomesvisible.

2-19fPostoperativeradiograph.

Once the crown and the root filling have been removed, the tooth is restored. The missing walls arereplacedso thata rubberdamclampcanbepositionedandastable four-walledaccesscavitycanbeprepared.


Access,RemovalofObturationMaterials,

andNegotiationofCanals


Afterboththecrownandtheposthavebeenremoved,thenextstepinretreatmentistoimprovethecoronalaccess, identify untreated canals, and remove any blockages (eg, obturation material, fracturedinstruments). Once all the canals have been located and previously uninstrumented areas have beennegotiated(oftenthemostdifficultstage),therootcanalsareprepared,cleaned,andobturatedinthesamewayasforinitialtreatment.Failureofinitialendodontictreatmentiscommonlyassociatedwiththefollowing:

–Lackofknowledgeoftoothanatomyandmorphology(coronalandradicular)–Theimpossibilityofproducinganaccurateimageofthethree-dimensionalpulpchamberonaradiograph–Restrictedvision–Thecomplexrootcanalanatomyofposteriorteeth,alongwiththerestrictedaccessinthisarea–PooraccesscavitydesignAccesscavitiesshouldallow the identificationandpreparationofcanals. Inadequateaccesshampers thisprocess and makes optimal preparation of the root canal system impossible. Poorly designed accesscavitiescanalsoprevent theestablishmentofstraight-lineaccess.This, in turn, leads toa lossofcontrolover instruments in theapical third;uncontrolleddentin removal can result inoverpreparation,blockages,andfracturedinstruments.

ImprovingAccess

Afterremovingboththecrownandthepost,theclinicianmustreassessandmodifytheaccesscavitybeforeattemptingtheremovalofrootfillingmaterial.Modificationstotheaccesscavityshouldincludethefollowing:

–Clearinganycarieslesionsorunsupportedenamel.–Thoroughdebridementoftheaccesscavityandpulpchamber.–Provisionofacoronal restoration.Thiscreatesa four-walledaccesscavity toactasa reservoir for the

irrigant.Italsofacilitatestheplacementofarubberdamclampandenablesastabletemporarydressingtobeplacedthatiscapableofresistingocclusalforcesandpreventingbacterialleakage.

–Extendingtheaccesscavityasnecessary,ofteninabuccolingualdirection.–Identifyingextracanals.Adetaileddescriptionoftheanatomiclandmarkstolocate,theclinicalstagestofollow,andthematerialstouseisfoundelsewhere(PertotandSimon,2003).Here,thebasicstagesarepresentedandsomeimportantpointsarehighlighted.

CanalAnatomyandClinicalImplications

Inthemaxilla

•IncisorsIncisorsusuallyhavesinglerootscontainingjustonecanal;occasionallyasecondcanalispresent(Figs3-1ato3-1c).Themost commonmistake is toprepare theaccesscavity too farbuccallybecauseofafailure to appreciate the palatal inclination of the tooth. This can result in coronal blockages during thepreparationstage,orevenaperforation.


3-1a,3-1b,and3-1cMaxillaryincisorscanoccasionallypresentwithtwocanals.Inthiscasethelateralincisorhastworootsandtwocanals(arrow).

•PremolarsPremolarscanpresentwiththefollowing:anovalrootwithacanalthatiswidenedbuccopalatally,anovalrootwithtwocanalsthatmaybeconnectedbyanisthmus,ortworootswithasingleroundcanalforeach.Thus,whenretreatingapremolar,ifthecliniciandiscoversasmallaccesscavityandasingleroundcanalslightly displaced from the center, it suggests that the original access cavity is inadequate and there islikelytobeanuntreatedcanal.

3-2aPreoperativeradiographofamaxillarysecondpremolarwithalateralradiolucency(arrow).


3-2bMidtreatmentphotograph(afterremovalofthepostandcrown)displayingtheinadequateaccesscavity.

3-2cExtendingtheaccesscavitylinguallyrevealstheovalcanal.

3-2dViewofthecanalafterthepreparationstage.


3-2ePostoperativeradiographdemonstratesthepresenceofalateralcanal.

3-2fRadiographtaken1yearpostoperativelyshowshealingofthelaterallesion.Unfortunately,thepostholewasoverpreparedinthiscase.

3-3aPreoperativeradiographofamaxillarysecondpremolarthathasaninadequaterootfillinginplace.


3-3bClinicalphotographoftheextendedaccesscavityandthetwopreparedcanals.

3-3cAngledpostoperativeradiographshowsthetwocanals.

Traditionally,inpremolarretreatmentcases,theaccesscavitypreparedduringtheinitialtreatmentisfoundtobeunderpreparedinabuccolingualdirection(Figs3-2aand3-2b).Beforeattemptingtoregainaccesstothecanals,theoperatormustextendthecoronalaccesscavitybucco-lingualsoanyuntreatedcanalscanbelocated(Fig3-2a). Incaseswithflattenedovalroots,aconventionalperiapicalradiographisnotsufficient,sincethemajorityoftheendodonticworkisperformedinabuccolingualdirectionandwillnotappearontheradiograph(Figs3-2dto3-2f).Maxillaryfirstpremolarssometimespresentwiththreecanals(twobuccalandonepalatal).Inthissituation,the access cavity should be prepared in a T shape with the horizontal branch extending mesiodistally,paralleltothebuccalwall,andtheverticalbranchextendingtowardthepalatalaspect.

•MolarsA molar access cavity that is insufficiently extended often causes difficulty with preparation of themesiobuccalcanal.Moreover,asecondmesiobuccalcanalisfoundin90%ofmaxillaryfirstmolarsandinalmost50%ofmaxillarysecondmolars.Thissecondcanalisfrequentlynotidentifiedandnottreated(Figs3-4ato3-4e).Occasionallythepalatalrootofamaxillarymolarhastwocanals.


3-4aPreoperativeradiographofamaxillarysecondmolarwithaninadequaterootfillinginplace.

3-4b,3-4c,and3-4dViewsoftheaccesscavityafterremovalofthecrown,debridementofthepulpchamber,andidentificationofthesecondmesiobuccalcanal.


3-4eAngledpostoperativeradiographdisplayingthefourcanals.

Inthemandible

•IncisorsandcaninesMandibularincisorsandcanineshaveaflattenedrootwitheitherasinglecanalor,in45%ofcases,twocanals.Theaccesscavitymustthereforebeovalinshape.Forretreat-mentprocedures,theaccesscavityshouldbeextendedbuccolinguallytoallowthecliniciantolookforasecondcanalandtoensuretherootcanalscanbeproperlycleanedandprepared(Figs3-5aand3-5b).

3-5aPreoperativeradiographofmandibularincisorsandcanines,eachofwhichhasanassociatedradiolucency.


3-5bRadiographtaken7yearspostoperativelydemonstratingthehealingthathasoccurred.Notethedouble-rootedcanine.

•PremolarsTheanatomyofmandibularpremolars ishighlyvariable,andconfigurations includeasingle rootwithasingleovalcanal,asinglerootwithtwocanals(Figs3-6aand3-6b),andtworootseachwithoneormorecanals (Figs 3-7a and 3-7b). Very rarely there may be three roots. The same rules listed earlier forextending the access cavity in maxillary premolars apply, but in the mandibular premolars the accesscavityshouldbeextendedslightlymorebuccallybecauseofthelingualinclinationoftheseteeth.

3-6aPreoperativeradiographofamandibularfirstpremolar;theendodontictreatmentfailureisaresultofpooraccesscavitydesign.


3-6bPostoperativeradiographafterretreatment.Themodifiedaccesscavityallowedbothcanalstobetreated.

3-7aPreoperativeradiographofamandibularsecondpremolardisplayinganinadequaterootfillingandafracturedinstrument.

3-7bPostoperativeradiographshowingthetwotreatedcanals.

•MolarsThemesiobuccalcanalinmandibularfirstandsecondmolarsisoftenunderpreparedbecausetheaccesscavityisnotextendedfarenoughbuccally.Thecanalorificeissituatedbelowthemesiobuccalcusp,soitisessentialthattheaccesscavityisextendedinthisdirection.Thespacebetweenthetwomesialcanalsshouldbeexploredandthepossibilityofathirdcanalinvestigated.Athirdcanalispresentin4%ofcases(Figs3-8ato3-8d).


3-8a,3-8b,3-8c,and3-8d(a)Themesialrootofmandibularmolarshasthreecanalsinalmost4%ofcases.(b)Herethethird(central)canalcanbeseenfromtheaccesscavityand(c)ontheangledpostoperativeradiograph.(d)Identificationand

treatmentofallofthecanalsresultedinhealingby24monthspostoperatively.

3-9aPreoperativeradiographofamandibularfirstmolarrevealinginadequateendodontictreatmentandperiapicalradiolucenciesassociatedwithboththemesialanddistalroots.


3-9bMidtreatmentviewoftwodistalcanals.

3-9cRadiographtaken3yearspostoperativelyshowingthefourcanalsanddemonstratingthathealinghasoccurred.

The distal root of mandibular molars has a second canal in almost 50% of cases. Where there is only asingle canal, it tends to be oval in shape and relatively large buccolingually. If a single round canal isdiscoveredslightlydisplacedfromthecenter,thelikelihoodofasecondcanalshouldbeinvestigated(Figs3-9ato3-9c).SomemandibularmolarsexhibitC-shapedcanalsthatjointhemesialanddistalcanals.

Materialsandequipment•RadiographsPreoperative radiographs, both conventional periapical views and angled views, in conjunction with acomprehensiveunderstandingofrootcanalanatomy,allowfortheidentificationofextracanals.•MagnificationtoolsToolstoimprovevisionsuchasloupes,microscopes,andenhancedlightingareinvaluableinendodontics.Theuseofmagnificationandanadditionallightsourcevastlyimprovesoperatingconditionsandgivesthecliniciangreatercontrol;itisespeciallyusefulinrootcanalretreatment,asitallowsaccessorycanalstobedetectedwhileminimizingtheriskofperforation.Themostfrequentandthemostdamagingperforationsaretheresultofusingrotaryinstrumentsinanuncontrolledmannerbyclinicianssearchingblindlyforaccessorycanals.•Long-shankbursOnce theaccesscavityhasbeenextended, theuseof long-shank low-speedburswithoutwaterspray isadvised(LNBurs012and014diameter,Dentsply-Maillefer).Thelongshankensuresthattheheadofthehandpiecedoesnotrestrictvision,thereforeenablingthepreparationtobedoneunderdirectvision(Fig3-10).•UltrasonictipsDedicatedendodonticultrasonictipsareavailabletoremovedentinsafelyandassistwiththeidentificationofaccessory canals (ProUltra Endo no. 2, Dentsply-Maillefer; ETBD and ET18D, Satelec). These are used


withoutwaterspraysotheoperator’svisionisnotimpaired.•DyeDyes such as methylene blue (Canal Blue, Dentsply) can prove helpful in locating root canals. A drop isplacedintheaccesscavityandleftforaminutebeforebeingwashedoff.Thedyeisabsorbedbythecanalorificesandisthmuses(andcracks)andmakestheanatomyvisible.

After preparation of the root canals, the access cavity should be filled with sodium hypochlorite andexaminedforbubbles.This“champagneeffect”isaresultofthereactionofhypochloriteonorganicresidueandindicateseitherthatthereisorganicdebrisremainingoranaccessorycanalhasbeenidentified.

3-10Long-shanktungstencarbideburs(LNBur,Dentsply)usedwithoutwatersprayatlowspeed(below1,000rpm)inamicro-handpieceallowdirectvisionoftheoperatingfieldandthereforeminimizetheriskofperforation.

Oncelocated,anyuntreatedaccessorycanalscanbeprepared,cleaned,andfilledinthenormalwayasifitweretheinitialtreatment(Figs3-11ato3-11c).Retreatmentofcanals,however,isfarlesspredictableandmaybecomplicatedbymanyfactors.Eachcasemustbemanagedonanindividualbasis.

3-11a,3-11b,and3-11cTreatmentofthemesiobuccalcanalinthismaxillarysecondmolarisconductedaccordingtoconventionalguidelinesforprimaryendodontictreatment.Retreatmentofthepreviouslytreatedcanalscouldproveless

predictable.


RemovalofObturationMaterialGeneralguidelinesRegardlessofthetechniqueadoptedforremovingobturationmaterial,somesimplerulesmustbefollowedtoavoidfurthercomplications.

1.Afterpenetratingjustafewmillimetersintothecanal,theclinicianmustreassesstheangulationofthepreparationandmodifyitasnecessarytoallowstraight-lineaccessandensuregoodcontroloftheinstruments(Figs3-12aand3-12b).Failuretogainstraight-lineaccessmayleadtocoronalblockages,makefurtherinstrumentationofthecanaldifficult,andincreasethechancesofcreatingaperforationorobstruction.ThisfirststageinrefiningtheaccesspreparationshouldbecompletedwithaGatesGliddenbur(Dentsply-Maillefer)orwithdedicatednickel-titaniuminstrumentsdesignedforthispurpose.Theinstrumentsmustneverbeforcedapicallybutshouldbecarefullyintroducedafewmillimetersintothecanalandthenwithdrawn,removingdentinontheupstroke.

3-12aIfcoronalaccessisnotmodifiedatthebeginningoftheprocedure,itwillbedifficulttoadvanceinstrumentsfurtherdownthecanal.Theriskofblockagesandperforationsishigh(arrow).

3-12bEliminatingthecoronalshoulderofdentinopensuptheaccesspreparation,thusensuringstraight-lineaccessforinstrumentation.


2.Theobturationmaterialshouldberemovedprogressivelyas the instrumentsareadvancedfurtherdownthecanal;thispreventsmaterialextrusionthroughtheapex.

3.Allfilesandinstrumentsshouldberegularlywipedcleanondampgauzesothecliniciancanassessthemforanysignsofdamageorlossofthreadingthatcouldleadtoinstrumentfracture.

4. If excessive resistance is encountered, instruments should not be forced. A radiograph may reveal thecause of the obstruction. Forcing instruments apically into a ledge is the chief cause of iatrogenicperforations during retreatment procedures. There are two possible causes for resistance: (1) there isobturationmaterialremaininginthecanal,buttheinstrumentbeingusedhastoolargeadiameter;and(2)theobturationmaterialhasbeenremovedandtheresistanceisduetoaledgeorcalcificationofthecanal.Inboththesesituations,afine,precurvedfileshouldbeusedtohelpnegotiatethecanalfurther;carefuluseoftheinstrumentwilleitherallowtheremainingobturationmaterialtoberemovedorenabletheledgetobebypassed.

IdentifyingtheobturationmaterialTheobturationmaterialmaybevisibleatthelevelofthecanalorifice,butthisisnotthecaseinteeththathavebeenrestoredwithapost-retainedcrown.

IfthematerialisnotvisibleatthecanalorificeAfter the removalofapost,any residualcement in thebaseof thepreparation (eg,zincphosphate,zincpolycarboxylate,glassionomer)hindersaccesstothecanalandinterfereswiththeactionofsolvents(Fig3-13a).Themosteffectivewayof removing thismaterial iswith theuseofultrasonic instruments (ProUltraEndo 6 to 8, Dentsply-Maillefer; or ET20 and ET25, Acteon) or wide-diameter ultrasonic files (diameter35/100,Acteon).Theseinstrumentsshouldbeusedonlyunderdirectvisioninordertoavoidperforationsortransportationof thecanal.Theultrasonic tip isplaced in thecanal, restingontheplugofmaterial (Fig3-13b),andactivatedforafewseconds.Thecanalisthenirrigatedanddried,andadropofsolventisplaced.Astainlesssteelhandfile isusedtocheckwhether thecementhasbeenremoved; if theplugofmaterialremains in place, the same procedure can be repeated. Once the residual cement has been eliminated,removaloftheobturationmaterialfurtherdownthecanalcanbeattempted(Figs3-13cto3-13e).

3-13aPreoperativeradiographofamandibularsecondmolar(fixedpartialdentureabutment)withaperiapicalradiolucency.

3-13bToremovetheresidualplugoflutingagent,anultrasonictipisplacedonthematerialandactivatedforseveralseconds.


3-13cWiththeplugofmaterialremoved,solventscanbeusedtodissolvetheobturationmaterial.

3-13dImmediatepostoperativeradiograph.Notetheextrusionofthesealantalongthesinustract.

3-13eRadiographtaken2yearspostoperativelydemonstrateshealingofthelesion.

IfthematerialisvisibleatthecanalorificeTheeasewithwhichtheobturationmaterialisremoveddependsonthenatureoftheobturationmaterial,theamountofcanalpreparationdonefortheinitialtreatment,thecurvatureofthecanal,andthelengthoftherootfilling.Themajorityofinadequaterootcanalfillingsareunsatisfactorybecauseofinsufficientpreparationand obturation of the entire root canal system. If the obturation material is soluble, the iatrogeniccomplications (eg, obstructions, sclerosis, curvature) are the clinician’s main concern; removal of thematerialshouldnotbedifficult.

Techniquesforremovalofobturationmaterial


Removalofpastes

Oncetheaccesscavityhasbeenmodified,thepulpchamberdebrided,andadditionalcanalslocated,aDG-16probe(Hu-Friedy)isusedtotestthehardnessoftheobturationmaterial.Adropofsolventisthenplacedinthepulpchambertoassessitseffectontheobturationmaterial.Althoughsomecanalsarestillobturatedwithhardpastes,themajorityofobturationpastesarezincoxide–eugenolbasedandarelargelydissolvable.Some examples include ethyl acetate solvents (DPC7, Dentsply; DMS IV, Dentsply), tetrachloroethylenesolvents(EndosolvE,Septodont;Désocclusol,PierreRolland),orangeessence(Dentsply),andxylene.

HardpastesIf theobturationmaterialproves insoluble(phenoplasticresinorBakelite)andthesolventsare ineffective,thematerialmustbedrilledoutorchippedoutusingacombinationofendodontictips(ProUltraEndo4and5,Dentsply-Maillefer;ET20andET25,Satelec)andultrasonicfiles(diameter20/100or25/100,Satelec);theendsof these instruments canbe sectioned to give themgreater cuttingability in the coronal part of thecanal.Theendodontic tipsbreakupthefirst fewmillimetersofobturationmaterial,andtheultrasonic filesarethenusedtoprogressfurtherdownthecanal.Ultrasonicinstrumentsshouldbeusedonlyunderdirectvision in straight portions of the canal. Once the first few millimeters of material have been removed,precurvedstainlesssteelhandfilesareusedtoadvancefurtherapically.Astheseobturationpastesareoftenharderthandentin,itisimpossibletousetactilefeedbacktohelpguidethedirectionoftheinstruments.Removalofhardpastescanbetimeconsuminganddifficult,especially incurved canals. Frequent radiographs, both conventional and angled views, should be taken to checkprogressandangulation,ensuringthereisnodangeroftransportingthecanalorcreatingaperforation(Figs3-14ato3-14d).Resin-basedroot fillingstendtobedensercoronallybecauseof theobturationtechniquethatisemployed;oncethiscoronalportionhasbeenremoved,progressionfurtherdownthecanalmightnotprovedifficult.Pooraccessandinadequatepreparationoftenresultsintheobturationofonlythecentralpartofovalcanals (premolars,mandibular incisorsandcanines,distal rootsofmandibularmolars,andpalatalrootsofmaxillarymolars).Insuchcases,onceaccesshasbeenmodified,handfilesshouldbeintroduceddownthelateralaspectofthecanal,alongsidetheobturationmaterial,intotheuntreatedregionofthecanal.

3-14ato3-14dRemovalofBakeliteobturationmaterialcanprovetimeconsumingandriskyevenincasesthatappearstraightforward.Frequentmidtreatmentradiographsallowtheangleoftheinstrumentstobecheckedandadjustedas

necessary,therebyavoidingperforations.

SoftpastesThis procedure relies on the use of instruments of sufficient rigidity and solvents. The dimensions of thecanal should be gauged and an instrument of appropriate diameter chosen. Large-diameter instrumentsshould be used first to clear the coronal part of the canal, allowing finer instruments to penetrate furtherapically.Softpastescanberemovedeffectivelywitheitherstainlesssteelhandfilesornickel-titaniumrotaryinstruments;removalwithrotaryinstrumentsislikelytobequicker.Theamountofsolventneededdepends


onthenatureandthehardnessoftheobturationmaterial.Ifexcessiveamountsareused,thematerialwilldevelopaliquidconsistency,makingitsremovalmoredifficult.Thematerialshouldbesoftenedenoughtoallowinstrumentsto“bite”intoitbutatthesametimeshouldbesolidenoughtoallowittobechippedaway,whichisparticularlyimportantwhenrotaryinstrumentsarebeingused.If a canal has been obturated to its full length, removal of the obturation material is relatively easy andshould not pose many problems. Nevertheless, care should be taken to ensure material is not extrudedthroughtheapex.Ifacanalhasbeenobturatedshortoftheapex,therearetwopossiblescenarios.(1)Theapicalportionofthecanal isnotcalcifiedorblocked; itneeds tobeexploredandnegotiatedwithsmall-diameterstainlesssteelhandfiles.(2)Aledgemayhavebeencreatedapicallyduringtheinitialtreatmentandthissectionofthecanalhaseventuallycalcified;suchsituationscanbecomplicatedfurtherbycurvatureofthecanalthatmayormaynotbedetected radiographically.Rotarynickel-titanium instruments shouldneverbeused tonegotiatethecanalinsuchcases.

InstrumentationStainlesssteelhandfilesForpractitionersnotequippedwithrotaryinstruments,thehandfileofchoiceisanH-file;thishasarelativelyaggressivepointthatallowsthepastetoberemovedasthefileisworkedinandoutofthecanalwhilebeingadvancedapically.AGatesGliddendrillisusedinitiallytoclearthefirst2to3mmofobturationmaterialfromthecanalorificesandtomodifytheaccesspreparation,alwaysworkingawayfromthefurcation(Figs3-15aand3-15b).Thisenablestheoperatortoachievestraight-lineaccessandalsocreatesareservoircoronally.Adropofsolvent isplaced in thecanalorificesandanH-file that is21mm long (filediametershouldbeappropriate forcanaldimensions) isused toprogressdownthecanal (Fig3-15c).The lateralwallsof thecanalarecleanedasthefile isadvancedandthecanal is irrigatedwithsodiumhypochlorite.Thecanal isthen dried, more solvent is introduced, and instrumentation of the canal is continued. When this large-diameter file begins tobendand cannot be takenany further apically, it is replacedwitha file of smallerdiameter (Figs 3-15d and 3-15e). When two successive files refuse to progress, a radiograph should betaken. If the canal is blocked, a small-diameterC+ -file is used tonegotiate the canal andestablish theworkinglength(Figs3-15fand3-15g).Theapicalportionof thecanalcanthenbeprepared,cleaned,andobturated(Fig3-15h).

3-15aPreoperativeradiographofamaxillaryfirstmolarwithaninadequaterootfilling.


3-15bRemovalofobturationmaterialalwaysbeginswithmodificationoftheaccesspreparationtoensurestraight-lineaccess.

3-15cOncethesolventhasbeenintroducedintothecanalorifices,asize25H-fileisused;theobturationmaterialisremovedasthefileadvancesdownthecanal.

3-15dAsize20H-fileisadvancedfurtherapically.Thefilesareprecurvedaccordingtothecurvatureofthecanal.


3-15eAsize15H-filecontinuestheapicalprogression.Instrumentsareneverforcedifablockageisencountered.

3-15fAprecurvedC+fileisnegotiatedpasttheblockage,providingaccesstotheapicalpartofthecanal.

3-15gWorkinglengthradiograph.Thecanalscanbeprepared,cleaned,andobturated.


3-15hPostoperativeradiograph.

Rotarynickel-titaniuminstrumentsAlthoughrotaryinstrumentsspecificallydesignedtoremoveobturationmaterialarenowavailable(R-EndoSystem,Micro-Mega;ProTaperUniversalretreatmentfiles,Dentsply),mostoftheexistingsystems(eg,Hero642, Micro-Mega; Hero Shaper, Micro-Mega; Flex-Master, VDW Endodontic Synergy; Mtwo, VDWEndodontic Synergy; ProFile, Tulsa Dental; K3, SybronEndo) can be used in a crown-down technique toremovesolubleobturationmaterials.

TheR-EndoSystemiscomposedofanRmhandfile(length17mm,diameter25/100,taper4%),whichisdesignedtopiercethesurfaceoftheobturationmaterial,andfiverotaryinstruments(Fig3-16):(1)a15-mmRefilewithatipsizeof25/100andataperof12%,(2)a15-mmR1filewithatipsizeof25/100andataperof8%,(3)a19-mmR2filewithatipsizeof25/100andataperof6%,(4)a23-mmR3filewithatipsizeof25/100anda taperof4%,and (5)a25-mmRs file to finishwitha tipsizeof30/100anda taperof4%.Theseinstrumentsareusedsequentially inorderofdecreasingtaper.TheyformpartoftheInGeTsystem(Micro-Mega) (Fig3-16) and are used in a specially designed high-speed handpiece with a small head,allowinggreatervisibilityandimprovedaccess.Theseinstrumentscanbeusedonlyinthespeciallyadaptedhandpieces,butanotherversionforusewithconventionalhandpiecesisavailable.

The ProTaper Universal Retreatment system includes three retreatment instruments of varying taper anddiameter(Fig3-17):(1)a16-mmD1withacuttingtipsizeof30/100andatapervaryingfrom9%forthefirst3mmto7%fortheremainderofitslength;(2)an18-mmD2withanon-cuttingtipof25/100andataperof8%forthefirst3mmand6%fortheremainderoftheinstrument;and(3)a22-mmD3withanon-cuttingtipof20/100andataperof7%forthefirst3mmand6%fortheremainderoftheinstrument.Thedecreasingtaperallowseachinstrumenttobeactivewhileavoidinga“screwing”effectandapotentialcoronalblockage.Theserotary instruments featureastandardhandleandcanbeused inconventionalnickel-titaniumhigh-speedhandpieces.

3-16R-EndoSystemincludestheInGeThigh-speedhandpieceandrotaryinstrumentsforremovalofobturationmaterial.(righttoleft)TheRmfileandtheinstrumentsRe,R1,R2,andR3.


3-17ProTaperUniversalsystemisdesignedspecificallyforremovalofobturationmaterial.Toptobottom:theinstrumentsD1,D2,andD3,withvaryingtaper.

Whichever system is used, instruments of wider diameter and greater taper are used initially to removeobturationmaterial fromthecoronalpartof thecanal; instrumentswithsmallerdiameterandsmallertapercan thenbeused toprogress furtherapically (Figs3-18aand3-18b).Thematerial is removedby slowlyadvancingtheinstrumentsdownthecanal,movingtheminandoutwithcontrolledapicalpressurebutnotexcessiveforce.Theinstrumentsmustbecleanedregularlyduringuse.Solventisaddedandthenextfileisusedtoprogressfurtherdownthecanal(Figs3-18cand3-18d).Assoonasanobstructionisencountered,aradiographistaken;ifaledgeisidentified,aprecurvedstainlesssteelhandfileisusedtonegotiatefurther(Figs3-18eand3-18f).Theledgeistheneliminated,andtheapicalpartofthecanalisprepared,cleaned,andobturated(Fig3-18gand3-18h).

Rotaryinstrumentsfacilitatethisstageoftheretreatmentprocessandsaveinvaluabletimefortheoperator.

Nevertheless,rotary instrumentscanonlybeusedtoremoveobturationmaterial thathasalreadybeensoftenedbyasolvent;theyshouldneverbeusedinanattempttobypassaledgeoranapicalobstruction.Ledges are frequently encountered during endodontic retreatment and must be addressed by usingprecurvedstainlesssteelhandfiles.

3-18aPreoperativeradiographofamaxillarypremolarwithaninadequaterootfilling.


3-18bRemovalofobturationmaterialwithProTaperD1.

3-18cRemovalofobturationmaterialwithProTaperD2.

3-18dRemovalofobturationmaterialwithProTaperD3.


3-18eIfanobstructionisencountered,theinstrumentsmustnotbeforcedapically.Aradiographistakentoverifythecauseoftheblockage.

3-18fTheapicalpartofthecanalisnegotiatedwithprecurvedstainlesssteelhandfiles,andtheworkinglengthisestablished.

3-18gTheapicalpartofthecanalispreparedandcleaned.


3-18hPostoperativeradiograph.

Removalofgutta-percha

Removal of gutta-percha generally poses no problems; it is usually more easily removed than otherobturationmaterialsunlessathermocompactiontechniquehasbeenusedforobturation.Ifcold lateralcondensationorasingle-conetechniquehasbeenused forobturation, it isnotadvisable toapplyasolvent;useofasolventwouldcausethegutta-perchaandthesealertoformastickypastethatisdifficult to remove. If thecoronalgutta-perchaappearsasacompactmass,aGatesGliddendrill isusedwithout solvent to open up the canal orifice and clear the first few millimeters of the canal (Fig 3-19a).Following this, thepreferred technique is touseanappropriatelysizedH-file toslowlyadvancedown thecanalalongthelengthofthegutta-perchainanattempttoremoveallthegutta-perchainonepiece(Fig3-19b).Oncethegutta-perchaisremoved,thecanalsarecleaned,prepared,andobturated(Figs3-19cand3-19d).

3-19aIfitisradiographicallyevidentthatgutta-perchahasbeenusedforobturation,aGatesGliddendrillisusedtoremovethecoronalportionofobturationmaterial.


3-19bAlarge-diameterHfileisthenadvancedslowlydownthecanalandrotatedinanattempttoretrievethegutta-perchaconesintact.

3-19cPostoperativeradiograph.


3-19dRadiographtaken3yearspostoperatively.Incertaincasesrotarynickel-titaniuminstrumentscanbeusedtoretrieveguttaperchaconesusingthesametechnique.

Incaseswherethegutta-perchaappearsasacompactmass,handfilesandrotaryinstrumentscanbeusedasdescribedearlierfortheremovalofpastes;thisallowseffectiveremovaloftheobturationmaterialwithoutdifficulty.Toremovegutta-percha,someauthorssuggesttheuseofrotarynickel-titaniuminstruments,withoutsolvent,atspeedsof700to1,200rpm.Whenusedatthesespeedswithoutanyformofcoolant,theinstrumentsheatthe gutta-percha, thereby softening it; owing to the design of the instruments, the softened obturationmaterial is propelled coronally. This technique should be used only in straight canals and might bedangerous because of the increased risk of the instrument screwing into the canal or fracturing; thistechniqueoffersnomajoradvantageovermorecontrolledmethods.

Whichever technique is used (rotary instruments or hand files) it is very important to remember thefollowingrule:Whenaninstrumentcannotbeadvancedfurtherdownthecanal,itmustnotbeforced.

Whenan instrumentcannotbeadvancedfurther, theoperatormust firstcheckthat there isstillobturationmaterialremainingwithinthecanalandthereisnoothercausefortheobstruction.Adropofsolventisthenaddedandasmaller-diameterinstrumentisadvancedapically.Attemptingtoforceaninstrumentapicallyinablockedcanalrisksfracturingtheinstrumentandincreasingtheledgeorevencreatingaperforation.

Removalofsilverpoints

Immediateretrievalofsilverpointsshouldneverbeattempted.Even ifasilverpointappears tobepoorlyadapted to thecoronal two-thirdsof thecanal, itmay fitwell in theapical third.Silverpointswilloftenbeaffectedbycorrosionandcanbequitefragile.Graspingthecoronalaspectofasilverpoint,withoutanypriorpreparationtoloosenit,risksfracturingthesilverpoint(Machtou,1993).

Theproceduretoremovesilverpointsisasfollows:

1.Thecoronalrestorationisremovedwithahigh-speedhandpieceandultrasonicinstruments;thisstepmustbeperformedwithcaretoensurethecoronaltipofthesilverpointisnotremoved(Figs3-20aand3-20b).Thepulpchamberisthendebridedwithultrasonicinstruments.

2.Solventisplacedinthepulpchamberandhandfilesareuseddownthecanalalongthelengthofthesilverpointtoremovethesealer(Fig3-20c).

3.Afterthesealeriseliminated,anultrasonicfilewithadiameterof15/100isintroduced,withcopiousirrigation,alongthelengthofthesilverpoint(Fig3-20d).Theultrasonicvibrationsaresometimessufficienttofreethesilverpointandremoveit.

4.Whenthesilverpointhasbeenloosened,thecoronalaspectcanbegraspedgentlywithSteiglitzforceps,anInstrumentsRemovalSystem(IRS,Dentsply),oraMasserannextractor(Micro-Mega)(Figs3-20eand3-20f).

5.Ifthesilverpointresistsremoval,itmustnotbeforced;ultrasonicvibrationcanbeapplieddirectlytotheforcepsholdingthesilverpointinanattempttoloosenit.


3-20aPreoperativeradiographofamaxillarymolarandpremolarobturatedwithsilverpoints.Notethelaterallesionassociatedwiththepremolarandtheperiodontalproblemsaffectingthemolar,whichnecessitatedthesectioningofthedistal

root.

3-20bThetipsofthesilverpointshavebeencarefullyuncoveredwithoutbeingdamaged.

3-20cAdropofsolventisplacedandhandfilesareusedtoremovethesealerfromaroundthesilverpoints.


3-20dThesilverpointsarethenvibratedwithultrasonicfiles,undercopiousirrigation.Itisonlyatthisstagethatthesilverpointscanberetrieved.

3-20ePostoperativeradiographofthepremolar.

3-20fRadiographtaken3yearspostoperatively.

Thetechniquesusedtoremovecarrier-basedobturationmaterial(ThermafilPlus,Dentsply;Soft-Core,AxisDental) resemble the techniques used to remove gutta-percha. In large or oval canals the carrier isembeddedinamassofgutta-percha in thecoronal two-thirds.A large-diameterH-file isusedtoeliminatethegutta-perchaaroundthecarrier.Oncethecarrierhasbeenfreed,theH-fileisrotatedintoitsothecarriercanbepulledandelevatedintact.Thesametechniquecanbeusedwithrotarynickel-titaniuminstruments.Large-diametertaperedinstrumentsareusedtoremovethegutta-perchafromalongsidethecarrier.Astheinstrumentsprogressapically, the canalwalls narrowand the carrier is generally rolledaround the rotary


instrumentandextractedcoronally.In round narrow canals where there is little gutta-percha between the carrier and the canal walls, failureresults from inadequate preparation. Solvents are of no use. The technique for removal of the carrierremains the same as for large canal but a smaller-diameter instrument must be used so that it can beinsertedbetweenthecanalwallsandthecarrier.Incaseswherethecarriercannotbeelevateddespitebeingloose,techniquesusedtoremovesilverpointscanbeemployed;thecoronaltipofthecarrieristhengentlygraspedandpulled.

NegotiatingtheuntreatedpartofthecanalIftheinitialrootfillingwasshortoftheapex,aftertheobturationmaterialisremovedtherearetwopossiblescenarios:(1)theapicalportionofthecanalcanbenegotiatedandasmall-diameterfile(08/100or10/100)can be introduced relatively easily; and (2) there is a blockage at the level where the existing root fillingends,withcalcificationoftheapicalportionofthecanal,andfurtherpreparationofthecanalisnotpossibleatthisstage.Negotiatingtheuntreatedpartofthecanaldependsonthecoronalaccesspreparation,howmuchobturationmaterialhasbeensuccessfullyremoved,thesizeoftheledge,andtheextentofthecalcification.Theaccesspreparationshouldprovidestraight-lineaccess to theapical third,enabling theoperator tomaintaingoodcontroloftheinstrumentswhileattemptingtonegotiatetheapicalportionofthecanal.

Itshouldalwaysbeassumedthataledgemightbepresentatthelevelwheretheexistingrootfillingends,andlarge-diameterfilesshouldneverbeforcedfurtherdownthecanaltoavoidtheriskoftransportingthecanalandcreatingaperforation.

Rotarynickel-titaniuminstrumentsmustnotbeusedtonegotiateblockedcanals;theseinstrumentscutonthe outer part of the curve and may worsen the existing ledge. To bypass the ledge and negotiate theuntreatedportionof thecanal, thecoronalportionof thecanalmust firstbeenlargedandcleaned;a finehandfile (10/100,08/100,or06/100)withaprecurved tip is thenusedwithachelatingagentandsodiumhypochlorite(Machtou,1993). Insuchcases,18mmor21mmC+files(Dentsply-Maillefer)canproveveryuseful.Thesefiles,available infoursizes(06,08,10,and15),are lessflexiblethantraditional filesof thesamedimension.Theyarethereforelesssusceptibletodeformationduringattemptstonegotiatethecanal.Ledgesareoftencreatedbyinstrumentsthatworkontheouterpartofthecurve;therefore,theprecurvedtipoftheinstrumentneedstobedirectedtowardtheinnerpartofthecurve,keepinginmindthatbuccalandlingualcurvatureswillnotbevisibleradiographically.

MandibularmolarcanalsMesialcanalsThesecanalshaveaprimarydistalcurvaturevisibleonradiographs(Fig3-21a)andasecondarycurvaturenotvisible radiographically: lingual for thebuccalcanal,andbuccal for the lingualcanal (Fig3-21b).Afterclearingtheobturationmaterialtotheleveloftheledge(Fig3-21c),aprecurved08or10C+filewithplentyofchelatingagentisintroducedintothecanal.Thefileshouldbeorienteddistallyandlinguallyforabuccalcanalanddistallyandbuccallyforalingualcanal(Fig3-21d).Oncethecanalisfound,thefilemustnotbewithdrawnlestthepathwaybelost.Thiscanbeoneofthemostfrustratingmistakesmadeduringendodontic retreatment.The fileshouldbeadvancedseveralmillimetersapicallybyrotatingtheinstrumentinaquarter-turnclockwise/counterclockwisemotion(Fig3-21e).Oncethefile is past the blockage, it is worked in and out with small, gentle movements; progressively largermovementswilleventuallyfreethefile.Thenextstepistosmoothoutthewallsofthecanalandeliminateanyledgescreatedbytheblockage.Aseries of precurved stainless steel hand files of increasing diameter (15, 20, 25, etc) is used to removedentinshouldersandcreateasmoothpreparation(Fig3-21f).Thesefilesareusedwithagentlein-and-outmotion.Thecanalneedsregular irrigationand,betweensuccessivefiles, itshouldbe instrumentedwithasize10filetoensurethecanalremainspatent.AnothertechniqueforeliminationofledgesinvolvestheuseoftheProTaperFinishingFile1(F1),whichhasatipsizeof0.20mmandataperof7%overthefirstfewmillimetersoftheinstrument.Ausefulfeatureofthisinstrumentisthelargeapicaltaper,whichallowsdentinledgestoberapidlyeliminated.Thisinstrumentmustnotbeuseduntilastainlesssteelhandfileofdiameter15orlargerhasbeenworkeddownthecanaltocreateaglidepath.FortheF1toentertheapicalportionofthecanal,itmustbeprecurveduntilthepointofpermanentdeformationso the tipcanenter thealreadyenlargedcanal.Toachieve this, the instrument isgraspedat its tipandcurved180degrees (the tipneeds topractically touch theshaftof the instrument).Whenreleased,theinstrumentwillretainacertainamountofdeformationthatallowsittore-enterthecanal.ThesameeffectcanbeachievedwiththeEndo-Benderpliers(SybronEndo),whichhaveoneflat jawandoneroundedconicjawthatallowthefiletobecurvedtovaryingdegreesdependingonwhereitispositionedin the pliers. However they are bent, the instruments must be initially curved with an exaggerateddeformationsothatthefinalcurvatureisgreatenoughtoallowtheinstrumenttoenterthecanal.OncetheProTaper F1 has advanced beyond the blockage, it is rotated clockwise and counterclockwise, movingprogressivelyfurtherdownthecanalwhileremovingtheobstruction(Fig3-21g).Small-diameterhandfilesareused toensurepatencyof thecanal,andaworking-length radiographcanbe taken (Fig3-21h).Thecanalisthenpreparedandcleaned.


DistalcanalAlthoughoftenwideinthecoronalregion,thedistalcanalnarrowsapicallyandmaypresentwithamarkeddistalcurvaturethatwasnotpreparedduringtheinitialendodontictreatment.Afterthecoronalportionoftheobturationmaterialhasbeenremoved(Fig3-21i),aprecurvedC+file(diameter08or10)shouldbeinsertedintothecanalwiththetiporientedtowardthedistalaspectsotheapicalpartofthecanalcanbenegotiated.Theworkinglengthisdeterminedandtheapicalportionofthecanalispreparedmanuallywithaprecurvedstainlesssteelhandfiletosize15(Fig3-21j).Handnickel-titaniuminstrumentscanbeusedtoprepareandcleansharpapicalcurvatures(Figs3-21kto3-21m).

3-21aPreoperativeradiographofamandibularmolarwithinadequateendodontictreatment.

3-21bDiagramhighlightingthedistalcurvatureofthemesialrootonaradiograph(left);thebuccalcurvatureofthelingualcanalandthelingualcurvatureofthebuccalcanalareapparentinprofile,butthesearenotvisibleradiographically.

Blockagestendtooccuratthelevelofthebuccalandlingualcurvature.


3-21cObturationmaterialisremoveddowntotheleveloftheobstruction.Astainlesssteelfile(diameter10or15)isinsertedintothecanalandaradiographistakentocheckthattheobturationmaterialhasbeensuccessfullyremovedandto

allowtheleveloftheblockagetobeassessed.

3-21dAprecurvedstainlesssteelC+handfileisinsertedintothebuccalcanalwithitstipdirecteddistallyandlingually,andintothelingualcanalwithitstipdirecteddistallyandbuccally.Thediagramdepictsasectionthroughthemesialrootand

showstheblockages(blue)andthecanals(red).Theoperatormustdirecttheinstrumenttipstowardtheseredareaswhentryingtonegotiatepasttheobstructions.

3-21eOncethecanalhasbeenlocated,thefileisadvancedasfaraspossiblewithclockwiseandcounterclockwiserotationalmovements,andthenaslowin-and-outmotionisused.


3-21fAseriesofprecurvedfilesofincreasingdiameterisusedtoeliminatetheshoulderandsmooththecanalwall.

3-21gThecanalwallscanalsobesmoothedwithaprecurvedProTaperF1handfileusedwithgentlepullingandrotationalmovements.

3-21hPatencyisachievedandtheworkinglengthisdetermined.Theapicalportionofthecanalisthenpreparedandcleaned.


3-21iRemovalofobturationmaterialfromthedistalcanalis3-21jThetipofaprecurvedstainlesssteelC+handfileisdirectedstoppedwhenanobstructionisencountered.

3-21jThetipofaprecurvedstainlesssteelC+handfileisdirecteddistallytoattempttolocatethecanal.Patencyisachievedandworkinglengthdetermined.

3-21kTheapicalcurvatureispreparedwithmanualProTaperfiles.


3-21lPostoperativeradiograph.

3-21mPostoperativeradiographviewedfromanotherangle.

PalatalcanalofmaxillarymolarsTheapicalportionsofthesecanalsoftendemonstrateabuccalcurvaturethatisnotvisibleonradiographs.Afineprecurvedhandfilemustbeorientedbuccallytoattemptnegotiationofthecanal.Oncetheledgehasbeenbypassed,itisnecessarytoevaluateeachsituationonacase-bycasebasisanddecidewhetherornottoremovetheobstructionentirely.Thisdependsonthepositionoftheledge,thesizeoftheobstruction,andtheamountofdentinthatwillneedtoberemovedtocleartheobstructionentirely.Asignificantledgerequiringalargeamountofdentinremovalmaypresentaconsiderableriskofweakeningthetoothorcreatingaperforation.Insuchcasesitmaybebestnottoattempttocleartheblockageentirely.Obturating the tooth can therefore prove difficult, since the gutta-percha points may bend when they areintroducedintothecanal.Bymarkingthecoronalaspectofthegutta-perchapoint,theoperatorcanmonitorthepointasitentersthecanal.Thegutta-perchapointcanbeprecurvedbeforeitisintroducedintothecanaltofacilitateitsplacement.

CleaningthecanalafterremovalofobturationmaterialAfter the working length has been determined and the canal prepared, any residual obturation materialshouldberemoved.Solventisplacedintothecanalandagitatedwithapaperpoint;thisnotonlycleansthecanalwallsbutalsodissolvesanysealer thatmayremain (eg, in isthmuses)after instrumentation.At thisstage,ifthepaperpointcomesoutstainedbydebris,thecanalisnotclean.Copiousirrigationwithsodiumhypochloritedisinfectsthecanalandremovesalltracesofsolventfromtherootcanalsystem.

CasesinwhichacanalcannotbenegotiatedIncaseswhere,despiteallefforts,theapicalportionofthecanalcannotbenegotiated,onlytheaccessiblepartofthecanalcanbeprepared,cleaned,andobturated.Thetoothmustbemonitoredradiographicallyatregularintervals.Iftherewasnolesionpreoperativelyandaseptictechniqueswereemployed,theprobabilityofalesionappearingisextremelylow,despitetheapicalportionofthecanalremaininguntreated.Inthesecases the reported success rate is high (Friedman, 1998 and 2002). Even if a lesion is presentpreoperatively,healingisstillseenin60%ofcases(Akerblöm,1984)(Figs3-22ato3-22c).


3-22aPreoperativeradiographofamaxillarypremolarwithalateralandperiapicallesion.

3-22bImmediatepostoperativeradiograph.Despiteallefforts,theapicalportionofthecanalcouldnotbenegotiated.Notetheobturationofthelateralcanal.

3-22cRadiographtaken6monthspostoperativelyshowinghealing.

Ineffect,removalofaleakingcoronalrestorationandafailingrootfillingundercopiousirrigationcleansestherootcanalsystemandsufficientlyreducesthebacterialloadsohealingcantakeplace.


Thus,endodontic retreatmentshouldnotbeconsidereda failuresimplybecause theapicalportionof thecanalwas leftuntreated.Postoperativemonitoring isessential.Adjunctive treatmentshouldnotbeofferedunlessthelesionincreasesinsize,doesnotdisappear,orbecomessymptomatic(Figs3-23ato3-23e).Adefinitivecoronalrestorationmustbeplacedimmediately.Delayingtheplacementofacoronalrestorationcompromisesthehealingprocessbecauseoftheriskofbacterialpenetrationandreinfection.Aprovisionalpost-retainedcrowndoesnotprovideagoodseal;however,apostandcoreorabondedcoreinconjunctionwithaprovisionalcrownisacceptableandrecommended.

3-23aPreoperativeradiographofamaxillarymolarinneedofendodonticretreatment.Thereisaperiapicallesionassociatedwiththemesiobuccalroot.

3-23bPostoperativeradiographshowingincompleteobturationofthemesialrootbecausetheapicalportionofthecanalcouldnotbenegotiated.


3-23cRadiographtaken6monthspostoperativelydemonstratingthepersistentlesionassociatedwiththemesialroot.

3-23dClinicalphotographoftheretrogradeobturationofthemesialroot.Notetheovalshapeofthecavity;thisenabledthecliniciantoprepareandobturatethetwocanalsinthisrootandtheisthmuswhichconnectsthem.

3-23eRadiographtaken7yearspostoperatively.

Iftheproblemwasclearlyendodonticinoriginandtheretreatmenthasbeenconductedproperly,thereisnojustification for not placing a definitive restoration. If the conventional retreatment should fail, a surgicalapproachwillbenecessaryandthecoronalrestorationwillbeleftuntouched.


ManagementofFracturedInstrumentsFracturedinstrumentsareaproblemcommonlyencounteredinendodontictreatmentandcanoccurwithanyinstrument,includingbarbedbroaches,stainlesssteelhandfiles,rotarynickel-titaniuminstruments,Lentulospiral fillers, and thermomechanical compaction devices, among others. Advances in technology (eg,ultrasonics, IRS) and the introduction of the operating microscope in particular now make it possible toremoveinstrumentfragmentsthatwouldinthepasthavebeenimpossibletoretrieve.Nevertheless,despitethesedevelopments,itisstillnotpossibletoremoveallfracturedinstruments.Theclinicianshouldattempttoretrieve the fragmentusing the techniquesandequipmentavailable,butdeterminedefforts todosomayresultinaweakenedrootoraperforation.

FactorsinfluencingtheremovaloffracturedinstrumentsAvarietyoffactorsaffecttheprognosisfortheretrievalofafracturedinstrument;thesemustbetakenintoconsideration so the chance of success and the limitations of treatment can be evaluated. If a properassessmentisperformedandtherightequipmentisavailable(mostimportantlyanoperatingmicroscope),thechanceofretrievingthefracturedinstrumentnears87%(Suteretal,2005).CanalanatomyThepossibilityofaccessingandthenbypassingafracturedinstrumentdependsontheshapeofthecanal,itsdiameter,thepresenceofanycurvaturesorconcavities,andthethicknessofthedentin.LocationofthefragmentThechanceof retrievinga fractured instrument ishigher if it lies in thecoronalpartof the toothand inastraightportionofthecanal.Aninstrumentlodgedaroundacurvecanberetrievedifitispossibletobypassorifatleastone-thirdoftheinstrumentisaccessible.Ifafracturedinstrumentliesapicaltoacurvature,theonlypossibilityistotrytobypassit;thechanceofsuccessfulretrievalisverylow.TypeofinstrumentThe level of difficulty of the procedure will depend partly on the instrument that fractured. In general, astainless steel hand file is easier to retrieve than a rotary nickel-titanium instrument, which may havethreadedintothecanalwalls.CauseoffractureThismaybedifficulttoascertaininitiallybutmayhelptheoperatordecideonthebestapproach.Morethanwiththeotheraspectsofretreatment,theprobabilityofretrievingafracturedinstrumentislinkedto clinician skill and available equipment. Some techniques for removal of fractured instruments can beperformedwithoutanyspecializedequipment(eg,negotiatingpastthefragment);otherremovaltechniques(eg,ultrasonicvibration)riskfurthercomplicationssuchasperforationsandthereforenecessitatetheuseofanoperatingmicroscope.

TechniquesfortheremovaloffracturedinstrumentsThelengthof timeneededtoremoveafracturedinstrument ishighlyvariableanddependsonthetypeofinstrument, the size of the fragment, and whether the instrument has threaded into the dentin. Carefulanalysisofconventionalandangledradiographswillallowthefollowingtobedetermined:

–Canalinwhichthefragmentislocated–Sizeofthefragment–Natureoftheinstrument(eg,handfileorrotaryinstrument)–Positionofthefragmentwithinthecanal–Rootanatomy(length,curvature,thicknessofdentinalwall)–Defectsintheinitialaccesspreparation

Retrieval of a fractured instrument should never be attempted with rotary nickel-titanium instruments,whichmaythemselvesfractureandcomplicatetheproblem.

FirststepThefirststep,irrespectiveofwhattypeofinstrumenthasfractured,istomodifytheaccesscavitytocreatestraight-lineaccesstothefragment.Thisstageisfundamental: itprevents instrumentsfrombinding inthecoronal portion and allows good instrument control to be maintained. It also ensures direct vision of thefracturedinstrumentunlessthefragmentissituatedbeyondacurvature.Thisstepiscompletedwithmanualnickel-titaniuminstrumentsand/orGatesGliddenburs(Figs3-24aand3-24b).SecondstepThegoalofthesecondstepistopassastainlesssteelhandfilelaterallyalongsidethefragment;asmall-diameter (08 or 10), precurved hand file should be used with copious amounts of chelating agent. If thecanalisovalinsection,itisrelativelyeasytomovethefilelaterallypastthefragment.However,ifthecanalisroundinsectionandtheinstrumentblockstheentirelumen,thiscanbedifficulttoachieve.Incanalsthatareoval intheircoronaltwo-thirds(eg,premolars),fracturedinstrumentstendtolodgeinthecenterofthecanal,andtheclinicianmustattempttointroducethefilealongonesideofthefragment.If it is possible to pass a file the length of the fragment, hand files of increasing diameter are used withcopiousirrigationtowidentheopening(Fig3-24c).Oneoftheseinstrumentsisthenheldinplacewithgentlepressure, and ultrasonic vibration is applied to it in an attempt to elevate out the instrument fragment byvibration(Fig3-24d).Thesameresultcanbeachievedwithanultrasonicfileofdiameter15/100(Satelecor


EMS) which can be introduced into the canal alongside the fragment and vibrated gently under copiousirrigation.

Beforeusingtheultrasonicinstrumentsinmulti-rootedteeth,itisadvisabletoplacecottonpledgetsintheothercanalorificestoensurethatifthefracturedinstrumentisretrieveditispreventedfromdroppingintoanothercanal(Fig3-24e).

Inthemajorityofcases,fracturedinstrumentscanberetrievedbythistechnique.Endodontictreatmentcanthen be completed as normal (Figs 3-24f to 3-24h). In cases where a file has been negotiated past thefracturedinstrumentbutthefragmentstillcannotberetrievedafterultrasonicvibrationisused,thecanalispreparedandobturated.Thusthefracturedinstrumentbecomesembeddedinamassofgutta-perchaduringtheobturationandrarelyposesfurtherproblems.ThirdstepIfthefracturedinstrumentcannotbebypassed,thenextstepinvolvesfreeingthecoronal2to3mmofthefragment by using ultrasonic instruments to create a gutter in the surrounding dentin. An attempt is thenmadetoremovethefragmentbyapplyingultrasonicvibration.Ifultrasonicvibrationisnoteffective,specializedinstrumentsdesignedforinstrumentremovalmustbeusedto grip the fragment. These steps are difficult andmust be performedwith caution. Use of an operatingmicroscopeisessentialtoensuregoodvision,andthetipoftheultrasonicinstrumentmustbevisibleasitisintroducedintothecanaltoavoidfurthercomplicationssuchasperforations.

3-24aPreoperativeradiographofamandibularmolarwithafracturedLentulospiralfillerinthemesialcanalandperiapicallesionsassociatedwithbothmesialanddistalroots.

3-24bThefirststepinvolvesmodifyingtheaccesscavitytoensurestraight-lineaccess.


3-24cAnattemptismadetonegotiatepastthefracturedinstrumentwithprecurvedhandfiles(diameterof08or10).Ifthissucceeds,thepathwayisthenwidenedwithlargerfiles.

3-24dAhandfileisheldinplaceandultrasonicvibrationisapplied.Anultrasonicfilecouldalsobeusedalongthelengthofthefracturedinstrument.

3-24eDuringthismaneuvertheothercanalorificesmustbeprotectedbycottonpledgetstopreventtheretrievedfragmentfallingintoanothercanal,ashappenedinthiscase.


3-24fOncethefracturedinstrumenthasbeenretrieved,theworkinglengthcanbedeterminedandthecanalsarethenprepared.

3-24gImmediatepostoperativeradiograph.

3-24hHealing6monthspostoperatively.

ThecanalisfirstenlargedcoronallywithGatesGliddendrills2,3,and4(Figs3-25aand3-25b)untilthetipofthedrillcanpenetratethecanalenoughtocontactthefracturedinstrument.AsecondGatesGliddendrill,whichhasbeenmodifiedtoremovethecuttingtip,isusedatlowspeedtocreatealedgeorshelfatthelevelofthefracturedinstrument(Fig3-25c).Onceaccesshasbeenachievedandthefragmentisvisible(Fig3-25d),titaniumProUltraEndotips(Dentsply)orET20andET25(Satelec)areusedtocreateagutteraroundthefragment(Fig3-25e).Aggressivecuttingtipsarenotadvisedotherthaninthecoronalportionofawide


root because they may remove excessive dentin and risk destroying the coronal part of the instrumentfragment, thuscompromisingaccess to the remainingapical part.Onceagutterhasbeencreated in thedentin, theultrasonic tip isvibrated (while incontactwith the fragment)and rotated inacounterclockwisedirection (Fig 3-25e). In certain cases the vibrations are enough to free the fractured instrument. Theultrasonic tip also can be gently wedged between the fractured instrument and the canal wall, whichsometimescausesthefragmenttosuddenlyfreeitself.Oncethecanalisopenedendodontictreatmentcanbecontinued(Figs3-25fand3-25g).

3-25aPreoperativeradiographofamandibularmolarwithafracturedinstrumentinthemesialroot.

3-25bThecoronalaccesscavityisenlargedtoimprovevisibilityandensurestraightlineaccesstothefragment.

3-25cAGatesGliddendrillwhosecuttingtiphasbeenremovedisusedatlowspeedtocreatealedgeatthelevelofthefracturedinstrument.


3-25dBeforeusingtheultrasonicinstruments,directaccesstothefragmentmustbeachieved.

3-25eUltrasonictips(ET20orProUltra6,7,or8)arethenusedtocreateagutteraroundthefragmentandfreethecoronalaspectofit.

3-25fThisproceduremustnotbeperformedotherthanunderdirectvision,oraperforationmayoccur.Theultrasonicvibrationsaresometimessufficienttoexpelthefragmentfromthecanal.


3-25gPostoperativeradiograph.

Theultrasonic instrumentsmustbeusedwithoutwater irrigationso that visual control canbemaintainedthroughout the step. Water spray can be used to remove any debris that is generated, but its use is notadvisedwhile the instrument isactivebecausetheoperator losessightof theworkingtip. Insomecases,although the tipof the fragmentmaybesuccessfully freed, theultrasonic vibrationdoesnotdislodge thefracturedinstrument.Thefinalpossibilityforretrievingthefragmentconsistsofusingadedicatedinstrumentremovalandretreatmentsystem.

UsingtheinstrumentremovalsystemMostoftheseretreatmentsystemsconsistofahollowtubethatisplacedoverthecoronaltipofthefracturedinstrument. Once the fragment has been grasped the whole assembly is twisted and the fragment isunscrewedandremovedfromthecanal.•The“homemade”systemusesahypodermicneedle(21or25gauge)withthebevelremoved;itmayneed

tobeshortened.Theneedleisplacedinthecanaloverthefracturedinstrumentsothatthecoronalaspectofthefragmentsitswithinthelumenoftheneedle.AnH-fileofappropriatelengthanddiameterisintroducedfromtheotherendoftheneedleandthenrotatedandtwisteduntilitlocksintothefracturedinstrument.Thefracturedinstrumentcanthenbeliftedoutofthecanal.

•Avariationofthistechniqueinvolvesplacingachemicallycuredcomposite(eg,CorePasteXP,Den-Mat)downtheneedleorusingthecompositewiththeCanceliersystem(seriesofhollowtubesofvaryingdiameters).Theneedleortubeisleftinplacefor5minutesandnotmoved.Oncethecompositehasset,thewholeensembleistwistedandunscrewedtoremovethefragment.Someauthorshaverecommendedtheuseofcyanoacrylateadhesiveinplaceofthecomposite,butthismethodislessreliableandmoredifficulttocontrol.

•TheMasserannkit(Micro-Mega)isaninstrumentremovaldevicethatworksonaconceptsimilartotheneedletechnique.Thissystemconsistsofahollowextractortube,awedge,andaseriesoftrephinesthatallowaguttertobecreatedaroundthefracturedinstrument.Thehollowextractortubeisplacedintotherootcanaltocovertheexposedcoronaltipofthefragment.Thewedgeisscrewedintothetube,trappingthefracturedinstrumentagainstthewallofthetubeandallowingitsremoval.AlargeamountoftoothtissueisdestroyedwhentheMasserannextractorisused;itshouldthereforenotbeusedunlessthefracturedinstrumentissituatedinawiderootandislocatedcoronally.Forthefracturedinstrumenttoberetrieved,thediameterofthetubemustbegreaterthanthatofthefragment.Ifthediameterofthetubematchesthatofthefracturedinstrument,theinsertedwedgewillacttopushthefragmentfurtherintothecanalratherthantoengageandsecureit.ThusitisstronglyadvisedthattheMasserannextractornotbeusedinnarrow,ovalcanalsunlessthetipofthefracturedinstrumentextendsupintotheaccesscavity.

•TheDentsply’sIRS(Fig3-26)issimilartotheMasserannextractorbuthascertainadvantages.LiketheMasseranndevice,theIRSconsistsoftwohollowtubesintowhichwedgescanbeinserted,buttheIRStubeshavethinnerwallsandsmallerdiametersthantheMasseranntubes(1mmfortheblackmicrotubeand0.8mmfortheredmicrotube).Thisallowsthemtobeadvancedfurtherdowntherootcanalandcauseslessdestructionoftoothtissue.Thedistalendofeachtubehasabevellededgetohelpitslideovertheedgeofthefracturedinstrument,guidingthefragmentintothelumenofthetube.Thisisparticularlyimportantincasesofcanalcurvaturewherethefragmenttendstobewedgedagainsttheouterwallofthecurve.Thetubeisalsodesignedwithacut-outwindowinthedistalend,whichallowsthetipofthefracturedinstrumenttobedisplacedoutthroughthewindowwhenthewedgeisinsertedandtightenedagainstthefragment.

Before the IRS can be used, the coronal access must be improved (Figs 3-27a to 3-27c), and a trenchshould be created around the fragment with the ultrasonic tips so that at least 3 mm of the fracturedinstrument isexposed.Theexposed fragment is thenvibratedwithultrasonic instruments(Fig3-27d).Anappropriatelysizedtube isselectedandgently introduced into thecanal topreventanydamage; itshould


slidepassivelyintothecanalandfitoverthefracturedinstrument.Thefine,narrowwallsthatallowthetubetopenetratefurtherintotherootcanalmayotherwisefracture.Incurvedcanals,thelongpartofthebevellededgeofthetubeshouldbeorientedagainsttheouterwallofthecurve.Thewedgeisinsertedintothetubeandtwisted inacounterclockwisedirection, thusengagingandsecuringthefragmentbywedging itwithinthelumenofthetube.Thetube-and-wedgeassemblyisthenremovedfromthecanal(Fig3-27e),allowingrootcanaltreatmenttobecontinued(Fig3-27f).This system is difficult to use when retrieving fractured instruments; it is better suited to the removal ofLentulospiralfillersorsilverpoints.

FracturedLentulospiralfillersAswithsilverpoints,itisimperativethattheoperatorresistthetemptationtopullonthevisibleportionofaLentulo spiral filler. Tugging on the fragment without any preliminary preparation risks fracturing theinstrument further.Even if thecoronalaspectof the fractured instrumentappears tobe free, the fragmentmaybe trappedapically.Moreover,asLentulospiral fillersareused in theobturationstageofendodontictreatment,thefracturedinstrumentislikelytobewellcoatedinsealer.Oncetheaccesscavityhasbeenmodifiedasnecessary,anH-fileofappropriatediameterisusedalongwithasolvent toeliminateasmuchsealeraspossible fromwithin thecanalandfromthethreadsof thespiralfiller.AnH-fileofdiameter25,30,orlarger(ifpossible)isinsertedbetweenthefracturedinstrumentandthecanalwallsorpassedbetweenthethreadsofthespiralfillertoengagethefragmentandattempttoremoveit(Figs3-28aand3-28b).Afterthesealerisclearedandasmanythreadsofthespiralfilleraspossiblehavebeen freed,eitheraMasserannextractor (if the fragment issituatedcoronally)oran IRScanbeused tograspthefracturedinstrumentandremoveitwithaclockwiserotationalmovement.Unlikeotherinstruments,whichare removedwithacounterclockwise “unscrewing”motion,Lentulospiral fillersare removedwitha“screwing”motion(Figs3-28cand3-28d).

3-26TheIRSisdesignedtoremovefracturedinstruments.LiketheMasserannsystem,itemploysahollowtubeandawedgetoinsertintothetube;however,theIRStubesarenarrowerandfinerthanthoseintheMasserannkit.

3-27aPreoperativeradiographofamaxillarylateralincisorwithtwofracturedinstruments(abarbedbroachandanickel-titaniuminstrument).


3-27bAGatesGliddendrillisusedtowidenthecanalforinstrumentation.

3-27cAmodified(shortened)GatesGliddendrillisusedtoestablishaledgearoundthefragment.


3-27dUltrasonictipsareusedtocreateagutterandfreethecoronal3mmofthefragmentsoitcanbevibrated.Inthiscase,vibrationalonewassufficienttoremovethefracturednickel-titaniuminstrument.

3-27eAnIRStubeisselectedandinsertedpassivelyintothecanaluntilitcoverstheexposedcoronaltipofthefracturedinstrument.Thewedgeisinsertedandtwistedcounterclockwise;theentireassemblycanthenberemovedfromthecanal.


3-27fImmediatepostoperativeradiograph.

Thermocompactiondevices–Ifalengthofonlyafewmillimetershasfracturedofftheinstrumenttip,possiblyfromexcessivepressureor

cyclicfatigue,thefragmentislikelytobeembeddedintheguttaperchaandwillbeeasytoremoveoncethegutta-perchaisremoved.

– If thedevicebrokebecause itwas rotated in thewrongdirection,a largeportionof the instrumentmayhavethreadeditselfintothecanalwallsand/orpenetratedtheperiapicalregion.Insuchcasesitisdifficultifnot impossible to retrieve the fractured instrument.Thecoronalaspectof the fragmentmustbe freedandthenvibratedforaconsiderableperiodoftimewiththeultrasonicinstruments.TheMasserannkitcanthenbeusedwithaclockwiserotationalmovement,similartothetechniqueusedforLentulospiralfillers.ThisisoneofthefewindicationsforusingtheMasserannkitratherthantheIRSdevice,astheIRSistoofragiletowithstandtheforcesneededtoretrieveathermocompactiondevice.

SummaryThelikelihoodofsuccessfullyretrievingafracturedinstrumentshouldbeevaluatedonacase-by-casebasis.Theclinician’sownskillmustbeconsideredinadditiontothevalueandfunctionofthetooth,theamountofdentin remaining, the location of the fragment, and the nature of the fractured instrument. None of thetechniquesforremovingfracturedinstrumentsguaranteesuccessfulretrieval,andseveraldifferentmethodsmayneedtobeattemptedinanefforttoremovethefragment.Ifa fractured instrument thatcannotbebypassedor removedblocksacanal, theapicalpartof thecanalmustbe leftuntreated(Figs3-29aand3-29b).Thecoronalaspect ispreparedandstraight-lineaccess iscreated;aftercopiousirrigation,thecanalisdriedandobturated(Fig3-29c).Acoronalrestorationisplacedto ensure the root canal system is well sealed, and the tooth is monitored (Fig 3-29d). If strict aseptictechniqueshavebeenemployedandanasepticworkingenvironmentwasmaintained,theresultsarelikelytobefavorable(Fig3-29e).

Endodontictreatment isnotanendin itself. Insomecasesthedecisionshouldbemadenottoretreat,especiallyifpreviousattemptshavebeenunsuccessful.Retreatmentproceduresriskweakeningthetoothsignificantlyandendangeringitslong-termsurvival.

A recent study (Spili et al, 2005) compared the success rates of 158 endodontically treated roots, somecontaining fracturednickel-titaniumorstainlesssteel instrumentsandsomewithno fractured instruments;theoverallsuccessrate1year(ormore)postoperativelywas93.7%.


3-28aPreoperativeradiographofafracturedLentulospiralfillerinalateralincisor.Evenifthecoronalaspectofthespiralfillerisvisible,itisimperativetoresistthetemptationtograspitandpull.

3-28bAnH-fileisusedwithasolventtocleanthecanalanddisengagethethreadsofthespiralfiller.


3-28cAtubefromtheIRSisplacedpassivelyintothecanalsothespiralfillersitswithinthelumenofthetube.Thewedgeistheninsertedandscrewedintoplacewithacounterclockwiserotation.Thewholeassemblyissubsequentlyremovedwith

aclockwiserotation.

3-28dPostoperativeradiograph.

3-29aPreoperativeradiographofamandibularmolarwithperiapicallesionsassociatedwithbothroots.


3-29bRadiographtakenduringtreatmentshowsafracturedinstrumentintheapicalregionofoneofthemesialcanals.

3-29cAnattempttobypasstheinstrumentwasunsuccessful,sothecoronalpartofthecanalhasbeenprepared,cleaned,andobturated.

3-29dRadiographtaken6monthspostoperativelydemonstrateshealing.Notethepostandcorethathasbeenplacedduringthismonitoringperiod.



Intheabsenceofpreoperativeperiapicallesions,thesuccessrateforteethcontainingfracturedinstrumentswas 98.4% compared to 96.8% for teeth without any fractured instruments; this difference was notstatistically significant. In the presence of preoperative periapical lesions, the success rate for teethcontainingfracturedinstrumentswas86.7%comparedto92.9%forteethwithoutanyfracturedinstruments;thisdifferencewasagainnotstatisticallysignificant.Therefore,thepresenceofafracturedinstrumentdoesnotaffectthesuccessratefortreatmentonatoothwithoutapreoperativelesion.Thesuccessratedeclinesonly slightly for treatment on a tooth with a preoperative lesion, as long as strict asepsis has beenmaintained before (sterilizing instruments), during (use of rubber dam, copious irrigation), and after(restorationandcoronal seal)endodontic treatment.Nevertheless, in caseswhere radiographicor clinicalsignsappearorpersist,theclinicianmustconsiderasurgicalapproach.

Unlikeconventionalendodontictreatment,forwhichthereisanestablishedprotocoltofollow,retreatmentcaseshavenosettreatmentprotocolbecauseofthehugevariationfromcasetocase.Themostrationalapproach to retreatment is to adopt basic guidelines that are always followed. The clinician should befamiliarwithvariousmethodsofretreatment,so ifonetechniqueshouldproveunsuccessful,alternativetechniquescanbeemployed.Eachcasemustbejudgedindependentlyofothers.ThedifferenttreatmentoptionsdiscussedinthischapteraresummarizedinFigs3-30ato3-30e.Evenwhentheretreatedcanalcannotbenegotiated to its full length, ifgeneralguidelinesare followed, theretreatmentprocedurewillimprovetheprognosisofthetoothbyreducingthebacterialloadintherootcanalsystem.It is the responsibility of all clinicians to acknowledge their individual limitations according to abilities,experience,andtheequipmentavailable.Theaimofretreatmentistoprovideaservicetothepatientbyimprovingtheexistingsituation.


3-30aAlgorithmforretreatmentinvolvingnonsolublematerials(ie,silverpointsorhardpaste).

3-30bAlgorithmforretreatmentinvolvingsoftpaste,gutta-percha,orThermafilo.


3-30cAlgorithmforretreatmentinvolvingafracturedinstrumentthatcanbebypassedlaterally.

3-30dAlgorithmforretreatmentinvolvingafracturedinstrumentthatcannotbebypassedlaterally.


3-30eAlgorithmforretreatmentinvolvingafracturedLentulospiralfiller.


ManagementofPerforations


Aperforation in endodontics is defined by theAmericanAssociation of Endodontics as “amechanical orpathologic communication between the root canal and the external tooth surface.” The resultingcommunicationcausesinflammationandlossoftheadjacenttissues.Resorptionofthesurroundingtissuesisinducedbybacteria,whichisalsothecasewithperiapicallesions.Perforations originate from one of two etiologies: (1) pathologic, following internal/external resorption ordental caries, or (2) iatrogenic, caused by clinician error during endodontic treatment. Only iatrogenicperforationsareconsideredinthischapter.Iatrogenic perforations occur in first-time endodontic treatment frompoor angulation during access cavitypreparationorfromthecliniciansearchingforcanals.Morefrequently,theyoccurinendodonticretreatmentwhilemodifyingtheaccesscavity,debridingthepulpchamber,searchingforcanals,usingrigidinstrumentsinanuncontrolledmannertoremoveobturationmaterialfromthecanalwithoutcheckingtheangulationoftheinstruments,orattemptingtoforceaninstrumentfurthertoovercomeablockage.Ineachofthesecases,theperforationsresultfromcuttinginstruments(drillsorultrasonics)usedblindlyorfromexcessivepressureexertedoninflexiblefilesthatareincorrectlyangledinthecanal.There is no universal protocol for the treatment of perforations.Differentmaterials can be employedanddifferentapproachescanbeadopted:surgical,nonsurgical,oracombinationofboth.Athoroughclinicalandradiographic assessment should be performed before choosing the most appropriate technique for aparticularcase.

FactorsInfluencingPrognosisandTypeofTreatmentTreatmentofperforationsandthesubsequentprognosisoftheaffectedteethdependonmanyfactors(FussandTrope,1996).

AgeoflesionanddegreeofbacterialcontaminationThesetwofactorsareunquestionablythemostimportantintermsoftheprognosis.Healingisfarlesslikelyaround a long-standing, contaminated perforation with associated bone resorption than around anuncontaminatedperforationthatisobturatedimmediately.Regardlessofthecauseoftheperforation,itmustbeisolatedandobturatedasquicklyaspossibletoavoidanybacterialcontamination.

SiteofperforationThelevelandthesiteoftheperforationaffectthechanceofbacterialcontaminationandtheaccessibilityoftheperforationfortreatment.

LikelihoodofbacterialcontaminationThe prognosis for perforations situated between the base of the gingival sulcus and the bony crest isgenerally poor. The larger and more coronal the perforation is (ie, perforations caused by poor burangulation during access cavity preparation), the higher the chance of contamination and resultantattachmentloss.

Forthisreasontheperiodontalstateofthetooth,whichisevaluatedbyprobingandperiodontalindices(eg,bleeding,plaqueindex),playsanimportantroleindeterminingtheprognosisofaperforationrepair.Acommunicationbetweentheperforationandthebaseofaperiodontalpocketcompromisesthechanceofsuccess.Theprognosisisfarworseifthelesionhasbeenpresentforsometime(Fig4-1).

AccessfortreatmentThe more coronal a perforation, the more visible and the more accessible it is; the more apical theperforation,themorelimitedtheaccess.

SizeandshapeofperforationAlargeovalperforation(eg,onecreatedonthemesialsurfacesofsingle-rootedteethwhenaburisangledincorrectlyduringaccesscavitypreparation) ismoredifficult toobturateandseal thanaroundperforation(eg,onecreatedinthepulpchamberfloorofamolar)(Fig4-2aand4-2b).

PresenceorabsenceofcorticalboneAperforation resulting incompletedestructionof thebonycortex (eg,abuccalperforationonamaxillaryanterior toothwhere thebonycortex is very thin,almostnon-existent) createsdirect contactbetween theperforationand theoverlyinggingiva.Thisshouldnotbe treated in thesamewayasaperforation that iswithinbone,evenifsomeboneresorptionhasoccurred.

ChoiceofmaterialforperforationrepairThechoiceofmaterialdependsontheclinicalsituation.Themainaimistoprovidealong-lastingrepairthatcreatesagoodsealusingabiocompatiblematerial.


4-1Alargeperforationthroughthepulpchamberfloorhasresultedinsignificantbonyresorptioninthefurcationarea.Inthiscasetheonlysensibletreatmentisextraction.

4-2aPerforationthroughthepulpchamberfloorofamandibularmolar.Despitethepresenceofalesion,periodontalprobingconfirmedtherewasnocommunicationbetweenthebaseofthegingivalsulcusandthefurcation.Thistypeoflesionhasa

favorableprognosis.

4-2bRadiographtaken5yearspostoperativelydemonstrateshealingofthefurcationafterretreatmentandperforationrepairwithProRootMTA.

MaterialsUsedforPerforationRepairA variety of differentmaterials can be used to repair perforations; the choice depends on the site of the


perforationandthetypeoftreatmenttobeperformed.Forsurgicaltreatmentofabuccalperforationatthelevel of the bony crest,where hemostasis can readily be achieved, useof an adhesivematerial suchasglassionomermaybeindicated.Howeveriftheperforationoccursinthepulpchamberfloor,mineraltrioxideaggregate(ProRootMTA,Dentsply)ismoreappropriate.Asmallrootperforationsituatedintheapicalthirdofacanalcanbedealtwithasa lateraloraccessorycanal.Afterbeingcleanedit isobturatedwithgutta-perchaexactlyasifitwereanothercanal.In some situations a surgical approach is required, and the perforation should be obturated with anonadhesive material (adhesive materials are affected by moisture contamination). In these cases,Intermediate Restorative Material (IRM, Dentsply) or SuperEBA (Harry J. Bosworth) may prove moresuitablethanProRootMTA,whichrequiresadeepercavityforretention.Thematerialthatiscurrentlyfavoredforthetreatmentofperforations,especiallythoseinthepulpchamberfloor, and for the treatment of teeth with open apices ismineral trioxide aggregate (ProRootMTA). Thismaterial,whichisentirelymineralincomposition,isaformofPortlandcement.Ithasbeenshowntobeverybiocompatible and to form a good seal, though itsmechanism of action remains unclear. The powder isdispensed insealedsachetsof1gand isavailable ingreyorwhite; the latterallows foramoreestheticresultwhenperformingpulp cappingor pulpotomies in anterior teeth.Although themanufacturers advisediscardinganyunusedpowderonceasachethasbeenopened,itcanbestoredinacleancontainer(eg,anempty film canister) and sealed to preventmoisture contamination.Whenmixedwith water, this powderproducesacolloidalgelthatwilltakeapproximately4hourstosetcompletely.Thissettingtimeaffectsthewayinwhichitisused.Duringplacementandwhileitisnotfullyset,theMTAcanbeeasilywashedoutofthecavity.Thus,anyprocedures forwhich irrigation isnecessaryshouldbecompletedbefore theMTA isplaced.After theMTAhasbeenplaced, it is sometimesadvisable to cover itwith amoist cottonpledget(squeezedtoremoveexcesswater)tohydratethematerialasnecessarytoachieveafullset.Inmostcases,themoistureprovidedbytheadjacenttissuesissufficient.Enoughpowder ismixedwithwatertoobtainarelativelythickpastewithaconsistencysimilartothatofatemporarycement.

Ifthemixistoothinorthematerialiscoveredwithawetratherthanamoistcottonpledget,thesettingreactioniscompromised.TheProRootMTAhasanalkalinepH(approximately13),anditssettingreactioniscompromisedbythepresenceofpus.CopiousirrigationwithsodiumhypochloriteandatemporarycalciumhydroxidedressinginthedefectshouldresolvetheinflammationandallowthepHtoreturntonormal.

Theusualworkingtimeofthematerialisapproximately5minutes,butitcanbeincreasedbycoveringthemixwithdampgauze.Studies have been published that clearly demonstrate the superior biocompatibility and sealing ability ofProRootMTAcomparedwithotherconventionalmaterialsusedforthetreatmentoflateralperforationsandperforationsof thepulp chamber floor (Leeet al, 1993;Nakataet al, 1998).Theperiodontal tissues thatcontacttheProRootMTAregeneratewiththeformationofacementum-liketissueoranepithelialattachmentwithdirectcontact(PittFordetal,1995;Torabinejadetal,1997;Hollandetal,2001).Oneoftheadvantagesofthismaterialliesinitshydrophilicnature;thispropertyallowsthematerialtoproduceagoodsealevenina cavity contaminated by blood or moisture (Torabinejad et al, 1994). MTA is currently considered thematerial of choice for the treatment of perforations, provided the indication for its use has been correctlyidentified.

PerforationsintheCoronalThirdPerforationsinthecoronalthirdaregenerallyeasiertoaccess,buttheprognosiscanprovelessfavorablethaninmoreapicalperforations.Thisdiscrepancyislinkedtotwofactors:(1)sizeandshapeofthedefectand(2)locationofthedefect.Theseperforationsaregenerallylargeandarecreatedwhenrotaryinstruments(burs,GatesGliddendrills)areusedforaccesscavitypreparation.Furthermore,sincetheperforationiscreatedlaterally,theinstrumentwill nothavebeenangledperpendicular to the root surface.The resultantperforation tends tobeoval inshape,andplacementofobturationmaterialinadefectlikethisisdifficulttocontrol.Iftheperforationissuprabony,theremaybeacommunicationbetweentheperforationandthebaseofthegingival sulcus or a periodontal pocket.Amultidisciplinary approach, including orthodontic traction and/orperiodontalsurgery,maybenecessary.

The clinician should routinely check for a communicationwith the sulcus by probing the affected areabeforeanydecisionaboutretreatmentismade.

Anteriorteeth

Perforations inmaxillary incisorsandcanines tend tooccuron thebuccalaspectwhenan instrumenthasbeenangledpoorlyduringaccesscavitypreparationorpost-holepreparation.Adefectmaybesuprabony,infrabony,or liepartiallyabovethebonycrestandpartially incommunicationwiththesulcus.Treatmentisdifferentineachcase,soperiodontalprobingisessentialtodeterminethenatureoftheperforation.


SuprabonyperforationIntheinstanceofsuprabonyperforation,repairofthedefect is integratedintothecoronalrestoration,withpriorcrownlengtheningifnecessary.

InfrabonyperforationThebuccalcortexofbonemustbeassessed.This isdonebyinsertionofalong,blunt instrument(eg,anamalgamplugger)intotheperforationwhiletheclinicianplacesafingeroverthebuccalaspectofthetoothinthecervicalregion.Iftheinstrumentispalpatedbeneaththegingiva,bonydestructionhasoccurred.Theextentofthebonydestructiondeterminesthetypeoftreatmentchosenandtheobturationmaterialused.•Ifthereisnocommunicationwiththegingivalsulcusandthebuccalbonehasnotbeendestroyed(Fig4-3a),itisnecessarytoadoptacoronalapproachandobturatetheperforationwithProRootMTA.Thecanalisfirstidentified,prepared,andcleaned(Fig4-3b).Perforationsgenerallyoccuronthebuccalaspect,sotheclinicianshouldlookforthecanalpalatally.Theperforationiscleanedwithasmallexcavatorandultrasonicinstruments,thenisolatedwithacottonpledget.Afterdryingthecanal,aprefittedguttaperchapointcoveredinsealerisplacedintothecanalandsectionedjustbeneaththeleveloftheperforation(Fig4-3c).Thisisthencondensedtoensuretheobturationoftheapicalpartofthecanal(Fig4-3d).Thecottonpledgetisremovedandtheperforationisobturated.ProRootMTAismixedwithenoughwatertoobtainapastewithaconsistencysimilartothatofCavit(3MESPE).ThematerialisloadedintotheMTAGun(Dentsply),adevicesimilartoanamalgamcarrierwitharangeofsmall-diameterstraightandcurvedtips(Fig4-3e).TheProRootMTAisdispensedintotheperforationanddelicatelycondensed,bringingthematerialintocontactwiththeadjacentperiodontaltissues;thisstagecanbedoneusingeitherapluggerorthebuttendofapaperpoint(Fig4-3f).Theaimisnottoobtainaperfectsealbycondensingthematerialasifitweregutta-perchabutsimplytobringitintocontactwiththetissues.ThismaneuverisrepeatedwithoneortwofurtheradditionsofMTAtocompletetheobturation,whichcanbecheckedradiographically(Fig4-3g).Thetoothcanthenberestoredduringsubsequentappointments(Fig4-3h).

4-3aPreoperativeradiographanddiagramdemonstratingamaxillarylateralincisorwithabuccalperforationcreatedduringpost-holepreparation.Conventionalright-angledradiographsofbuccalperforationscanbemisleadingandmaynotreveal

thedefect.


4-3bThecanalislocatedandexistingobturationmaterialisremoved.Thecanalisthenpreparedandcleaned.RubberdamhasbeensecuredwithWedjets(Coltène/Whaledent)placedbeneaththecontactpointsoftheadjacentteeth;resinisused

tobondthedamtothetoothundergoingtreatment.

4-3cAgutta-perchapointispreparedandaradiograph(left)istakentocheckthatitreachestothefulllengthofthecanal.Oncethecanalhasbeendried,thegutta-perchapointiscoveredinsealerandinsertedintothecanal.Itissectionedjust

belowtheleveloftheperforationusingaheatedinstrumentsuchasaBuchananSystemBPlugger(SybronEndo).

4-3dThegutta-perchapointisthencondensedwithaheatedinstrumenttoensurethattheapicalportionofthecanaliswellsealed.


4-3eProRootMTAisloadedintotheMTAGun.

4-3fProRootMTAisdispensedintotheperforation(left)andthendelicatelybroughtintocontactwiththetissueswiththeaidofaplugger.Thismaneuverisrepeateduntiltheobturationiscompleteandtheperforationdefectissealed.


4-3gAradiographistakentochecktheplacementofthematerial.

4-3hRadiographtaken1yearpostoperatively.Clinicalexaminationrevealsthatthetoothisfunctionalandperiodontallysound.

•Incaseswheretheperforationisincommunicationwiththesulcusorliespartlyaboveandpartlybelowthebonycrest,obturationfromthecoronalaspectisdifficult(Fig4-4a).Dependingonthelengthoftheroot,themesiodistaldimensionsoftheaffectedtooth,andtheanticipatedestheticresult,rapidorthodontictractionmaybeindicatedtopositiontheperforationabovethebonycrest.Alternatively,asurgicalapproachmaybeadopted,inwhichtheperforationisexposedwithafull-thicknessflapandboneisremovedtoallowgoodaccesstotheperforation.Oncegoodhemostasishasbeenachieved(Fig4-4b),theperforationissealedwithanadhesivematerial(Figs4-4cand4-4d)toprovideanimmediateseal.Regularclinicalandradiographicmonitoringisessential(Figs4-4eand4-4f).


4-4aPreoperativeradiographanddiagramdemonstratingacentralincisorwithabuccalperforationandfracturedLentulospiralfiller.Clinicalexaminationrevealeddestructionofthebuccalcortexandaperforationlyingpartlyaboveandpartly

belowthebonycrest,communicatingwiththesulcus.

4-4bViewoftheperforationoncegranulationtissuehasbeencurettedaway,boneremoved,andhemostasisachieved.


4-4cViewoftheperforationafterobturationwithanadhesivematerial(Dyract,Dentsply).Thematerialwaspolishedafterplacement.

4-4dImmediatepostoperativeradiograph.Therepairedperforationisvisible(arrow).

4-4eand4-4fClinicalphotographandradiographtaken8yearspostoperatively.Therightcentralincisor,extracted4yearspreviouslybecauseoftrauma,hasbeenreplacedwithafixedpartialdenture.


In theabsenceofabonycortexandwhereadirect communicationexistswith thebuccalaspect, useofProRootMTAisnotrecommendedbecauseitmaycrumbleandwashawaybeforeitisfullyset.

Posteriorteeth

Inposterior teeth, perforations in the coronal thirdaredealtwith in the samewayas theyare inanteriorteeth.Access ismoredifficult,andsurgicalororthodontic treatment iscomplicatedby theriskof furcationinvolvement.Aftertheperforationisidentifiedonapreoperativeradiograph(Fig4-5a), it iscleanedandirrigated(Fig4-5b).ProRootMTA isdispensed into theperforationa littleata timefromtheMTAGun;with thehelpofapluggerorthebuttendofapaperpoint,theMTAisdelicatelybroughtintocontactwiththeadjacenttissues(Figs4-5cand4-5d).Amoistcottonpledget,squeezedtoremoveexcesswater,isplacedoverthematerial,and a temporary filling is placed in the tooth. It is advisable to prepare and obturate the canals beforerepairing the perforation defect. In thisway, the perforation is disinfected by the hypochlorite bathing theaccesscavityduringcanalpreparation.ObturatingthecanalsbeforerepairingthedefectalsopreventsanyProRoot MTA from falling into the canals during the perforation repair. Nevertheless, in certain cases inwhich it is impossible to dry the root canal systemadequately, the canals cannot be obturated first. Theentrances to the prepared canals must be protected with cotton pledgets during the placement of theProRoot MTA. The canals are then obturated at a later visit (Fig4-5e). A coronal restoration should beplacedassoonaspossibleaftercompletionoftheendodontictreatment.Regularclinicalandradiographicexaminationisnecessarytomonitorthetooth(Fig4-5f).

4-5aPreoperativeradiographofamaxillarymolarwithabuccalperforationthroughwhichalargeamountofobturationmaterialhasbeenextruded.

4-5bAlarge-diameterH-filewasusedtoremovetheextrudedgutta-percha.Thepalatalcanalwasalsoclearedofobturationmaterial.


4-5cTheProRootMTAisloadedintotheMTAGun,dispensedintotheperforation(left),andplacedincontactwiththeadjacenttissues.Inthiscase,theperforationwasrepairedbeforethecanalswereobturatedbecauseofdifficultieswith

moisturecontrol.

4-5dTheperforationrepairisverifiedradiographically.Inthiscase,theperforationwascreatedbuccaltothetwobuccalcanals(redarrow).

4-5ePostoperativeradiographafterobturationofthecanals(completedatasubsequentvisit).



FurcationorStripPerforationsLateral perforations in the furcation region occur after over–instrumentation of the inner furcalwall of thecanals.Knownasstripperforations,thesecanoccurinanyroot.Mesialrootsofmolarsaremostfrequentlyaffected (Fig 4-6) because of their specific anatomy, which includes a concavity that is not evidentradiographicallyandcanalsthatareoff-centerinrelationtothefurcation.Uniformremovalofdentinduringcanalpreparationmayleadtoperforationsintheinterradicularwalls.Stripperforationsaredifficulttotreatbecausetheedgesofthedefectareirregular.Theseperforationstendtoberelativelylargewiththin,jaggededgesresemblingatearoraripinthecanalwall.Ifthedefectisnotrepaired,theresultinginterradicularbonelosswillinevitablyleadtoeventuallossofthetooth.Astripperforationcanoftengounnoticedduringcanalpreparation. Itmaybecomeevidentonlyafter thecanal isdried,whenadropofbloodmaybeseenonapaperpointaftercontactwith theperforationsite.Treatmentshouldbeattemptedasfollows:hemostasis isobtainedandthecanal isobturatedbyplacingagutta-perchapointintotheapicalportionofthecanal,sectioningitjustbelowtheleveloftheperforationandthencondensingit.Inthisway,theapicalpartofthecanalisobturatedwithgutta-perchauptotheleveloftheperforation.TherestofthecanalisobturatedwithProRootMTA.Inothercases,theinnerfurcalwallofthecanal,weakenedduringthepreparationstage,cangivewayunderthe pressure of obturation; sealer and dentin debris pass through the perforation and enter the furcationregion. Often, only when the postoperative radiograph is taken does it become apparent that a stripperforation has occurred and the root canal system is not adequately sealed.Someauthors recommendimmediatesurgicalinterventiontosealthedefect,thusavoidingperiodontalinflammationandresultantboneloss.Surgical treatmenthasabetterprognosis ifcompletedwhile thetooth isperiodontallysound.Afteracoronal restoration has been placed, a full-thickness flap is raised. Preserving a cervical band of bone,interradicularboneisremovedtoallowtheareatobeaccessedandcleaned.Dentinchipsandsealerarecurettedaway,andthegutta-perchaisburnishedagainstthewalloftherootcanal.Treatment results from strip perforations remain unpredictable, and there are few guidelines available.Treatment options include repairing the defect and restoring the tooth, sectioning the affected root, orextractingthetoothandplacinganimplant.Theseshouldbediscussedwiththepatient,andtheadvantagesanddisadvantagesofeachmustbeclearlyexplained.


4-6Stripperforationinthefurcationregionofamandibularmolar.

PerforationsofthePulpChamberFloorUnlike lateral perforations, which tend to be oval in shape, perforations of the pulp chamber floor aregenerallyroundandthereforeeasiertoobturate.Theprognosisisneverthelessdependentontheproximityofthesulcusandthepresenceofacommunicationbetweentheperforationandtheoralcavity.Aswithallperforationsthemaingoalistopreventbacterialcontamination.Thus,ifaperforationiscreatedduring access cavity preparation, repair should be made at the same visit and not delayed until asubsequentappointment.Inthecaseofapre-existingperforation,thegoalofobtainingagoodsealremainsthesame,buttheproceduremayvarydependingontheclinicalscenario(Fig4-7a).Afterrubberdamhasbeenplacedandtheaccesscavitymodified,thestagesoutlinedbelowshouldbefollowed(Box4-1).

Box4-1Stagesoftreatmentforrepairingthepulpchamberfloor

1.Thecanalsarelocatedandtheperforationidentified.

2.Thecanalsarepreparedundercopiousirrigationwithsodiumhypochloriteandthenobturated(Fig4-7b); a cotton pledget is used to protect the perforation and prevent sealer being extruded through thedefect.

3.TheperforationisobturatedwithProRootMTA.ThematerialisloadedintotheMTAGun,dispensedintotheperforation(Fig4-7c),andthencarefullypackedintothedefectusinganamalgampluggerorthebuttendofapaperpoint(Fig4-7d).ThepluggerselectedforusemustbeofapproximatelythesamediameterastheperforationtoenabletheoperatortopacktheMTAproperlyagainstthetissues.Ifthepluggeristoosmall, there is a risk of forcing the material into the furcation region. Because of the excellentbiocompatibility ofMTA, extrusion of thematerial will not compromise healing, but the excessmaterialservesnopurposeandthereforeshouldbeavoidedasmuchaspossible.

4.Oncetheperforationhasbeenobturated,amoistcottonpledget isplacedoverthesiteofrepair,andthecanaliscoveredwithatemporarydressing(Fig4-7e).

5.Betweenappointments,theProRootMTAhastimetoreachafullset,butacoronalrestorationmustbeplaced as soon as possible to ensure a good seal. Regular clinical and radiographic monitoring isnecessary(Fig4-7f).

Insomesituations theperforationmustbe repairedbefore thecanalsareobturated. If thecanalsarenotready for obturation at the end of the appointment (eg, existing root canal filling remaining, toothsymptomatic,moisturecontroldifficult),theperforationrepairshouldneverthelessbecompletedratherthanbeingdelayeduntilthenextvisit;thisallowsthematerialtoreachafullsetbetweenappointments.InthesecasesitisprudenttoprotecttheentrancestothecanalsbeforeplacingtheMTA.Onceset,ProRootMTAisverydifficulttoremove.


4-7aPreoperativeradiographofamandibularmolarwithaperforationofthepulpchamberfloor,whichisnotevidentradiographically.Periodontalprobingrevealedanormalsulcusdepth.

4-7bClinicalphotographoftheperforationclosetotheentranceofthedistalcanal.Thecanalshavebeencleanedandobturated.

4-7cProRootMTAisdispensedintotheperforationwiththehelpoftheMTAGunandthendelicatelypackedintothedefect.


4-7dClinicalphotographoftheperforationafterobturation.

4-7ePostoperativeradiographdemonstratingtheperforationrepair(arrow)andtheobturatedcanals.



PerforationsoftheMiddleandApicalThirdsoftheCanalPerforationsinthemiddlethirdofthecanaltendtooccuronthebuccalorlateralaspectoftherootduringinappropriate post-hole preparation, as the clinician searches for canals or, more commonly, when aninstrumentisforcedapicallyinanattempttonegotiateablockedorcalcifiedcanal.Thechoiceoftreatmentdependson thesizeandsiteof theperforation, thepresenceofapost,and thenatureandqualityof thecoronalrestoration.Whenattemptingretreatmentviaacoronalapproach,twoproblemsarelikely:difficultyin(1)identifyingthesite of perforation and (2) locating the “true” canal. Identifying the site of the perforation can be difficultbecauseitmaybelocatedonanyofthetooth’ssurfaces.Aradiographprovidesonlylimitedinformation,andan additional angled view can be helpful. The “true” canal is elusive because the perforation is oftenaccompaniedbyablockageinthetrue,anatomiccanal.Asaresult,instrumentstendtoentertheperforationsite(“false”canal)ratherthantheunpreparedorpreviouslyobturatedtruecanal.Thetechnicaldifficultyintreatingperforationsinthemiddleandapicalthirdsviaacoronalapproachstemsfrom poor visibility and the fact that the true and false canals will follow a common path for severalmillimetersandthenbifurcateinaregionwhereaccessandvisionareseverelylimited.Furthermore,iftheperforationwascreatedduringanattempttonegotiateablockedorcalcifiedcanal, findingthepathof theoriginalcanalcanprovetobeverydifficultorevenimpossible.However, when a perforation results from overpreparation of a canal, during post-hole preparation forexample, finding the path of the true canal is relatively easy because the canal will have already beenenlargedduringinitialpreparation.Ifcoronalaccessisfeasible,theaccesscavityismodifiedandthecoronalpart of the canal enlarged so the true canal can be located. The treatment that follows depends on thediameterofthecanalandthesizeoftheperforation.

SmallperforationsAsmall-diameterperforationcanbetreatedintwoways:1.As an additional canal. The working length of the perforation is determined, and the false canal isprepared,cleaned,andfilledexactlyasifitwereanordinarycanal.2.Asalateralcanaloranapicaldelta.Inthiscase,oncethetruecanalislocated(Figs4-8aand4-8b),itispreparedandcleaned(Fig4-8c).Theperforationisfilledasifitwasalateralcanal,andwhengutta-perchaiscondensed into themaincanal,sealer is forcedalong thepathof the lateralcanalorperforationdefect(Figs4-8dand4-8e).Thisprocedureismuchmoredifficultiftheperforationislocatedapically(Fig4-9a).Inthecaseofacurvedcanal, findingthetruecanalcanproveparticularlydifficult ifnot impossible.Aftertheexistingrootcanalfillinghasbeenremovedfromthecoronalpartofthecanal,theperforationisclearedofanyobturationmaterial.Aprecurvedsmall-diameterstainlesssteelhandfileisusedtosearchforandlocatetheapicalpathofthetruecanal(Fig4-9b).Oncefoundandnegotiated,thecanalispreparedtoitsfulllengthandcopiouslyirrigated.Alltheinstrumentsusedinthissequenceshouldbeprecurvedsothattheycanbeplaceddirectlyintothecanalwithoutriskofenteringthefalsecanalandwideningtheperforation.Thegutta-perchapointmustalsobeprecurvedtoallowitsfittinginthecanal.Thegutta-perchapointiscoveredwith


sealerandinsertedintothecanal;ifthereisanydoubtaboutitsposition,aradiographcanbetakentocheckthat the gutta-percha point is in the correct position. It is then compacted using vertical compaction.Hydraulic pressure is sufficient to allow obturation of the perforation (Fig 4-9c). Postoperative follow-upallowsthetoothtobeassessedandmonitored(Fig4-9d).Incaseswhere the truecanalcannotbenegotiateddespiteseveralattempts, theperforation ismeasuredandthenpreparedandfilledlikeanormalcanal.Surgicalinterventionwithretrogradefillingmaybeindicatedifclinicalorradiographicsignsdevelopandfurtherretreatmentbecomesnecessary.

4-8aRadiograph(providedbythereferringpractitioner)demonstratingasmall-diameterfileinabuccalperforationthathadbeenaccidentallycreatedduringeffortstoremovetheexistingobturationmaterial.

4-8bPreoperativeradiograph.


4-8cRadiographdemonstratingthepathofthecanalthatwasfound.RubberdamisheldinplacewithWedjets.

4-8dRadiographoftheobturatedcanalandtheobturatedperforation.Inthiscasetheperforationwastreatedlikealateralcanal.Onlythemaincanalwasprepared,undercopiousirrigation,andobturatedwithgutta-percha.



4-9aPreoperativeradiographdemonstratinganapicalperforation(redarrow)probablycreatedasaresultofalarge-diameterstainlesssteelhandfilebeingusedwithexcessivepressure.Thetrueapicalopeningofthismandibularmolarin

factliesdistaltotheperforation(yellowarrow).

4-9bAftertheexistingrootcanalfillinghasbeenremoved,precurvedsmall-diameterhandfilesareusedtofindthetruepathway.


4-9cAseriesofprecurvedinstrumentsisusedtopreparetheapicalpartofthecanal,andthecanalisthenobturatedwithguttaperchausingwarmverticalcondensation.Theperforationisobturatedbyhydraulicpressureinthesamewaythatan

apicaldeltawouldbe.

4-9dRadiographtaken3yearspostoperatively.

LargeperforationsLarger perforations should be obturated with ProRoot MTA. These bigger defects are often caused byexcessivepost-holepreparation(Fig4-10a).Beforetreatmentstarts,periodontalprobingmustbeperformedtocheck that there isnocommunicationbetween theperforation, the lesion,and thebaseof thegingivalsulcus.Thepostisremovedasdescribedinchapter2.

Box4-2Clinicalprotocolforobturatingperforations

1.Theportionofthecanalcoronaltotheperforationiscleanedanddisinfected.

2.Afine,precurvedhandfileisusedtofindthepathoftheapicalpartofthecanal.Thecanalispreparedanddisinfectedintheconventionalmanner(Fig4-10b).

3.Agutta-perchapointisadjustedtotheworkinglength,andtheapicalpartiscoveredwithsealerbeforebeinginsertedintothecanal.Thegutta-perchapointissectionedjustbelowtheleveloftheperforation(Fig4-10c)andthencondensed(Fig4-10d).

4.TheperforationisobturatedwithProRootMTA.ThisisdispensedfromtheMTAGun(Fig4-10e)andthencarefullypackedintothedefectwithapluggerorthebuttendofapaperpoint(Fig4-10f).

5.Amoistcottonpledgetisplacedintheaccesscavityandcoveredwithatemporarydressing.

6.Adefinitivecoronalrestorationmustbeplacedassoonaspossible.Regularclinicalandradiographicfollow-up allows healing to be assessed and will help determine if further adjunctive treatment isneeded(Fig4-10g).


4-10aPreoperativeradiographdemonstratingafurcationdefectthatcorrespondstoaperforationcreatedduringpreparationforthepostinthedistalcanal.Clinicalexaminationrevealedtheintegrityoftheepithelialattachmentandconfirmedthe

absenceofacommunicationbetweentheoralcavityandthelesion.Acoronalapproachwasdecided.

4-10bAfterremovingthepost,thecanalsarelocated,existingobturationmaterialisremoved,andcanalpreparationiscompletedundercopiousirrigation.

4-10cThecanalisdriedandapreparedgutta-perchapointwithsealerontheapicalaspectisinsertedintothecanal.Itisthensectionedjustbelowtheleveloftheperforation(left)andcondensedapically.


4-10dRadiographtoassesstheapicalobturationofthedistalcanal.

4-10eProRootMTAisplacedintotheperforationwiththeMTAGun.

4-10fAdditionalProRootMTAisplacedintothecanalandgentlypackedintothedefectusingapluggerorthebuttendofapaperpoint.Aradiographallowstheobturationtobeassessed.


4-10gRadiographtaken2yearspostoperatively.

Incaseswherepost removal looksdifficultand there isahigh riskof fracturing the rootbyattempting todislodgethepost,asurgicalapproachmaybeindicatedforfirst-linetreatment(Fig4-11a).A full-thicknessflap is raised to provide access to the lesion. Granulation tissue is removed by curettage. The defect ispreparedwithsurgicalultrasonictipsandthenobturated. If theroot filling in theapicalpartof thecanal isinadequate,thiscanbedealtwithatthesametimebyresectingtherootendandplacingaretrogradefilling.The bony cavity is cleaned and debrided and the flap sutured in place. Postoperative radiographs allowhealingtobemonitored(Figs4-11band4-11c).Such clinical situations can be difficult to manage, especially if the post extends to the level of theperforation. In these cases it is difficult, if not impossible, to create a cavity deep enough and retentiveenough to ensure a good seal. Thismust be taken into considerationwhen treatment options are beingdiscussed.Iatrogenicperforationsoccurringduringendodontictreatmentareparticularlydispleasingfortheclinicianandcanhavesignificant implications for thepatient.Fearofcreatingaperforationoftenpreventspractitionersfrom undertaking retreatment when it is indicated. It is imperative that every effort be made to avoid aperforationbyfollowingthesimpleguidelines(Box4-3)thatareoftenneglected.

4-11aPreoperativeradiographofalateralincisorwithadistalperforationatthebaseofthepost.Inthiscase,itwasdecidedthat,giventhesizeofthepostandtheamountofremainingrootstructure,thetreatmentwouldbeperformedfromasurgical

approach.


4-11bImmediatepostoperativeradiographshowingtheperforationrepairandtheretrogradeobturation.

4-11cRadiographtaken1yearpostoperatively.

Box4-3Generalguidelines

Preoperativeradiographsallowthecliniciantodeterminetheangulationofthetoothforcorrectpositioningofinstruments,theshapeandcontentsofthepulpchamber,andthepossibilityofanyblockedcanals.

Additionallightingandmagnificationvastlyimproveoperatingconditions;theoperatormustmaintaindirectvisualaccesstocuttinginstrumentsinthepulpchamber.Usefulaidsincludeloupesoramicroscope,long-shankburssotheheadofthehandpiecedoesnotrestrictvision,andultrasonicinstrumentsdedicatedtoendodonticretreatment.

During removal of obturation material, instruments must never be forced apically if resistance isencountered.Radiographstakenduringthisstageoftreatmentwillallowassessmentofthecauseoftheblockage.

Ifaperforationshouldoccurduringtreatment,themaingoalistopreventbacterialcontamination.


Withapre-existingperforation,theextentofdamagetothetoothandtheperiodontaltissuesmustfirstbeassessed;a treatmentplancanbedevisedaftera thoroughclinicaland radiographicexamination.Theultimateaimistoobtainagoodsealusingwhichevertechniquesandmaterialsaredeemedmostsuitableinthatparticularcase.


TreatmentofTeethwithOpenApices


Teethwith openapicesareparticularly complex tomanage.Thewidthof the root canal, the largeapicalopening,andthethinrootcanalwallsmakethepreparation,cleaning,andgutta-perchaobturationoftheseteethmoredifficultthantreatmentofatoothinwhichrootformationiscomplete.

ImmatureTeethRootsareformedbyodontoblastsinahealthypulp.Dentinislaiddowninacoronal-apicaldirectionandinacentripetal manner, thus progressively reducing the size of the canal lumen. If the tooth is subjected totrauma,theneurovascularbundlethatissituatedapicallymaybedamaged.Theresultisoneoftwopossibleclinical scenarios: (1) the foramen is large enough that over a period of several weeks revascularizationoccursbetweenthesurroundingperiapicaltissuesandthepulptissue;or(2)thevascularsupplyislost,thepulpaltissuebecomesnecrotic,andlossofthedentin-formingcellscausesrootformationtocease.Aftertraumaitisoftendifficulttodeterminethepulp’sstatus.Applicationofathermalstimulusmaybefeltbythepatient,but this isnotaguarantee that thepulpwill retain longtermvitality.Vitality testing,particularlythermal stimulation, evaluates pulpal response and the integrity of nerve fibers but does not assess thevascularization of the pulp tissue. Immediately after trauma, nerve fibers may persist even though thevascularsupplyhasbeeninterrupted.Intheabsenceofbloodflowwithinthetissues,thefiberswillrapidlybecomehypoxicanddisappear. It isonlyatthisstage,sometimesseveraldaysaftertheincident, thatthevitalitytestswillbenegativeandthediagnosisofnecrosiscanbemade.Itisthereforeimportantinthedaysandweeksaftertraumatoperformrepeatvitalitytestsandcheckthereproducibilityofresults,beforemakingadecisionabout the tooth’svitality.Furthermore, followinga traumaticepisode thenerve fibers ina toothmaybeunable to transmitnerve impulses forashortperiod.Thisphenomenon isknownaspulpal shockand does not signal loss of pulp vascularization. This is commonly seen in immature teeth; the neuronalnetworkisincompletelyestablishedatthisage,andthereforeadisorderedresponsetoastimulusmayoccurthatdoesnotindicatetruenecrosis.Itisthereforecrucialthatthepractitionerdoesnotperformapulpectomyonthedayoftheincidentpurelyonthebasisthatthermalstimulationdoesnotelicitaresponse.Emergencytreatmentshouldbecompletedonlyasnecessary; thepatientshouldbeevaluatedseveraldays laterandthenagainafteraperiodofseveralweekstorepeatthevitalitytests.Electricpulptestsarethemostreliablediagnostictool.Thelevelatwhichthestimulusevokesaresponsecanbenotedandresultscomparedoveraperiodoftime,whichgivesanideaoftheevolutionofthepulpalstate:– If the value or reading falls over time, the nerve fibers are becoming more easily stimulated and the

prognosisisgood.–Conversely,ifthevalueincreases,thenervefibersarebecominghypoxicandthereisahighchancethat

necrosiswillensue.Monitoring (short-, medium-, and long-term) is essential in such a situation. A pulpectomy should beconsideredonlyinthefollowingsituations:–Significantpainindicatingapulpitis(rare)–Absenceofclinicalsignsbutcontinuednegativethermaltestsafteramonitoringperiodofseveralweeks,

and/orincreasedelectricpulptestreadingsfrommonthtomonthuntilthereisnoresponseatall–Discontinuationofroot formation(determinedradiographicallyoverseveralmonths)signalingthe lossof

dentin-formingcells–Clinicalsignsofinfection(eg,abscess,fistula).–Appearanceofanapicalradiolucency,suggestingalesionofendodonticorigin.Thismustbeapproached

withcaution,however,becausetheradiographicappearanceofnormaltrabecularbonearoundtheapexofanimmaturetoothisverysimilartotheradiographicappearanceofalesionofendodonticorigin.

TreatmentbyApexogenesisApexogenesisisthebiologicprocessresponsiblefortheformationoftherootontheapexofthetoothandthecompletionoftheapex’sgrowth.Treatmentbyapexogenesisreferstoaprocedurethatallowstheroottip of an immature tooth to continue forming after trauma; this is done by protecting and conserving thedentin-formingcellsbykeepingthepulpvitalifpossible.Incasesofpulpexposurethroughcoronalfracture,asuperficialpartialpulpotomyshouldbecompletedassoonaspossible;thismustbefollowedupbydirectpulpcappingtopreventbacterialcontaminationandnecrosis.A number of materials have been proposed for use in pulp capping. Calcium hydroxide has long beenrecognizedasasuitablematerialthatiscapableofstimulatingtheformationofadentinbridgetoprotecttheunderlying pulp. Currently, ProRoot MTA appears to be the material of choice for direct pulp capping. Itstimulatestheformationofahardtissuebridgethat, intermsofstructureandsealingability, issuperiortothoseinducedbyothermaterials(Aeinehchietal,2003).DespitethedevelopmentofnewmaterialssuchasMTA,withitswiderangeofpossibleuses,asuperficialpartialpulpotomyandpulpcappingshouldnotbeperformedonan inflamedpulp(Figs5-1ato5-1f).Thistreatment should therefore not be performed on a carious, symptomatic tooth; Pulp capping should belimitedtothetreatmentofpulpalexposuresfollowingtraumawithanassociatedcoronalfracture.Assoonasthepulpcomesintocontactwiththeoralcavity,thesuperficialpulpallayeriscontaminatedandinflammatoryprocesses are activated in response. A partial pulpotomy to a depth of 2 mm is sufficient to remove this


superficiallayerofcontaminatedpulptissue.Thispulpotomyisperformedwitharoundtungstencarbideburonacontra-anglehandpieceorwithultrasonicsurgicalinstrumentscombinedwithwaterirrigation.Theburselectedforuseshouldbeslightlylargerthanthepulpexposuretoallowsimpleremovaloftheinfectedpulptissue; care must be taken not to catch the pulp on the rotating instrument and cause complete pulpextirpation.A largepaperpointwithabuttenddipped in2.5%sodiumhypochlorite isused toapply lightpressure to thepulp for5minutes toachievehemostasis.MTA isplaceddirectlyover thepulpandgentlypackedintoplaceusinglargedrypaperpoints.Thecoronalrestorationmustbeplacedassoonaspossible.

5-1aThis7-year-oldchildsufferedtraumatotherightmaxillarycentralincisor(seeninamirror),resultinginacoronalfracturewithpulpalexposure.Theconcomitantluxationhasbeenreducedandasplintplaced.Rubberdamcouldnotbe

used,sotheoperatingfieldiskeptdrywithcheekretractorsandaspiration.

5-1bRadiographshowingthatrootformationofthemaxillarycentralincisors,particularlythatontherightside,isincomplete.


5-1cPartialpulpotomyperformedwithsurgicalultrasonicinstrumentscombinedwithwaterirrigation.

5-1dProRootMTAplaceddirectlyoverthepulpandcondensedwithalarge-diameterpaperpoint.Glassionomercementisthenusedtoprovideagoodcoronalsealuntiladefinitiverestorationcanbeplaced.

5-1ePostoperativeradiograph.


5-1fRadiographtaken18monthspostoperativelyshowsthatrootformationcontinuednormally(possiblyevenslightlyquickerthantheadjacentnontraumatizedintooth).Prompttreatmentandtheuseofabiocompatiblematerialwithgood

sealingpropertiesallowedthevitalityofthetoothtobemaintained.

TreatmentbyApexificationIncaseswherethetooth’svascularsupplyhasbeeninterrupted,thepulpbecomesnecroticandendodontictreatment is indicated. Endodontic treatment of immature teeth has long been considered a challenge.Differences in morphology cause inherent difficulties: the presence of thin dentinal walls and thereforereducedmechanicalresistanceofthetooth;thesizeofthecanallumenandforamen,andtheabsenceofanapicalconstriction,whichmakesitdifficulttocreateanapicaltaperandachievethedesiredresistanceformto facilitateobturation;and thesometimesdivergentnatureof thecanalwalls,dependingon thestageatwhichrootformationceased.Numerous techniques and materials have been proposed to induce apical closure, a process known asapexification(Webber,1984).Thesearebasedoneitherofthefollowing:–Theuseofcertainmaterials,primarilycalciumhydroxide,whichdirectlyinduceapicalclosure.Onceapical

closurehasbeenachievedby theformationofamineralizedtissuebarrier, thecanalcanbeobturated.Theseproceduresaretimeconsumingandtheresultsunpredictable.

–Theplacementofanapicalplug (eg, collagen, tricalciumphosphate,andmore recentlyProRootMTA),whichenables theoperator toobturate thecanalat thesamevisitand restore the toothwithout furtherdelay.Apicalclosureoccursnaturallyovertime.

Theprincipalfactorsforsuccessfulapexificationinclude–Thoroughdebridementanddisinfectionoftherootcanalsystem.–Goodobturationoftherootcanalsystemandagoodapicalseal.–Thepositionoftherootapex.Apexificationisimpossibleiftheapexofthetoothisnotsituatedwithinthe

bonycortex.Insuchcasesasurgicalapproachisnecessarytoresecttherootendsoagoodsealcanbecreated;theformationofahealthyperiodontalmembraneindicateshealing.

ApexificationwithcalciumhydroxideThistechniqueisthemostcommonlydescribedintheliterature.Atemporarycalciumhydroxidedressingisplacedintherootcanalandthenchangedatregularintervalsuntilahardtissuebarrierhasformed.Oncethiscanalclosureoccurs,thecanalisobturatedconventionallywithgutta-percha.Rubberdamisfittedandthecanalisdisinfected.Thecanalmustbeinstrumentedtoremovethesuperficialinfected layer of dentin and predentin; large-diameter H-files are used on each of the canal walls. Theworkinglengthisdeterminedradiographically.Copiousirrigationwith2.5%sodiumhypochloriteisessentialto ensure that the canal is properly disinfected; this must be done with care to avoid forcing sodiumhypochlorite through theapex.Thecanal is driedwith largepaperpointsanddressed temporarilywithacalciumhydroxide–basedmedicament.

PurecalciumhydroxidePurecalciumhydroxideisproducedbymixingthepowderwithsterilewater;themixtureisthenwrappedingauzetoremoveexcesswater.Thematerialhasapaste-likeconsistencyandcanbeplacedintothecanalusinganamalgamcarrier.Itisthencondensedwithalargepaperpointorapluggerthathasbeendippedin


thecalciumhydroxidepowder.Furtherpasteisaddeduntil thecanal isfilledwithcalciumhydroxidetothecementoenameljunction.

CommercialpreparationsofcalciumhydroxideMany laboratories now produce calcium hydroxide–based root canal medicaments (eg, Pulpdent paste,Pulpdent;Calasept,NordiskaDental;Hypocal,Ellinan;Calxyl,OCO-Präparate).Generallydispensed inasyringe, the material is deposited directly into the canal and then gently condensed with the butt end ofpaperpoints.Theconsistencyandeaseofuseofthematerialmakestheoverallmanipulationofthematerialfareasier.Nevertheless, theconcentrationofcalciumhydroxidevariesbetweenmanufacturers,dependingontheamountofadditivessuchasmethylcellulose.Thismustbetakenintoconsiderationwhenchoosingaproduct. The action of these products relies on the material having direct contact with the tissues. It isthereforeimportanttoestablish,bywhatevermeanspossible,thatthecalciumhydroxideis incontactwiththeapicaltissuesbutisnotbeingforcedthroughtheapicalforamen.ThealkalinepHofthesubstancecouldbeharmfultothesurroundingtissuesiflargeamountsareextrudedthroughtheapex.Theaccesscavityisthen obturated. The coronal seal is an important factor in determining the success of treatment; if it isinadequate,bacterial contaminationwill followand thecalciumhydroxidedressingwill dissolve, inevitablyleading to failure.Because thenext stageof treatmentwill notbeperformed for severalweeks,asimpletemporarydressingisnotsufficient. It ispreferabletousecompositeoraglass-ionomercement.Becausecalciumhydroxidehasaradiographicappearancesimilartothatofdentin,aradiographtakenmidtreatmentallowsverificationthatthecanalhasbeenwellobturatedwithcalciumhydroxide(Figs5-2aand5-2b).

Follow-upThelengthoftimenecessarytoachieveapicalbarrierformationdependsonthestageofdevelopmentofthetooth,thedivergenceoftheradicularwalls,andthepresenceofanyapicalpathology.Regular follow-up of the patient is important and allows the clinician to monitor the coronal seal of theprovisional restoration. Radiographs permit assessment of the apical barrier formation; if the calciumhydroxideappearstobedissolving,whichwillberadiographicallyevident,itwillneedtobereplaced.

ReplacingthetemporarycalciumhydroxidedressingThecalciumhydroxideisreplacedevery3monthsuntilanapicalbarrierforms.Ateachappointmentrubberdam must be placed and the coronal restoration removed. The canal is carefully rinsed and cleaned toremovealloftheexistingdressing;anultrasonicendodonticfilecanbeusedbutmustbekeptclearofthecanalwalls.With a small-diameter file adjusted to the estimated working length, the formation of an apical barrier iscarefullyassessed.Ifapicalclosurehasoccurredandisevidentradiographically,replacementofthecalciumhydroxide is not necessary and the canal can now be obturated. If this is not the case, the dressing isreplaced and the access cavity sealed. Histologically the hard tissue barrier appears to be made up ofosteoid-like and cementoidlike tissue. It does not provide a complete seal, and a degree of permeabilityremains.Itisthereforeimperativetocompletethetreatmentbyobturatingthecanalwithgutta-percha(Fig5-3).

5-2aPreoperativeradiograph.


5-2bCalciumhydroxidehasasimilarradiographicappearancetodentin,sooncethecanalisfilleditisnolongervisibleradiographically.

5-3Regularreplacementofthecalciumhydroxidedressingintherootcanalofthismaxillaryincisorhasallowedtheformationofanapicalbarrierapproximately3mmthick(redarrow).Theremainderofthecanalwasthenobturatedwith

gutta-percha.

Ifanyclinicalsignsdevelopbetweenappointments, thedressing is removed, thecanal isdisinfected,andthe dressing is replaced. If orthodontic treatment is underway, the calcium hydroxide treatment must becontinued to avoid the risk of root resorption, and definitive obturation cannot be considered until theorthodonticretentionphase.

DifficultiesassociatedwiththistechniquePlacing regular calcium hydroxide dressings to induce a hard tissue barrier is a well-recognized form oftreatmentandhasbeenused formore than30years.Despite the reliabilityof this formof treatment, thetechniquehassomedrawbacks:•Thecalciumhydroxidechangesmustbedoneoverseveralmonths,ifnotyears.Thecooperationofthe

patientisthereforeakeyfactorinthesuccessofthetreatment.•Untiltheapicalbarrierappears,definitiveobturationcannotbecompleted,andthecanalthereforeremains

emptyandveryfragileforthedurationofthetreatment.Moreover,intheabsenceofadefinitivecoronalrestoration,thereisasignificantriskofbacterialinfiltrationandreinfectionoftherootcanalsystembetweenappointments.

•Placingthecalciumhydroxidedressingscanbetechnicallydifficult,particularlyintheapicalregionswherethecanalwallsmaybeparallelorevendivergent.RepeatedandprolongedextrusionofthecalciumhydroxideintheperiapicalregionmeansitsalkalinepHcouldprovokeaninflammatoryresponseinthe


adjacenttissues.Recent publications (Andreasen et al, 2002; Doyon et al, 2005), have suggested that the mechanicalproperties of dentin may be impaired by continued exposure to calcium hydroxide. This is particularlysignificantbecauseoftheincreasedrisktoteethalreadypredisposedtohavingthin,fragiledentinalwalls.

Teethundergoingsuch treatmentare thereforeat riskof fracturing; thismay result in lossof the tooth,especiallyinthecaseofimmatureanteriorteeth.

ApexificationwithmineraltrioxideaggregateTo overcome these difficulties and risks, clinicians have long sought a material that could provide animmediate and impermeable apical plug. Different materials, namely those used for periodontal surgery,havebeenproposed.Despitethebiocompatibilityofthesematerials,theyprovideonlyapoorsealbecausetheydonotadhere todentin,which limits theiruse inendodonticsconsiderably.StudiesonProRootMTAoverthepast10yearshavedemonstrateditsperfectbiocompatibilityanditsexcellentsealingproperties.Itiscurrentlythematerialofchoiceforapexification.TheaimistocreateanapicalbarrierbyplacingaplugofProRootMTA,whichthenhardens(Box5-1).Theendodontictreatmentcanbecompletedatasecondvisit,andthetoothisthenrestored.Apicalclosureandthe development of a hard tissue layer occur physiologically over time and are accompanied by theformationofarelativelynormalperiodontium(Shabahangetal,1999;Felippeetal,2006).Theadvantageofthis technique is being able to complete treatment in two visits without a delay—it avoids the need forcalciumhydroxidechangesandmultipleappointments.Furthermore,thecoronalrestorationcanbeplacedalmostimmediately,limitingtheriskofrootfracture.

Box5-1TechniqueforplacementofanapicalplugofProRootMTA

1.Preoperativeradiographsarenecessarytoestimatethe lengthof thetoothandthediameterof theapicalopening.Agoodqualityradiographisessentialsothattreatmentcanbecompletedaswellaspossible(Fig5-4a).

2.Afteranesthesiahasbeenadministered,anymissingwallsof the toothare restoredbefore rubberdamisfitted.

3.Duringaccesscavitypreparation,overhangingenamelanddentinshouldberemoved,andallcanalorificesshouldbeassessedforvisibility.Straight-lineaccesstotheapicalthirdofthecanalshouldbecreatedwherepossible.Inmaxillarycentralincisors,forexample,oncethepalatalextentofthepulp roof has been removed, the large straight canal often allows direct vision of the apical third(Figs5-4band5-4c).

4. Large-diameter H-files are used to instrument the canal walls, thus removing predentin and thesuperficiallayerofinfecteddentin.Apexlocatorscannotbeusedforwidecanalswithalargeopenapex;workinglengthmustthereforebedeterminedbytakingaradiographwithalarge-diameterfileinsitu.

5.As inconventionalendodontic treatment, thecanal isdisinfectedbycopious irrigationwith2.5%or3%sodiumhypochlorite (Fig5-4d). The irrigating solution will visibly effervesce as organic debrisdissolves (known as the champagne effect), and irrigation of the canal must continue until theeffervescenceceases.

6. If there is a calcium hydroxide dressing in place, ultrasonic tips or files are used to eliminate anytracesofitfromthecanal(Fig5-4d).Oncethedisinfectioniscomplete,thecanalisdriedwithlarge-diameterpaperpoints.

7.AdedicatedMTAcarrier,theMTAGun,isneededtodepositthematerialintothecanal.Designedwithastraight tipandavailablewith tipsofvaryingsizes, itallowspreciseplacementofProRootMTAdirectly intotheapical thirdof thecanal.AradiographistakenwiththeMTAcarrier inthecanaltodeterminehowfarthetippenetrates(Fig5-4f).Itshouldlie1-2mmshortoftheapex,leavingspacefortheapicalplugtobeplaced(Fig5-4f).

8.TheProRootMTAismixedonaglassslabandloadedintotheMTAcarrierbeforebeingplacedattheapex(Fig5-4h).Unlikeothertraditionalmaterialsusedindentistry,ProRootMTAisamaterial thatdoesnotneed tobecondensed.With thebuttofapaperpointoraplugger thematerial isgentlypackedintoplaceandtherebybroughtintocontactwiththeadjacenttissues(Fig5-4h).

9.Toensurethematerialisevenlydispensed,anultrasonictipcanbevibratedagainstthecrownofthetooth;thiswillalsocauseanyexcesswaterinthemixtorisetothesurfacewhereitcanbeabsorbedwithpaperpoints.

10.Aradiographatthisstageallowsassessmentofthepositionoftheapicalplug(Fig5-4h).Ifitistoofarfromtheapicalforamen,itcanbeadjustedwithalarge-diameterendodonticplugger.


11.MoreMTAisaddeduntila5-mmplugiscreatedapically;thisthicknessofmaterialensuresagoodapicalseal(Figs5-4kand5-4l).

ProRootMTAwill reacha fullsetonlyafteraminimumof4hours inadampenvironment.Amoistcottonpledgetisplacedintothecanal,andtheaccesscavityissealedtemporarily.Treatmentcannotbecompletedinonevisit sinceadefinitive restorationcanbeplacedonlyafter theProRootMTA is fullyset.Thecanalshould not be entirely filled with ProRoot MTA in case the tooth might need to be prepared for a post-retainedcrowninthefuture.Itshouldbekeptinmindthat,onceset,thematerialisverydifficulttoremove.At thenextappointment,whichmaybe the followingday, the temporarydressing is removedanda right-angledprobeisusedtocheckthattheProRootMTAhassetfully.Ifapost-retainedcrownisnotnecessary,therestofthecanalisfilledconventionallywithguttaperchaandasealer(Figs5-4mand5-4n).Inimmatureanterior teeth, it ispreferablenot toextend thegutta-perchaobturation to the levelof thecementoenameljunction. Indeed, thindentinalwalls render these teethparticularlysusceptible to fracture.To reinforce thetreated tooth, it isadvisable to restore thecoronalpartof thecanal (to the levelof crestalbone)and theaccesscavitywith composite. If the root isparticularly short (relatively common in immature teeth), theremaynotbesufficientspaceforgutta-perchainterpositionbetweenthepostandtheMTAplug.SomeauthorsrecommendtheuseofacalciumhydroxidedressingpriortoplacementoftheProRootMTAapicalplug.Recentstudieshaveshownthat thisconfersno therapeuticadvantage.Furthermore, thesealresulting from this technique is inferior to that obtained with immediate placement of ProRoot MTA(Hachmeisteretal,2002;Felippeetal,2006).

5-4aPreoperativeradiographofamaxillaryleftcentralincisor.Thetoothhasbeentreatedwithcalciumhydroxideforseveralmonthsinanattempttoinduceapexification,buttherehasbeennoimprovement.Ithasbeendecidedtotreatthe

toothwithMTAovertwovisits.


5-4band5-4cTheaccesscavityisadjustedtoensuregoodaccessforinstrumentationandirrigation.Oncethepalatalextentofthepulproofhasbeenremoved,thelargestraightcanalallowsforgoodcontrolofinstruments,evenintheapical

third.

5-4dand5-4eThecanalisdisinfectedbycopiousirrigationwithsodiumhypochlorite.H-filesareusedtoremovethesuperficiallayerofinfectedpredentin.Ultrasonicinstrumentsensureoptimumcleaning:alltracesofcalciumhydroxidemust

beeliminatedbeforethecanalisobturated.


5-4fand5-4gThetipoftheMTAGunisplacedintothecanal,andaradiographistakentoconfirmtheworkinglength.Thecarrierlies1to2mmshortoftheapex,leavingspaceforplacementoftheapicalplug.ArubberstopontheMTAGunmarks

theworkinglength.

5-4h,5-4i,5-4jTheProRootMTAis(h)depositedattheapexand(i)gentlypackedintoplacewiththebuttofapaperpoint;(j)thisfirststageischeckedbytakingaradiograph.


5-4kand5-4lFurtheradditionsofMTAcompletetheobturationandcreateanapicalplugof4to5mm.Theplugiscoveredwithamoistcottonpledget,andaprovisionalrestorationisplacedfor24hours.

5-4mand5-4nAtthesecondvisit,arightangledprobeisusedtocheckthattheMTAhasreachedafullset.Theremainderofthecanalisobturatedwithgutta-percha.Acoronalrestorationcanbeplacedimmediately.

Intermediatecalciumhydroxidedressingsarenecessaryonlyincertainsituations.Whetheracanal is tobeobturatedwithMTAorconventionallywithgutta-percha, thedecisionofwhen toobturate is based on the same criteria. If an inflammatory exudate persists or the tooth is symptomatic,obturationwithProRootMTAshouldbepostponed;otherwise itssettingreactionmaybecompromised.Adrycanal isaprerequisiteforobturation.Inthepresenceofaninflammatoryexudate,thetoothisdressedwithcalciumhydroxideforseveraldays(orevenweeks)untilandryenvironmenthasbeenestablished(Figs5-5ato5-5e).


5-5aPreoperativeradiographofacentralincisorwithanacuteapicalabscess.

5-5bCoronalaccessanddrainageoftheabscess.

5-5cThecanalcouldnotbeadequatelydried,soobturationwaspostponed.Atemporarycalciumhydroxidedressingwasplacedinthecanal.


5-5dAtthenextvisit,goodconditionsenabledsuccessfulplacementofanapicalplugofMTA.

5-5eRadiographtaken18monthspostoperativelyshowsevidenceofbonyhealing.


5-6Radiographtaken10monthsafterplacementofanMTAplug.Apicalclosure(redarrow)canbeseen.

Postoperative follow-up: Endodontic treatment of the tooth is completed over the course of two visits.Regularclinicalandradiographicfollow-upallowshealingtobemonitoredandapicalclosuretobeassessed(Fig5-6).

ManagementofOtherCaseswithOpenApicesManagement of teeth with wide-open apices often involves the treatment of immature maxillary incisors.Thereare,however,othersituationswhensimilarmanagementisrequired.

HorizontalrootfractureEndodontictreatmentisnotalwaysnecessaryfollowingahorizontalrootfracture,particularlyifthefractureline lies below the level of the bony crest. Nevertheless, if the coronal fragment becomes necrotic,endodontictreatmentmustbeperformed.Theapicalfragment,however,isleftuntreated;itcanberemovedsurgicallyifalesiondevelops.Iftheportionoftheroottobetreatedislargeatthelevelofthefractureline,obturationwithProRootMTAasdescribedpreviouslyisthetreatmentofchoice(Figs5-7ato5-7d).

FailureofapicalsurgeryWhen apical surgery has failed, subsequent orthograde endodontic retreatment may be indicated eventhoughthisdoesnotfollowthenormal,logicalorderoftreatment.Endodonticsurgerywithroot-endresectionoftenleavesacanalwithanapexthatislargeindiameter.Ifacanal is to be obturated postoperatively, it may therefore present with an abnormally large or misshapenapical foramen due to the retrograde preparation that has previously been completed. In these cases,placementofanapicalplugofProRootMTAandconventionalobturationisthetreatmentofchoice(Figs5-8ato5-8d).


5-7aPreoperativeradiographofanincisorwithahorizontalfractureintheapicalthird.

5-7bFollowingpulpnecrosis,thecoronalfragmentwascleanedandobturated.Theapicalfragmentwasleftuntreated.AradiographwastakentoassesstheadequacyoftheMTAplug.


5-7cImmediatepostoperativeradiograph

5-7dRadiographtaken1yearpostoperatively.Thereisnosignofinfection,andabonycallushasformedatthefracturesite.Mobilityofthetoothiswithinphysiologiclimits.


5-8aDespiteapicalsurgery,alesionofendodonticoriginpersistsattheapexofthispremolar.

5-8bRoot-endresectionandretrogradepreparationwithultrasonicinstrumentshavetransformedthenarrow,circularforamenintoanelongatedopening

5-8cObturatingthiscanalwithgutta-perchawouldbetechnicallyverydifficulttodo.ApicalobturationwithMTAisthepreferredtreatment.


5-8dRadiographtaken18monthspostoperativelydemonstratesalmosttotalhealingofthelesion.

AlternativeTreatmentOptionsAlthoughapexificationisthetreatmentofchoiceforteethwithopenapices,therearealternativetreatmentoptions.

Placementofanapicalplugofgutta-perchaThequalityofendodonticobturationisdirectlyrelatedtothequalityofthecanalpreparation.Thefirststepduringobturationistoadaptthemasterconeintheapicalthirdofthecanal.Inatoothwithanopenapex,atapered preparation is almost impossible to achieve for the reasons described previously (Fig5-9a). The“customizedcone”techniqueinvolvestakinganimpressionoftheapicalthirdwithgutta-perchatocreateacustomizedapicalplug.ThistechniqueisalsousedtofillthecoronalpartoflargecanalsafterapexificationwithcalciumhydroxideorafterplacementofanMTAplug.Ifthecanalisverywide,anextra-largegutta-perchapointiscreatedbymergingseveralgutta-perchapointstogether.Thegutta-perchapointsarecarefullysoftenedinaflameandthenfusedtogetherbybeingrolledbetweentwoglassslabsormanipulatedwithalargespatula.Thesizeanddiameterofthenewgutta-perchapoint are adapted to the dimensions of the canal (Fig5-9b). The larger end of the gutta-percha point isdipped in chloroform for2or 3 seconds to soften the surface.Thesoftenedpoint is thenplaced into thecanal,whichhasbeenfilledwithhypochlorite.Thegutta-perchapointisplacedalittleshorterthanworkinglengthandmovedupanddownforafewsecondstoallowmoldingittotheshapeoftheapicalthirdofthecanal.Itisthenremovedanddippedinsodiumhypochlorite(Fig5-9c).Oncethecanalhasbeendried,thegutta-perchapointisalsodriedandcoveredwithsealer,placedintothecanal,anddelicatelycondensed(Fig5-9d).

5-9aPreoperativeradiographofamandibularmolarwithalargeapex.


5-9bAnextra-largegutta-perchapointispreparedbyplacingseveralgutta-perchapointstoptobottomalongsideeachother.Afterthegutta-perchapointshavebeensoftenedinaflame,theyarerolledbetweentwoglassslabsormanipulated

withalargespatula,whichfusesthemtogether.

5-9cAradiographistakentocheckthefitofthegutta-perchapoint.Theendoftheextra-largegutta-perchapointisdippedinchloroformfor2to3secondsandplacedintothecanal.Theguttaperchamoldsitselftotheshapeofthecanalwalls.


Obturationwiththecustomizedconetechniqueistechnicallydifficultandmayposecertainproblems:–Incanalswithdivergentwallswherepreparationisimpossible(eg,blunderbussapex),themoldedgutta-

perchapointcannotberemovedfromthecanalwithoutbecomingdeformedanddistorted.–Theendofthegutta-perchapointissoftenedwithasolventtoallowittomoldtotheshapeofthecanal;

the action of this solvent cannot be controlled and may continue even after obturation has beencompleted.Agoodlong-termsealcannotthereforebeguaranteed.

–Cliniciansneedtobeexperiencedwiththistechniquetoproduceagoodresult.For these reasons, and because of the availability of new materials such as MTA, the customized conetechniqueisnowrarelyusedtotreatteethwithopenapices.


ApicalsurgeryGiven thedifficultiesofobturating largecanals,apicalsurgeryand retrogradeobturationwithamalgamorglass ionomer was often proposed as the treatment of choice. However, apical surgery is no longerconsideredasfirst-linetreatmentbecauseofthesimplicityandthereproducibilityofapexificationtreatmentwith MTA. Similarly to endodontic retreat-ment, surgery is second-line treatment to deal with failingconventionalendodontictreatmentandshouldbeconsideredinthefollowingsituations:long-termfailureoftreatment, persistent symptoms, a tooth that proves impossible to obturate well in the apical third, or anabscessthatindicatesarecurrentproblemofendodonticorigin.During the surgical procedure, the lesion is curetted and the existing obturation material is assessed todetermine if it reacheda full set. If thematerial isnot fullyset, it is removedand retrogradeobturation iscompleted.Ifthematerialappearstohavesetandhardened,thereisnoreasontoreplaceit;thelesionissimplycurettedandthesurfaceoftheobturationmaterialissmoothed(Figs5-10ato5-10d).Managementofteethwithopenapicesofteninvolvestreatingtraumatizedimmatureteethinyoungpatients.It is clear that surgery should be avoided if possible. On the other hand, if surgery is necessary, goodorthogradeobturationmayavoidtheneedforretrogradeobturationatthetimeofsurgery.

5-10aBothmaxillarycentralincisorspresentedwithperiapicallesionsofendodonticorigin.

5-10bRadiographshowingfavorableprogressandtheformationofanapicalbarrierattheapexofthemaxillaryrightcentralincisor.However,theabsenceofanysignsofhealingattheapexofthemaxillaryleftcentralincisorindicatestheneedfor

surgery.


5-10cOncethelesionhadbeencuretted,itbecameapparentthattheMTAhadneversetfully;aninadequatesealwasthereforethereasonforthefailure.Retrogradepreparationwascompletedandthecanalwasre-obturatedwithMTAto

ensureagoodseal.

5-10dRadiographtaken9monthspostoperativelyshowsthatthelesionishealingandapicalclosurehasoccurred.


PrognosisandRetreatment


Thirtyyearsago,extractionwasconsideredthetreatmentofchoicewheneverendodonticfailureoccurred.Greaterunderstanding,newtechnologies,improvementsinpaincontrol,advancesinrestorativetechniques,and above all, better information for the public have led to high expectations and demands. Patientsnowadayshopetomaintaintheirnaturaldentitionforaslongaspossible.Thisexplainswhy,althoughitisadifficultprocedure toperform,endodontic retreatment isnowundertakenonalmostadailybasis indentalpractices.Furthermore,withanagingpopulation,itislikelythatmoreandmoreteethwillneedretreatmentinfutureyears.Manyauthorshavelookedattheprognosisofendodontictreatment.Epidemiologicstudiesshowthat1.4%to10.0%ofexaminedteeth(treatedoruntreated)carryanapicallesionthatisevidentradiographically.Thesamestudiesconclude that24.5% to46.0%of these lesionsareassociatedwith teeth thathavealreadybeenendodontically treated.Numerousepidemiologic studieshaveanalyzed theprognosisof endodontictreatmentandretreatment.Todate,21studieslookingatbetween50and1,462,936teethreportasuccessrate ranging from 58% to 88%. Can endodontic retreatment therefore be considered a predictableprocedure? Despite adopting a rational approach to endodontic retreatment, practitioners rarely reach aunanimousdecisiononwhetheratoothneedstoberetreated.Finally, does the longevity of a tooth depend solely on the success or failure of endodontic treatment?Approaching the problem from this angle suggests that the practitioner alone is responsible for anunfavorabletreatmentoutcome.Itdoesnottakeintoaccountextrinsicfactorsthatmaydirectlyorindirectlyinfluence the appearance of an inflammatory periapical lesion, such as extraradicular infection, anatomiccomplexities, complications related to the initial endodontic treatment, or fractures. A recent tendencydiscourages use of the somewhat restrictive termssuccess and failure in favor of the termshealing andnonhealing tomoreappropriately reflect theoverall stateof healthof theperiradicular tissues (Friedman,2002).

EndodonticDiseaseandItsManagementEndodontic disease is caused by infection of the root canal system. The presence of bacteria and theirtoxinsinthecanalcausesirritationofthesurroundingboneattheapicalforamenandanyotherportalsofexit(apicalorlateral).Theperiapicallesionisthereforethehost’sresponsetobacterialassault; itappearsradiographicallyasaradiolucentarea.Severaltermsareusedtodescribethistypeoflesion.Themostcommonphraseisapicalperiodontitis.Morerecently,thetermlesionofendodonticorigin(LEO)hasbeenproposedtoimplytheinflammatoryratherthaninfectiousnatureof the lesionaswell as its location in theperiodontium,which is not necessarily apical;aboveall,itreflectstheendodonticoriginofsuchalesion.The development of a radiographic lesion and the appearance of symptoms are the only criteria fordeterminingifdiseaseispresent.Oftenthetoothisasymptomatic,sincethemajorityoftheselesionsareofachronicnature.Destructionofboneindirectlyconfirmsthepresenceofbacteriaintherootcanalsystem.Thedisappearanceoftheradiolucentareafollowingtreatmentindicatesboneremineralizationandthereforehealingofthelesion.Itistheonlyclinicalmeansofconfirmingtheefficacyofthecanaldisinfectionandtheadequacyofthesealprovidedbytherootfilling.

Thepractitionermustconsiderendodonticinfectionadiseaseandtheperiapicallesionaconsequenceofthe disease. Thus, treatment should be focused on dealing with the root canal system and not oneradicating the lesionseenwithin thebone.Simplesurgicalenucleationofgranulation tissueoracystdoesnotthereforetreatthedisease.Recurrenceoftheinfectionisinevitable,asbacteriamaypersistandmultiplyintherootcanalsystem.

AssessmentofPeriodontalHealthTheappearanceofaradiolucencyonaradiographindicatesthepresenceofaninflammatorylesionwithinthebonebutrevealsnofurtherinformationregardingthehistologicnatureofthelesionoritsdevelopmentover time. The chronology of disease is important. Limiting the term healthy to teeth without periapicallesionsandreferringtoatoothwitharadiolucencyashavingassociatedpathology isextremelysimplistic.Lesions do not appear and disappear immediately; bone destruction and remineralization happens overmonthsorevenyears.Atooththathasrecentlyhadinadequateendodontictreatmentperformedonitshouldbeconsideredpotentiallydiseased.Ifaradiographistakenandthelesionisnotvisible,itmayappearthatthe treatmentwassuccessful.Similarly,a tooth thathasrecentlyhadagoodquality root fillingplacedbuthasanassociatedradiolucencyshouldstillbeconsideredpotentiallyhealingdespitetheradiolucencyvisibleatthisstage.Thesesituationsdemonstratethecomplexityofendodonticdiseaseanditstreatment.Aseriesof radiographs taken at different time intervals after retreatment is necessary to allow the quality of thetreatmenttobeassessed.As with all diseases, it is essential to take into consideration the development and progression of thepathology.Anincreaseordecreaseinsizeofalesionovertimehaslongbeenconsideredtheonlymethodof assessing healing. Ørstavik, in proposing the Periapical Index (PAI), suggested evaluating the bonetrabeculaeintheinflammatoryzoneandscoringitonascaleof1to5(Ørstaviketal,1986).Inthisway,bycomparingradiographstakenatdifferentintervals(approximatelyevery3to6months),anychangesinthe


lesioncanbemonitored.Ørstavikalsorecommendedamonitoringperiodof12monthstofullyunderstandtheprogressionofthelesion;inhisprospectivestudiesheshowedthat90%ofteethwithsignsofhealingat12months eventually underwent complete healing. For large lesions, complete healing can take up to 8years.Iftreatmenthasbeencompletedwellandthecoronalsealismaintained,thehealingprocessrarelyreverses.

PrognosisofEndodonticTreatmentandRetreatmentEpidemiologic studiesperformed in variouscountries show that thepercentageof inadequateendodontictreatmentrangesfrom33%to79%,andtheprevalenceofradiographiclesionsofendodonticoriginvariesfrom20%to65%(Friedman,1998).

Initialtreatment–Intheabsenceofaradiographiclesion,thesuccessrateofinitialendodontictreatmentvariesfrom83%to100%, with no significant difference seen between treatment on vital pulps and treatment on nonvitalteeth.Morethan75%ofallfailures(withlesionsappearingaftertreatment)wereidentifiedinthefirstyearafter treatment. Thusa follow-upappointment 1 year postoperatively is generally predictive of the finaloutcome.

–Incaseswherearadiographiclesionexistspreoperatively,thesuccessrateforinitialtreatmentvariesfrom46%to93%.Thisvariability isduetodifferentmethodologiesemployed instudyprotocolsanddifferentcriteria used to evaluate results. Almost 89%of lesions thatwill eventually heal show signs of healingduringthecourseof thefirstyearafter treatment. If treatmenthasbeenperformedproperly, thehealingprocessrarelyreverses.

However, teeththathaveundergoneapexificationtreatmentwithcalciumhydroxidehavearelapserateof8%;thiscanoccur2to3yearsafterdefinitiveobturationhasbeenperformed,despiteinitialsignsofhealing.Thesedelayedfailuresarethoughttoberelatedtoporosityoftheapicalbarrierassociatedwithadefectivecoronalseal.

Retreatment– In the absence of a radiographic lesion, reported success rates of endodontic retreatment are high,between89%and100%.

–Incaseswherearadiographiclesionexistspreoperatively,however,thesuccessratevariesbetween56%and 84%, lower than the reported success rates for initial treatment. Obstructions and blockagesencounteredduringendodontic retreatmentprevent thoroughcleaninganddisinfectionof therootcanalsystemandthereforelowerthesuccessrates;obstructionsincludeblockages,ledges,obturationmaterialthat adheres to the canal walls and harbors bacteria, fractured instruments, and calcified canals(Friedman,1998;GorniandGagliani,2004).

In one of the few prospective studies published (Farzaneh et al, 2004), twomain factors were found toinfluencesuccessratesininitialtreatmentandretreatment:–Presenceofapreoperativelesion:Successrateswerenegativelyaffected.– Operative technique: Higher success rates were reported in teeth treated with the Schilder technique(canals prepared in a step-by-step manner and obturated with gutta-percha using a warm verticalcondensation technique) than in teeth prepared with the step-back technique and obturated with coldlateralcondensation.

Inretreatmentcasesthepresenceofaperforationwasalsofoundtoaffectsuccessratessignificantly.

FactorsThatCanInterferewithHealingSeveral possible causes of failure of good endodontic treatment and retreatment have been recognized(Siquiera, 2001; Nair, 2006). Several main factors have been identified as being responsible for thepersistenceofaperiapicallesiondespitecompletionofadequateendodonticretreatment.

IntracanalbacteriaRetreatmentaimstoeliminatebacteriaandremoveallnecroticdebrisfromtherootcanalsystem,therebycuttingoffthebacterialnutrientsupplyandpreventingfurtherproliferationofmicro-organisms.Nevertheless,persistenceofbacteriaintherootcanalsystemisoftencitedasthereasonforlesionsthatpersistmonthsafter retreatment.Theorganisms thatpersistafter retreatmentaredifferent from those found inuntreatedcanals; only a few species appear to survive. The dominant organisms seen are Enterococcus andStreptococcus,butActinomycesandCandidahavealsobeenimplicated.Thesemicro-organismssurviveinniches(eg,lateralcanals,irregularitiesindentin)thatareinaccessibletotheirrigatingsolutions(Nair,2006).

PeriradicularinfectionDuringcanalpreparationandinstrumentation,bacteriamaybeforcedintotheperiapicalregion,wheresomespecies are capable of surviving (Nair, 2006). Furthermore, some bacteria appear to have the ability tomigrateintotheperiapicalareaandformabiofilmontherootsurface.Thesemicro-organismsareresistanttothehost’simmuneresponseandbecomeasourceofinfection(Noirietal,2002).Atthispointthedisease


isnolongerendodonticbutperiradicular,andthuscannotbetreatedbyorthogradetreatmentalone;apicalsurgeryisindicated.Theseresistantmicro-organismstendtobedifferentthanthenormalintracanalspecies(eg,ActinomycesisraeliandPropionibacteriumpropionicum).

ForeignbodyinthelesionAforeignbodyinaperiapicallesion,particularlysealerorgutta-percha,isoftenthoughttocausedisease.Itappears, however, that the extrudedmaterial supports themicro-organisms instead of acting as a directirritant itself. It is very difficult, if not impossible, to eliminate these foreign bodies with an orthogradeapproach. In such cases, apical surgery is indicated. Other substances, including cellulose fibers (frompaperpoints)andstarchparticles(frompowderedgloves),havebeen identified inrefractory lesions(Nair,2006).

HistologicnatureofthelesionIt is a commonmisconception that periapical granulomasmay heal after endodontic treatment but cysticlesionswillnot.Numerousstudies(Nair,2006)haveshownthattherearetwotypesofcyst:–“Bay”cystscommunicatewiththepulpofthetooth.Thesecystsrespondlikegranulomasanddisappearifirritants in the root canal system are eliminated. Nevertheless it is important to acknowledge thatcontrollingmoisture contamination in such circumstancesmayprove very difficult.A poorly dried canalmayimpairthequalityoftheobturationandthereforeindirectlyleadtofailure.

–“True”cystshaveanepithelialliningthatrendersthelesionaseparateentitywithnocommunicationwiththerootcanalsystem.In thesecases,disinfectionof therootcanalwillnotbringabouthealingorbonyinfillbecauseofthenatureofthelesion.Supplementalsurgerytoenucleatethecystisnecessary.

It is impossible to determine the nature of the lesion preoperatively, so in each of these casesmanagement starts with endodontic treatment or retreatment followed by a period of clinical andradiographicmonitoring.Thosecasesthatappeartobefailingcanthenbetreatedsurgically.

PoorcoronalsealTheeffectofapoorcoronalsealon theprognosisofendodontic treatment isclearlydemonstrated in theliterature.Bacterialcontamination,aresultofadeficientcoronalrestoration,leadstoreinfectionoftherootcanal system and subsequent failure. To provide favorable conditions for healing, a definitive coronalrestoration (cast restoration or post-retained crown) should be placed within 30 days after obturation.Meanwhile,aprovisionalrestorationmustbeplacedtobringthetoothbackintoocclusion;afunctionaltoothis preferred, if not essential, to stimulatehealingof theperiodontal tissues.Aprovisional crowndoesnotprovideanadequateseal.Deciding when to place a definitive restoration can be difficult. Good retreatment ensures completedisinfectionofthecanal;thisasepsisisthenmaintainedbyobturationofthecanalandprovisionofacoronalseal. If theclinician is confident retreatmenthasbeenproperlyperformedandyetpathologypersists, theproblem is likely to be an extraradicular rather than intracanal infection. Apical surgery should then beconsidered.Thissurgicalprocedurewillnotbeaffectedbythepresenceofacoronalrestoration.

EndodonticSurgery:AnAdjuncttoTreatmentOnceorthograderetreatmenthasbeencompletedandacoronalrestorationprovided,radiographsshouldbetakenat3,6,and12monthstoassesstheprogressofthelesionandtomonitoranychanges.Ifthelesiondoesnot reducebetween twosuccessiveappointmentsand/orclinicalsymptomsarise, thepersistenceofinfectionisconfirmed.Therearetwotherapeuticalternativesatthispoint:–Incaseswithalargelesion,orintheabsenceofanyclinicalsymptoms,aperiodoffurthermonitoringmaybeconsidered.Amonitoringperiodofjust1yearmaynotbeindicativeofdefinitivelong-termprognosis.

–Incaseswithsmallormoderatelysizedlesions,ifthereisnosignofhealing,ifthePAIisunfavorable,orifclinicalsignsandsymptomshaveappeared(eg,pain,abscess,sinustract),asurgicalapproachshouldbeconsidered(Box6-1).

Surgery,inthemajorityofcases,isadjunctivetreatmenttocomplementtheorthogradetreatmentandshouldnotbeseenasasubstitute.

Box6-1Mainindicationsforsurgery

Recurrentclinicalsignsorsymptomsappearorpersistafterretreatment

Signsofhealing(orotherfavorablechanges)areabsent12monthsafterretreatment(Figs6-1ato6-1e)

Obstructions (eg, blockages, calcified canals, fractured instruments) that cannot be bypassed render ittechnically impossible to complete satisfactory endodontic treatment from an orthograde approach. Iftheseblockagespreventdisinfectionoftheapicalpartofthecanal,surgicalinterventionisjustified.

Removalof thecoronalrestoration is likely tocausesignificantharmto theunderlyingtooth.This is the


only indication for surgery as an alternative to orthograde treatment rather than as complementary toorthogradetreatment.

Regardless of indication, the advantages and disadvantages of each course of treatment (retreatment orsurgery)shouldbetakenintoconsiderationandevaluated(Box6-2).Ifthereisanydoubtwhethertoperformconventional orthograde or surgical retrograde retreatment, orthograde retreatment should be attemptedfirst.Themaingoalofapicalsurgery isexactly thesameasthatoforthogradetreatment: toeliminatebacterialirritants.Thetwotreatmentsdifferonlyintechnique.Inendodonticsurgeryafull-thicknessflapisraised,awindowiscreatedintheoverlyingbone,andtheinflammatorytissueiscurettedaway.Aftertheapicalthirdispreparedwithultrasonictips,thecanalisdriedandaretrograderootfillingisplaced.Aretrograderootfillingisnecessaryevenifthecanalhaspreviouslybeenobturated.Root-endresectionandcurettageeliminatethelesionbutdonotaddressthesourceof infection,namelybacteriawithinthecanal.Root-end resection and curettage alone lead to reinfection, since bacteria remain within the root canalsystem.Furthermore,evenifthemaincanalhasbeenpreparedandobturatedviaanorthogradeapproach,root-endresectionoftenexposesanisthmusthathasnotbeenpreparedorobturated;thismustthereforebeincludedintheretrogradepreparation(Figs6-2ato6-2e).

6-1aPreoperativeradiographofamaxillarylateralincisorshowsaperiapicallesionandextrusionofmaterialthroughtheapex.

6-1bRadiographtaken12monthspostoperativelydemonstratesthepersistenceofthelesiondespitetheendodonticretreatment.


6-1cAsurgicalapproachisadopted.Thelesioniscuretted,theapexoftherootissectioned,andthelastfewmillimetersoftherootarepreparedandobturatedwithProRootMTA.



6-1eRadiographtaken10monthspostoperativelydemonstrateshealingandbonyinfill.

In certain situations, retrograde endodontic treatment can be considered a first-line treatment. This isparticularly truewhen removalofapost runsahigh riskof fracturing the rootorcausingaperforation. Insuchcases,everyeffortshouldbemadetocleanandprepareasmuchoftherootcanalaspossiblefromaretrogradeapproach(Figs6-3ato6-3f).Unfortunately,limitedaccessintheposteriorregions,theanatomyand locationofsomeroots,anda lackofsuitable instrumentsoftenpreventsdeepenoughobturation intothe canals. In themajority of cases, it is technically difficult to retreat a canal along its full length fromasurgical approach. If a simple apical plug of 2 to 3mm is placed in an unfilled, infected canal, residualbacteriawill inevitably,over time,migrate into theperiapical tissues.Even if favorablesignsappear in thefirst fewmonthsafter treatment, these remainingbacteriawill eventually causea recurrenceofperiapicalpathology.Forthisreason,thelengthofthecanaltobetreatedviaaretrogradeapproachshouldbeasshortas possible.Conventional orthograde endodontic treatment is performedon the accessible portion of thecanal;afteramonitoringperiod,asurgicalapproach isadopted toallowpreparationandobturationof theapicalpartofthecanalthatwasimpossibletodisinfectintheconventionalway(Friedman,2005).

Box6-2Factorsinfluencingthesuccessofsurgery

Orthograde retreatment prior to surgery. Success rates for apical surgery performed after failure ofretreatment are higher (84% to 91%) than success rates for surgery performed directly after failure ofinitial treatment.This isprobablybecause if initial treatment fails, thebacteriaresponsible for thefailureremain within the canal and retrograde obturation is not sufficient to isolate and protect the periapicalregion.However,ifretreatmentisperformedwellyetstillfails,thebacteriaresponsibleforfailurearelikelyextraradicularandwillbeeliminatedbyroot-endresectionandcurettage.

Useofabiocompatiblematerialtocreateagoodsealforretrogradeobturation.Tocreateconditionsfavorableforhealing,itisnecessarytoeliminatebacteriafromwithinthecanalandpreventanyresidualbacteriaor their toxins frommigrating into theperiapicalarea.A root-end filling is thereforeessential tomaintainthesealprovidedbythegutta-percha.

Surgicalmethodandtechnique.Currenttechniquescomplementedbytheuseofmagnificationdevicesand specially designed equipment (eg,micro-mirrors, ultrasonic instruments for retrograde preparation,biocompatiblematerialstoprovideagoodseal[ProRootMTA])considerablyimprovethesuccessrates.

Qualityofthecoronalrestoration,whichmustprovideagoodsealandpreventreinfection.


6-2aPreoperativeradiographofasymptomaticmaxillarypremolarwithapersistentlesionseveralmonthsafterretreatment.

6-2bRoot-endresectionexposesthecanals(obturatedwithgutta-percha)andrevealstheisthmusconnectingthem.

6-2cRetrogradecavitypreparedwithultrasonicinstruments.ThecanalsandtheisthmuscannowbeobturatedwithProRootMTA.


6-2dImmediatepostoperativeradiograph.

6-2eRadiographtaken6monthspostoperativelydemonstratesalmostcompletehealing.

Inconclusion,recommendedtechniquesforinitialendodontictreatmentarewelldocumented;andiftheyareperformed well, success rates are high. Endodontic retreatment is an attempt to manage an alreadycompromisedtooth.Comparedtoprimaryendodontictreatment,thisprocedureistechnicallymoredifficulttoperform, has greater risks involved, and is clinically more unpredictable. Clinicians should thereforeendeavor to complete initial endodontic treatment to the best of their abilities so that retreatment, bydefinition more difficult and more risky, is avoided. When failures do present, successful retreatmentdependson theclinician’sknowledgeofmaterialsand techniques,experience,acknowledgmentofability,andpatience.


6-3aGiventheshapeofthepostandthethindentinalwalls,removingtherestorationfromthismaxillarypremolarcouldendangertheunderlyingtooth.Surgicalendodontictreatmentisadvised.

6-3bObturationmaterialisremovedfromthecanaluptothelevelofthepostusingaprecurvedultrasonicK-file.


6-3cRadiographtakenduringtreatmenttoverifythatallobturationmaterialhasbeenremoved.

6-3dThecanalisdisinfectedwith2%chlorhexidine,dried,andobturatedwithProRootMTA


6-3eImmediatepostoperativeradiograph.

6-3fRadiographtaken9monthspostoperatively.Eliminationofbacterialirritantsandretrogradeobturationhaveallowedhealingtotakeplace.

Incaseswhereorthogradetreatmenthasbeenunsuccessful,endodonticsurgery,performeddiligentlyandmethodically,istheonlyalternativeandprovidesapotentialmeansofsavingthetooth.


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