factors effecting survival of teeth with nonsurgical root

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Master's Theses (2009 -) Dissertations, Theses, and Professional Projects

Factors Effecting Survival of Teeth withNonsurgical Root Canal Therapy Including aMulti-State Outcome AnalysisAlex MooreMarquette University

Recommended CitationMoore, Alex, "Factors Effecting Survival of Teeth with Nonsurgical Root Canal Therapy Including a Multi-State Outcome Analysis"(2018). Master's Theses (2009 -). 463.https://epublications.marquette.edu/theses_open/463

https://epublications.marquette.edu

https://epublications.marquette.edu/theses_open

https://epublications.marquette.edu/diss_theses

FACTORSEFFECTINGSURVIVALOFTEETHWITHNONSURGICALROOTCANALTHERAPYINCLUDINGAMULTI-STATEOUTCOMEANALYSIS

By,

AlexC.Moore,D.M.D.

A Thesis submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for

the Degree of Master of Endodontics

Milwaukee, Wisconsin

May 2018

ABSTRACT

FACTORSEFFECTINGSURVIVALOFTEETHWITHNONSURGICALROOTCANALTHERAPYINCLUDINGAMULTI-STATEOUTCOMEANALYSIS

AlexC.Moore,D.M.D.MarquetteUniversity,2017

Objective:Tostudythefactorseffectingthesurvivalofteethwithnon-surgicalrootcanaltherapy(NS-RCT)andtocomparethetransitionsbetweenfailurestatesforteethtreatedwithNS-RCTbasedoninitialprovidertype.Methods:Insuranceclaimswereanalyzedfor438,487initialNS-RCTprocedurestodeterminetheeffectofprovidertype,patientage,toothposition,presenceofpost/core,andcrownat90daysontoothsurvival.KaplanMeiersurvivalestimateswereevaluatedfor1,3,5,and10yearsandadjustedhazardratios(aHR’s)werecalculated.Amulti-statemodelwithsixtransitionswascreatedusingthe‘mstate’Rpackage.Results:Overallsurvivalwas98.2%at1year,94.4%at3years,90.8%at5years,and82.8%at10years.Ten-yearsurvivalrateswere84.5%and81.9%forteethtreatedbyendodontistsandotherproviders,respectively.Inthemultipleregressionanalysis,significantdifferencesinsurvivalwerefoundcomparingNS-RCTprovider(otherprovidervs.endodontist,aHR1.31[1.27,1.35])andtoothlocation(molarvs.anterior,aHR1.26[1.21,1.31]).IncreasingageatNS-RCTwassignificantlyassociatedwithagreaterhazardofextraction.Placementofcore/postandcrownwithin90dayswereeachsignificantlyassociatedwithareducedhazardofextraction(aHR=0.74[0.72,0.76]andaHR=0.53[0.51,0.54]).MostteethtreatedbyNS-RCThadnosubsequenttreatmentinterventions.Teeththatwereretreatedweremorelikelytobeextractedthanteeththatdidnothavesuchanintervention.Teethweremorelikelytobeextractedthanretreated.Ifatoothhadanon-surgicalretreatmentandsubsequentlyasurgicalretreatment,thenitwasmorelikelythatthesurgicalinterventionoccurredduringthefirstyearoftreatment.Conclusion:SurvivalratesofNSRCTtreatedteetharehigheramongteethtreatedbyendodontists,whenacrownwasplacedwithin90-daysofNSRCTandamongyoungerpatients.NS-RCTfailuresaremostlikelytoresultintoothextraction.Whenretreatmentisperformed,itismorelikelytobenon-surgicalandretreatmentinanyformincreasesthelikelihoodforfutureextraction.NS-RCTsinitiallyperformedbynon-endodontistsalsohaveagreaterchancefornon-surgicalretreatmentorextraction.

i

ACKNOWLEDGEMENTS

AlexC.Moore,D.M.D.

IwishtothankMarquetteUniversityforgivingmetheopportunitytofulfill

mydreamofbecominganendodontist.Iwanttospecificallythankthefacultyinthe

endodonticdepartmentincludingDr.SheilaStover,Dr.LanceHashimoto,Dr.

MohamedIbrahim,Dr.JosephGaffney,andDr.JosephdeGuzmanfortheireducation

andguidancegivingmetheskillsandknowledgenecessarytothriveinthis

program.TheirmentorshiphasbeencriticalinmeachievingmygoalsandIam

forevergratefulfortheirsupport.

Iwanttothankmyco-residentsKandaceYee,ScottMacDonald,Gordon

Barkley,JonIrelan,SukbumYoo,HunterHousley,andMaxMontatskiy.Theyeach

havemaderesidencyextremelyenjoyableaswellashelpingmetogrowpersonally

andprofessionally.Ihadablastduringmytwoyearsandlookforwardto

continuingthefriendshipsthatIhavemade.

IwouldliketothankDr.PradeepBhagavatulawhohasbeenextremely

helpfulthroughoutmyentireprojectfromdevelopmentoftheconceptthroughthe

publicationprocess.Hehasbeenextremelysupportiveofthisprojectandhasbeen

criticalinmecompletingit.Dr.FrederickEichmillerwasessentialinprovidingthe

datathatthisentireprojectwasbasedoffof.Theknowledgeandabilitiesofthe

biostatisticiansattheMedicalCollegeofWisconsin,LisaReinandAnikoSzabo,have

beenessentialandwithoutthemthisstudywouldnotbepossible.

ii

Lastbutnotleast,Iwouldliketothankmyfamilyfortheircontinuedsupport

throughoutmyentireeducation.Ithasbeenanextremelylongprocessandthey

haveencouragedmetheentireway.Iwouldnothavebeenabletoachieveanything

withouteverythingtheyhavedoneformetogettothispoint.

iii

TABLEOFCONTENTS

ACKNOWLEDGEMENTS........................................................................................................................i

LISTOFTABLES......................................................................................................................................iv

LISTOFFIGURES......................................................................................................................................v

INTRODUCTION........................................................................................................................................1

LITERATUREREVIEW...........................................................................................................................3

MATERIALSANDMETHODS..............................................................................................................13

RESULTS......................................................................................................................................................16

DISCUSSION................................................................................................................................................36

CONCLUSIONS...........................................................................................................................................43

BIBLIOGRAPHY...................................................................................,.....................................................44

iv

LISTOFTABLES

Table1:Inclusion/ExclusionCriteria………….……………………..………………………………..14

Table2:Summaryofvariablesbasedonnumberofcases....................................................19Table3:Survivalestimatesofendodonticallytreatedteeth................................................20

Table4:Survivalestimateofendodonticallytreatedteethbasedontoothlocation.…………………………………………………………………………………………………………….21Table5:Survivalestimateofendodonticallytreatedteethbasedonprovidertype…………………………………………………………………………………………………………………..24Table6:Survivalestimateofendodonticallytreatedteethbasedonpatientage……………..………..………..………..………..………..………..………..………..……………………….…25

Table7:Survivalestimatesofendodonticallytreatedteethwithcore/postmaterial…………..………..………..………..………..………..………..………..………..…………….……....26

Table8:Survivalestimatesofendodonticallytreatedteethbasedonpresenceofacrown.....………..………..………..………..………..………..………..………..………..………..………..……28Table9:MultipleCoxproportionalhazardsregressionresults.Adjustedhazardratiosforvariablesaffectingtoothsurvival……………………..……………..……………………………………………………..………………....30

v

LIST OF FIGURES

Figure1:Survivalestimatesofendodonticallytreatedteeth..............................................20Figure2:Survivalestimateofendodonticallytreatedteethbasedontooth

location…………………..………..………..………..………..………..………..………..……………………….22

Figure3:Survivalestimateofendodonticallytreatedteethbasedonprovidertype............………..………..………..………..………..………..………..………..………..…………………......23

Figure4:Survivalestimateofendodonticallytreatedteethbasedonpatientage……………..………..………..………..………..………..………..………..………..………..……….............24

Figure5:Survivalestimatesofendodonticallytreatedteethwithcore/postmaterial.....………..………..………..………..………..………..………..………..………..………………........26

Figure6:Survivalestimatesofendodonticallytreatedteethbasedonpresenceofacrown…………………………………………..……………………………………………………………………27Figure7:Cumulativeincidenceofthefirstfailureeventtooccurfollowingtheinitialrootcanal(nonsurgicalretreatment,surgicalretreatment,orextraction)...................31Figure8:Cumulativeincidenceofthefirstfailureeventtooccurfollowingtheinitialrootcanal(nonsurgicalretreatment,surgicalretreatment,orextraction)basedonprovidertype…………………………….……………………………………………………………………....31Figure9:Multi-statemodelcreatedusingthe‘m-state’Rpackagewith6transitionsbetweenfailurestates(nofailure,nonsurgicalretreatment,surgicalretreatment,extraction)..................................................................................................................................................32Figure10:Transitionsbetweenfailurestatesinthemulti-statemodel(nofailure,nonsurgicalretreatment,surgicalretreatment,extraction)basedontime……………33

Figure11:Cumulativehazardplotdemonstratingtimetothetransitionstatebasedoninitialprovidertype(endodontistblack,otherred)….………..…….…..………………....34

Figure12:Plotoftransitionprobabilitiesofendodonticallytreatedteeth……...….....35Figure13:Plotoftransitionprobabilitiesofendodonticallytreatedteethbasedonprovidertype…………………………………………..…………………………………………………………36

1

INTRODUCTION

ThepioneeringstudiesinendodonticsbyMollerandKakehashi

demonstratedthatthemainetiologyinthedevelopmentofapicalperiodontitisis

thepresenceofbacteriaandtheirbyproductswithintherootcanalsystem(1,2).

ThesepremisesleadHerbertSchilder,thefatherofmodernendodontics,todescribe

themechanicalandbiologicalobjectivesthatneedtobefulfilledinordertoallow

forsuccessfultherapy(3).Heproposedcleaningandshapingandobturation

protocols,manyofwhicharestillutilizedtothisday.Inaccomplishingthese

objectives,itbecamepossibletoachievepredictablysuccessfuloutcomesin

endodontics.

Thesuccessratesofendodontictherapyhavebeenstudiedextensivelyand

demonstratearangefrom81%to97%(4,5,6).Eventhoughthereareamyriadof

studiesindicatingfactorsthataffecttheprognosisofthetreatment,thereare

limitedstudiesinvestigatingtheimpactthatthetreatingclinicianhasonthe

outcome(7,8).Thesestudiesdemonstratedthattoothsurvivalwashigherwhenan

endodontistperformedtherootcanaltherapycomparedtoageneraldentist.

However,thesestudiesdidnotfurtherevaluatetheratesofretreatmentbasedon

theinitialprovidertype.Lazarskiin2001comparedtheoutcomesofrootcanal

therapybetweenanendodontistorageneraldentistandevaluatedtheincidencesof

extraction,retreatment,andsurgicalretreatment(9).Lazarskiwasabletoidentify

thetrueoutcomeoftheendodontictherapybyevaluatingthecombinedincidenceof

2

extractionandendodonticretreatment.However,therehasnotbeenadditional

researchcorroboratingtheseresults.

Inordertofurtherevaluatethetrueoutcomeofendodontictherapybasedon

theinitialprovidertype,aninsurancedatabasestudywascompleted.Insurance

databasestudiesarelimitedastheyonlyaccountfortreatmentthathasbeen

submittedtotheinsurancecompany.However,theyprovideareal-world

evaluationoftreatmentbeingrenderedinaprivatepracticeenvironment

encompassingalargedemographic.DeltaDentalofWisconsinprovidedtheir

electronicinsuranceclaimsrecordandenrollmentdatabaseencompassinga

thirteen-yearperiodfrom2000-2013.Theclaimswereanalyzedtocomparethe

trueoutcomeofendodontictherapybasedoniftheinitialproviderwasan

endodontistorageneraldentist.

3

LITERATUREREVIEW

NonsurgicalRootCanalTherapy

Theprimarygoalsofnonsurgicalrootcanaltherapy(NS-RCT)include

removingtherootcanalsystemcontents,eliminationofadversesignsorsymptoms,

promotionofhealingandrepairofperiapicaltissues,andthepreventionoffurther

breakdownofperiapicaltissues(10,11).Inseveralclassicstudies,apical

periodontitishasbeenshowntobetheresultofmicroorganismsandtheir

byproductsintherootcanalsystem(1,2,11).Inthesestudies,itwasshownthat

teethwilldevelopapicalperiodontitiswhenmicroorganismsarepresentbutwill

notifthepulpsareaseptic(1,2,11).Thisleadtothehypothesisthatinordertohave

resolutionofapicalperiodontitis,therootcanalsystemmustbedisinfectedtothe

pointthatthebodycanallowforhealing.Itwasshownthatthesuccessratesfor

rootcanaltherapywerehigherinsituationsthatbacteriawerenotabletobe

detectedthroughculturing(12).Thereisnowafurtherunderstandingofthe

presenceofabiofilmintherootcanalsystemofinfectedteethandthedifficultyto

fullyeradicatethemicroorganisms(13).Asaresultofthebiofilm,bacterial

resilience,andthelimitationsinthechemomechanicaldebridement,thecurrent

beliefisthatmicroorganismscannotbecompletelyeliminatedfromtherootcanal

systemregardlessoftechniquesutilized(14,15).Fortunately,rootcanaltherapyhas

stillbeenshowntobeveryeffectiveinamultitudeofstudieswithsuccessrates

rangingfrom90-96%(16,17).

4

Thereareawidevarietyofopinionsandtechniquesregardingtheprocessof

completechemomechanicaldebridementalthoughitiswellacceptedthata

thoroughcleaningandshapingwillleadtothebestpossiblesuccess.Petersetal.

foundthatthroughinstrumentationalone,35%oftherootcanalremained

unchanged(18).This,alongwithastudybyBystromandSunqvistshowedthat

handinstrumentationandsalinedidnotproduceasterilecanalsystem,led

researcherstounderstandachemicalcomponentwasnecessarytodisinfectthe

canalsystem(19).Therationalefortheuseoffilesistodisruptthebiofilm

mechanicallywhilealsocreatingasuitableshapethatallowsforirrigationtoreach

theapexofthetooth(3).Throughameta-analysis,itwasfoundthatthehighest

successrateswereachievedwhentherootcanaltherapyterminatedwithin1mmof

theradiographicapex(20).Ithasbeensuggestedthatthecanalmustbeenlargedto

amasterapicalsizeofatleast0.30mminordertoallowforirrigationtoreach1mm

shortoftheapex,whileothershavearguedthatlargersizedpreparationswill

increasethechemomechanicaldebridementoftherootcanalsystem(21,22).Once

thecanalhasbeenpreparedtoitspropersize,avarietyofirrigantshavebeen

suggestedforproperdisinfection,butthemostpopularremainsodiumhypochlorite

(NaOCl)andethylenediaminetetraaceticacid(EDTA)(23).NaOClisantibacterial

andremovesorganicdebriswhileEDTAremovestheinorganicportionofthesmear

layer(24,25,26).Thismodelofchemomechanicaldebridementdoesnotallowfor

completesterilityoftherootcanalsystem(14,15).However,itrepresentsthe

generalpracticeprotocolforrootcanaltherapy,whichallowsforhighlevelsof

success(16,17).

5

SuccessversusSurvival

Thereareconflictingopinionsregardingwhatconstitutessuccessfultherapy

inendodontics(27,28).Strindbergcameupwithstringentcriteriaclaimingthat

successrequiresbothnosymptomsandnoperiapicalradiolucency(27).Friedman

hasdescribedpossibleoutcomesofendodontictherapyashealed,healing,disease,

andfunctionalretention(28).Functionalretentiondescribesasituationwherethe

patientisasymptomaticandfunctional,butaperiapicalradiolucencyispresent.

Thus,ithasbeensuggestedthattheprimarygoalofthetherapyisforthetoothtobe

retainedandasymptomaticandthesecondarygoalisforresolutionofapical

periodontitis(28).IntheoutcomestudybyNg,patientswereasymptomaticand

functionalin91%ofthecasesbutaccordingtotheStrindbergcriteriathesuccessof

thetherapydecreasedto83%(29).Thisdemonstratesthatthesuccessrateswill

changebasedonthedefinitionofsuccessthatisused,whichiswhyitisimportant

tohaveastandardizedclassificationofsuccessfultreatment.

Therehavebeenalimitednumberofstudiesregardingthesuccessand

failureratesofrootcanaltherapybasedontheprovidertype(7,9).Burryfound

thatat5and10years,thesurvivalofteethendodonticallytreatedbyageneral

dentistwaslowerthaniftheyweretreatedbyanendodontist(7).Survivalwas

definedasatooththatwasnotextracted,retreatednon-surgically,orretreated

surgically.Thatmeansthatatoothwithanuntowardeventmaystillexhibit

survivalandthusthestudydidnotmeasuretruesurvival.

6

NonsurgicalRootCanalTreatmentFailure

Eventhoughthesuccessratesarehighinendodontictherapy,therewill

alwaysbecasesthatwillfailforavarietyofreasons(15).Thereisaconstant

interactionbetweenthehumanbodyandtheinfectionstemmingfromtheroot

canalsystemandgoalofrootcanaltherapyistoshiftthependulumfrominfection

torepair.Acompromisedimmunesystemisasignificantpredictorforendodontic

treatmentoutcome,whichshowsthatanindividual’simmuneresponsecanimpact

thesuccessofthetreatment(30).Therearevariationsinthecomplexityand

resistanceoftheinfectionpresentandhowpatientsrespondtotheendodontic

therapy.Treatmentsthatmayworkononeindividualmightnotbesufficientto

fullyalleviatethesymptomsorallowforresolutionoftheinfectioninanother

individual.

Thecategoriesdescribingcausesforpersistentapicalperiodontitisinclude

intraradicularinfection,extraradicularinfection,foreignbodyreactions,andtrue

cysts(31).Theprimarycauseofendodonticfailureispersistentbacterialinfection

resultingfrominadequateasepticcontrol,missedcanals,inadequate

chemomechanicaldisinfection,leakingrestorations,andextrudeddebrisinfected

withmicroorganisms(17,31,32).Ithasbeenshownthatbacteriaareoften

organizedinabiofilm,whichmakesthemmuchlesssusceptibletothe

chemomechanicaldisinfectionutilizedinrootcanaltherapy(33,34).Also,certain

bacteriaaremorevirulentthanothersandcanbeaprimaryreasonforendodontic

failure.Forexample,Enterococcusfaecalishasbeenshowntobepresentinhigher

7

concentrationsrelativetootherbacteriaincasesofpersistentdisease(35).E.

faecalishasbeenshowntoaggressivelyinvadedentinaltubules,suppress

lymphocytes,andberesistanttocalciumhydroxide(Ca(OH)2)(36,37,38,39).These

virulencefactorsincombinationwiththelimitationsofourabilitytoaddressthe

entirerootcanalsystemarepossiblereasonsforendodonticfailure.

Alongwithmicrobialfactors,thepatients’providerscanhaveadirectimpact

onendodonticsuccessbythequalityoftreatmentrendered.Temporary

restorationsleakovertimeandifthetoothisnotrestoredpromptly,thesuccessof

therootcanaltherapydecreases(29,40).Iatrogeniccomplicationssuchas

fracturedinstruments,untreatedcanals,perforations,orextrusionofmaterials

decreasethelikelihoodforendodonticsuccess(41).Theprovidertypehasalso

beenimplicatedinaffectingendodonticsurvival(7).

NonsurgicalRetreatment

Despitethemanycausesforendodonticfailure,rootcanaltherapystill

achievessuccessratesof86-96%(7,13,16).Inthesesituationswhererootcanal

therapyisnotsuccessful,thepatientandproviderdecideifthebestcourseof

treatmentisforextractionorendodonticretreatment.Thegoalfortheretreatment

isthesameastheinitialtherapy,whichistoremovethecausativefactorforthe

infectionandallowforhealingtooccur(10).StabholzandFriedmandevelopeda

rationalefordecidingfurthertreatmentonapreviouslyendodonticallytreated

tooththatincludedsurgery,re-treatment,follow-up,ornotreatment(42).Oneof

thecriticalfactorsindecidingifatoothwithfailingrootcanaltherapyisgoingto

8

undergosurgicaloranonsurgicalretreatmentisthequalityofthepreviousfilling

(42).Thisisbecausethemainobjectiveofnonsurgicalretreatmentistocorrect

deficienciesintheinitialtreatment.Iftheproviderdeterminesthattheycan

increasethequalityoftherootcanaltherapyandnavigatepreviouslyunaddressed

canalspacewithoutdrasticallyweakeningthetoothstructure,thenthetreatment

decisionwouldbetoretreatnon-surgically(42).Nonsurgicalretreatmenthas

demonstratedsurvivalratesof82-93%andshouldbeconsideredasthefirstline

treatmentforanendodonticfailureifthetoothisrestorable(4,43,44,45).

SurgicalRetreatment

Eventhoughorthograderetreatmentistypicallythetreatmentofchoicefor

recurrentendodonticinfection,endodonticmicrosurgeryisaverysuccessfuland

valuableprocedureinresolvingsuchaninfection(46).Therationaleforsurgical

treatmentremainsthesameasintraditionaltherapyinthatthegoalistoreducethe

presenceofmicroorganismsintherootcanalspace(47).Onedifferenceisthat

throughsurgicalintervention,theprovidercanaddresstheextraradicularinfection

withcurettageandremovaloftheinflamedperiapicaltissues.

Insituationswherematerialsareextrudedoutsideoftherootcanalsystem,

theycanharbormicroorganismsthatcanresultinachronicinflammatoryreaction

(48).Thelesionsthatariseareofinflammatoryoriginandaretheresultofchronic

irritationfromthemicroorganismsresidingintherootcanalsystemor

extraradicularly(47).Ithasevenbeenfoundthatpaperpointscaninducechronic

apicalperiodontitis(49).Eventhoughmostlesionsofendodonticoriginare

9

granulomas,roughly15%ofthelesionsarecysts(50).Cystsaretheresultof

proliferationofepithelialrestcellsoftheperiodontalligament(51,52).Thesecells

proliferateasaresultofaninflammatorystimulusinwhichtheyencompassthe

irritant(53).Iftheyareatruecystandnotapocketcyst,surgicalendodontic

therapywillnotresolvetheinfectionandtheywillneedtobesurgicallyremoved

(54,55).

Whenthequalityoftheinitialtreatmentisunlikelytobeimprovedorwhena

nonsurgicalretreatmentwouldcompromisecriticaltoothstructure,thensurgical

retreatmentispreferred.Itisatthisjunctionwheretheprovidermustmakethe

decisionthatbothallowsforthebestchanceofresolutionoftheinfectionwhilealso

balancinglongtermprognosis,patientfinances,desires,risks,andbenefitsofeach

treatment.

Core/PostandCore

Ithasbeenwellestablishedthatthequalityofthecoronalrestorationhasa

directimpactonthesuccessoftheendodontictherapy(56,57,58).Arestorationnot

onlypreventsbacterialcontaminationintotherootcanalspace,butalsoreplaces

brokendowntoothstructure.Themostcommonlyusedmaterialsforcorebuildups

aredentalamalgamandcomposite.Alongwithbeinguserfriendly,amalgamhas

thebenefitsofhighcompressivestrength,wearresistance,andstiffness(59).

However,amalgamisbrittleandhasalowertensilestrengththancomposite,which

iswhytheymusthavesufficientbulkinordertodecreasetheirchancesoffracture.

Fortunately,corebuildupstypicallyrequiregreaterthan2mmofmaterial,whichis

10

sufficientenoughtoprovideadequatestrengthforthematerial.Dentalamalgams

alsohavethebenefitofundergoingslightcorrosion,whichcreatesasealbetween

therestorationandtoothstructurepreventingleakage(60).

Compositerestorations,alsoknownasresin-basedcomposites,areusedto

replacemissingtoothstructureandprovideincreasedestheticscomparedto

amalgam(61).Therearedefinitivebenefitsanddrawbackstousingcompositein

dentistry,soitisuptothedentisttodecidewhichisthebestmaterialforthe

specificsituation.Compositecorebuildupsutilizeabondingsystemsothatthe

restorationwillhavemicromechanicalretentiontotheenamelanddentin(59).

However,compositedoesundergopolymerizationshrinkage,whichcanleadtoa

gapbetweentherestorationandthetoothstructureallowingforleakageand

recurrentcaries(61).Additionaldisadvantagesincludeexhibitingmoreocclusal

wear,moretimeconsumingtoplace,andtheyaremoretechniquesensitiveasthe

operatingsiteneedstobeproperlyisolatedinordertopreventfluidcontamination

(60).Newercompositematerialshavebeendevelopedthatdiminishthedrawbacks

thattheearliergenerationshadincludinghavingsuperiordurability,wear

resistance,anddecreasedshrinkage(61).Withalloftheadvancesinmaterialsand

techniques,itiscriticalthatthedentiststaysuptodateintheirknowledgebasein

ordertoutilizethebestpossiblematerialtoaddressthespecificsituationthatthe

patientspresentwith.

Teeththatareendodonticallytreatedaretypicallystructurallycompromised

asaresultofpreviousrestorationsorcaries.Whenthereisextensivelossof

coronaltoothstructure,postplacementisvaluablefortheretentionofthecoreand

11

crown(62).Thereareavarietyofcategoriesofpostsincludingactiveorpassive,

parallelortapered,prefabricatedorcustom,metalorfiberorceramic.Theyeach

havetheirownindicationbuttheprimarygoalistoretaintherestorationandthe

crownwhenthereisnotenoughremainingtoothstructuretodoso.Placementofa

postcanbeatechniquesensitiveprocedureandpreviousstudieshaveshownthat

successratesareincreased20%whenarubberdamisused(63).Postplacement

involvescreatingspaceforpostplacementbutitiscriticaltominimizethe

enlargementofthecanalasitdoesweakentheroot(64).Anoversizedpost

preparationspacealongwithuseofarigidpostwillpredisposethetoothtofracture

(65).However,postswithanelasticmodulusclosertodentin,suchasfiberposts,

canmoreevenlydistributetheforcewithintheroot.Fiberpoststypicallyfailfrom

debondingwhichreducestheriskofrootfractures(66).However,ifametalpostis

placedinanoverlyenlargedcanal,thenthetoothishighlypredisposedtosuffering

afracture(64,65).Themostcriticalfactorinpreventingrootfracturesispreserving

naturaltoothstructureinboththecoronalandradicularareas.

Regardlessofthefinalrestorationchosen,itisalsocriticalthatsuch

restorationtakesplaceinatimelyfashionastopreventmicrobialleakageintothe

canals(67).Leakagestudieshaveshownthattemporaryfillingmaterialswillallow

forbacterialcontaminationoftherootcanalspacewithin30daysandbacterial

endotoxinwillpresentevensooner(68,69).Thatiswhyifthereisobvious

contamination,aretreatmentmaybeconsideredpriortothefinalrestoration

placement(70,71).Successfulendodontictherapyreliesheavilyonthepresenceof

aqualityrestorationplacedinatimelyfashion(56).

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Crown

Teeththatrequireendodontictherapytypicallyhaveweakenedtooth

structurepriortotherapyaresultoftrauma,caries,orpreviousrestorations.Ina

long-termstudyatanendodonticspecialist’soffice,itwasdeterminethatthemain

causesoftoothlossafterrootcanaltherapyarecrownandrootfractures(4).

Additionally,inastudybyVireinvestigatingthecauseofendodonticallytreated

toothfailure,hefoundthat59%oftheteethwereextractedasaresultofa

prostheticfailurewhereasonly8%wereextractedduetoendodonticreasons.Vire

alsofoundthatteethsurvivedalmosttwiceaslongifacrownwasplacedafterthe

rootcanaltherapy(72).IthasbeenshownthatanMODpreparationcanweaken

thetoothsignificantlyanddecreasethefractureresistanceby40-60%(73).

Endodonticallytreatedteethareweaker,butitwasdemonstratedthatendodontic

proceduresandaccesscavityonlydecreasetherelativestiffnessby5%whereas

merelyanocclusalcavitypreparationhasa20%effect(74).Basedonthisdata,it

seemsthatthelossoftoothstructurefromcariesorpreviousrestorationsisgoing

tobeamoresignificantfactoronthelikelihoodoffractureswhencomparedtothe

endodontictreatment.

Aquilinofoundthatteeththatdidnothaveacrownplacedsubsequenttothe

rootcanaltherapywerelostataratesixtimesthoseteeththathadacrownplaced

(75).Thiscouldbeexplainedthatteethwithoutaproperrestorationweremore

pronetoleakageandtheyaremorelikelytohavecatastrophiclossoftooth

structure.Aminoshariaeandothersfoundthatanendodonticallytreatedtooththat

13

didnothaveapermanentrestorationhadasurvivalrateof58%,butifacorebuild-

upwasplacedwithoutacrownitincreasedto71%.However,ifacorewasplaced

alongwithacrown,thenthesurvivaljumpedupto84%.Additionally,ifthatcrown

wasplacedwithin4monthsoftherootcanaltherapy,thetoothwasthreetimes

morelikelytosurvivethanifthecrownwasplacedafterfourmonths(76).Itis

clearthatpromptrestorationwithacorebuild-upfollowedbycrownplacementhas

asignificanteffectontoothsurvivalafterrootcanaltherapy.

MATERIALSANDMETHODS

Thedataforthisstudywasobtainedfromtheelectronicinsuranceclaims

recordandenrollmentdatabaseforDeltaDentalofWisconsin.Thedatabase

included491,915initialnonsurgicalrootcanaltherapiesthatoccurredbetween

January1,2000andDecember31,2013.OfthetotalnumberofNS-RCTs,438,487

werecompletedonpermanentteethandhada90-daycontinuousfollow-up

withoutfailure.Ninetydaysaftertheinitialtherapywasusedasalandmarkin

ordertoassessthepresenceorabsenceofapost/coreandorcrown.Thisstudy

excluded34,616teeththatdidnothaveatleast90daysofcontinuousfollow-upand

the3,376thatfailedwithinthe90days.Survivaltimeswerecalculatedfromthe

landmarked90daysaftertheNS-RCT(Table1).

14

N Inclusion/exclusion

step 0: 491915 Total NS-RCT's step 1: 488943 Include: First NS-RCT per patient/tooth step 2: 476479 Include: Permanent teeth numbers 1-32 step 3: 438487 *Include: At least 90 days continuous follow-up

Table1:Inclusion/ExclusionCriteria

TheinitialeventwasaNS-RCTonananterior,premolar,ormolartoothas

definedbytheCodeonDentalProceduresandNomenclature(CDT).TheD3310

codeincludesinitialNS-RCTofamaxillaryormandibularcentralincisor,lateral

incisor,orcanine.TheD3320codeincludesinitialNS-RCTofamaxillaryor

mandibularfirstorsecondpremolar.TheD3330codeincludesinitialNS-RCTofa

maxillaryormandibularmolar.

Extraction,nonsurgicalretreatmentandsurgicalretreatmentofthetooth

thathadtheinitialNS-RCTwereconsidereduntowardevents.Thecaseswere

followedandconsideredsuccessfuluntiltheCDTcodesrepresentingextraction,

nonsurgicalretreatment,orsurgicalretreatment(apicoectomy)wereencountered.

Ifthetoothwasretreated,eithernon-surgicallyorsurgically,itcontinuedtobe

followedandfurtherinterventionswererecorded.

Thepresenceofthecore,postandcore,andcrownwasrecordedat90days

afterinitialNS-RCT.ItwasdeterminedbythepresenceoftheCDTcodeindicating

thatacore,postandcore,orcastpostandcorehadbeenplaced.Presenceofthe

CDTcodefortheplacementofametallic,non-metallic,orstainlesssteelcrownswas

evaluatedat90daysaftertheinitialNS-RCT.

Foreachoftheinitialencounters,informationwasobtainedregardingthe

15

toothlocation(anterior,premolar,molar),ageofthepatient,andtheprovidertype.

Providertypesweredividedintoendodontists,whomgraduatedfromanAmerican

DentalAssociationaccreditedUnitedStatesendodonticresidencyprogram,and

non-endodontists(orotherproviders).

Oncethevariablesweredefined,thedatawasanalyzedusingSASversion9.3

(SASInstituteInc.,Cary,NC).Astatisticalsignificancelevel(alpha)of0.05wasused

throughout.Thesurvivaltimeistakenasthetimefromlandmark(90dayspost-

procedure)toextraction.Kaplan-Meiersurvivalestimateswereevaluatedfor1,3,5,

and10years(Figure1,Table3).Clusteringwithinsubject(thesamepatientmay

havemultipleteethwithrootcanals)wasaccountedforbyusingthesandwich

estimatortoobtainrobuststandarderrorestimates.Coxproportionalhazards

regressionwasusedtocomparesurvivaldistributionsbetweencategoriesforeach

predictor;thisp-valueisnotadjustedforothervariablesormultipletesting(Tables

4,5,6,7,8,Figures2,3,4,5,6).

InregardstothemultipleCoxproportionalhazardsregressionanalysis,the

survivaltimewastakenfromthe90-daypost-RCTlandmarktoextraction.Adjusted

hazardratios(aHR’s)werecalculatedusingmultipleCoxproportionalhazards

regressionanalysis;sandwichestimatorwasusedtoobtainrobuststandarderrors

thatadjustforwithin-subjectcorrelation.Eachhazardratioestimateisadjustedfor

allothervariablesinthemodel(Table9).

Cumulativeincidenceplotswereconstructeddemonstratingtheincidenceof

thefirstfailureeventtooccurfollowingNS-RCT(nonsurgicalretreatment,surgical

retreatment,extraction).Anadditionalplotdemonstratedtheprobabilityof

16

untowardeventscomparingtheinitialprovidertype(Figures7,8).

Amulti-statemodelwithsixtransitionswascreatedusingthe‘m-state’R

package(onlytransitionstoahigherlevelofre-interventionwereallowed).The

cumulativehazardandtransitionprobabilitiesfromthemodelwereplottedforall

NS-RCTproceduresandseparatelybyinitialprovidertype(Figures9,10,11).The

plotoftransitionprobabilitiesdemonstratestheprobabilityofatoothwithNS-RCT

transitioningtoafailurestateandcomparesthembasedontheprovidertypes

(Figures12,13).

RESULTS

Aftertheinclusion/exclusioncriteriawereappliedtothedataset,therewere

438,487patientencountersthatresultedinnonsurgicalrootcanaltherapy.Table2

demonstrated138,655procedureswerecompletedbyanendodontistandanon-

endodontistcompleted299,832.Endodontistscompleted31.6%oftheprocedures

whilenon-endodontistscompleted68.4%oftheprocedures.OfthecaseswhereNS-

SRCTwasperformedbyendodontists,99,205(71.5%)weremolars,25,220(18.2%)

werepremolars,and14,230(10.3%)wereanteriors.Ofthecaseswhereaprovider

otherthananendodontistperformedNS-RCT,141,877(47.3%)weremolars,

96,600(32.2%)werepremolars,and61,355(20.5%)wereanteriors.Basedona

Chi-squaredanalysis,therewasasignificantdifferenceintoothlocationbetween

thedifferentprovidertypes(p<0.001).

Themeanageofthepatientsinthisstudywas44.7,whileageofthepatients

ofendodontistswas46.4andtheageofthepatientsofnon-endodontistswas43.9

17

yearsold.Themedianageofthepatientsinthisstudy,patientsoftheendodontists,

andpatientsofthenon-endodontistswere46,48,45,respectively.BasedonaT-test

analysis,theseresultsareasignificantdifference(p<0.001).

Subjectswerecategorizedbasedonageinfivegroups.Subjectsintheage

group0-17yearsconstituted16,123(3.7%)cases,ages18-35having99,319

(22.7%)cases,ages36-53having194,831(44.4%)cases,ages54-71having

121,121(27.6%)cases,andages71+having7,093(1.6%)cases.Inregardsto

endodontists,ages0-17had5,060(3.6%)cases,ages18-35had24,903(18%)

cases,ages36-53had61,790(44.6%)cases,ages54-71had44,159(31.8%)cases

andages71+had2743(2.0%)cases.Inregardstonon-endodontists,ages0-17had

11,063(3.7%)cases,ages18-35had74,416(24.8%)cases,ages36-53had133,041

(44.4%)cases,ages54-71had76,962(25.7%)casesandages71+had4,350(1.5%)

cases.BasedonaChi-squaredanalysis,therewasasignificantdifferenceintheages

ofthepatientsbetweenthedifferentprovidertypes(p<0.001).

Ofthe438,487encounters,276,611(63.1%)hadacoreorapostandcore

placedwithin90dayswhile161,876(36.9%)didnothaveacoreorapostandcore

placed.Encounterswithendodontistsresultedin79,949(57.7%)caseshavingthe

coreorpostandcoreplacedwithin90dayswhile58,706(42.3%)didnothavea

coreorpostandcoreplaced.Encounterswithnon-endodontistsresultedin

196,662(65.6%)caseshavingthecoreorpostandcoreplacedwithin90dayswhile

103,170(34.4%)didnothaveacoreorpostandcoreplaced.BasedonaChi-

squaredanalysis,therewasasignificantdifferenceinthepresenceofacoreorpost

andcoreat90daysofthepatientsbetweenthedifferentprovidertypes(p<0.001).

18

Ofthe438,487encounters,121,549(27.7%)hadacrownplacedwithin90

dayswhile316,968(72.3%)didnothavecrownplaced.Encounterswith

endodontistsresultedin37343(26.9%)caseshavingthecrownplacedwithin90

dayswhile101,312(73.1%)didnothaveacrown.Encounterswithnon-

endodontistsresultedin84,206(28.1%)caseshavingthecrownplacedwithin90

dayswhile215,626(71.9%)didnothaveacrownplaced.BasedonaChi-squared

analysis,therewasasignificantdifferenceinthepresenceofacrownat90daysof

thepatientsbetweenthedifferentprovidertypes(p<0.001)(Table2).

19

All

(n=438487)Endodontist(n=138655)

Otherprovider(n=299832)

p-value Test

Toothlocation <.001 Chi-squared

Anterior 75585(17.2%) 14230(10.3%) 61355(20.5%) Pre-molar 121820(27.8%) 25220(18.2%) 96600(32.2%) Molar 241082(55.0%) 99205(71.5%) 141877(47.3%)

AgeatNSRCT <.001 T-test

Mean(SD) 44.7(14.1) 46.4(14.0) 43.9(14.0) Median[Min,Max] 46.0[0.0,99.0] 48.0[0.0,99.0] 45.0[1.0,96.0]

FreqMissing 0 0 0

AgeatNSRCT <.001 Chi-squared

0-17 16123(3.7%) 5060(3.6%) 11063(3.7%) 18-35 99319(22.7%) 24903(18.0%) 74416(24.8%) 36-53 194831(44.4%) 61790(44.6%) 133041(44.4%) 54-71 121121(27.6%) 44159(31.8%) 76962(25.7%) 71+ 7093(1.6%) 2743(2.0%) 4350(1.5%) Core/postwithin90days <.001 Chi-

squaredNocore/postwithin90days 161876(36.9%) 58706(42.3%) 103170(34.4%)

Core/postwithin90days 276611(63.1%) 79949(57.7%) 196662(65.6%)

Crownwithin90days <.001 Chi-

squared

Nocrownwithin90days 316938(72.3%) 101312(73.1%) 215626(71.9%)

Crownwithin90days 121549(27.7%) 37343(26.9%) 84206(28.1%)

Table2:Summaryofvariablesbasedonnumberofcases

20

Figure1:Survivalestimatesofendodonticallytreatedteeth

Survival Nevents Natrisk0year — — 4384871year 98.19%[98.14%,98.23%] 6889 3263723year 94.38%[94.29%,94.46%] 9884 1859665year 90.83%[90.70%,90.95%] 5454 10528710year 82.84%[82.57%,83.11%] 4848 17762

Table3:Survivalestimatesofendodonticallytreatedteeth

21

Table4:Survivalestimateofendodonticallytreatedteethbasedontoothlocation

UsingaKaplan-Meierestimator,thesurvivalrateswere98.19%at1year,

94.38%at3years,90.83%at5years,and82.84%at10years(Figure1,Table3).

Thesurvivalrateswerefurtherdividedbytoothlocationandanteriorteethhada

survivalrateof98.54%at1year,94.94%at3years,91.21%at5years,and83.28%

at10years(Figure2,Table4).Premolarteethhadasurvivalrateof98.39%at1

year,94.83%at3years,91.39%at5years,and83.74%at10years.Molarshada

survivalrateof97.98%at1year,93.98%at3years,90.33%at5years,and82.23%

at10years.

Survival Nevents NatriskAnterior0year — — 755851year 98.54%[98.45%,98.63%] 945 562203year 94.94%[94.74%,95.14%] 1585 317025year 91.50%[91.21%,91.80%] 878 1773010year 83.28%[82.61%,83.95%] 823 2792Pre-molar0year — — 1218201year 98.38%[98.31%,98.46%] 1701 908253year 94.83%[94.67%,94.98%] 2576 523015year 91.39%[91.16%,91.62%] 1493 2998510year 83.74%[83.25%,84.23%] 1330 5267Molar0year — — 2410821year 97.98%[97.92%,98.04%] 4243 1793273year 93.98%[93.86%,94.10%] 5723 1019635year 90.33%[90.16%,90.50%] 3083 5757210year 82.23%[81.87%,82.60%] 2695 9703

22

Figure2:Survivalestimateofendodonticallytreatedteethbasedontoothlocation

Whencomparedbytheprovidertype,thesurvivalratesforatoothtreated

withNS-RCTbyanendodontistwere98.25%at1year,94.9%at3years,91.84%at

5years,and84.94%at10years(Figure3,Table5).Thesurvivalratesforatooth

treatedwithNS-RCTbyanon-endodontistwere98.16%at1year,94.14%at3

years,90.38%at5years,and81.93%at10years(Figure3,Table5).

23

Figure3:Survivalestimateofendodonticallytreatedteethbasedonprovider

type

Thesurvivalratesfortreatedteethineachoftheagegroupswereevaluated

at1,3,5,10yearsaftertheinitialtherapy.Fortheagegroup0-17years,thesurvival

rateswere99.05%at1year,96.36%at3years,94.04%at5years,and89.36%at

10years(Figure4,Table6).Fortheagegroup18-35,thesurvivalrateswere

98.54%at1year,95.06%at3years,91.94%at5years,and85.13%at10years.

Fortheagegroup36-53,thesurvivalrateswere98.17%at1year,94.60%at3

years,91.24%at5years,and83.38%at10years.Fortheagegroup54-71,the

survivalrateswere97.89%at1year,93.40%at3years,89.13%at5years,and

79.7%at10years.Fortheagegroup71yearsandover,thesurvivalrateswere

97.03%at1year,91.29%at3years,86.32%at5years,and75.82%at10years.

24

Table5:Survivalestimateofendodonticallytreatedteethbasedonprovidertype

Figure4:Survivalestimateofendodonticallytreatedteethbasedonpatient

age

Survival Nevents NatriskEndodontist0year — — 1386551year 98.25%[98.18%,98.33%] 2106 1029403year 94.90%[94.75%,95.04%] 2727 574815year 91.84%[91.63%,92.05%] 1428 3219310year 84.94%[84.46%,85.41%] 1197 5115Otherprovider0year — — 2998321year 98.16%[98.11%,98.21%] 4783 2234323year 94.14%[94.04%,94.25%] 7157 1284855year 90.38%[90.22%,90.53%] 4026 7309410year 81.93%[81.61%,82.26%] 3651 12647

25

Survival Nevents Natrisk0-17

0year — — 161231year 99.05%[98.89%,99.21%] 133 124233year 96.36%[96.00%,96.72%] 260 70095year 94.04%[93.51%,94.58%] 129 360410year 89.36%[88.02%,90.72%] 90 310

18-350year — — 993191year 98.54%[98.46%,98.63%] 1183 673163year 95.06%[94.88%,95.25%] 1730 332625year 91.94%[91.66%,92.22%] 814 1727010year 85.13%[84.50%,85.77%] 633 2720



71+0year — — 70931year 97.03%[96.61%,97.45%] 185 54033year 91.29%[90.50%,92.08%] 261 30345year 86.32%[85.20%,87.45%] 131 163510year 75.82%[73.53%,78.19%] 112 220

Table6:Survivalestimateofendodonticallytreatedteethbasedonpatientage

Thesurvivalratesoftheteethwithoutacoreorapostandcoreplaced

within90dayswere97.35%at1year,92.57%at3years,88.68%at5years,and

80.74%at10years(Figure5,Table7).Thesurvivalratesofteethwithacoreora

postandcoreplacedwithin90dayswas98.68%at1year,95.45%at3years,

92.11%at5years,and84.11%at10years.

26

Figure5:Survivalestimatesofendodonticallytreatedteethwithcore/post

material

Survival Nevents NatriskNocore/postwithin90days0year — — 1618761year 97.35%[97.27%,97.43%] 3749 1205173year 92.57%[92.42%,92.73%] 4684 692445year 88.68%[88.47%,88.90%] 2293 4005410year 80.74%[80.32%,81.17%] 1945 7565Core/postwithin90days0year — — 2766111year 98.68%[98.63%,98.73%] 3140 2058553year 95.45%[95.36%,95.55%] 5200 1167225year 92.11%[91.96%,92.26%] 3161 6523310year 84.11%[83.76%,84.45%] 2903 10197

Table7:Survivalestimatesofendodonticallytreatedteethwithcore/postmaterial

27

Thesurvivalratesoftheteethwithoutcrownplacedwithin90dayswere

97.76%at1year,93.33%at3years,89.47%at5years,and81.01%at10years

(Figure6,Table8).Thesurvivalratesoftheteethwithacrownplacedwithin90

dayswas99.31%at1year,97.16%at3years,94.44%at5years,and87.71%at10

years.

Figure6:Survivalestimatesofendodonticallytreatedteethbasedonpresence

ofacrown

28

Survival Nevents NatriskNocrownwithin90days0year — — 3169381year 97.76%[97.70%,97.81%] 6182 2356943year 93.33%[93.22%,93.44%] 8387 1341855year 89.47%[89.31%,89.62%] 4325 7560210year 81.01%[80.68%,81.33%] 3771 12654Crownwithin90days0year — — 1215491year 99.31%[99.26%,99.36%] 707 906783year 97.16%[97.04%,97.28%] 1497 517815year 94.44%[94.24%,94.64%] 1129 2968510year 87.71%[87.23%,88.18%] 1077 5108

Table8:Survivalestimatesofendodonticallytreatedteethbasedonpresenceofacrown

TheMultipleCoxproportionalhazardsregressionresultscomparedsurvival

timesofteethbasedondifferentvariables.Thelargertheadjustedhazardratio

(aHR),thegreaterlikelihoodofextractioncomparedtothereferencecategory.In

comparingprovidertypeofanon-endodontisttoanendodontist,theaHRwas1.308

(p<0.001)(Table9).Thismeansthatatoothismorelikelytobeextractedifthe

initialprovidertypeisnotanendodontist.Whencomparingtoothlocation,theaHr

comparingapremolartoananteriortheaHRwas1.044(p<.043),whichis

statisticallysignificantbutnottothesameextentastheothervariables.However,

whencomparingamolartoananteriortheaHRwas1.255(p<0.001)meaninga

molarismorelikelytobeextractedthanananteriortooth.

Theagegroupswereeachcomparedtothereferenceagegroupof0-17

becausethatagegrouphadtheleastlikelihoodofextraction.Whencomparingthe

agegroupof18-35to0-17theaHRwas1.385(p<0.001)(Table9).When

29

comparingtheagegroupof36-53to0-17theaHRwas1.602(p<0.001).When

comparingtheagegroupof54-71to0-17theaHRwas2.055(p<0.001).When

comparingtheagegroupof71andolderto0-17theaHRwas2.861(p<0.001).As

thepatientageincreased,thelikelihoodofextractionincreasedwiththelargestaHR

beingthe71andolderagegroup.EveryagegrouphadastatisticallysignificantaHR

whenbeingcomparedtothe0-17agegroup.

TheaHRofatoothwithacoreorapostandcorecomparedtolackingacore

orapostandcorewas0.741(p<0.001).Thetoothwasmorelikelytobeextractedif

therewasnotacoreorapostandcorepresentat90daysaftertheNS-RCT.The

aHRofatoothwithacrowncomparedtolackingacrownwas0.525(p<0.001).The

toothwasmorelikelytobeextractediftherewasnotacrownpresentat90days

aftertheNS-RCT.

30

N=438487 aHR 95%CI p-valueRCproviderOtherprovidervs.Endodontist 1.308 [1.271,1.347] <0.001

ToothlocationPre-molarvs.Anterior 1.044 [1.001,1.089] 0.043Molarvs.Anterior 1.255 [1.207,1.305] <0.001Age18-35vs.0-17 1.385 [1.267,1.514] <0.00136-53vs.0-17 1.602 [1.471,1.746] <0.00154-71vs.0-17 2.055 [1.885,2.240] <0.00171+vs.0-17 2.861 [2.547,3.215] <0.001Core/postCore/postwithin90daysvs.Nocore/postwithin90days 0.741 [0.723,0.760] <0.001

CrownCrownwithin90daysvs.Nocrownwithin90days 0.525 [0.507,0.542] <0.001

Table9:MultipleCoxproportionalhazardsregressionresults.Adjustedhazardratiosforvariablesaffectingtoothsurvival

Thefollowingplotsdemonstratethecumulativeincidenceofthefirstfailure

tooccurfollowingtheinitialrootcanaltherapy(Figures7,8).Italsocomparesthe

incidencebasedontheinitialprovidertype.Thereisaveryhighprobabilitythat

thetoothwillnotundergoafailureevent,butifitdoes,thenmostlikelyitwillbe

extracted.Ifitisgoingtoberetreated,itismorelikelytoberetreatednon-

surgicallythansurgically.Whencomparingendodontiststootherproviders,atooth

initiallytreatedbyanendodontistislesslikelytoberetreatedorextracted(Figure

8).

31

Figure7:Cumulativeincidenceofthefirstfailureeventtooccurfollowingthe

initialrootcanal(nonsurgicalretreatment,surgicalretreatment,orextraction).

Figure8:Cumulativeincidenceofthefirstfailureeventtooccurfollowingthe

initialrootcanal(nonsurgicalretreatment,surgicalretreatment,orextraction)basedonprovidertype

32

6possibletransitions

tofrom root_canalnon_surgical_rtsurgical_rtextractionroot_canal NA 1 2 3non_surgical_rt NA NA 4 5surgical_rt NA NA NA 6extraction NA NA NA NA

Observedtransitionfrequencies: tofromroot_canalnon_surgical_rtsurgical_rtextractionnoeventtotalenteringroot_canal04030193525186407336438487non_surgical_rt0011742234914030surgical_rt 00027917732052extraction 00002588725887

ObservedtransitionProportions tofromroot_canalnon_surgical_rtsurgical_rtextractionnoeventroot_canal0.0000000000.0091906940.0044129020.0574384190.928957985non_surgical_rt0.0000000000.0000000000.0290322580.1047146400.866253102surgical_rt0.0000000000.0000000000.0000000000.1359649120.864035088extraction0.0000000000.0000000000.0000000000.0000000001.000000000

Figure9:Multi-statemodelcreatedusingthe‘m-state’Rpackagewith6transitionsbetweenfailurestates(nofailure,nonsurgicalretreatment,surgical

retreatment,extraction)

Ofthe438,487teeththathadinitialNS-RCT,407,336hadnosubsequent

event,25,186wereextracted,4,030wereretreatednon-surgicallyand1,935were

retreatedsurgically(Figure9).Ofthe4,030teeththatwereretreatednon-

surgically,3,491hadnosubsequentevent,422wereextracted,and117were

surgicallyretreated.Ofthe2,052teeththatweretreatedsurgically,1,773hadno

subsequenteventwhile279wereextracted.

Thecumulativehazardplotshowedthesetransitionsovera12-yearperiod

(Figure9,10).Teeththatwereretreatedsurgicallyornon-surgicallyweremore

likelytobeextractedthanteeththatdidnothavesuchanintervention.Teethwere

33

morelikelytobeextractedthanretreated.Teethweremorelikelytoberetreated

non-surgicallythansurgically.Ifatoothhadanonsurgicalretreatmentandthen

subsequentlyhadasurgicalretreatment,thenitwasmorelikelythatthesurgical

interventionoccurredduringthefirstyearoftreatment.

Figure10:Transitionsbetweenfailurestatesinthemulti-statemodel(nofailure,nonsurgicalretreatment,surgicalretreatment,extraction)basedon

time

34

Thecumulativehazardplotsdemonstratethetimetothetransitionstate

basedoninitialprovidertypewithendodontistsrepresentedinblackandnon-

endodontistsinred,respectively(Figure11).Atooththatwastreatedbyanon-

endodontistwasmorelikelytoundergononsurgicalretreatmentorextractionthan

iftheinitialtherapywasprovidedbyanendodontist.Thetransitionsofnonsurgical

retreatmenttosurgicalretreatment,nonsurgicalretreatmenttoextraction,and

surgicalretreatmenttoextractionbasedonthedifferentprovidertypesyielded

confidenceintervalswithtoomuchoverlaptomakeanyconclusions(Figure11).

Figure11:Cumulativehazardplotdemonstratingtimetothetransitionstatebasedoninitialprovidertype(endodontistblack,otherred)

35

Theplotoftransitionprobabilitiesdemonstratesthatmostteeththatwere

treatedbyNS-RCThadnosubsequenttreatmentinterventionsattheendofthe10-

yearfollow-upperiod(Figure12).However,ifaninterventionisgoingtooccur,the

probabilityishigherthatitwillbeanextractioncomparedtoaretreatment.When

comparinganon-endodontisttoanendodontisttheprobabilityofatoothbeing

retreatedorextractedishigheriftheinitialproviderwasnotanendodontist(Figure

13).

Figure12:Plotoftransitionprobabilitiesofendodonticallytreatedteeth

36

Figure13:Plotoftransitionprobabilitiesofendodonticallytreatedteeth

basedonprovidertype

DISCUSSION

Theprimaryobjectivesofthisstudyweretoevaluatethefactorsthataffect

endodonticsuccessandtofurtherunderstandtheimpactthetypeofclinicianhason

thefinaloutcomeofatoothtreatedwithNS-RCT.Itisimportanttounderstand

whatimpactsendodonticsuccessandtoothsurvivalsothatthecliniciancanbest

practiceevidence-baseddentistry.Understandingtrueoutcomesisalsoimportant

sothatthepatientscanhaveproperexpectationsandaninformedconsentofthe

expectedresultsoftheirtreatment.

InutilizingtheDeltaDentalofWisconsininsurancedatabase,thisstudyhad

accesstoaverylargepatientbase,butthereareobviouslimitationsinsuch

insurancestudies.Thisstudylackspatientdiversityasitonlyevaluatespatients

37

withDeltaDentalinsuranceandpatientswithoutitmaybeinadifferent

demographicgroup.Also,thisstudycanonlyevaluatethedatasubmittedtoDelta

Dentalandifinformationisnotsubmittedorimproperlycoded,thenthatwillnotbe

representedinthedata.AspatientslosetheirDeltaDentalinsurancecoverage,they

arenolongerfollowedinthisstudyandanysubsequentinterventionstotheteeth

cannotberecorded.Therewerearatherlargepercentageofpatientsthatwerelost

duringthefollow-upperiodbecausetheirdentalinsurancecoveragechanged,

whichimpactsthevalidityofthedata.

Inretrospectiveinsurancestudies,thereisnotawaytohavestandardization

oftheprovidersorattempttounderstandtherationaleforatreatmentdecision.

Theycannotprovideinsightintothequalityoftreatmentprovidedorifproper

techniqueswerefollowed.Theinabilitytounderstandtherationalefortreatment

canunderestimatesurvivalasprovidersmaybeextractingteeththatareotherwise

restorableorchoosingnottoretreatatooththatmayhaveagoodchanceofsuccess

infavorofanimplant.Itisalsoimpossibletoconsideradditionalfactorsthatmay

affectthesurvivalsuchastheperiodontalhealthofthepatient,pulpaland

periradiculardiagnosisofthetoothpriortotreatment,orremainingtoothstructure

priortotreatment.Additionally,becausethisstudyisevaluatingsurvival,theteeth

inthisstudythathavesurvivedmaynotactuallybeatruesuccessfultreatment.

Thiswouldbethecaseininstancesthattheteethcouldhavelesionsassociatedwith

them,causingthepatientspain,orbenon-restorable.Also,toothlosscanoccur

unrelatedtoendodonticreasons.

38

However,eventhoughtherearelimitationsregardingthisstudy,thereare

multiplebenefitsthatallowthestudytoyieldmeaningfulinformation.Byhaving

accesstotheDeltaDentalofWisconsin’sentiredatabase,thisstudyhasaverylarge

studypopulation.Thislargestudypopulationallowsthestatisticalanalysisto

detectminordeparturesfromthenull.Theimmensedatasetcanminimizethe

effectsofvariationsintreatmentorproviders.Italsoprovidesawaytostudytooth

survivalandtrueoutcomesofteethtreatedbyNS-RCTintherealworld.Many

studiesareperformedinresidencyprogramsorevaluatingahandfulofprivate

practices,wherethereisalimitationasitisonlyrepresentativeoftheirofficeand

thetreatmentanddecisionsbytheirreferringdentists(4,45).Withthisstudy,we

haveaccesstothetrueoutcomeofteethtreatedacrosstheentirestateofWisconsin

withabroadvarietyofpatientsandproviders.Becauseitisaretrospectivestudy,

theprovidersareunawarethattheyaretakingpartofthestudysoiteliminatesthat

formoftreatmentbias.Thisallowsforthisstudytoyieldreal-worldoutcomesand

provideinformationastothetreatmentbeingprovidedtothepopulationatlarge.

Thefirstcriteriatoevaluateinthisstudyarethecaseselectionbasedonthe

providertype.ItwasfoundthatendodontistsareperformingNS-RCTonmore

premolars/molars,onolderpatients,andhavingsignificantlyfewercoresand

crownsplacedinatimelyfashion.Eachofthesecriteriahavebeenpreviously

establishedasbeingsignificantfactorsinthesurvivalofendodonticallytreated

teeth(5,29,77).Basedonthecaseselectionrepresentedinthisstudy,whichis

representativeofatypicalprivatepractice,theteethendodontistsaretreatinghave

ahigherpredispositiontofailurejustbasedontoothtypeandpatientage(78).In

39

addition,accordingtoYee,thefailureratesofendodonticallytreatedteethwere

greaterwhenthecoreisnotplacedwithin60days(29).Thiscouldbefrom

bacterialcontaminationofthetemporaryfillingorofacatastrophicfractureofthe

toothwhileinaweakenedstate(67,69).Whenanendodontistperformedtheroot

canaltherapy,thepatientshadcoresplacedwithin90days8%lessthanifageneral

dentistperformedtheinitialNS-RCT.Thisisasignificantdifferenceandcanimpact

thesuccessoftheendodontictherapy.Itisimportantforendodontiststo

emphasizetheneedforapromptfinalrestorationbythereferringdentist,orto

considerplacingthecoreatthetimeofthecompletionoftheendodontictherapy.It

isinterestingtonotethatonly26-28%ofpatientshadacrownplaced90daysafter

rootcanaltherapy.Thiscanbeduetolackoffinances,inabilitytogetpromptcare

bythereferringdentist,persistingsymptoms,orotherfactors.Howeverthisstudy

foundthatthepresenceofacrownwithin90daysofNS-RCThadthegreatest

impactondecreasingtoothextraction.ThisisinagreementwithAquilinowho

foundthatteeththatwerenotcrownedwerelostataratesixtimesteethwitha

fixedrestoration(75).

However,thisstudydiddemonstratesuccessratesofnonsurgicalrootcanal

therapyconsistentwithpreviousstudies(14,15,16,17).Eventhoughendodontists

aretreatingthemorechallengingandcompromisedcases,attenyears,theteeth

treatedbyendodontistshada85%survivalwhiletheteethtreatedbynon-

endodontistshadasurvivalrateof82%.Thesuccessforallprovidersinthisstudy

decreasedwithmulti-rootedteeth,aspatientageincreased,andwiththelackofa

coreandcrownplacedwithin90days.

40

Incorroborationwithpreviousstudies,premolarsandmolarswereshownto

haveadecreasedsurvivalcomparedtoanteriorteeth(5).Itismorecommonfor

multi-rootedteethtohaveisthmuses,lateralcanals,accessorycanalsandother

areasthatproviderswillnotbeabletofullychemo-mechanicallydebride(13,79).

Posteriorteetharealsosubjecttomoreocclusalforcesandaremorelikelytohave

fractures,whichincreasethelikelihoodoftoothextraction(80).Alongwithtooth

typedecreasingtoothsurvival,patientagehadasimilareffect.Aspatientsage,teeth

becomemorecalcified,whichcanincreasethedifficultyofthetreatment.Thereis

alsoanincreaseinpriorcariesandrestorationsthatcanweakentheteethover

time.Witholderpatients,theirteethhavehadtowithstandmoreforcesandthus

wouldhaveahigherpredispositiontocracksandfractures(80).Theriskof

periodontaldiseaseincreaseswithage,whichalsowillimpactthesurvivalofteeth

treatedintheolderagegroups.Toothlossmaynotbeofendodonticorigininthese

situations,butitisstillusefulforbeingabletogiveamoreinformedprognosisfor

thesepatients(81).

Themulti-stateanalysisinvestigatedeachofthedifferenttransitionstates

thatcanoccursubsequenttoendodontictherapy.Whentherewasanintervention

afterNS-RCT,mostoftenthetoothwasextractedbutifitwasretreated,therewasa

greaterlikelihoodofanonsurgicalretreatmentthanasurgicalretreatment.

Extractingendodonticallytreatedteethmaybeduetonon-restorability,patient

finances,crownorrootfractures,orproviderphilosophy.Cliniciansmaylack

confidenceinthesuccessofretreatmenttherapyleadingtoincreasedpressureto

replace‘failed’endodonticallytreatedteethwithimplants(82).However,Kim

41

foundthatafterprimaryendodonticfailure,themostcost-effectivetreatmentwas

microsurgery.Thiswasfollowedbynonsurgicalretreatment,thenextractionand

fixedpartialdenture,andtheleastcosteffectivetreatmentwasasingleunitimplant

(83).Nonsurgicalretreatmentshouldbeconsideredasthefirstlinetreatmentfor

anendodonticfailureifthetoothisrestorable(4,43,45).Themulti-stateanalysis

foundthatteethnon-surgicallyretreatedorsurgicallyretreatedhadsimilar

probabilitiesofbeingextracted,whichwasmuchhigherthanteeththatdidnothave

secondarytreatmentaftertheNS-RCT.

Inarecentsurvey,nearly50%ofactiveendodontistsintheUnitedStatesfelt

thattheydidnotreceiveadequateinstructiononmicrosurgicaltechniqueduring

theirresidency(84).Thiscanresultinprovidersmoreoftenelectingtoeithernon-

surgicallyretreatanendodonticfailureortorecommendextractionbasedontheir

comfortlevel.Insituationswherethecanalmorphologywasalteredduringthe

endodontictherapy,thesuccessoftheretreatmentdroppedto47%(43).Inthese

situations,endodonticmicrosurgeryisamorepredictableandsuccessfuloptionfor

treatment(83).Withthecost-effectivenessinmind,itisimperativethat

endodontistsbecomeadequatelytrainedinendodonticmicrosurgeryinorderto

feelcomfortableandconfidentprovidingsuchtreatmentoptionswiththebest

prognosisfortheirpatients.

Whenatoothwasretreatednon-surgicallyfollowedupbysurgically,this

interventionoccurredmuchmorelikelyinthefirstyearafterthenonsurgical

retreatment.ThiscorroboratesthefindingsofSalehrabiandRotsteinwhofound

thatsuchinterventionusuallyoccurredsoonaftertheretreatment(6).Such

42

therapycouldbeexplainedbyaniatrogeniceventduringtreatmentorpoor

treatmentplanningbyoptingforanonsurgicalretreatmentwhentheclinician

wouldnotbeabletoaddresstheetiologyoftheproblem(43).Thiswouldforcethe

cliniciantoprovideasurgicalinterventioninsituationsofpersisting

signs/symptoms,suspectedpresenceofacyst,rootfractureorotherunspecified

reasons.However,duetothelimitationsofthestudy,therationaleforsuch

treatmentisunknown.

43

CONCLUSION

Withintheconstraintsandlimitationsofthisstudy,itwasconcludedthat

endodontistsaremoreoftentreatingthetypesofteeththathavebeenshownto

havedecreasedlong-termsurvival.PatientshavingNS-RCTperformedby

endodontistsarealsonothavingtheirfinalrestorationsplacedinaprudenttime

frameasoftencomparedtoifadifferentprovidercompletedtheNS-RCT.Provider

type,patientage,toothtype,andrestorationafterrootcanaltherapywereall

significantlyassociatedwithtoothsurvival.Themulti-stateanalysisprovidesa

usefulwaytoevaluatethetrendsofthedifferenttransitionsthatcanoccurtoa

toothinitslifetimeandgiveinsightintotrueoutcomes.

44

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