PathwayofthePulp10thEditionToothMorphologyandAccessCHAPTERCOMPONENTSOFTHEROOTCROOTCANATOMYOFTHEAPICALOBJECTIVESANDGUIDELINESFORPREPARATIONMECHANICALPHASESOFACCESSAccessCHALLENGINGACCESSTeethWithMinimalorNoHeavilyRestoredTeethThoseWithFullVeneerTeethWithCalcifiedCCrowdedRotatedERRORSINACCESSMORPHOLOGYANDPREPARATIONSFORINDIVIDUAL腔內部并到達根尖孔的技術。Thehardtissuesurroundingthedentalpulpcantakeavarietyofconfigurationsandshapes.Athoroughknowledgeoftoothmorphology,carefulinterpretationofangledradiographs,andadequateaccesstoandexplorationofthetooth’sinteriorareprerequisitesfortreatment.Magnificationandilluminationareindispensableaids.Thischapterdescribesandillustratestoothmorphologyandexinsthetechniquescrucialtoachievingunobstructeddirectaccesstotheroot andapicalforamina.Thischapterisdividedintoeightmajorsections:componentsoftherootcrootcanatomyoftheapicalobjectivesandguidelinesforaccesspreparation,6）開preparation,(6)challengingaccess(7)errorsinaccess(8)morphologyandaccess Onlyaftercorrectcompletionofthisphaseoftherapycantheclinicianperformthoroughshaandcleaningandthree-dimensional(3-D)obturation.Theoptimalendodonticresultisdifficulttoachieveiftheaccessisnotproperlyprepared.Theclinicianmusthaveanunderstandingofthecomplexityoftherootcsystemtounderstandtheprinciplesandproblemsofshaandcleaning,todeterminetheapicallimitsanddimensionsofpreparations,toperformmicrosurgicalproceduressuccessfullyandtocorrectprocedural關系。仔細地閱讀兩個或者的不同水平角度拍攝的術前片也很必要。這些術前片將提供非常重要的根管形態(tài)信息。醫(yī)生必須知道X光管的傾斜角度會直20-4040單一的術前片，對于制定后續(xù)的根管治療方案，會有風險。FIG.7-1Periapicalradiographscanrevealcluestorootcmorphology.Abruptdisappearanceofthelargecinthemandibularpremolarsusuallysignifiesac圖7-1根尖片可以揭示根管形態(tài)。下頜前磨牙中粗大根管影像的突然意味盡管如此，傳統X100%叉的試驗。當用快速的方法鑒定時（以根管狹窄區(qū)的突然作為判斷分叉的依據），如果從單一的X根管形態(tài)。在此同時，近年來CBCT的應用可以極大程度地幫助理解根管系統前片、用鋒利的根管探針檢查髓室底、用1%亞甲基藍將髓室底染色、用推薦使用EDTA沖洗并隨后用干燥髓室底以便得到更好的探查視野。FIG.7-2Allowingsodiumhypochlorite(NaOCl)toremaininthepulpchambermayhelplocateacalcifiedrootcorifice.Tinybubblesmayappearinthesolution,indicatingthepositionofthe幫助分析根管口的具置。如：上頜磨牙MB251%82%。另一個研究實驗結果是，使用帶燈的頭戴式放大鏡的MB241%，鏡的發(fā)現率為94%。再一個研究數據是：在顯微鏡下，上頜第一磨牙的MB2發(fā)90%，第二上磨牙MB260頭戴式放大鏡與根管顯微鏡相比，上磨牙MB2FIG.7-3Thedentaloperatingmicroscope(DOM)hasvastlyimprovedlocatingandnegotiatingofcanatomy.FIG.7-4Majoranatomiccomponentsoftherootc這個系統的外形，接近牙齒的外形。但是，牙齒的生理老化，病變，咬沖洗的問題。通過多角度的X光片，可以觀察到這些根管彎曲的存在，和彎曲程度。彎曲根管，可能是全長度的緩彎或者尖部的急彎、S型的雙彎曲根74%11%的分布在中三分之一，15%FIG.7-5Mandibularfirstmolarshowingafurcationc(FC,arrows).F,Furcation;PC,pulpchamberfloor;RC,rootc.7-5下頜第一磨牙X線牙片顯示分支根管(FC,arrowsF,FurcationPC,pulpchamberfloor;根管RC,rootc7-6幾率為13%。中有80%發(fā)生在遠中根）。

FIG.7-6Accessorycsoccurinthreedistinctpatternsinthemandibularfirstmolars.In13%asinglefurcationcextendsfromthepulpchambertotheintraradicularIn23%alalcextendsfromthecoronalthirdofamajorrootctothefurcationregion(80%extendfromthedistalrootc).About10%havebothla andfurcationcs.DP,Distobuccal;MB,mesiobuccal;P,*FiguresrepresentpercentageoftheFromVertucciFJ:Rootcanatomyofthehumanpermanentteeth,OralSurgOralMedOralPathol58:589,1984.*FiguresrepresentpercentageoftheFromVertucciFJ:Rootcanatomyofthehumanpermanentteeth,OralSurgOralMedOralPathol58:589,1984.根據電子顯微鏡（SEM）4-720μm0-20%3612一下磨牙為32%，第二下磨牙為24%。FIG.7-7AElectronphotomicrographofthepulpchamberfloorofamandibularfirstmolar.Multipleaccessoryforaminacanbeseen(arrows),rangingfrom20to140μm(×20).B,Electronphotomicrographofthefurcationsurfaceofamandibularfirstmolar.Multipleaccessoryforaminacanbeseenonthefurcationsurface(×30).D,Distalc;M,mesialcs.7-7A2020-140μmB30DM下牙側枝孔的幾率（56%）比上牙略高（48%）也沒有聯系。通過X一項基于200顆恒牙采樣，用0.5%亞甲基藍染色的研究。24%的上下第一磨牙中，20%16%

FIG.7-8APretreatmentradiographofamandibularfirstmolarshowingfurcationandperiradicularBOne-yearfollow-upradiographshowingsignificanthealing.(CourtesyDr.RaedS.Kasem,B一年術后片顯示了愈合良好ROOTC從早期的Hess和Zurcher時始到近期的研究，都揭示了根管系統7-9A良好的復雜根管形態(tài)的例子。在圖7-9B中可以看到，術前片中看不到另外FIG.7-9AMandibularfirstpremolarwiththreeseparaterootstrifurcatingatmidroot.7-9AFIG.7-9Bradiographofthethreeviews.Smallcsdivergingfromthemainccreateaconfigurationthatisdifficulttoprepareandobturate7-9B從不同的X預備和生物充填非常。FIG.7-10rootsectionofapremolarshowingaribbon-shapedc圖.7-10枝和交匯。Weine7-11所示的四種形態(tài)。另為以下8中類型：FIG.7-11Diagr ticrepresentationofVertucci’sc圖.7-11Vertucci第五型：髓室底處單根管，到尖部 第七型：髓室底處單根管，在中間再匯合，根尖化，參見前表7-17-2）10001000223%，上頜第二磨牙的MB7-12A7-12B13根管，根管口通常都位于髓室。如果根管口是橢圓形，則必須用預彎的K銼全面地檢查。如圖7-14.FIG.7-14.Anovalorificemustbeexploredwithapicallycurvedsmallinstruments.Theclinicianshouldcethefiletipintheorificewiththetipcurvedtothebuccalsidewhentryingtolocatethebuccalc.Acurvedfiletipiscedtowardthepalatetoexploreforthepalatalc.B,Buccal;P,palatal.FIG.7-AInamandibularsecondmolarwithtwocs,bothorificesareinthemesiodistalmidline.BIftwoorificesarenotdirectlyinthemesiodistalmidline,asearchshouldbemadeforanothercontheoppositeside,usingKrasnerandrankow’slawsofanatomyintheareaof“X.”D,Distal;M,mesial.B如果兩個根管口不在近遠線上，應該在圖中X位置，在中線的另一方，即圖中的X位置探查根管口。II型），通常都是沿著頰舌向分開。而舌側的一個根管通常都會有急彎。有時候接近直角！如圖7-16所示。有專家把這種情況描述成h型。頰側的根管通常是hFIG.7-16A,MesialviewofamandibularpremolarwithaVertuccitypeVcconfiguration.Thelingualcseparatesfromthemaincatnearlyarightangle.B,Thisanatomyrequireswideningofaccessinalingualdirectiontoachievestraight-lineaccesstothelingualc.Thisshouldbedonewiththedentaloperatingmicroscope.Theguidelinesdescribedinthefollowingsectionsareessentialforthecompletionofanidealaccess根的位置和。醫(yī)生根據這些獲得VisualizationoftheLikelyInternalBecauseinternalanatomydictatesaccessshape,thefirststepinpreparinganaccessisvisualizationofthepositionofthepulpspaceinthetooth.Thisvisualizationrequiresevaluationofangledperiapicalradiographsandexaminationoftoothanatomyatthecoronal,cervical,androotlevels.Diagnosticradiographshelptheclinicianestimatethepositionofthepulpchamber,thedegreeofchambercalcification,thenumberofrootsand s,andtheapproximatec Palpationalongtheattachedgingivaaidsthedeterminationofrootlocationanddirection.Theclinicianusestheinformationfromtheseassessmentstochoosethedirectionofinitialbur全依賴咬合面結構會非常。對咬臨床失敗的原因。KrasnerandEvaluationoftheCementoenamelJunctionandOcclusalTraditionally,accesscavitieshavebeenpreparedinrelationtotheocclusalanatomy.However,completerelianceontheocclusalanatomyisdangerousbecausethismorphologycanchangeasthecrownisdestroyedbycariesandreconstructedwithvariousrestorativematerials.Completedependenceontheocclusalanatomymayexintheoccurrenceofsomeproceduralerrors.Inoneastudyinvolving500pulpchambers,KrasnerandRankowfoundthatthecementoenameljunction(CEJ)wasthemostimportantanatomiclandmarkfordeterminingthelocationofpulpchambersandrootc orifices.Thestudydemonstratedtheexistenceofaspecificandconsistentanatomyofthepulpchamberfloor.Theseauthorsproposednineguidelines,orlaws,ofpulpchamberanatomytohelpcliniciansdeterminethenumberandlocationoforificesonthechamberfloor(Fig.7-CEJ法則：在CEJ平面等。這就意味著CEJ重1）Lawofcentrality:ThefloorofthepulpchamberisalwayslocatedinthecenterofthetoothattheleveloftheCEJ.2）Lawofconcentricity:ThewallsofthepulpchamberarealwaysconcentrictotheexternalsurfaceofthetoothattheleveloftheCEJ,thatis,theexternalrootsurfaceanatomyreflectstheinternalpulpchamberLawoftheCEJ:ThedistancefromtheexternalsurfaceoftheclinicalcrowntothewallofthepulpchamberistheThroughoutthecircumferenceofthetoothattheleveloftheCEJ,makingtheCEJisthemostconsistentrepeatablelandmarkforlocatingthepositionofthepulpchamber.Firstlawofsymmetry:Exceptforthemaxillarymolars,c orificesareequidistantfromalinedrawninamesio-distaldirectionthroughthecenterofthe95%的實驗牙齒符合這些規(guī)則。由于C5%的pulpchamberSecondlawofsymmetry:Exceptforthemaxillarymolars,c orificeslieonalineperpendiculartoalinedrawninamesio-distaldirectionacrossthecenterofthepulpchamberfloor.Lawofcolorchange:Thepulpchamberfloorisalwaysdarkerincolorthanthewalls.Firstlawoforificelocation:Theorificesoftherootc sarealwayslocatedatthejunctionofthewallsandthefloor.Secondlawoforificelocation:Theorificesoftherootc sarealwayslocatedattheanglesinthefloor–wallThirdlawoforificelocation:Theorificesoftherootc sarealwayslocatedattheterminusoftheroots’developmentalfusionlines.Morethan95%oftheteeththeseinvestigatorsexaminedconformedtotheselaws.Slightlyfewerthan5%ofmandibularsecondandthirdmolarsdidnotconformbecauseoftheoccurrenceofC-shapedanatomy.FIG.7-23Diagr ticrepresentationofKrasnerandrankow’sfirstandsecondlawsofsymmetryandfirstthroughthirdlawsoforificelocation.D,Distal;M,mesial.7-23KrasnerandRankow的第一和第二對側面進行，而后牙通常都從咬合面開始預備。這樣做，是為了更方便張下尖牙的開髓從咬合面開始，這

PreparationoftheAccessThroughtheLingualandOcclusalAccesscavitiesonanteriorteethusuallyarepreparedthroughthelingualtoothsurface,andthoseonposteriorteetharepreparedthroughtheocclusalsurface.Theseapproachesarethebestmeansofachievingstraight-lineaccessanddiminishingestheticandrestorativeconcerns.SomeauthorshavemendedthatthetraditionalanterioraccessformandibularincisorsbemovedfromthelingualsurfacetotheincisalsurfaceinselectedThisallowsbetteraccesstothelingualcandimprovescdebridement(Fig.7-24).FIG.7-24Anincisalaccessonmandibularanteriorteethmayallowforimprovedstraight-lineaccessandcdebridement.7.24一顆下尖牙，髓腔預備從上方開以放置橡皮障來封閉唾液的感

RemovalofAllDefectiveRestorationsanBeforeEntryIntothePulpChamber，theclinicianmustremovealldefectiverestorationsbeforeenteringtherootcsystem.Withanopenpreparation,c aremucheasiertolocate,andsha,cleaning,andobturationaremucheasiertoInonestudy,itwasdeterminedthatclinicianswereabout40%morelikelytomissfractures,caries,andmarginalbreakdownifrestorationswerenot yremoved.Workingthroughrestorationsalsoallowsrestorativedebristo emoreeasilylodgedinthec (seeFig.7-74,Allcariousdentinmustberemovedduringaccesspreparation.Thisremovalpreventsirrigatingsolutionsfromleakingpasttherubberdamintothemouthandpreventscariousdentinanditsbacteriafromenteringtheroot system.IfachamberwallisperforatedduringremovalofcariousFig.7-74,DAllowingdebristofallintocorificesresultsinaniatrogenicmishap.Amalgamfillingsanddentindebrisblockcorifices,preventingpropershaandcleaning.Completeremovaloftherestorationandcopiousirrigationhelppreventthisproblem.7-74.D修復體的碎屑掉進了根管內部，造成根管口的局部堵塞。徹底去除髓腔的預備，意味著牙齒中RemovalofUnsupportedToothPreparationofanaccessresultsintheremovalofpartofthecentralportionofthetooththerebyreducingthetoocclusalstresses.Aftercompletingthepreparation,theclinicianshouldremoveallunsupportedtoothstructuretoassessrestorabilityandtopreventtoothfracture.Unnecessaryremovalofsoundstructureshouldbe備出一個不理想的根管形態(tài)（根尖CreationofAccessWallsThatDoNotRestrictStraightorDirect-linePassageofInstrumentstotheApicalForamenorInitialC Completecliniciancontroloverallenlargingandfillinginstrumentsisvital.Sufficienttoothstructuremustberemovedtoallowinstrumentstobecedeasilyintoeachc withoutinterferencefromc particularlywhenac curvesseverelyorleavesthechamberflooratanobtuseangle.Hence,accessdesignisdependentnotonlyontheorificelocation,butalsoonthepositionandcurvatureoftheentirec .Thewallsoftherootc ratherthanthewallsoftheaccesspreparation,mustguidethepassageofinstrumentsdownthec .Failuretofollowthisguidelineresultsintreatmenterrors,includingrootperforation,misdirectionofaninstrumentfromthemainc (ledgeformation),instrumentseparation,orcreationofanincorrect shape(apicaltransportation).Followingthisguidelineminimizestheoccurrenceofproceduralerrorsandizestheeffectivenessofsha,cleaning,andobturationinstruments后，再上橡皮章MicroOpener是在上橡皮障之前探是不銹鋼材質，有一定柔韌性的手用器械，具有04，06錐度的工作根管口確定了之后，再開始上橡皮DelayofDentalDam cementUntilDifficultC sHaveBeenLocatedandConfirmedDifficultycanariseingainingaccessintoteeththatarecrowdedandrotated,fracturedtothe margin,heavilyrestoredandcalcified,orpartofafixedprosthesis.IntheseSituations，theclinician’sbestcourseofactionmaybetopreparetheinitialpartoftheaccessbeforecingthedentaldamsothattheinclinationofrooteminencescanbevisualized;thisinformationcanbeusedasanindicatorofthedirectionofthelongaxisofthetreatedtooth.Micro-Openers(DENTSPLYMaillefer,Tulsa,OK)(Fig.7-25)areexcellentinstrumentsforlocatingc orificeswhenadentaldamhasnotbeenced.Theseflexible,stainlesssteelhandinstrumentshave#.04and#.06taperedtips.Theyalsohaveoffsethandlesthatprovideenhancedvisualizationofthepulpchamber.Thedentaldammustbecedoncetheroofofthepulpchamberhasbeenpenetratedandthec FIG.7-25SetofMicro-Openers(DENTSPLYMaillefer,Tulsa,forcidentificationand圖7-25登士柏公司的Micro-Location,Flaring,andExplorationofAllRootC Asharpendodonticexplorerisusedtolocatec orificesandtodeterminetheirangleofdeparturefromthepulpchamber.Next,allcorificesandthecoronalportionofthecsareflaredtomakeinstrumentcementeasier.Thec sarethenexploredwithsmall,precurvedK-files(#6,#8,or#10).Theclinicianmusttakecaretokeeptheseinstrumentswithintheconfinesofthecsystemuntiltheworkinglengthhasbeen ydetermined.Alubricatingagent(e.g.,rC-Prep[ DentalProducts,PlymouthMeeting,PA],awater-basedpreparationthatwillnotcongealvitalpulptissue),maybeusedoninstrumentsandintroducedintothec .Congealedpulptissuemayformacollagenplugthatblockstheapex,preventingcompleteshaandInspectionofthePulpChamber,UsingandAdequateMagnificationandilluminationparticularlyimportantinrootc especiallyfordeterminingthelocationof s;negotiatingconstricted,curved,andcalcifiedc s;anddébridingandremovingtissueandcalcificationsfromthepulpchamber.Enhancedvisionallowsthecliniciantoseeinternaldentincolorchangesandsubtlelandmarksthatmaynotbevisibletotheunaidedeye.Surgicalloupes,endodonticendoscopes,andtheDOMaresomeofthecommerciallyavailableinstrumentsthatcanhelptheclinicianplishthesegoals.AcliniciantrainedinmicroscopictechniqueshasabetterchanceoflocatingandnegotiatingintricaterootcTaperingofWallsandEvaluationofAdequacyforaCoronalAproperaccessgenerallyhastaperingwallswithitswidestdimensionattheocclusalsurface.Insuchapreparation, sdonotpushthetemporaryrestorationintotheanddisrupttheseal.Atleast3.5mmoftemporaryfillingmaterial(e.g.,Cavit[3M,St.Paul,MN])isneededtoprovideanadequatecoronalsealforashorttime.recently,c orificeplugsofcomposite,glassionomer,andmineraltrioxideaggregate(ProrootMTA;DENTSPLYTulsaDentalSpecialties,Tulsa,OK)haveshownpromiseinreducingriskofbacterialcontaminationofthecsystemwhenmicroleakageoccursatthecoronal–restorativemargins.MECHANICALMECHANICALPHASESOFACCESS#17Thepreparationofanaccessrequiresthefollowingequipment:Magnificationand#17operativeUltrasonicunitand起碼，醫(yī)生也需要使用一個帶外接Theaccesscannotbeprepared ywithouttheuseofmagnificationandanappropriatelightsource.Attheleast,theclinicianneedssurgicalloupeswithanauxiliarylightsource(seeChapter6).TheDOMisthepreferredmeansofmagnificationand道的時候，喜歡全程使用高速手機。在預備到了牙本質的時候，經些。遇到有難度的情況，比如鈣化Anexperiencedclinicianwithgoodtactileawarenessislikelytoperformmostphasesofaccesspreparationwithahigh-speedhandpiece.Afterpenetrationofthedentin,alessexperiencedclinicianmaybenefitfromtheincreasedtactileawarenessofferedbyaslow-speedhandpiece.Forchallengingaccesspreparations,especiallythoseinvolvingcalcifiedandrecededpulpchambers,evenexperiencedcliniciansmaysacrificecuttingspeedandefficiencyinfavoroftheincreasedcuttingcontroloftheslow-speedhandpieceoranultrasonictipusedwiththeDOM.圓頭鎢鋼車針(2,4,6號鎢鋼球醫(yī)生喜歡用鎢鋼裂鉆和砂球鉆。鎢鋼裂鉆和砂球鉆的優(yōu)勢在于同不足的醫(yī)生使用這幾款車針時，會對髓室底和側壁造成不必要的。

Numerousburshavebeendevelopedtoassisttheclinicianwithaccesspreparation.Providingadetailed,unabridgedlistoftheseburswouldbedifficult,andmostclinicianshavetheirownsetofpreferredaccessburs.Inreality,creatinganaccessthatmeetsthepreviouslystatedguidelinesismoreimportantthanworryingaboutwhichbursareusedintheprocess.ThisdiscussionthereforecoverssomeofthemorecommonaccessbursRoundcarbideburs(sizes#2,#4,and#6)(Fig.7-26)areusedextensivelyinthepreparationofaccesscavities.Theyareusedtoremovecariesandtocreatetheinitialexternaloutlineshape.Theyalsoareusefulforpenetratingthroughtheroofofthepulpchamberandforremovingtheroof.Somecliniciansprefertouseafissurecarbidebur(Fig.7-27)oradiamondburwitharoundedcuttingend(Fig.7-28)toperformtheseprocedures.Theadvantageofthefissurecarbideanddiamondround-endbursisthattheyalsocanbeusedforsomeoftheaxialwallextensionsoftheaccesspreparation.However,whenthesebursareusedforthispurposebyinexperiencedclinicians,theircuttingendscangougethepulpfloorandaxialwalls(seeFig.7-75,A).FIG.7-26Accessburs:#2,#4,and#6roundcarbideburs.FIG.7-27Accessbur:#57fissurecarbide7-2757FIG.7-28Accessbur:round-endcuttingtapereddiamondbur.裂鉆還可以幫助整平根管口邊

Fissurecarbideanddiamondburswithsafetytips(i.e.,noncuttingends)(Fig.7-29)aresaferchoicesforaxialwallextensions.Theycanbeusedtoextendandfavorablyorienttheaxialwallsofthepulpchamber.Becausetheyhavenocuttingend,theburscanbeallowedtoextendtothepulpfloor,andtheentireaxialwallcanbemovedandorientedallinonenefromtheenamelsurfacetothepulpfloor.Suchatechniqueproducesaxialwalls gougesasthefinalaccessextensionsarecreated.Fissurecarbideanddiamondbursalsocanbeusedtoleveloffcusptipsandincisaledges,whichareusedasreferencepointsfortheworkinglengthFIG.7-29Accessburs:Safety-tiptapereddiamondbur(left);safety-tiptaperedcarbidebur(right)圖7-294號圓頭砂車針(球鉆)。砂車針相對與鎢鋼車針產生的較小，本質的時候，效率更高。圖.7-302號，4號，球形開髓砂

Rounddiamondburs(sizes#2and#4)(Fig.7-30)areneededwhenendodonticaccessmustbemadethroughporcelainorceramometalrestorations.Diamondbursarelesstraumatictoporcelainthancarbidebursandaremorelikelytopenetratetheporcelainwithoutcrackingorfracturingit.Theyshouldalwaysbeusedwithwaterspraytocontrolheatbuildupinporcelainrestorations.Afterpenetratingtheporcelaintheclinicianshouldswitchtoacarbideburformetalordentinpenetrationbecauseofthisbur’sgreatercuttingFIG.7-30Accessburs:#2and#4rounddiamondburs.Atrendinrestorativedentistryistheincreaseduseofzirconia-basedcrownsandonlays.Zirconiahasdifferentmechanicalandthermalcharacteristicsthanmetal.Carbidebursdonotcutzirconiaefficientlyorsafely.Zirconiaisabrittlematerialand,whencut,candevelopcracksthatpropagatethroughtheframeworkandleadtoeventualfailureofthecrownoronlay.Diamondbur–manufacturingcompaniesareawareof失敗。砂車針的廠家，真對這個好的中等沙?；蛘吒毜纳沉５纳败囜?。在開髓過程中，這些砂重，只能使用。能是銀合金，全金屬鑄造，或者是

theseissuesandtheyarecurrentlyintroducingmedium-andfine-gritdiamondbursthatefficientlycutzirconia.Thesediamondbursshouldbeusedwithcopiouswaterpraytominimizeheatbuildupinthezirconiacrownsduringaccesspreparations.Also,somediamondbursdegraderapidlywhencuttingthroughzirconiaandshouldbethrownawayafteroneuse.Manyteethrequiringaccesspreparationshavemetalrestorationsthatmustbepenetrated.Theserestorationsmaybeamalgams,all-metalcastrestorations,ormetalcosofporcelainfusedtometalcrowns.Atransmetalbur(Fig.7-31)isexcellentforthispurposebecauseofitsexceptionalcuttingefficiency.Topenetrateametalrestoration,theclinicianshouldalwaysuseanewtransmetalburwithwatersprayfor alcuttingeffectFIG.7-31Accessbur:Transmetal時候，長柄圓頭車針（如比BrasselerMuellerBur和登士柏公司生產的LNBur）都是不錯的選擇。位于加州的CJMengineering公司生產的MunceDiscoveryBur與MuellerBurn類似，但是桿部更加堅硬，有些型號齒更遠，可以保證精細操作時視線7-32長柄球鉆（開髓車針A:Mueller B:LN

Ifatoothhasarecededpulpchamberandcalcifiedorifices,theclinicianoftenmustcutintotheroottolocateandidentifythec orifices.Extended-shankroundburs,suchastheMuellerbur(BrasselerUSA,Savannah,GA)(Fig.7-32,A)andtheLNbur(DENTSPLYMaillefer,Tulsa,OK)(Fig.7-32,B),areusefulforthispurpose.TheMunceDiscoverybur(CJMEngineering,SantaBarbara,CA)issimilartotheMuellerbuthasastiffershaftandisavailableinsmallerheadsizes.Theextra-longshankofthesebursmovestheheadofthehand-pieceawayfromthetooth,improvingtheclinician’svisibilityduringthisdelicateprocedure.Asanalternative,ultrasonicunitsoffergoodvisibilitywithprecisioncutting.FIG.7-32Accessburs.A,Muellerbur.B,LNbur.７－３４所示，在預敞的時候，１處過度去除牙本質，否則會容易引Oncetheorificeshavebeenlocated,theyshouldbeflaredorenlargedandblendedintotheaxialwallsoftheaccess.Thisprocesspermitstheintracinstrumentsusedduringshaandcleaningtoenterthec (s)easilyandeffortlessly.Gates-Gliddenburscanbeusedforthispurpose,startingwithsmallersizesandprogressingtothelargersizes(Fig.7-33).Morerecently,#.12taperedrotaryendodonticfiles(Fig.7-34)havebeenusedfortheflaringandblendingprocedure.Whenusingeitherofthesetwotechniquesforcflaring,theclinicianmustguardagainstremovingexcessivedentinonthefurcationsideofarootc,whichcouldcreatea“strip”FIG.7-33Accessburs.A,Gates-Gliddenburs,1through6.B,Gates-Gliddenburs,shortshank(left)andregularshank圖.7-33A1-6號GGFIG.7-34Accessbur:12%tapernickel–titaniumorificeopener.7-35CKDentalIndustries生產的JW-17探針，起到同樣的作用，但是更細一EndodonticExplorer,EndodonticSpoon,#17OperativeExplorerVarioushandinstrumentsareusefulforpreparingaccesscavities.TheDG-16endodonticexplorer(Fig.7-35)isusedtoidentifyc orificesandtodeterminecangulation.TheJW-17endodonticexplorer(Fig.7-35)(CKDentalIndustries,Orange,CA)servesthesamepurpose,butitsthinner,stiffertipcanbeusefulforidentifyingcalcifiedc s.Theendodonticspoon(Fig.7-36)canbeusedtoremovecoronalpulpandcariousdentin.A#17operativeexplorerisusefulfordetectinganyremainingpulpchamberroof,particularlyintheareaofapulphorn(Fig.7-FIG.7-35Accessinstruments:DG-16endodonticexplorer(top);JW-17endodonticexplorer上圖DG-16下圖JW-FIG.7-36Accessinstrument:EndodonticFIG.7-37removalofthepulphornisevaluatedwitha#17operativeexplorer.7-38所示的超聲設備和根管治療的超聲尖在髓腔通道預備容易遮擋視線的傳統頭相比，超針要小，而且的涂層在探查根管UltrasonicUnitandAnultrasonicunit(Fig.7-38)andtipsspecificallydesignedforendodonticprocedurescanbevaluableaidsinthepreparationofaccesscavities.Ultrasonictips(Fig.7-39)canbeusedtotroughanddeependevelopmentalgroovestoremovetissueandexploreforc s.Ultrasonicsystemsprovideoutstandingvisibilitycomparedwithconventionalhandpieceheads,whichtypicallyobstructvision.Fineultrasonictipsaresmallerthanconventionalroundburs,andtheirabrasivecoatingsallowclinicianstosandawaydentinandcalcificationsconservativelywhenexploringforcFIG.7-39EndodonticultrasonicAccessAnteriorAccess在髓腔通路預備的過程中，預&下前牙的預備步驟。這節(jié)將具體展再講每個牙位的具體形態(tài)和預備方Manyofthesamestepsareusedinsimilartoothtypestoprepareanaccess.Thefollowingdiscussionoutlinesthestepsformaxillaryandmandibularanteriorteeth.ToothspecificaccessconcernsareillustratedanddiscussedinthesectionMorphologyandAccessPreparationsforIndividualTeeth,laterinthe—般先去除齲質，再進入髓菌的風險降到最低。有缺陷的永久修復體，不論是銀合金，樹脂根管（或者兩者都被）。全面去系統內部。（7-74所示）。如果。 Cariestypicallyisremovedearly,beforethepulpchamberisentered.Thisminimizestheriskofcontaminationofthepulpchamberorrootc (s)withbacteria.Defectivepermanentrestorations,whetheramalgams,compositeresins,orcrowns,mustberemovedentirelytopreventcoronalleakagefromcontaminatingthepulpchamber,therootc (s),orbothaftertheendodonticappointment.Removalofdefectivepermanentrestorationsalsopermitsstraight-lineaccessandpreventsrestorativefragmentsfrom inglodgedintheroot system(seeFig.7-74,D).Ifrecurrentdecayisdetectedored,thepermanentrestorationmustberemovedentirelytopreventcoronalcontaminationofthepulpFIG.7-74DAllowingdebristofallintoc fillingsand orifices,preventingpropershaandcleaning.Completeremovaloftherestoration help 7-74D碎屑落入根管口將引起醫(yī)源性事故。銀充填物或者牙本質會堵住根管口，對成型和沖洗造成妨礙。完全去除修復體和大量的沖洗可以避免類似事故的發(fā)對于完好無損的沒有出現復發(fā)性齲質的修復體的管理需要進行判40%。醫(yī)生有時候應該保為對橡皮障的支撐。在修復體沒操作結束后，需要全部去除，然后Themanagementofintactpermanentrestorationswhenrecurrentcariesisnotpresentrequiressomejudgment.Amalgamandcompositerestorationstypicallyareremovedentirelytoimprovevisibilityduringthesearchforrootcorifices.Asstatedinanearlierstudy,clinicianswereabout40%morelikelytomissfractures,caries,andmarginalbreak-downifrestorationswerenotcompleyremoved.However,theclinicianmaywanttoretaintheproximalportionofaclassIIrestorationthatextendssub-gingivallytoaidinrubberdamisolation.Whenpartsofexistingpermanentrestorationsarenotremoved,theclinicianusuallycanwidentheaccessopeninglargerthanisidealattheexpenseofremovingrestorativematerial,notsoundtoothstructure.Theremainingpermanentrestorationmaterialisremovedattheendoftheappointmentbeforethetemporaryrestorationisced.腔通道進行修補。醫(yī)生和都應該Oftencliniciansdecidetoperformendodontictherapythroughintactcrownsratherthanremovingorrecingthem.Theseaccesscavitiesarerepairedaftercompletionoftherootcprocedure.Thepatientandtheclinicianmustrealizethatvisibilitycanbecompromisedinthesecircumstances,particularlyifaDOMisnotused.Thecliniciancanenhancevisibilitybybevelingthecrown’scavosurfacemarginsandbymakingsureallaxialwallsareglassy在確定了齲質和修復體的處理方案之后，醫(yī)生開始著手牙的舌7-40A所示）2號，4號球鉆或持一致（7-40B），大小為最終的髓腔通道截面的一半或者四分之質，使用高速效率更高。與舌側面保持垂直直到初始輪廓被創(chuàng)InitialexternaloutlineOncecariesandrestorationshavebeenaddressed,thecliniciancreatesaninitialexternaloutlineopeningonthelingualsurfaceoftheanteriortooth.Thisstepoftenisperformedduringtheremovalofcariesandrestorations.Fo