文案綜合二講課pathway 10

PathwayofthePathwayofthePulp10thEdition第二后，醫(yī)生應(yīng)該評估是否此時直線通圖。7-45鎳鈦銼器械分離。因為Straight-lineaccessAfterthelingualshoulderhasbeenremovedandtheorifice(s)flared,theclinicianmustdeterminewhetherstraight-lineaccesshasbeenachieved.Ideally,anendodonticfilecanapproachtheapicalforamenorthefirstpointofcanalcurvatureun-deflected.Unnecessarydeflectionofthefilecanresultinnumerousconsequencesrelatedtolossofinstrumentcontrol.Deflectedinstrumentsfunctionundermorestressthanun-deflectedinstrumentsandaremoresusceptibletoseparationduringtheshapingandcleaningprocess(Fig.7-FIG.7-45Separationofarotaryendodonticinstrumentasaresultofunder-extendedaccesspreparationratherthancanalbinding.鍵部位的通道，會影響成型和清洗作，容易形成臺階，偏移和尖部被鍵部位的通道，會影響成型和清洗作，容易形成臺階，偏移和尖部被如圖7-46不合適的通道預(yù)備。方向，型成了臺階。外壁被過度預(yù)備了，并形成了拉直Deflectedinstrumentsalsolackaccesstocriticalareasofthecanalandthereforedonotshapeandcleaneffectively.Attemptstoshapeandcleanwithoutstraight-lineaccessoftenleadtoproceduralerrorssuchasledging,transportation,andzipping(Fig.7-46).FIG.7-46Inadequateaccesspreparation.Thelingualshoulderwasnotremoved,andincisalextensionisincomplete.Thefilehasbeguntodeviatefromthecanalintheapicalregion,creatingaledge.Aledgeisaniatrogenicallycreatedrootcanalwallirregularitythatmayimpedeplacementofanintra-canalinstrumenttotheapex.Transportationoccursintheportionofthecanalapicaltoacurvaturewhencanalwallstructureoppositethecurveisremoved,tendingtostraightenthecanalcurvature.Zipping,orellipticationoftheapicalforamen,occurswhenanoverextendedfiletransportstheouterwalloftheapicalforamen.Conversely,un-deflectedinstrumentsprovidebettertactilesensation,whichisnecessaryfor“feeling”thecanalanatomyand的銼（初尖銼）無壓迫地到達(dá)根尖孔或者第一個彎曲時，銼針在根管的銼（初尖銼）無壓迫地到達(dá)根尖孔或者第一個彎曲時，銼針在根管以獲得直線如路。如圖7-47所示。圖7-47A,部分牙本質(zhì)的舌側(cè)肩和清洗。B.舌側(cè)肩全部去除后，得“feeling”howthefileisperformingintherootcanalsystem.Straight-lineaccessisevaluatedbyinsertingintothecanalthelargestfilethatfitspassivelytotheapicalforamenorthepointofthefirstcanalcurvature.Thisinternallengthcanbedeterminedbymeasuringadiagnosticpretreatmentperiapicalradiograph.Thefileisinsertedgentlyandwithdrawnastheclinician“feels”forcanalbindingordeflection.Ifdeflectionisdetected,theclinicianmustreevaluatetheadequacyoflingualshoulderremovalbeforechangingtheincisaledgepositionoftheaccesspreparation.Inadequateremovalofthelingualshouldercausesthefiletodeflectinafacialdirection,andaninexperiencedclinicianmayoverextendtheincisaledgeoftheaccesspreparationinanattempttoachievestraight-lineaccess(Fig.7-47).FIG.7-47A,Thelingualledgeofdentinremains,deflectingthefiletowardthelabialwall.Asaresult,portionsofthelingualcanalwallwillnotbeshapedandcleaned.B,removalofthelingualledgeresultsinstraight-line如圖7-14所示。Visualinspection如圖7-14所示。VisualinspectionoftheaccessTheclinicianshouldinspectandevaluatetheaccesscavity,usingappropriatemagnificationandillumination.Althoughthiscanbedoneduringanystageofthepreparation,itshouldalwaysbedoneatthispoint.Theaxialwallsattheirjunctionwiththeorificemustbeinspectedforgroovesthatmightindicateanadditionalcanal.Theorificeandcoronalcanalmustbeevaluatedforabifurcation(seeFig.7-14).RefinementandsmoothingofrestorativemarginsThefinalstepinthepreparation繼續(xù)向切端預(yù)敞，直到銼能站直。Ifthelingualshoulderhasbeenadequatelyremovedandthefilestillbindsontheincisaledge,theaccesscavityshouldbeextendedfartherincisallyuntilthefileisnotdeflected.Thefinalpositionoftheincisalwalloftheaccesscavityisdeterminedbytwofactors:(1)completeremovalofthepulphornsand(2)straight-lineaccess.咬合力過大時，容易形成冠部的滲anaccesscavityistorefineandsmooththecavosurfacemargins.Roughorirregularmarginscancontributetocoronalleakagethroughapermanentortemporaryrestoration.Properrestorativemarginsareimportantbecauseanteriorteethmaynotrequireacrownasthefinalrestoration.Definite,smoothcavosurfacemarginsallowthecliniciantoplaceandfinishacompositeresinfinalrestorationwiththeprecisionnecessarytominimizecoronalleakage.Suchleakagecouldjeopardizethesuccessoftherootcanalprocedure.Anotherfactortheclinicianmustconsiderwhenfinalizingtheaccessmarginsofamaxillaryanteriortoothisthatthefinalcompositeresinrestorationwillbeplacedonafunctionaltoothsurface.Theincisaledgesofthemandibularanteriorteethslideoverthesemaxillarylingualsurfacesduringexcursivejawmovement.Thereforetherestorativemarginsofmaxillaryanteriorteethshouldbecreatedtoallowabulkofmaterialatthemargin.Buttjointmarginsareindicatedratherthanbeveledmargins,whichproducethincompositeedgesthatcanfractureunderexcursivefunctionalloadsandultimatelyresultincoronalleakage.Obviously,iftheanteriortoothrequiresacrownasthefinalrestoration,theaccesscavosurfacemarginbecomesalesscriticalfactor.、Removalof、RemovalofCariesandPermanentThediscussionofcariesandpermanentrestorationremovalpresentedintheprevioussection,AnteriorAccessCavityPreparations,appliesequallytoposteriorteeth.Posteriorteethrequiringrootcanaltherapytypicallyhavebeenheavilyrestoredorthecariousprocessisextensive.Suchconditions,alongwiththecomplexpulpanatomyofposteriorteeth,canmaketheaccessprocesschallenging.但是也有很多區(qū)別，值得單獨的討PosteriorAccessCavityTheprocessofpreparingaccesscavitiesonposteriorteethissimilartothatforanteriorteeth,butenoughdifferencesexisttowarrantaseparatediscussionIndividualanteriorPleaseseethefiguresinthesectionMorphologyandAccessCavityPreparationsforIndividualTeeth,laterinthechapter.顆完好的牙齒，開髓的位置必須認(rèn)真思考。如圖7-48所示，上前磨牙而如圖7-49，由于下前磨牙的冠面要適當(dāng)進(jìn)行補償性調(diào)整（圖7-InitialexternaloutlineTheremovalofcariesandexistingrestorationsoftenaccomplishesthecreationofaninitialexternaloutlineform.Aswithanteriorteeth,thepulpchamberofposteriorteethispositionedinthecenterofthetoothattheleveloftheaccessstartinglocationmustbedeterminedforanintacttooth.Inmaxillarypremolarsthispointisonthecentralgroovebetweenthecusptips(Fig.FIG.7-48A,Startinglocationforaccesstothemaxillarypremolar(X).B,Initialoutlineform(darkarea)andprojectedfinaloutlineform(dashedline).B,Buccal;L,lingual.Crownsofmandibularpremolarsaretiltedlinguallyrelativetotheirroots(Fig.7-49),andthestartinglocationmustbeadjustedtocompensateforthistilt(Fig.7-50).7-49下前磨牙的冠沿牙根的縱軸7-49下前磨牙的冠沿牙根的縱軸7-A下頜第一前磨牙通道口位置B下頜第一前磨牙通道口位置C下頜第二前磨牙通道口位置D下頜第二前磨牙通道口位置FIG.7-49Thecrownofamandibularpremolaristiltedlinguallyrelativetotheroot.B,Buccal;L,lingual.FIG.7-A,Mandibularfirstpremolarandaccessstartinglocation(X)(occlusalview).B,Mandibularfirstpremolarandstartinglocation(proximalview).C,Mandibularsecondpremolarandaccessstartinglocation(X)(occlusalview).D,Mandibularsecondpremolarandstartinglocation(proximalview).B,Buccal;DL,distolingual;L,lingual;ML,mesiolingual.牙因為向舌側(cè)傾斜的角度較小，所7-51所示，為了決定磨牙Inmandibularfirstpremolarsthestartinglocationishalfwayupthelingualinclineofthebuccalcusponalineconnectingthecusptips.Mandibularsecondpremolarsrequirelessofanadjustmentbecausetheyhavelesslingualinclination.ThestartinglocationforthistoothisonethirdthewayupthelingualinclineofthebuccalcusponalineconnectingthebuccalcusptipandthelingualgroovebetweenthelingualcuspsTodeterminethestartinglocationformolaraccesscavitypreparations,theclinicianmustestablishthemesialanddistalboundarylimitations(Fig.7-51).Evaluationofbite-wingradiographsisanaccuratemethodofassessingthemesiodistalextensionsofthepulpchamber.Themesialboundaryforboththemaxillaryandmandibularmolarsisalineconnectingthemesialcusptips.Rarelyarepulpchambersfoundmesialtothisimaginaryline.Agoodinitialdistalboundaryformaxillarymolarsistheobliqueridge.Formandibularmolarstheinitialdistalboundaryisalineconnectingthebuccalandlingualgrooves.Formolarsthecorrectstartinglocationisonthecentralgroovehalfwaybetweenthemesialanddistalboundaries.7-A7-A上磨牙的髓室近遠(yuǎn)中邊界和開B下磨牙的髓室近遠(yuǎn)中邊界和開FIG.7-51A,Mesialanddistalboundaryofamaxillarymolarshowingtheaccessstartinglocation(X).B,Mesialanddistalboundaryofamandibularmolarshowingtheaccessstartinglocation(X).D,Distal;M,mesial;MB,mesiobuccal;ML,PenetrationofthepulpchamberContinuingwiththesameroundortaperedfissurebur,theclinicianchangestheangleofpenetrationfromperpendiculartotheocclusaltabletoanangleappropriateforpenetrationthroughtheroofofthepulpchamber.Inpremolarstheangleisparalleltothelongaxisoftheroot(s)bothinthemesiodistalandbuccolingualdirections.Failuretoanalyzethispenetrationanglecarefully2號球鉆，磨牙用號球鉆，打穿牙釉質(zhì)并穿透牙本質(zhì)1毫米左右，然后改用帶錐度的裂做到最終大小的一半或者四分之三管的開口形狀為菱形。無論如何，口的實際位置之前，髓腔輪廓暫時Penetrationthroughtheenamelintothedentin(approximately1mm)isperformedwitha#2roundburforpremolarsanda#4roundburformolars.Ataperedfissureburmaybeusedinsteadofroundburs.Theburisdirectedperpendiculartotheocclusaltable,andaninitialoutlineshapeiscreatedataboutonehalftothreefourthsitsprojectedfinalsize.Thepremolarshapeisovalandwidestinthebuccolingualdimension.Themolarshapeisalsoovalinitially;itiswidestinabuccolingualdimensionformaxillarymolarsandinamesiodistaldirectionformandibularmolars.Thefinaloutlineshapeformolarsistriangular(forthreecanals)orrhomboid(forfourcanals);however,thecanalorificesdictatethepositionofthecornersofthesegeometricshapes.Therefore,untiltheorificeshavebeenlocated,theinitialoutlineformshouldbeleftasanoval.7-52上磨牙的開髓角度朝向最大的根管口（腭側(cè)）有感受到落空感，醫(yī)生應(yīng)該立即停canresultingougingorperforationbecausepremolarrootsoftenaretiltedrelativetotheocclusalplane.Inmolarsthepenetrationangleshouldbetowardthelargestcanal,becausethepulpchamberspaceusuallyislargestjustocclusaltotheorificeofthiscanal.Therefore,inmaxillarymolarsthepenetrationangleistowardthepalatalorifice,andinmandibularmolarsitistowardthedistalorifice(Fig.7-FIG.7-52Angleofpenetrationtowardthelargestcanal(palatal)inamaxillarymolar.B,Buccal;P,palatal.Aswithanteriorteeth,penetrationislimitedtothedistancemeasuredonapretreatmentradiographtojustpenetratetheroofofthepulpchamber.Ifthedrop-ineffectisnotfeltatthisdepth,theclinicianshouldcarefullyevaluatetheangleofpenetrationbeforedrillingdeeper.Inmulti-rootedposteriorteeth,theclinicianmustguardagainstlateralandfurcationperforations.Aggressiveprobingwithanendodonticexploreroftencanhelplocatethepulpchamber.A、BDGG鉆去牙本質(zhì)肩領(lǐng)/安全車針修邊CompleteroofAroundbur,ataperedfissurebur,orasafety-tipdiamondorcarbideburisusedtoremovetheroofofthepulpchambercompletely,includingallpulphorns(Fig.7-53,AandB).Visibilityproblemscausedbyvitalpulphemorrhageshouldbehandledasdescribedintheprevioussectionforanteriorteeth(seeAnteriorAccessCavityPreparations).Thegoalistofunnelthecornersoftheaccesscavitydirectlyintotheorifices,andasafety-tipdiamondorcarbideburperformsthistasknicely;itcanbesetonthepulpfloorandtheentireaxialwallshapedatonetimewithlittlechanceofgouging(Fig.7-54).Thesafety-tipdiamondorcarbideburispassedbetweentheori-ficesalongtheaxialwallstoremovetheroof,tapertheinternalwalls,andcreatethedesiredexternaloutlineshapeFIG.7-53A,Pulproof/pulphornremoval.Theroundburhooksunderthelipofthepulphorn.B,Theburisrotatedandwithdrawninanocclusaldirectiontoremovethelip.C,removalofacervicaldentinbulge.AGates-Gliddenburisplacedjustapicaltotheorificeandwithdrawninadistoocclusaldirection.D,Asafety-tiptapereddiamondburisusedtoblendandfunneltheaxialwallfromthecavosurfacemargintotheorifice.7-557-55所示，部分根管口從IdentificationofallcanalInposteriorteethwithmultiplecanals,thecanalorificesplayanimportantroleindeterminingthefinalextensionsoftheexternaloutlineformoftheaccesscavity.Ideally,theorificesarelocatedatthecornersofthefinalpreparationtofacilitatetheshapingandcleaningprocess.Internally,theaccesscavityshouldhaveallorificespositionedentirelyonthepulpfloorandshouldnotextendintoanaxialwall.Extensionofanorificeintotheaxialwallcreatesamouseholeeffect(Fig.7-55),whichindicatesinternalunderextensionandimpedesstraight-lineaccess.Insuchcasestheorificemustberepositionedontothepulpfloorwithoutinterferencefromaxial FIG.7-54Safety-tipcarbideburisusedtoshapetheaxialwallinoneplanefromtheorificetothecavosurfacemargin.B,Buccal;P,palatal.FIG.7-55AFIG.7-55AMouseholeeffectcausedbyextensionoftheorificeintotheaxialwall.OrificethatliescompletelyonthepulpB該使用安全車針或者GG鉆來去7-53C,DRemovalofthecervicaldentinbulgesorificeandcoronalInanteriorteeththelingualshoulderistheinternalanatomicstructurethatmustberemovedasanimpedimenttostraightlineaccess.Inposteriorteeththeinternalimpedimentsarethecervicaldentinbulgesandthenaturalcoronalcanalconstriction.Thecervicalbulgesareshelvesofdentinthatfrequentlyoverhangorificesinposteriorteeth,restrictingaccessintorootcanalsandaccentuatingexistingcanalcurvatures.Thesebulgescanberemovedwithsafety-tipdiamondorcarbidebursorGates-Gliddenburs.Theinstrumentsshouldbeplacedattheorificeleveland在牙本質(zhì)凸起被去除之后，用GG在牙本質(zhì)凸起被去除之后，用GG預(yù)敞。使用GG鉆時，向根分叉相反操作。另一個選項就是使用10%或者12%錐度的機用鎳鈦開口銼預(yù)敞根管口。預(yù)敞后的根管口，需要有7-56從髓室通道向下滑的時候，不會遭leanedtowardthedentinbulgetoremovetheoverhangingshelf(seeFig.7-53,CandD).access.Insuchcasestheorificemustberepositionedontothepulpfloorwithoutinterferencefromaxialwalls.Aftertheshelfhasbeenremoved,theorificeandconstrictedcoronalportionofthecanalcanbeflaredwithGatesGliddenburs,whichareusedinasweepingupwardmotionwithlateralpressureawayfromthefurcation.Analternativemethodistousea#.10or#.12taperedengine-drivennickel–titaniumfiletoestablishtheuppercanalshape.Astheorificeisenlarged,itshouldbetaperedandblendedintotheaxialwallsothatthecliniciancanslidefromthecorneroftheexternaloutlineformdowntheaxialwallintotheorificewithoutencounteringanyobstructions(Fig.7-56)FIG.7-57AfiberopticlightFIG.7-57Afiberopticlightcanappliedtothecervicalaspectofthecrowntohelpobtainmaximalvisibilitywithmagnification.Trans-illuminationoftenrevealslandmarksotherwiseinvisibletotheunaidedeye.7-57光纖光源投射到牙頸部位VisualinspectionofthepulpchamberPleaserefertotheearliersectionunderAnteriorAccessCavityPreparations;andFig.7-57.Straight-lineaccessAswithanteriorteeth,straight-lineaccessisparamounttosuccessfulshaping.Filesmusthaveunimpededaccesstotheapicalforamenorthefirstpointofcanalcurvaturetoperformproperlyduringshapingandcleaning.Theclinicianmustassesseachcanalforstraight-lineaccessandmakealladjustmentsnecessarytoachievethisgoal(seeFig.7-56,O).挑戰(zhàn)髓腔通道預(yù)備：CHALLENGING挑戰(zhàn)髓腔通道預(yù)備：CHALLENGINGACCESSTeethwithminimalornoclinicalSeveralfactorscancausethelossofasignificantportionofatooth’sclinicalcrown.Cariesleftuntreatedcancauselossofcoronaltoothstructure.Badlydecayedteethtypicallycanfractureunderocclusalfunctionbecauseoftheunderminedandunsupportedremainingtoothstructure.Similarly,teeththathavebeenheavilyrestoredwithamalgam,compositeresin,orglassionomerrestorativematerialscanhaveminimalcoronaltoothstructure.individualposteriorPleaseseethefiguresinthesectionMorphologyandAccessCavityPreparationsforIndividualTeeth,laterinthechapter.RefinementandsmoothingoftherestorativemarginsInbothtemporaryandinterimpermanentrestorations,therestorativemarginsshouldberefinedandsmoothedtominimizethepotentialforcoronalleakage.Thefinalpermanentrestorationofchoiceforposteriorteeththathaveundergonerootcanaltherapyisacrownoronlay.7-58所示。髓7-59所Xrestorativematerialsprovidenoextra-coronalsupportforthetooth,andthefillingscanfalloutduringocclusalfunction,leavinglittleornoclinicalcrownremaining.Externaltraumacancausetheclinicalcrowntofracture,sometimesshearingofftothefreegingivalmargin.Creatinganaccesscavityonatoothwithlittleornoclinicalcrownmightseemtobeasimpleprocedure.Inyoungteeth,traumaticfracturesoftenexposethepulpchamber,makingpreparationeasy.However,inolderteeththathavehadcariesorlargerestorations,thepulpchamberstypicallyhaverecededorcalcified.Lossofsignificantcoronalanatomytoguidepenetrationanglescanmakeaccessquitedifficult.Beforebeginninganaccesscavityontheseteeth,theclinicianshouldstudytheirrootangulationonpretreatmentradiographsandexaminethecervicalcrownanatomywithanexplorer(Fig.7-58).PulpchambersarelocatedatthecenterofthecrownattheleveloftheCEJ.Accessoftenisstartedwithoutadentaldaminplacesothatrooteminencescanbevisualizedandpalpatedasaccessisattempted(Fig.7-59).Becausetheexternalrootanatomyisformedbyodontoblastsinthepulp,byvisualizingtherootanatomybothradiographicallyandclinically,theclinicianshouldhaveagoodideaofaccesspenetrationangles.EveryeffortismadetostaycenteredwithintherootforFIG.7-58TheFIG.7-58Thecervicalareaofthetoothexploredbeforeaccessis7-58向在近遠(yuǎn)中方向上有了偏差，再轉(zhuǎn)角拍片，看是否在頰舌向有偏差。觀察了這兩張片子后，如果發(fā)現(xiàn)偏橡皮障，按照前面所述的操作指thebestchanceoflocatingthepulpcanal.Thedepthofpenetrationneededtoreachthepulpcanalismeasuredonapretreatmentradiograph.Iftheclinicianreachesthisdepthwithoutlocatingthecanal,tworadiographsshouldbetakenbeforetheprocessproceeds.Astraight-onradiographshowswhetherthepreparationisdeviatinginamesialordistaldirection.Applyingthebuccal-objectrule,anangledradiographshowsabuccalorlingualdeviationinpenetration.Aftercheckingtheseradiographs,thecliniciancanredirectthepenetrationangleifnecessaryandmovethepreparationapically.Assoonasthepulpcanalisidentified,thedentaldammustbeplacedandtheaccesspreparationfinalized,usingtheguidelinesdiscussedearlierinthisFIG.7-59FIG.7-59Accesspreparationwhentheanatomiccrownismissing.A,Amandibularfirstpremolarwiththecrownmissing.B,Anendodonticexplorerfailstopenetratethecalcifiedpulpchamber.C,Along-shankroundburisdirectedintheassumedlongaxisoftheroot.D,Perforationoftherootwall(arrow),resultingfromtheclinician’sfailuretoconsiderrootangulation.E,Palpationofthebuccalrootanatomywithoutadentaldaminplacetodeterminerootangulation.F,Correctburangulationafterrepairoftheperforationwithmineraltrioxideaggregate(MTA;DENTSPLYTulsaDentalSpecialties,Tulsa,OK).Thedentaldamisplacedassoonasthecanalisidentified.重度修復(fù)的的牙齒（包括瓷貼面重度修復(fù)的的牙齒（包括瓷貼面全冠，很少會精確復(fù)制牙冠的固有形的時候，冠-根角度通常也會變化。如圖7-60所示正常進(jìn)入牙齒內(nèi)部，造成髓室通道預(yù)備的視線極差。所有這些因素，單獨圖7-57光纖光源的透光照明，可以幫HeavilyRestoredTeeth(IncludingThoseWithFullVeneerCrowns)Restorativematerialsoftenaltertheexternalanatomiclandmarksonthecrownofatooth,makingaccesspreparationdifficult.restorativematerialsandfullcrownsrarelyreproducetheoriginaltoothanatomyintheexactsameposition.Thecrown-to-rootangulationoftenisalteredwhenlargerestorationsorcrownscorrectocclusaldiscrepancies(Fig.7-60).FIG.7-60Accesscavityerrorresultingfromalterationoftheoriginaltoothcontoursbyafullveneercrown.A,Originalcrowncontourofthetooth.B,Afullveneercrownisusedtochangetheoriginalcrowncontourforestheticpurposes.C,AccessperforationresultingfromrelianceonthefullveneercrowncontourratherthanthelongaxisoftheBC,依據(jù)瓷貼面的形狀（沒有依據(jù)牙根方向）開髓，導(dǎo)致了側(cè)穿Mostrestorativematerialsblockthepassageoflightintotheinternalaspectsofthetooth,resultinginpoorvisibilityduringpreparationoftheaccesscavity.Allthesefactors,singlyortogether,complicatethe大塊的修復(fù)體。（如圖7-61）大塊的修復(fù)體。（如圖7-61）preparationofaccesscavitiesonheavilyrestoredteeth.TheDOMandtransilluminationofthecervicalareaofaheavilyrestoredtoothcangreatlyimprovevisibilityandreveallandmarksthatotherwisewouldbemissed(seeFig.7-57).Inmostcases,completeremovaloflargerestorationsisthewisestcourse(Fig.7-61).7-A7-A需要根管治療的重度修復(fù)的第二上磨B，F(xiàn)IG.7-61A,Inaheavilyrestoredmaxillarysecondmolarthatrequiresrootcanaltherapy,theclinicianmayattemptaccesstothecanals.Pretreatmentradiographsdemonstratethreeimportantfactors:(1)areinforcingpinisinplace(arrow);(2)atleasttwothirdsofthecoronalportionisrestorativematerial;and(3)themesiobuccalcanalappearscalcified(arrow).Thesefactorssuggestcompleteexcavation.B,Apatientmayaskthecliniciantoattemptanunexcavatedsearchforthecanals;thismayresultinafurcalperforation,C,C,更安全保守的方法是去除銀汞合D,醫(yī)生可以更順暢地進(jìn)行根管治療，有。去除這些修復(fù)體，可以幫助醫(yī)生性會增加40%。良好的視線，也可以到根管中。（7-74D）。完全去除compromisingtheprognosis.Insuchcasesthepatientshouldbeengagedinthedecisiontocontinuetreatment,whichunquestionablyinvolvesremovaloftheexistingrestoration.C,Asafer,moreconservativeapproachistoremovetheamalgam,thepin,andanyoldcements.Carefulexcavation,usingenhancedvision,resultsinaccesstothepulpchamber.D,Thecliniciannowcanperformsoundrootcanaltherapy,followedbyinternalreinforcementandfullcoverage.Theserestorationsoftenhaveleaky,defectivemarginsorrecurrentcariesorboth.Removingtherestorationallowstheclinicianbettervisibilityoftheinternalanatomicstructuresthroughdirectvisualizationandincreasedlightpenetration.Withincreasedvisibilitythecliniciancancheckforrecurrentcariesandfracturelinesonthepulpchamberwallsorfloor.Asstatedearlierinastudy,cliniciansare40%morelikelynottodetecttheseanomalieswhenrestorationsarenotremovedcompletely.Bettervisibilityalsomakeslocatingrecededorcalcifiedcanalseasier.Coronalleakageoftenoccurswhenpartsoflargerestorationsareleftinthetoothbecausetherestorationsareloosenedbythevibrationoftheaccessdrilling.Anotherreasontoremovetheserestorationremnantscompletelyistopreventpiecesoftherestorativematerialfromfallingintotherootcanal.Instrumentscanrubagainstrestorationfragmentsduringshapingandcleaning,creatingfilingsthatcanbecarriedintothecanalsystem(seeFig.7-74,D).Completeremovalpreventstheseproblems.管。例如，第五類洞沖天修復(fù)經(jīng)常引管。例如，第五類洞沖天修復(fù)經(jīng)常引62所示，剩余的根管部分都可以通過7-A根面齲和牙周病引起的鈣化情況下，進(jìn)行的第五類修復(fù)B,鈣化的根管口阻礙進(jìn)入根管。從頰Completeremovalofanextensiverestorationfromthecervicalregionofthetoothpermitsmoredirectaccesstotherootcanal(s).Forexample,classVrestorationsoftencausecalcificationofthecoronalcanal,makinglocationofthecanalthroughtheocclusalapproachquitedifficult.removaloftheclassVrestorationallowsmoredirectaccesstothecalcifiedcanal,whichmakeslocationandtreatmentmucheasier.Anyremainingcanalscanbetreatedthroughtheconventionalocclusalaccesscavity(Fig.7-62).FIG.7-62A,ExtensiveclassVrestorationnecessitatedbyrootcariesandperiodontaldiseasethatledtocanalcalcification(arrow).B,Accesstothecanalisoccludedbycalcification.removalofthefacialrestorationmayberequiredtoobtainaccessfromthebuccalsurface.Whenanextensiverestorationisafullorpartialveneercrown,therestorationmustbeevaluatedthoroughly.Ifanyconcernsariseaboutrecurrentdecayorleakymargins,the住髓室。此時，只能靠醫(yī)生全神貫開髓。金剛砂球鉆也許好用，但是混可能導(dǎo)致瓷裂。如圖7-63crownshouldberemovedbeforetheaccesscavityisprepared.Removalofthecrownallowseliminationofallrecurrentcariesandimprovesthevisibilityofthepulpspaces.Creationofanaccessthroughanintactfullorpartialveneercrownshouldbedonewithcaution.Whensuchrestorationsareplaced,theyoftenchangethecrown-to-rootangulationtocorrectpre-existingocclusaldiscrepancies.Fullveneercrownsalsocanaltertoothrotation.Boththesesituationsmakethepreparationofaccesscavitieschallenging.Pretreatmentradiographscanbehelpful,butthemetalinthefullveneercrownoftenmaskstheunderlyingpulpchamber.Inthesesituationstheclinician’sbestapproachistostayascenteredinthetoothaspossible,usingallavailableclinicalandradiographicinformation.TheDOMandtransilluminationoftheCEJarevaluableaidesinthisprocess.Metalveneercrownsarebestpenetratedwithnew,sharpcarbideburs.Roundbursworkwell,buttungstencarbidetransmetalbursaremoreefficient.Thesecrosscutfissurebursarespecificallydesignedtocutthroughmetalrestorativematerials.Porcelainorceramometalrestorationsmustbehandleddelicatelytominimizethepotentialforfracture.Theclinicianshouldusearounddiamondburandcopiouswaterspraytopenetratetheporcelain.Afterporcelainpenetration,atransmetalburandcopiouswatersprayshouldbeusedtopenetratethemetalcoping;thewatersprayminimizesheatbuildup,whichcouldfracturetheporcelain(Fig.7-63).A,B,在用金剛砂球鉆預(yù)備出初始開髓口后，改用鎢鋼合金裂鉆切割金屬層C,建立直線通道，保證器械可以直接,循。在完成髓室通道的時候，醫(yī)生應(yīng)洗，并使全冠就位。FIG.7-63Accesscavitypreparationthroughaceramometalcrown.A,Arounddiamondburisusedtopenetratetheporcelain.B,Aftertheaccessoutlinehasbeenmadewiththerounddiamondbur,atransmetalburisusedtocutthroughthemetal.C,Preparedaccesscavity,whichallowsadirectapproachtothecanals.D,TestfilescanbeplacedontheaccesscavitywallswithoutimpingementManyclinicianstendtobetooconservativewhenpreparinganaccesscavitythroughaveneercrown.Anattempttosavethecrownoftenleadstoanunder-extendedpreparation.Alltheguidelinesforaccesscavitypreparationsdiscussedearliermustbefollowed.Whenthepreparationiscomplete,theclinicianshouldsearchthemarginsandinternalspacesforcaries,leakage,andfractures.Ifnoproblemsarediscovered,theclinicianmayproceedwithshapingandcleaning,leavingthefullveneercrowninplace.鈣鈣的全部或者局部鈣化。如圖7-64所和老化）經(jīng)常會引起根管系統(tǒng)的狹窄。在根管通向根尖的方向，鈣化程存在，并且應(yīng)該全部被預(yù)備，沖洗，充填直至根尖。7-64有臨床癥狀（冷熱過敏和酸甜過敏）的術(shù)前片。第一下磨牙沒有進(jìn)行根管治療，因為牙髓測試有活力。TeethWithCalcifiedApretreatmentradiograph(Figs.7-64and7-65)oftenappearstorevealtotalornearlytotalcal