华西口腔修复理想桥基牙

华西口腔修复理想桥基牙第1页/共20页Theidealabutmenttoothcontainsavitalpulp.Ifmostnotbeinferredfromthisthatatreatedtoothwithaproperlyfilledrootcanalisnotsuitableasabridgeabutment;clinicalevidenceindicatesthatinproperlyselectedcasessuchtreatedteethhaverenderedyearsofvaluableservicetothepatientwithoutanyharmfuleffects.Nevertheless,thefirstrequisiteinpreparingvitalteethforthereceptionofbridgeretainersispulpconservation.理想的基牙应该是活髓牙。大多数情况下不能这样推断：完善根管治疗后的牙齿不适合作基牙。临床证据表明合理选择的病例中这样的牙齿可以在患者体内服役很多年，没有任何危害。但对作为承担桥固位体的活髓牙来讲，首先要必须考虑的就是保存活髓。第2页/共20页Everyeffortshouldbemadeduringthecuttingoperationstoavoidoverheatingorirritatingthepulpinordertopreventitsfuturedegenerationordeath.Thosepreparationsarecontraindicatedwhichbringtheretainertooclosetothepulp,thusexposingittocontinuousthermalshocks;ifexistingconditionsindicatetheprobabilityofsuchanoccurrence,everypercautionshouldbetakentoreducethedangertoaminimum.在牙体预备时应该尽一切努力来避免过热或激惹牙髓，其目的是预防以后的牙髓变性或坏死。这些牙体预备是不当的，使固位体过于接近牙髓，这样就使牙髓会受连续的热刺激；如果存在的现象表明有可能会出现这样的情况，应该非常的小心来将这种危险减少到最小。第3页/共20页Tobesuitableforuseasabridgeabutment,atoothmusthavesufficientbulktowithstandtheforcestoforceitwillbesubjectedafterthebridgeisattachedtoit.Thisphysicalrequirementisfrequentlycompromisedintheefforttoconservethepulpofatoothwhichisextensivelydecayed.要想成为理想的桥基牙，固定桥戴上之后，在承受力的时候，牙齿必须要有足够的体积来抵抗外力。这种物理方面的要求经常会影响到大面积龋坏的牙齿保存牙髓的活力。第4页/共20页Aspreviouslyindicated,abutmentteethsustainforcesofatypeandmagnitudewhichtheunattachedtoothisnotrequiredtobear;hence,thetypeandamountofperiodontalmembraneattachmentareitemsofimportanceandshouldbedeterminedseparatelyforeachabutmenttooth.正如前面谈到的那样，基牙承受了单个牙齿本身不用承受的特定类型和大小的力；因此，每个基牙附着的牙周膜的种类和牙周膜面积是很重要的，并且都应该分别被评价。第5页/共20页Althoughtheidealabutmentisonewhichhasnormalamountofperiodontalattachment,manyteethlackingone-thirdtoone-halfofthenormalamount,whenindiciouslyselected,itisquestionablewhethersuchatoothshouldbeusedasanabutment.Theamountofalveolarboneisdeterminedbytheextentofperiodontalattachmentandthetypeofbonepresentreflecteditsdegreeoffunction.虽然理想的桥基牙有正常的牙周附着，但很多牙齿的牙周附着是正常量的2/3到1/2，在进行明智的选择的时候，这样的牙齿是否应该用作基牙仍是一个问题。牙槽骨的牙由牙周附着的程度来决定，并且骨的类型表现出的它所反应的功能的情况。第6页/共20页Inoperativedentistrycavitiesarepreparedprimarilytoreceivefillingswhichrestorethatpartofthetoothlostbecariesoraccident.Infixedpartialdentureprosthesisalargeproportionoftheteethreceivingbridgeretainersaresoundandnoncarious;occasionallyamonocarioustoothisused.Polycariousteeth,thosewithmorethanonecariouslesion,areoftenrestoredwithacompletecrowninsteadofwiththeintracoronalorpartialveneertypeofretainers.Thelocationofacavityinanabutmenttoothisalsoadeterminingfactor.有效的牙齿洞型被预备主要是放充填物，而充填物则用来修复因龋坏或意外原因而丢失的部分牙体组织。在固定义齿修复体中很多粘接桥固位体的牙齿是完整无龋坏的；多龋的牙齿有不止一个的龋损，通常用全冠而不是冠内或部分的贴面类型的固位体。基牙上龋洞的位置也是一个决定性的因素。第7页/共20页QuestionableabutmentWhilemostabutmentscanberestoredwithcompletecrowns,theemploymentofintracoronalorpartialveneertypeofretainershasdefinitelimitations.Beforeapprovingatoothtoserveasanabutment,itsdegreeofcalcificationshouldbeestablished;enamelthathasnotbeenproperlycalcified,butthatissoftandchalky,willnotfurnishasuitablewallagainstwhichthemarginofthecastingmaybefinished.Someteethhaveopalescentdentin;thesearequestionableforuseasabutmentstocarryretainersoftherthancompletecrowns.Inpolycariousteeththesuitabilityofanabutmentisdeterminedtoalargedegreebytheamountanddistributionofhealthytoothstructurethatisleftafterthecariouspartshavebeenremoved.虽然大部分的桥基牙可以用全冠来修复，但冠内或部分贴面的固位体有一定的局限。在决定一个牙齿用作桥基牙之前，它的钙化程度应该被评价。如果釉质矿化不全或者是软的，白垩色，就不能提供一个合适的壁来抵抗完成的铸造体的边缘。一些牙齿有乳光牙本质，用作一些非全冠固位体的桥基牙就有一些问题。多龋的牙齿是否适合作为基牙在很大程度上由将龋坏去除掉后余留下的健康的牙齿结构的量和位置来定。第8页/共20页Theconstructionofabridgeretainer,otherthanacompletecrown,frequentlyoffersseriousmechanicalandbiologicalproblemsonabadlyabradedtooth.Duetothereducedcoronalheightofsuchatooth,littleopportunityisfoundtodevelopsufficientmechanicalretentionandstillnotendangerthepulp.Itismuchbetter,whensuchteethareencountered,toemploythecompleteveneertypeofretainer.非全冠的桥固位体的结构经常会在一个重度磨损的牙齿上引起严重的机械或生物学问题。过度磨损的牙齿因为降低了冠的高度，很难获得足够的机械固位，也会累及牙髓。当遇到这样的牙齿时，用全贴面类型的固位体会更好。第9页/共20页Attimesteethegressbeyondtheirnormalocclusalplanetoapointwhere,tousethemasbridgeabutments,itisnecessarytogrinddownaconsiderableportionoftheocclusalthirdofthecrown.Suchteetharenotusuallyinocclusalcontactwiththeopposingarch.Theamountofsuchverticaldisplacementvariesfrom1mm.toapointwheretheteethtouchthemucosaoftheoppositearch.有时牙齿会伸长超过了他们所在的正常的合平面，用他们作为桥基牙时，必须将牙冠合1/3磨去相当多的一部分。这样的牙齿通常和对合牙没有咬合接触。这样的垂直移位的量会从1mm到牙齿接触到对合牙弓的粘膜。第10页/共20页Wheretheegressionofsuchatoothhasexceededone------fourththenormalheightofitscrown,itsuseasanabutmentusuallyrequiresthatthepulpberemoved.Wherethenecessaryamountofreductioncanbemadewithoutencroachinguponthepulp,thesamephysicalandbiologicalhandicapsprevailasinthecaseofanabradedtooth.Anegressedtoothisfurtherhandicappedsinceitdoesnothaveaperiodontalmembraneofnormal,functionalwidth;neitherdoesitpossessasupportingboneofnormalstructure.Suchteethareofquestionablevaluewhenusedasbridgeabutments.

当牙齿伸长超过了牙冠高度的1/4，用它作为基牙时通常要进行杀髓。减少的量要求不累及牙髓，和牙齿过度磨损的情况一样，也存在同样的物理和生物学方面的障碍。伸长的牙齿还有其他问题，因为它没有正常的牙周膜，生物学宽度；也不具备正常的支持骨的结构。这样的牙齿用作桥基牙时是有问题的。第11页/共20页Amalposedormalrelatedtoothisnotnecessarilycontraindicatedasanabutment.Thedecidingfactorsarewhetherasuitablecanbepreparedforitandwhethertheforceswhichwillbetransmittedtothetoothafterthebridgeisplacedwillbeofamagnitudeanddirectionwhichcanbetoleratedbythetoothanditsinvestingtissues.Themalpositionsmaybevaried,suchasatiltingofthetoothmesiodistallyorbuccolingually;arotationofthetoothaboutitsownaxisandamigrationbodilyofteethintonewpositionsandmalrelationsinthearch.错位的或错合的牙齿不是作为基牙的禁忌症。其决定因素是看它是否可以预备出合适的外形，固定桥就位后传递到牙齿上的力量的大小和方向是否超过出了牙齿及牙周组织的耐受范围。错位可以纠正过来，如近远中或颊舌向倾斜的牙齿、扭转的牙齿其自身的长轴和整体的移位可以到新的位置，及牙弓中的错合。

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Thereisnoobjectiontotheuseofanomaliesasabutments,providedthattheyhaveasoundbiologicalrelationshipwiththeinvestingandsupportingtissuesandthattheircoronalcontourissuchastoaffordsufficientmechanicalretention.Suchteeth,however,rarelyareemployedforintracoronalorpartialveneertypesofretainers;thecompletecrownispreferred.并不反对用畸形牙作为基牙，只要他们和周围及支持组织有一个正常的生物学的关系，并且他们的冠的外形可以提供足够的机械固位力。但这样的牙齿，很少用作冠内或部分贴面类型的固位体，通常采用全冠来冠位。第13页/共20页Whenanabutmentisloose,theetiologyfortheexistingconditionshouldbedetermined.Ifitisduetoperiodontalinfection,excessivebonedestruction,orothersimilarcauses,itsuseasbridgeabutmentshouldnotbeconsidereduntiltheexistingconditionshavebeencorrectedandtheircausesremoved.当基牙松动时，存在这种情况的原因应该被确定。如果是因为牙周感染，过多的骨破坏，或其他类似的原因，直到存在的情况得以改善或他们的病因被去除，才可以考虑将其作为桥基牙。

第14页/共20页Occasionallythereisthepossibilityofusingatoothwitharesectedorafracturedrootasanabutment.Whilesuchaconditioncurtailstheprobablelifeofabridge,therearetimeswhensuchaprocedureisjustified.Theprognosisismorefavorableinthosecaseswheretherootisusedtocarryonlyanindividualcrown.有时可能会用残根作为基牙。当遇到这种情况的时候会减少固定桥的理论寿命。当这样的治疗方案是合理的时候仍可以维持一段时间.在残根只用作独立的单冠修复的时候，预后更好。第15页/共20页RootlengthofabutmentIntheidealabutmentaproportionaterelationshipexistsbetweenthelengthsofthecrownandtheroot.Wheretherootisexcessivelyshort,eithercongenitallyorduetoaresorption,itcannotfurnishthenecessarysupporttothecrownorresistancetotheforcesofmasticationdevelopedduringthevariousmovementsofthemandible.Theadditionalforcesinherentinabridgewillcausesuchteethtofailasabutments.理想基牙应有一个恰当的冠根比。无论是先天的牙根过短，还是因为再吸收导致的牙根过短，它都不能给牙冠提供足够的支持力，或者抵抗在下颌进行各种各样的运动时所产生的咀嚼力。与桥体相连从而增加在的力量会导致这样的基牙失败。

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