華西口腔修復(fù)理想橋基牙第1頁/共20頁Theidealabutmenttoothcontainsavitalpulp.Ifmostnotbeinferredfromthisthatatreatedtoothwithaproperlyfilledrootcanalisnotsuitableasabridgeabutment;clinicalevidenceindicatesthatinproperlyselectedcasessuchtreatedteethhaverenderedyearsofvaluableservicetothepatientwithoutanyharmfuleffects.Nevertheless,thefirstrequisiteinpreparingvitalteethforthereceptionofbridgeretainersispulpconservation.理想的基牙應(yīng)該是活髓牙。大多數(shù)情況下不能這樣推斷：完善根管治療后的牙齒不適合作基牙。臨床證據(jù)表明合理選擇的病例中這樣的牙齒可以在患者體內(nèi)服役很多年，沒有任何危害。但對作為承擔(dān)橋固位體的活髓牙來講，首先要必須考慮的就是保存活髓。第2頁/共20頁Everyeffortshouldbemadeduringthecuttingoperationstoavoidoverheatingorirritatingthepulpinordertopreventitsfuturedegenerationordeath.Thosepreparationsarecontraindicatedwhichbringtheretainertooclosetothepulp,thusexposingittocontinuousthermalshocks;ifexistingconditionsindicatetheprobabilityofsuchanoccurrence,everypercautionshouldbetakentoreducethedangertoaminimum.在牙體預(yù)備時應(yīng)該盡一切努力來避免過熱或激惹牙髓，其目的是預(yù)防以后的牙髓變性或壞死。這些牙體預(yù)備是不當(dāng)?shù)?，使固位體過于接近牙髓，這樣就使牙髓會受連續(xù)的熱刺激；如果存在的現(xiàn)象表明有可能會出現(xiàn)這樣的情況，應(yīng)該非常的小心來將這種危險減少到最小。第3頁/共20頁Tobesuitableforuseasabridgeabutment,atoothmusthavesufficientbulktowithstandtheforcestoforceitwillbesubjectedafterthebridgeisattachedtoit.Thisphysicalrequirementisfrequentlycompromisedintheefforttoconservethepulpofatoothwhichisextensivelydecayed.要想成為理想的橋基牙，固定橋戴上之后，在承受力的時候，牙齒必須要有足夠的體積來抵抗外力。這種物理方面的要求經(jīng)常會影響到大面積齲壞的牙齒保存牙髓的活力。第4頁/共20頁Aspreviouslyindicated,abutmentteethsustainforcesofatypeandmagnitudewhichtheunattachedtoothisnotrequiredtobear;hence,thetypeandamountofperiodontalmembraneattachmentareitemsofimportanceandshouldbedeterminedseparatelyforeachabutmenttooth.正如前面談到的那樣，基牙承受了單個牙齒本身不用承受的特定類型和大小的力；因此，每個基牙附著的牙周膜的種類和牙周膜面積是很重要的，并且都應(yīng)該分別被評價。第5頁/共20頁Althoughtheidealabutmentisonewhichhasnormalamountofperiodontalattachment,manyteethlackingone-thirdtoone-halfofthenormalamount,whenindiciouslyselected,itisquestionablewhethersuchatoothshouldbeusedasanabutment.Theamountofalveolarboneisdeterminedbytheextentofperiodontalattachmentandthetypeofbonepresentreflecteditsdegreeoffunction.雖然理想的橋基牙有正常的牙周附著，但很多牙齒的牙周附著是正常量的2/3到1/2，在進(jìn)行明智的選擇的時候，這樣的牙齒是否應(yīng)該用作基牙仍是一個問題。牙槽骨的牙由牙周附著的程度來決定，并且骨的類型表現(xiàn)出的它所反應(yīng)的功能的情況。第6頁/共20頁Inoperativedentistrycavitiesarepreparedprimarilytoreceivefillingswhichrestorethatpartofthetoothlostbecariesoraccident.Infixedpartialdentureprosthesisalargeproportionoftheteethreceivingbridgeretainersaresoundandnoncarious;occasionallyamonocarioustoothisused.Polycariousteeth,thosewithmorethanonecariouslesion,areoftenrestoredwithacompletecrowninsteadofwiththeintracoronalorpartialveneertypeofretainers.Thelocationofacavityinanabutmenttoothisalsoadeterminingfactor.有效的牙齒洞型被預(yù)備主要是放充填物，而充填物則用來修復(fù)因齲壞或意外原因而丟失的部分牙體組織。在固定義齒修復(fù)體中很多粘接橋固位體的牙齒是完整無齲壞的；多齲的牙齒有不止一個的齲損，通常用全冠而不是冠內(nèi)或部分的貼面類型的固位體?；郎淆x洞的位置也是一個決定性的因素。第7頁/共20頁QuestionableabutmentWhilemostabutmentscanberestoredwithcompletecrowns,theemploymentofintracoronalorpartialveneertypeofretainershasdefinitelimitations.Beforeapprovingatoothtoserveasanabutment,itsdegreeofcalcificationshouldbeestablished;enamelthathasnotbeenproperlycalcified,butthatissoftandchalky,willnotfurnishasuitablewallagainstwhichthemarginofthecastingmaybefinished.Someteethhaveopalescentdentin;thesearequestionableforuseasabutmentstocarryretainersoftherthancompletecrowns.Inpolycariousteeththesuitabilityofanabutmentisdeterminedtoalargedegreebytheamountanddistributionofhealthytoothstructurethatisleftafterthecariouspartshavebeenremoved.雖然大部分的橋基牙可以用全冠來修復(fù)，但冠內(nèi)或部分貼面的固位體有一定的局限。在決定一個牙齒用作橋基牙之前，它的鈣化程度應(yīng)該被評價。如果釉質(zhì)礦化不全或者是軟的，白堊色，就不能提供一個合適的壁來抵抗完成的鑄造體的邊緣。一些牙齒有乳光牙本質(zhì)，用作一些非全冠固位體的橋基牙就有一些問題。多齲的牙齒是否適合作為基牙在很大程度上由將齲壞去除掉后余留下的健康的牙齒結(jié)構(gòu)的量和位置來定。第8頁/共20頁Theconstructionofabridgeretainer,otherthanacompletecrown,frequentlyoffersseriousmechanicalandbiologicalproblemsonabadlyabradedtooth.Duetothereducedcoronalheightofsuchatooth,littleopportunityisfoundtodevelopsufficientmechanicalretentionandstillnotendangerthepulp.Itismuchbetter,whensuchteethareencountered,toemploythecompleteveneertypeofretainer.非全冠的橋固位體的結(jié)構(gòu)經(jīng)常會在一個重度磨損的牙齒上引起嚴(yán)重的機(jī)械或生物學(xué)問題。過度磨損的牙齒因為降低了冠的高度，很難獲得足夠的機(jī)械固位，也會累及牙髓。當(dāng)遇到這樣的牙齒時，用全貼面類型的固位體會更好。第9頁/共20頁Attimesteethegressbeyondtheirnormalocclusalplanetoapointwhere,tousethemasbridgeabutments,itisnecessarytogrinddownaconsiderableportionoftheocclusalthirdofthecrown.Suchteetharenotusuallyinocclusalcontactwiththeopposingarch.Theamountofsuchverticaldisplacementvariesfrom1mm.toapointwheretheteethtouchthemucosaoftheoppositearch.有時牙齒會伸長超過了他們所在的正常的合平面，用他們作為橋基牙時，必須將牙冠合1/3磨去相當(dāng)多的一部分。這樣的牙齒通常和對合牙沒有咬合接觸。這樣的垂直移位的量會從1mm到牙齒接觸到對合牙弓的粘膜。第10頁/共20頁Wheretheegressionofsuchatoothhasexceededone------fourththenormalheightofitscrown,itsuseasanabutmentusuallyrequiresthatthepulpberemoved.Wherethenecessaryamountofreductioncanbemadewithoutencroachinguponthepulp,thesamephysicalandbiologicalhandicapsprevailasinthecaseofanabradedtooth.Anegressedtoothisfurtherhandicappedsinceitdoesnothaveaperiodontalmembraneofnormal,functionalwidth;neitherdoesitpossessasupportingboneofnormalstructure.Suchteethareofquestionablevaluewhenusedasbridgeabutments.

當(dāng)牙齒伸長超過了牙冠高度的1/4，用它作為基牙時通常要進(jìn)行殺髓。減少的量要求不累及牙髓，和牙齒過度磨損的情況一樣，也存在同樣的物理和生物學(xué)方面的障礙。伸長的牙齒還有其他問題，因為它沒有正常的牙周膜，生物學(xué)寬度；也不具備正常的支持骨的結(jié)構(gòu)。這樣的牙齒用作橋基牙時是有問題的。第11頁/共20頁Amalposedormalrelatedtoothisnotnecessarilycontraindicatedasanabutment.Thedecidingfactorsarewhetherasuitablecanbepreparedforitandwhethertheforceswhichwillbetransmittedtothetoothafterthebridgeisplacedwillbeofamagnitudeanddirectionwhichcanbetoleratedbythetoothanditsinvestingtissues.Themalpositionsmaybevaried,suchasatiltingofthetoothmesiodistallyorbuccolingually;arotationofthetoothaboutitsownaxisandamigrationbodilyofteethintonewpositionsandmalrelationsinthearch.錯位的或錯合的牙齒不是作為基牙的禁忌癥。其決定因素是看它是否可以預(yù)備出合適的外形，固定橋就位后傳遞到牙齒上的力量的大小和方向是否超過出了牙齒及牙周組織的耐受范圍。錯位可以糾正過來，如近遠(yuǎn)中或頰舌向傾斜的牙齒、扭轉(zhuǎn)的牙齒其自身的長軸和整體的移位可以到新的位置，及牙弓中的錯合。

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Thereisnoobjectiontotheuseofanomaliesasabutments,providedthattheyhaveasoundbiologicalrelationshipwiththeinvestingandsupportingtissuesandthattheircoronalcontourissuchastoaffordsufficientmechanicalretention.Suchteeth,however,rarelyareemployedforintracoronalorpartialveneertypesofretainers;thecompletecrownispreferred.并不反對用畸形牙作為基牙，只要他們和周圍及支持組織有一個正常的生物學(xué)的關(guān)系，并且他們的冠的外形可以提供足夠的機(jī)械固位力。但這樣的牙齒，很少用作冠內(nèi)或部分貼面類型的固位體，通常采用全冠來冠位。第13頁/共20頁Whenanabutmentisloose,theetiologyfortheexistingconditionshouldbedetermined.Ifitisduetoperiodontalinfection,excessivebonedestruction,orothersimilarcauses,itsuseasbridgeabutmentshouldnotbeconsidereduntiltheexistingconditionshavebeencorrectedandtheircausesremoved.當(dāng)基牙松動時，存在這種情況的原因應(yīng)該被確定。如果是因為牙周感染，過多的骨破壞，或其他類似的原因，直到存在的情況得以改善或他們的病因被去除，才可以考慮將其作為橋基牙。

第14頁/共20頁Occasionallythereisthepossibilityofusingatoothwitharesectedorafracturedrootasanabutment.Whilesuchaconditioncurtailstheprobablelifeofabridge,therearetimeswhensuchaprocedureisjustified.Theprognosisismorefavorableinthosecaseswheretherootisusedtocarryonlyanindividualcrown.有時可能會用殘根作為基牙。當(dāng)遇到這種情況的時候會減少固定橋的理論壽命。當(dāng)這樣的治療方案是合理的時候仍可以維持一段時間.在殘根只用作獨立的單冠修復(fù)的時候，預(yù)后更好。第15頁/共20頁RootlengthofabutmentIntheidealabutmentaproportionaterelationshipexistsbetweenthelengthsofthecrownandtheroot.Wheretherootisexcessivelyshort,eithercongenitallyorduetoaresorption,itcannotfurnishthenecessarysupporttothecrownorresistancetotheforcesofmasticationdevelopedduringthevariousmovementsofthemandible.Theadditionalforcesinherentinabridgewillcausesuchteethtofailasabutments.理想基牙應(yīng)有一個恰當(dāng)?shù)墓诟?。無論是先天的牙根過短，還是因為再吸收導(dǎo)致的牙根過短，它都不能給牙冠提供足夠的支持力，或者抵抗在下頜進(jìn)行各種各樣的運(yùn)動時所產(chǎn)生的咀嚼力。與橋體相連從而增加在的力量會導(dǎo)致這樣的基牙失敗。

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