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1、IdealabutmentTheidealabutmenttoothcontainsavitalpulp.Ifmostnotbeinferredfromthisthatatreatedtoothwithaproperlyfilledrootcanalisnotsuitableasabridgeabutment;clinicalevidenceindicatesthatinproperlyselectedcasessuchtreatedteethhaverenderedyearsofvaluableservicetothepatient
2、withoutanyharmfuleffects.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。Everyeffortshouldbemadeduringt
3、hecuttingoperationstoavoidoverheatingorirritatingthepulpinordertopreventitsfuturedegenerationordeath.Thosepreparationsarecontraindicatedwhichbringtheretainertooclosetothepulp,thusexposingittocontinuousthermalshocks;ifexistingconditionsindicatetheprobabilityofsuchanoccur
4、rence,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。Tobesuitableforuseasabridgeabutment,atoothmusthavesufficientbulktowithstandtheforcestoforc
5、eitwillbesubjectedafterthebridgeisattachedtoit.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。Aspreviouslyindicated,abutmentteethsusta
6、inforcesofatypeandmagnitudewhichtheunattachedtoothisnotrequiredtobear;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。
7、Althoughtheidealabutmentisonewhichhasnormalamountofperiodontalattachment,manyteethlackingone-thirdtoone-halfofthenormalamount,whenindiciouslyselected,itisquestionablewhethersuchatoothshouldbeusedasanabutment.Theamountofalveolarboneisdeterminedbytheextentofperiodontalatt
8、achmentandthetypeofbonepresentreflecteditsdegreeoffunction.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
