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1、Ideal abutment,The ideal abutment tooth contains a vital pulp. If most not be inferred from this that a treated tooth with a properly filled root canal is not suitable as a bridge abutment; clinical evidence indicates that in properly selected cases such treated teeth have rendered years of valuable
2、 service to the patient without any harmful effects. Nevertheless, the first requisite in preparing vital teeth for the reception of bridge retainers is pulp conservation. 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。,Every effort s
3、hould be made during the cutting operations to avoid overheating or irritating the pulp in order to prevent its future degeneration or death. Those preparations are contraindicated which bring the retainer too close to the pulp, thus exposing it to continuous thermal shocks; if existing conditions i
4、ndicate the probability of such an occurrence, every percaution should be taken to reduce the danger to a minimum.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。,To be suitable for use as a bridge abutment, a tooth must have suff
5、icient bulk to withstand the forces to force it will be subjected after the bridge is attached to it. This physical requirement is frequently compromised in the effort to conserve the pulp of a tooth which is extensively decayed.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
6、的活力。,As previously indicated, abutment teeth sustain forces of a type and magnitude which the unattached tooth is not required to bear; hence, the type and amount of periodontal membrane attachment are items of importance and should be determined separately for each abutment tooth.正如前面谈到的那样，基牙承受了单个牙
7、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。,Although the ideal abutment is one which has normal amount of periodontal attachment, many teeth lacking one-third to one-half of the normal amount, when indiciously selected, it is questionable whether such a tooth should be used as an abutm
8、ent. The amount of alveolar bone is determined by the extent of periodontal attachment and the type of bone present reflected its degree of function.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。,In operative dentistry cavities are prep
9、ared primarily to receive fillings which restore that part of the tooth lost be caries or accident. In fixed partial denture prosthesis a large proportion of the teeth receiving bridge retainers are sound and noncarious; occasionally a monocarious tooth is used. Polycarious teeth, those with more th
10、an one carious lesion, are often restored with a complete crown instead of with the intracoronal or partial veneer type of retainers. The location of a cavity in an abutment tooth is also a determining factor.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
11、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。,Questionable abutment,While most abutments can be restored with complete crowns, the employment of intracoronal or partial veneer type of retainers has definite limitations. Before approving a tooth to serve as an abutment, its degree of calcification should b
12、e established; enamel that has not been properly calcified, but that is soft and chalky, will not furnish a suitable wall against which the margin of the casting may be finished. Some teeth have opalescent dentin; these are questionable for use as abutments to carry retainers of ther than complete c
13、rowns. In polycarious teeth the suitability of an abutment is determined to a large degree by the amount and distribution of healthy tooth structure that is left after the carious parts have been removed. 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
14、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。,The construction of a bridge retainer, other than a complete crown, frequently offers serious mechanical and biological problems on a badly abraded tooth. Due to the reduced coronal height of such a tooth, litt
15、le opportunity is found to develop sufficient mechanical retention and still not endanger the pulp. It is much better, when such teeth are encountered, to employ the complete veneer type of retainer.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。,A
16、t times teeth egress beyond their normal occlusal plane to a point where, to use them as bridge abutments, it is necessary to grind down a considerable portion of the occlusal third of the crown. Such teeth are not usually in occlusal contact with the opposing arch. The amount of such vertical displ
17、acement varies from 1mm. to a point where the teeth touch the mucosa of the opposite arch. 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。,Where the egression of such a tooth has exceeded one-fourth the normal height of its crown, its use as an abutm
18、ent usually requires that the pulp be removed. Where the necessary amount of reduction can be made without encroaching upon the pulp, the same physical and biological handicaps prevail as in the case of an abraded tooth. An egressed tooth is further handicapped since it does not have a periodontal m
19、embrane of normal, functional width; neither does it possess a supporting bone of normal structure. Such teeth are of questionable value when used as bridge abutments.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。,
