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1、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 service to the p
2、atient 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 should be made during
3、 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 indicate the probability
4、 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 sufficient bulk to withstand
5、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的活力。,As previously indicat
6、ed,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
7、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 abutment.The amount of alveolar bone
8、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 prepared primarily to receive filling
9、s 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 than one carious lesion,are often resto
10、red 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。
11、,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 be established;enamel that has not been pro
12、perly 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 crowns.In polycarious teeth the suitability of a
13、n 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
14、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,little opportunity is found to develop sufficient mechani
15、cal 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。,At times teeth egress beyond their normal occlusal plane
16、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 displacement varies from 1mm.to a point where the teeth touch the
17、 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 abutment usually requires that the pulp be removed.Where the necessa
18、ry 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 membrane of normal,functional width;neither does it possess a suppo
19、rting 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。,A malposed or malrelated tooth is not necessarily contraindicated
20、 as an abutment.The deciding factors are whether a suitable can be prepared for it and whether the forces which will be transmitted to the tooth after the bridge is placed will be of a magnitude and direction which can be tolerated by the tooth and its investing tissues.The malpositions may be varie
21、d,such as a tilting of the tooth mesiodistally or buccolingually;a rotation of the tooth about its own axis and a migration bodily of teeth into new positions and malrelations in the arch.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
22、的长轴和整体的移位可以到新的位置，及牙弓中的错合。,There is no objection to the use of anomalies as abutments,provided that they have a sound biological relationship with the investing and supporting tissues and that their coronal contour is such as to afford sufficient mechanical retention.Such teeth,however,rarely are emp
23、loyed for intracoronal or partial veneer types of retainers;the complete crown is preferred.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。,When an abutment is loose,the etiology for the existing condition should be determined.If it is due to periodont
24、al infection,excessive bone destruction,or other similar causes,its use as bridge abutment should not be considered until the existing conditions have been corrected and their causes removed.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。,Occasionally there is the
25、possibility of using a tooth with a resected or a fractured root as an abutment.While such a condition curtails the probable life of a bridge,there are times when such a procedure is justified.The prognosis is more favorable in those cases where the root is used to carry only an individual crown.有时可
26、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。,Root length of abutment,In the ideal abutment a proportionate relationship exists between the lengths of the crown and the root.Where the root is excessively short,either congenitally or due to a resorption,it cannot furn
27、ish the necessary support to the crown or resistance to the forces of mastication developed during the various movements of the mandible.The additional forces inherent in a bridge will cause such teeth to fail as abutments.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
28、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。,The acceptable abutment,therefore,must be a healthy tooth,both individually and in relationship to its environment;it must be capable of supporting the additional forces to which it will be subjected as part of the fixed partial denture;its preparation must be such that
29、 its retentive power will be sufficient to resist the normality of the pulp and insure the continued integrity of the tooth structure against fracture.因此理想的基牙它本身及与周围的环境的关系都必须是健康的牙齿；作为固定修复义齿的一部分，它必须能够支持额外的力量.基牙的预备时在维护足够固位力的同时还必须确定基牙的牙髓活力以及确保牙齿结构的连续完整,防止折断。,While the prime mechanical function of a retainer is to unite the body of the bridge with the abutment,it must also restore the form,function,and the esthetics of the latter,at the same time forestalling any future harm to both and its adjacent tissues.虽然固位体的主要的力学性能是将桥体和基牙连为一体，但它还必须恢复基牙的形态、功能和功能中的美观，同时防止任何对基牙本身和相邻组织的损伤。,
