625401511104 【文献推荐】固定修复如何作咬合记录 _
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【文献推荐】固定修复如何作咬合记录

 

Jaw relation records for fixed prosthodontics

Jaw relation records are a fundamental and crucial component of pro¬viding accurate, high-quality fixed restorations. A disciplined and efficient practitioner understands that the use of accurate records minimizes the need for intraoral adjustments before prosthesis delivery and can there¬fore reduce overall treatment time and cost. Because all dental materials have their inherent limitations and because there exists variability in intra¬oral conditions, learning to minimize discrepancies in making jaw relation records is critical.
This article reviews the concepts of jaw relation records (or interocclusal records) and discusses the selection of interocclusal records for a variety of clinical situations. In addition, articulator choice, the purpose of a facebow, and materials for jaw relation records are discussed. Some ‘‘pearls’’ are offered to help avoid common problem areas, including making impressions, pouring impressions, mounting casts, and making interocclusal records.
General principles
If the goal of restorative treatment is to maintain a patient’s pretreatment intercuspation and vertical dimension of occlusion (VDO), casts should be mounted in a manner that maintains the same tooth-to-tooth relationship that existed before treatment. This maximum intercuspal position (MIP) facilitates treatment and works with the patient’s existing occlusion. The vast majority of cases treated fall within this MIP category. The situation becomes more difficult if a patient requires extensive treatment or if the VDO needs to be altered. In these circumstances, a reproducible maxillo¬mandibular position from which treatment is performed is essential and requires a centric relation record made at the terminal hinge axis. This article deals with situations where the patient’s MIP and VDO do not change as a result of treatment.
Function of the jaw relation record
Jaw relation records, or interocclusal records, have the following functions:
(1) They provide the stability or support that the casts of the remaining dentition lack, (2) they reduce chair time for the delivery of the restoration, (3) they reduce the likelihood of making restorations in hyperocclusion or with¬out occlusal contacts, and (4) they reduce the chance of perforation of re¬storations being inserted with excessive adjustment or having to adjust the opposing dentition inappropriately.
For opposing casts to relate well, there must be a tripod of vertical support and horizontal stability between the two casts. A minimum of three widely spaced tooth-to-tooth contacts should be present during mounting to ensure adequate stability. Casts that rock or wobble due to an insufficient tripod require an interocclusal record to stabilize them before mounting. Full-arch working and opposing casts frequently have sufficient occluding natural teeth to accurately position the casts in a stable MIP occlusion, and horizontal stability is generally present when there is good intercuspation between teeth. However, in a patient with worn occlusal surfaces, although a solid vertical tripod may be obtained, the horizontal stability may be inadequate to accurately mount the casts. The goal of the interocclusal record is to provide the support or stability that the casts of the remaining dentition lack.
Interocclusal records used to mount casts in MIP can be separated into two categories: (1) records made when a tripod of vertical support is avail¬able from the remaining tooth-to-tooth contacts (an ‘‘existing tripod’’ inter¬occlusal record) and (2) records made when a tripod of vertical support is not available from the remaining tooth-to-tooth contacts (a ‘‘created tripod’’ interocclusal record) [1].
The existing tripod interocclusal record
When there is a tripod of widely spaced contacts and good intercuspation of the teeth, an interocclusal record is not needed. In this situation, hand articulation is the most accurate means of mounting a mandibular cast to a maxillary cast. Practitioners frequently waste time and materials making an interocclusal record when one is not needed. In addition, the use of an interocclusal record when hand articulation is sufficient creates a potential for error because the record can often prevent the casts from fully inter¬cuspating (Figs. 1 and 2). Therefore, full-arch impressions made for a mini¬mum number of teeth being restored usually need no interocclusal record due to the number of intact occlusal contacts.

固定修复如何作咬合记录。从而,在缺牙很少的时候,取全口的模型能保证完整的咬合接触而无需做咬合记录。[/color]

咬合记录是制作既精确又高质量固定修复体的根本和关键。训练有素的临床牙医明白精确的咬合记录能保证做到最少口内调合,从而可以节省整体治疗的时间和费用。基于各种齿科材料性能都有其内在的局限性,患者的口内情况也是千变万化,所以掌握如何减少咬合记录误差就非常关键。

本文回顾了咬合记录的一些概念,探讨了根据不同的临床情况选择不同的咬合记录方法。此外,还讨论了合架的选择,上面弓的目的以及一些咬合记录材料的性能。本文还提出了一些“金点子”来避免如取模,倒模型,上牙合架,取咬合记录常犯的错误。

一般性原则
如果某个患者修复计划是保持治疗前的牙尖交错关系以及咬合高度,咬合记录就要保持原有的牙尖交错关系。大多数的咬合记录方式都属于这一类。但是遇到患者的咬合高度需要改变之类的多方治疗时,咬合记录的难度就会加大;这时,稳定的上下颌关系就很关键,需要在正确铰链轴的上记录正中关系。但是本文的案例咬合记录方式是最大牙尖交错合与咬合高度不改变的。


咬合记录的功能

颌位关系记录,或者咬合关系记录的功能如下:
1 咬合记录能提供余留牙列没有的稳定和支持
2 咬合记录能减少临床调牙合而节省椅旁操作时间
3 咬合记录能减少修复体咬合抬高或降低的可能性
4 咬合记录能减少因为过度调牙合导致修复体穿孔或不得不调改对合牙的可能性

为了达到上下颌模型接触完好,需要在垂直向上、下颌有三角鼎立接触以及水平向稳定不位移。颌间最少要有分散得比较开的三点牙齿接触才能保持上下颌之间的稳定性。缺乏足够的鼎型接触会导致上下颌模型摇来摆去,在上牙合架前需要用咬合记录来稳定。工作模和对合模都有完整的牙齿可以将上下颌稳定在最大牙尖交错合上,水平向的稳定性也会因为尖窝间紧密的接触关系而获得。而那些合面磨损的病例虽然在垂直位上能达到稳定的鼎型接触,但是水平向稳定性就无法保证。咬合记录的目的就是提供模型的支持与稳定。

最大牙尖交错合的咬合记录分为两类:
1 模型余留牙能提供稳定的鼎型三角接触
2 模型余留牙无法提供稳定的鼎型三角接触

模型余留牙能提供稳定的鼎型三角接触的咬合记录

有足够三角鼎型接触和稳定的尖窝接触的模型不需要咬合记录。这时只要将上下颌模型用手来稳定就可以精确上牙合架。有些牙医对这样的模型还要做咬合记录无非是浪费时间,浪费钱,而且这么做还会因为咬合记录材料对模型精确定位造成影响。见[color=green]图一图二

In patients where vertical support is adequate but horizontal stability is lacking, an interocclusal record is needed to mount casts. Elastomeric materials such as polyvinylsiloxane are ideal for making interocclusal records where only horizontal stability is needed [2,3]. However, their accuracy can be compromised if they are not properly trimmed. These records should be carefully trimmed to remove all areas of the record that contact soft tissues and the axial surfaces of the teeth (Fig. 3). This is done to minimize the areas where the casts and the record touch, allowing the practitioner to visualize how the casts seat into the record and ensuring that the record provides only the horizontal support, with the contacting teeth providing the vertical support.

那些垂直向很稳定而水平向不稳定的患者模型就需要作咬合记录。弹性聚乙烯材料适合作需要水平稳定型咬合记录。但是这种材料假如修整的不好效果就要打折。[color=red]那些和软组织以及牙体轴面接触的区域要修掉.目的是让模型和记录材料接触面积最小,医生可以直视模型是如何与咬合记录接触,确保咬合记录只是保证模型水平向的稳定性,垂直向的稳定性由接触的牙齿提供。[/color]

The created tripod interocclusal record

A tripod of opposing teeth is present but without occlusal contacts
A practitioner has to ‘‘create’’ a tripod of vertical support where one does not exist to mount opposing casts. A classic example of a created tripod interocclusal record is a fully dentate patient who has teeth #18 through #20 prepared for a fixed partial denture. Although the teeth are well positioned around the dental arch, the tooth preparations prevent the existence of the third leg of the tripod. In this situation, the tripod has to be created so that the working and opposing casts can be mounted accurately. The materials best suited for this purpose are those that are soft at placement and then become rigid before their removal from the mouth, such as waxes, resins, zinc oxide and eugenol pastes, and impression plasters. The materials of choice for the general practitioner are resins (DuraLay [Reliance Dental, Worth, Illinois] or GC Pattern Resin [GC America, Alsip, Illinois]) or waxes. Resin placed conservatively between the tooth preparations and the opposing teeth creates the needed leg of the tripod for mounting (Fig. 4). The practitioner should avoid the elastomeric materials for this situation because these materials exhibit compressibility and rebound, often resultingin an inaccurate mounting that may lead to the need for excessive adjust¬ments upon delivery of the restoration or the possibility of no occlusion between the restoration and the opposing teeth.


模型余留牙无法提供稳定的鼎型三角接触

对合有牙齿但是没有稳定的三角鼎型接触,需要用咬合材料来作“做”出这个鼎足。典型的例子比如左下5×7固定桥预备,尽管余留牙都接触完好,但是因为牙备整个鼎型结构就缺了一条腿。这时需要用咬合记录保证来恢复缺损的鼎足来保证准确上合架。适合的记录材料应当是放置入口内的时候是柔软的,拿出口腔的时候是硬的。比如蜡,树脂,氧化锌丁香油粘固粉,印模材料等等。全科大夫可以选择树脂或者蜡。将适量的树脂放在预备体和对合牙之间就能“做”出那条缺失的鼎足。不能选用弹性材料来记录,因为弹性材料有被压缩和反弹的特性而不适合做鼎足的恢复材料。结果就是上合架不准确,做出来的修复体不是咬合过高需要口内大量调合或者咬合太低修复体和对合牙无接触

Opposing teeth are absent at one or more desired tripod stops
When teeth are absent at one or more potential tripod stops, a record base-occlusion rim is indicated to obtain support from the edentulous ridge. The practitioner may use a record base-occlusion rim made on a cast or can make an intraoral segmental interocclusal record composed of rigid setting materials that do not displace the soft tissues of the edentulous ridge at the time of placement. If the choice is a record base-occlusion rim, the record base must be made on the castMoon that is to be mounted and not on earlier made diagnostic casts [4]. A record base made on one cast does not predictably transfer to another cast due to differences between the casts. These discrepancies are the result of minor differences in soft tissue dis¬placement and tooth position and differences from the dimensional accuracy of impression materials and dental stones.
The record base is adapted to the edentulous portion of the cast and often to the lingual surfaces of the remaining teeth to enhance stability and retention (Fig. 5). Record bases usually are made from light-activated resin or autopolymerizing resin. The occlusion rim is able to function only as a substitute for a leg of a tripod when the record base is stable in the mouth and on the cast. The occlusion rim can easily and cheaply be made from baseplate wax to imprint the cusp tips of the opposing teeth, or other mate¬rials may be used, including metal-impregnated wax or the more rigid of the elastomeric interocclusal recording materials (eg, Blu-Mousse; Parkell, Farmingdale, New York).
If the working cast with crown preparations contains the edentulous areas where tripod stops are desired, the record base cannot be made until the final impression is made, poured, and separated and the cast is trimmed. This usually requires that the patient make a separate brief appointment for a jaw relationship record before fabrication of the restorations. However, if the edentulous areas are located in the opposing arch, the practitioner who has planned ahead may have the record base-occlusion rim made on the opposing cast before the final impression visit, allowing the interocclusal record to be made at the final impression appointment.
Because of the popularity of the elastomeric materials for interocclusal records, they are often abused. One situation where this is the case is when there is an absence of a tripod of support and there is a need to create the tripod. Polyvinylsiloxane and polyether are ineffective materials when creating a tripod of support due to their inherent compressibility. Although the materials are easy to use for interocclusal records, their use during the mounting of the casts can be technique sensitive. It is difficult to objectively determine the amount of force that should be exerted on the casts when mounting them with the interocclusal record. Too much force can cause compression of the elastic record, resulting in some part of the casts placed too closely together, and too little force can allow for inadequate seating of the cast into the record, resulting in casts that are too far apart. Therefore, despite the relative accuracy and dimensional stability of elastomeric materials and their ease of use and convenience, their use in these cir¬cumstances is likely to result in an inaccurate mounting and subsequent difficulty in delivering the final restorationMoon because of no occlusion or a resulting heavy occlusion
.

对合的牙齿缺失导致一条或两条鼎足缺失

当牙齿在一个或者两个鼎足区都有缺失,就需要无牙区的颌堤来做咬合记录。医生可以使用在模型上做的颌堤或者在口内采用不会导致软组织变形的材料直接做咬合记录。如果采用的是模型上做颌堤,模型不要用诊断模型而要用上合架的模型。因为软组织受压情况的不一致,用的印模材,灌制的石膏导是不一致的,因而研究模型和做修复体的模型是不一致的。

记录蜡堤的基托与缺牙区牙槽脊相适应并且与余留牙舌侧相适应以提高基托的固位与稳定。基托用光固化树脂或者自凝塑料来做,蜡堤只是起到在稳定的基托上来恢复鼎足的作用。用来做蜡堤的材料可以是基托蜡,用来记录对合的牙尖型状;也可以是metalimpregnated蜡或是更硬的弹性咬合记录材料。如果带有牙备的工作模型上的无牙区正好要作为鼎足记录,那么要等工作模型取好,灌制好石膏后才可以做咬合记录。患者要为此短期内再次复诊。但如果缺牙区是在对合模,医生可以预先将基托合蜡堤做好,这样在取工作模型的时候就可以做咬合记录了。

因为弹性记录材料广为流行而被滥用。其中一个例子就是当鼎足缺失而需要做一个鼎足的时候。聚乙烯材料和聚醚材料 因为其可被压缩的特性而不适合用来恢复鼎足,尽管使用这些材料非常简单,但是用它们做咬合记录材料上合架是件技术型非常敏感的工作。到底要用多大的力量来在上合架的时候固定住记录材料非常难确定,力量太大会将记录材料压缩而导致颌间距离减小,力量太小又会 导致颌间距离加大。 尽管弹性记录材料相对比较精确,空间稳定性也好,使用也方便,但是把它用在该场合会导致上合架不精确而咬合导致最终修复体或是咬合过高,或是咬合过低。

The use of prosthesis frameworks

For a variety of clinical conditions, a fixed metal framework or a metal framework for a removable partial denture can be used to support an interocclusal record. The benefit of using a metal framework to support an interocclusal record is that the metal framework usually has more stability and retention than a record base-occlusion rim. For instance, when one is remounting casts after the metal try-in of fixed restorations, the recording material may be added directly to the metal framework [5]. The framework may carry an elastic material to make a segmental existing tripod record or a rigid material to contact the opposing teeth and make a created tripod record. When a practitioner requests a metal framework to be returned for try-in before porcelain application, not only should the metal be examined for fit, but also the opportunity should be taken to verify the accuracy of the articulation of the working casts. The added time in verifying the articu¬lation could save considerable time at the insertion appointment.
When fabricating fixed restorations in combination with a removable partial denture (RPD), jaw relation records are often difficult due to the difficulty in achieving good stability of a record base and occlusion rim. The fitted framework of the RPD can be used as a record base, and the occlusion rim can be formed directly into the meshwork areas [4,5] (Fig. 6). The framework adds retention and stability for an interocclusal record, thereby increasing its accuracy.


使用假牙支架

临床大量的病例可以用其固定修复支架或活动义齿的金属支架来承附咬合记录,优点是它的稳定性和固位力比基托好。如在试金属内冠再次上合架的时候就可以直接戴着内冠做咬合记录。用支架可以在其上放置弹性材料来帮助做鼎足,放置硬质材料和对侧的牙齿接触来直接做鼎足。当医生需要临床试内冠时,不但要检查内冠是否合适,还要用它来做帮助来记录咬合。虽然这么做多用了一点时间,但是在临床戴牙的时候却节省了大量的时间。
在制作固定活动联合修复时,因为基托蜡堤很难稳定而咬合记录往往比较难。原有的活动支架可以用来做记录支架,蜡堤可以直接固定在网上(图4,5),可以既提高稳定又增加固位因而精确度更高。

Articulator choice

When fabricating fixed and removable prostheses, the use of an ad¬justable articulator usually reduces the amount of intraoral adjustment needed. A more anatomically sized articulator, such as a programmed adjustable or a semiadjustable articulator, better reproduces the mandibular border movements compared with a simple hinge articulator. An articulator that is more true to human size allows the restoration to be adjusted by the technician to a greater degree and to a closer approximation of the patient’s intraoral situation. A full-size adjustable or semi-adjustable articulator is an excellent investment for the dentist who does a substantial amount of crown and bridge.

Purpose of a facebow

The purpose of a facebow transfer is to orient the maxillary cast to the transverse axis of the articulator. Its use is limited to adjustable and semi-adjustable articulators. Facebows are not necessary if there will be no change in the VDO. However, if any alteration of the VDO is planned, as in a full-mouth rehabilitation, a facebow (and a full-sized articulator) should be used. Another positive aspect of using a facebow is that it makes it easier to mount a maxillary cast to a full-sized articulator.

Avoiding errors and inaccuracies

Inaccuracies in jaw relations can be caused by a number of factors besides a poor interocclusal record. Errors can be introduced anywhere from im¬pressions to cast accuracy to problems with the articulation of the casts. These areas are often overlooked and are as important for overall accuracy as the interocclusal record.
All impression materials, all dental stones or plasters, and all inter¬occlusal materials have inherent inaccuracies: they shrink or expand. Learn¬ing how to minimize these inaccuracies improves the end product and results in a more successful outcome to the practitioner and to the patient.
Accuracy of dental casts and their subsequent successful articulation are essential when trying to maximize quality while minimizing treatment time with a patient. The following ‘‘pearls’’ elucidate common problem areas and discuss how to handle them.

Movement during setting of material

Movement of the impression tray during the setting time of the im¬pression material leads to inaccuracy. Minor movement while making an impression for study casts may not be too harmful in the overall scheme of treatment; however, the same movement for a final impression is detrimental to the fabrication of a fixed restoration. Once the tray with impression material is seated in the mouth, it is essential that any movement by the operator or the patient be prevented. An impression tray should never be left in a patient’s mouth without being stabilized by the practitioner or dental assistant. Additionally, a patient should not be allowed to close into a full-arch impression tray at any time; the practitioner’s or dental assistant’s fingers should prevent this from occurring.
Impression material dislodged from the impression tray
Dislodged impression material occurs most frequently with alginate impression material. If a plastic stock tray is used and if the impression tray is not adequately painted with adhesive, the alginate has to rely solely on the perforations in the tray and may separate from the tray as the impression is removed from the mouth. This may happen with a metal stock tray as well because adhesive is generally not used in these trays for added security. Once distorted, the alginate cannot be pushed back into place; a new impression has to be made. This separation of alginate from the impression tray may be overlooked as a non-essential factor or may go unnoticed. Separation of the impression material from the tray is a common cause of inaccurate casts.
Although less likely than with alginate, the same separation of impression material from an impression tray may occur with elastomeric final impres¬sion materials. After removing any impression from a patient’s mouth, the overall adherence of the impression material to the tray should be examined. This step reduces cast inaccuracies and the resultant errors in the fabrication of a restoration.

Laying alginate on tabletop with long extensions

Alginate impression material that is unsupported by an impression tray is under stress. Using an impression tray that does not adequately match a patient’s arch size runs the risk that a large portion of the alginate will be unsupported and therefore may become distorted. In addition, after an alginate impression is made, the practitioner usually places it on a countertop with the overextended alginate in direct contact with the flat surface. Any direct pressure on the unsupported alginate distorts the impression. Ideally, an impression as discussed would be made and then disinfected and poured in dental stone while being held in a holding ‘‘tree’’ so the impression tray hangs from its handle rather than rests on the countertop (Fig. 7).

合架选择


使用可调合架常能减少口内调合时间。更贴近解剖结构的合架比如全可调或半可调合架比简单合架更能模拟下颌的边缘运动。更贴近真人尺寸的合架能让技工最大程度调改修复体,更能接近口内真实的情况。对做很多冠桥修复的牙医来说,买个全可调或半可调合架是一笔精彩的投资。

面弓的目的

面弓的目的是将上颌体模型定位在合架的水平铰链轴上。只有半可调或全可调合架才用得上面弓。如果不用改变患者的咬合高度,面弓就不必用了(译者注:该观点不对吧?)。而像全口咬合重建的患者,垂直距离需要改变,就要使用面弓和全可调合架。用面弓的另一个好处是上颌体上合架变得更简单了。


避免错误,消除不精确

咬合记录不精确除记录没有做好外还有很多因素。从取模,灌模到上合架都有可能出错。很多环节都被忽视,但是要确保整体的精确度每个环节都是重要的。
所有的印模材料,牙科石膏,咬合记录材料都有其固有的不精确性:有的会收缩,有的会膨胀。掌握最大程度控制这些材料不精确性能提高修复体的质量,给患者、医生以更好的结果。
模型和随后上合架的精确度对最大程度提高修复体质量以及减少治疗时间来说非常关键。下面的这些“金点子”讨论分析了一些常见的问题,以及如何处理这些问题。

印模材凝固的过程中有移动

印模材料还没有固化前移动托盘会导致误差。取研究印模时托盘小位移对整个治疗危害或许不大。但是取固定修复体的终印模同样的小位移时有危害。一旦盛有印模材的托盘在口内就位,医生和患者要避免托盘的任何移动。一直要待印模材在口内固化整个托盘都要由医生或助手固定好。任何时候都不要让患者咬在托盘上,医生或医助要用手指防止其发生。
印模材脱模
脱模的现象最常发生于藻酸盐印模材取模。如果取模用的是没有涂粘结剂塑料的托盘, 印模材就单靠托盘的筛孔固位,当托盘从口内脱位时,容易产生脱模现象。因为不常规使用粘结剂,即使用金属托盘取模,脱模现像也会发生,而一旦发生脱模现象,需要重新取模而不能简单地把脱开部分压回复位。藻酸盐脱模现象可能被忽视为非关键问题而没有得到足够的重视。脱模是模型不准确的一个常见原因。
虽然不像藻酸盐脱模现象这么普遍,但是弹性完成印模材同样有脱模现象。取出托盘的时候要常规检查一下印模附着在托盘的情况,可以减少最终修复体的误差。

托盘藻酸盐后缘过长摆放在桌面上(形成误差)

没有托盘承载的藻酸盐会下沉,给患者取模型时选用尺寸和牙弓不符合的托盘就可能导致大块的藻酸盐无托盘承载而发生形变。此外,在取模完成后,医生往往将带有溢出托盘边缘的藻酸盐印模膏往桌子一放,导致没有托盘承载的藻酸盐受压变形。理想的情况应该将托盘放置在树状架子上消毒和灌模,这样模型就不会像摆放在平面的桌面那样受影响变形。(图七)

Pouring casts on time

Certain impression materials, such as reversible and irreversible hydro-colloids (alginate), must be poured promptly after making an impression, or rapid distortion occurs. After disinfection of either impression material, a cast should be poured immediately. Failure to do so causes loss of water from the impression material. This loss of water distorts an impression and produces inaccuracies in the cast that affect the working dies for a fixed restoration or the articulation of the casts. It is important when using any impression material to read the manufacturer’s recommendations for the maximum time allowable before pouring the impression to reduce inaccuracies.

Casts have major blebs on occlusal surfaces affecting articulation

The majority of dental casts have ‘‘blebs’’ on the occlusal surfaces of the teeth. If they are large enough and go unnoticed, the articulation of casts can be significantly altered, leading to a false mounting of the casts. The occlusal surfaces of the teeth on the casts should be free of these blebs, which interfere with the proper relationship of the casts. After impressions are poured and before mounting the casts, the occlusal surfaces should be examined and freed of any major blebs that would interfere with an accurate intercuspation of the teeth.

Hand articulate whenever possible

In a fully dentate patient with good maximum intercuspation and a widely spaced tripod, the most accurate method of relating casts is by hand articulation. The use of an interocclusal record in such a situation can result in (1) the inability to accurately mount the casts due to the thickness of the recording materials (see Figs. 1 and 2), (2) wasted time, and (3) wasted material and, therefore, money.

Heels of the casts touch

Casts that are improperly trimmed may have interferences that make mounting difficult. One common site for this is the heel of the casts. Casts that extend too far posteriorly behind the retromolar pad and the maxillary tuberosity often interfere when the casts are mounted. Sometimes this goes unnoticed, especially when these extensions are preceded by edentulous areas. Touching heels prevents interocclusal records from fitting accurately to the casts and results in inaccurate mountings.

‘Mush bites’’

When a patient is asked to bite into a large amount of material, it is often impossible to determine whether their teeth are coming into contact with one another because the amount of material obscures the practitioner from visualizing good tooth contact (Figs. 8 and 9). In addition, when applying the material for this type of record, if part of it sets while the rest of it is dead soft, the accuracy is compromised. In general, interocclusal records should be made with a minimum of material between the teeth or applied to a record base.

及时灌模


有些印模材料比如可逆或不可逆藻酸盐材料要立即灌制模型,不然就会马上变形。消毒后就得灌模,不这么做印模材会脱水。脱水后灌制的模型就不准确,结果影响了代型的精确度在使用印模材之前仔细阅读厂家推荐的灌模说明书很重要,说明书会注明最短多少时间内应当灌模来避免误差。

模型合面有小瘤子影响咬合

绝大多数的齿科模型牙表面有小瘤子,如果瘤子够大又没有引起注意就会导致咬合偏移很多,上合架就不准。咬合表面不要留有小瘤子,模型在上合架前要仔细检查过,去除这些影响牙齿尖窝锁结关系的小瘤子。

只要可能就用手来固定咬合

如果患者牙列完整,牙齿尖窝锁结关系良好,鼎足分得足够开,最好对模型关系的方法是用手。而采用咬合记录则会因为咬合记录材料厚度的原因导致模型对不准,浪费时间,材料,钞票。

模型后端

模型没有修整好有可能造成上合架出问题,常见没有修好的部位是模型的后端。 模型太过延展超过磨牙后垫或上颌结节都会影响上合架。这在后端游离缺失的情况常有发生。过度伸展的模型后缘会导致咬合记录无法到位而造成上合架不准确。

大块咬合记录

如果患者咬过大块的咬合记录材料,因为记录材料太多医生就无法确定牙齿患者是否牙齿都接触到位。此位,咬过于大块的记录材料有的位置已经固化而有的部位还是柔软的,咬合精度会降低。总之,咬合记录材料要少用些。(图八图九)。

Mouth open during triple tray impression

When a patient bites into a large amount of impression material, the teeth frequently do not make contact. Triple tray impressions are notorious for this because it is often difficult to visualize tooth contact with the impression material in a patient’s mouth (Fig. 10). It may not be noticed until the dental laboratory pours the impression and mounts the casts that the patient had not closed completely. When using triple trays, it is essential that the practitioner runs the patient through the motion and discusses with them what it should feel like when they close down through the material. One should not assume that the patient would close all the way through the material without proper instruction. In addition, the teeth on the opposite side of the arch to be impressed should be examined, and contacts should be visualized between the teeth before making the impression. When the impression is seated in the mouth and the patient closes, the practitioner should re-examine these same tooth contacts to ensure that they are the same. If not, there is likelihood that the patient did not close correctly or fully through the impression material.

用triple 托盘做咬合记录牙齿不接触


. 患者咬合大块状的记录材料时牙齿往往是不接触的。名声不太好的Triple托盘做咬合记录就有这样的问题,因为医生无法确定患者的牙齿是否接触(图十)这个问题可能被忽视,等模型灌好上合架时才会发现患者没有完全咬到位。用triple托盘,医生要向患者告知,咬到位是什么感觉。不如此而指望患者咬合记录做好不太现实。咬合前要检查对合的牙齿和咬合接触的时候是个什么情况。当患者咬上记录材料后,医生需要再次检查咬合的情况是否一致,如果有出入,很可能就是患者闭合动作没有做好或者是没有咬穿记录材料。

Casts moved during articulation

When mounting dental casts onto an articulator, it is essential that the maxillary and mandibular casts be joined in such a way as to avoid any potential movement. Even in patients with good intercuspation, if the casts are not held immobile during mounting, any slight movement translates into some amount of discrepancy. There are multiple methods of mounting casts. The best method is the use of a combination of rigid sticks and compound or sticky wax (Fig. 11). The casts must be dry when using these materials to avoid any movement. Sticky wax placed directly onto the opposing teeth can also be used; however, when the sticky wax is removed, the teeth often break off the cast or are severely broken.

上合架的时候模型移动


上合架的时候上下颌模型要固定好不会产生移动很关键。即便是尖窝关系锁结很好的模型,没有固定好也会有微小移动而产生误差。有很多上合架的方式,最好的一种是用粘蜡固定硬木棒的方式。(图十一)使用时模型一定要干燥也可以用粘蜡直接固定模型对合牙齿,但是这样在分开上下颌模型的时候常常牙会折裂甚至模型严重损坏。

Using a second pour of your final impression

Most practitioners send their final fixed impressions to a dental labo¬ratory to be poured. The laboratory does the cast and die work and re¬turns the restoration to the dentist. An important and often overlooked service that the laboratory can provide is to pour a second unsectioned cast of the final impression. This second pour may be more accurate than the cast with sawed dies for adjusting the occlusion and the contacts. The dies of a working cast have some amount of mobility due to the pindexing system, a fact that makes getting perfect contacts difficult. In addition, the adjacent and opposing teeth on a stone cast invariably are abraded during restoration fabrication. Using a solid, unsectioned second pour allows the dental technician to examine the proximal and occlusal contacts achieved on the working casts and to improve these contacts when deficient before returning the restoration to the dentist for delivery. This step can reduce the number of returns of the restorations to the laboratory for the addition of proximal and occlusal contacts and can make delivery of final restorations easier and more pleasurable.

Materials for interocclusal records

The most commonly used materials for interocclusal records are the fast-setting elastomeric interocclusal registration materials or wax. Elastomeric materials such as polyvinylsiloxane are well suited for making interocclusal records where only horizontal stability is needed. However, their accuracy can be compromised if they are not properly trimmed. These records should be carefully trimmed to remove all areas of the record that contact soft tissues and the axial surfaces of the teeth. This is done to minimize the areas where the casts and the record touch, allowing the practitioner to visualize how the casts seat into the record and ensuring that the record provides only the horizontal support with the contacting teeth providing the vertical support. To assure accuracy, only cusp tips of opposing teeth should be registered in the material used. Excess material that flows on the axial surfaces of natural teeth invites error when repositioning the working casts in the registration. The following adage says it well: ‘‘In most instances, a minimal amount of registration material will give a maximum amount of accuracy.’’


灌制两付终模型

大多数医生把模型寄给技工中心灌制,技工中心灌模、做代型再完成修复体给医生。很重要的一点也是容易被技工中心忽略的一点是终印模灌制两付模型。因为钉道系统的关系,代型模型会有些轻微的移位造成完成完美接触比较困难,而第二付模型比分割过的代型模更精确更利于修复体邻面与合面的调整此外,在修复体制作过程中,邻牙和对合牙齿都不可避免地有磨损。利用第二付未切割的模型,技师可以检查邻接点和合面接触关系,如不到位,在修复体返回医生前可以再完善一下。这个环节可以减少因为邻接点和咬合关系不良造成的返工率,从而使得医技交流更简单,更舒心。

咬合记录材料

最常用的咬合记录材料是快速凝固的弹性记录材料和蜡。诸如硅橡胶类的弹性咬合记录材料很适合只需要水平向稳定性的咬合记录。但是,如果修整不妥,精确性就要打折。那些和软组织以及牙体轴面接触的部分都要修去。如此可以达到记录材料和模型最小范围内接触,医生可以检查牙齿的接触情况,那些具有垂直向稳定性的模型能确保咬合记录只提供水平向的稳定性。为准确起见,对合模的牙尖只要记录到尖部即可。材料多了只会增加误差。这话说得好“大多数情况下,最少的记录材料可以保证最大的精确度”

References
[1] Freilich   MA, Altieri JV, Wahle JJ. Principles for selecting interocclusal records for articulation of dentate and partially dentate casts. J Prosthet Dent 1992;68:361–7.
[2] Balthazar-Hart Y, Sandrik JL, Malone WFP, Mazur B, Hart T. Accuracy and dimensional stability of four interocclusal recording materials. J Prosthet Dent 1981;45:586–91.
[3] Fattore LD, Malone WFP, Sandrik JL, Mazur B, Hart T. Clincial evaluation   of the accuracy of interocclusal recording materials. J Prosthet Dent 1984;51:152–7.
[4] McGivney GP, Castleberry DJ. McCracken’s removable partial denture prosthodontics. 8th ed. St. Louis: CV Mosby; 1989.
[5] Warren K, Capp N. A review of principles and techniques for making interocclusal records for mounting working casts. Int J Prosthodont 1990;3:341–8.


 

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