8: Gold crowns

Chapter 8 Gold crowns

John Radford, Brian Stevenson

Chapter contents

Introduction 103
General considerations 103

Targeted history and examination 103
Sharing of information (for real consent) 104
Indications for full coverage gold crowns 104
Contraindications to full coverage castings 104

Absolute contraindications 104
Steps in tooth preparation for a gold crown 105

General considerations 105

Occlusal design 105
Whether or not to remove previous restorations before preparation for the casting? 106
Where to finish the gold crown preparation with respect to the gingival margin? 106
Burs and instruments 106
Allocation of time between performing basic preparation outline and refining the preparation 107
Has the use of adhesive cements relegated many of the traditional design characteristics to the archive? 107
Tooth preparation for gold crowns 107

Occlusal reduction 107
Axial reduction 110
Preparation/design characteristics specific to a three-quarter gold crown 112
Other castings 114
Making the provisional restoration 114
Impression taking 114
Recording the occlusion 114
Summary 114

Introduction

Are gold castings the Cinderella of advanced restorative dentistry? Anecdote would suggest they are excellent restorations; dentists often think that they are the restoration of choice but patients frequently state that the dental aesthetic associated with them is unacceptable. It should be borne in mind that the outcome for gold crowns may appear more favourable because dentists provide such restorations for patients they consider would benefit most; that is, patients are highly selected.

So why should dentists be competent in providing castings, particularly as the provision of densely sintered ceramic restorations are continually being refined? As health care professionals there is an imperative to discuss with the patient the advantages and disadvantages of all restorative options. Indeed, not doing so may result in consent being invalid. A carer’s role is to empower the patient such that they can decide how they wish their dental treatment to be advanced.

It is traditional to consider full gold crowns, three-quarter crowns or variations of such, and overlays separately. However, there is commonality between the provisions of such restorations. Such shared characteristics will be stated, but when there are differences, these will be identified. This chapter will exclude gold inlays and onlays which are discussed in Chapter 12.

General considerations

Targeted history and examination

These are central to offering the patient what is considered in their best interest. A history should identify the pertinent and ignore the trivial.

Sharing of information (for real consent)

Common to all aspects of treatment, it is important to discuss with the patient their history and examination findings, and to offer different treatment options. The patient should be given time to make an informed choice and contemporaneous clinical notes must be made of this process. If the treatment is of high impact, as is often the case with advanced operative procedures, the decision-making process and the agreed treatment approach should be confirmed in writing.

Indications for full coverage gold crowns

These are listed in order, the first being the most common:

• When a plastic restoration has a history of repeated failure within a short defined time interval (Figure 8.1A). This would include failed adhesive restorations used in the management of tooth wear.
• When difficulty has been experienced in placing a large direct restoration with an adequate contour, contact point and occlusal contacts.
• As a retainer for a fixed prosthesis (see Chapter 19).
• To minimize the real risk of tooth fracture, for example after endodontic treatment (Figure 8.1B). Many authorities consider that an overlay/onlay may be the most appropriate restoration for a tooth that has been root-treated.
• To include design characteristics to accommodate a metal-based removable prosthesis (Figure 8.2). Such an indication per se may be difficult to justify and the decision to crown the tooth will take other factors into consideration, such as its restorative status. The patient must be made aware that any oral health gain must outweigh the removal of tooth tissue and resources required to provide such restorations.
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Figure 8.1A The large restoration in the upper left first molar tooth has undergone repeated fracture. To place a direct restoration in this tooth with adequate contour and contact areas, would be clinically demanding.

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Figure 8.1B The lower left first molar tooth has reduced structural integrity and, as a consequence, the disto-lingual cusp has fractured. A full gold crown is indicated in order to preserve the remaining core and coronal tooth tissue.

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Figure 8.2 Full coverage gold crown on lower right second molar. A rest seat, mesial guide plane and mesio-lingual undercut have been created to optimize the success of the removable cobalt chromium prosthesis.

Contraindications to full coverage castings

Contraindications to providing such restorations include a lifestyle which adversely influences oral health; these are relative and can usually be overcome should the patient so wish. This must be supported by evidence of change such as quitting smoking, modifying the use of erosive drinks, dietary changes to reduce the frequency of sugar consumption or improved home care. Other ‘dental’ contraindications such as ‘active’ caries, ‘active’ periodontal and periradicular disease have been discussed in Chapters 1–3.

A targeted preventative and preparatory phase is at the heart of a treatment plan which includes the provision of successful laboratory fabricated restorations. If this has not been carried out as part of the treatment plan, apart from the dentist not discharging their moral and statutory covenant/contract, a prosecuting barrister may claim, for example: ‘My client would not have consented to this crown if they had been informed beforehand of the subsequent necessity for endodontic therapy…or regenerative periodontal procedures etc.’

Partial coverage castings may be the restoration of choice in certain circumstances. For example, if full coverage preparation removes the bulk of the remaining tooth structure.

Absolute contraindications

These are few. Systemic sclerosis could be such an example as the patient may not be able to open their mouth sufficiently to receive such treatment. Profound xerostomia would also be considered by some to be another absolute contraindication but this has to be balanced against the alternative treatment of repeat restorations and loss of function. Another would be if the patient was fearful (dental anxiety). However, supportive therapy may facilitate them receiving such treatment.

Funding and access to health care should never be a contraindication.

Steps in tooth preparation for a gold crown

General considerations

Occlusal design

• Conformative or reorganized occlusion. The dentist can elect to adopt a conformative approach or to reorganize the occlusion. A conformative approach is when the patient is given the same occlusal configuration after the fitting of the restoration as when they attended for the preparation; the occlusion remains unchanged. A reorganized approach is when the relationship between the maxilla and mandible is changed by the gold crown/prosthesis. This approach is usually adopted when most or all of the occluding teeth are to be restored in complex full mouth rehabilitations. In this section, only a conformative approach will be described.
• Incisal/canine/anterior guidance. It may be considered more useful to tease this subject apart by considering disclusion of teeth in excursive movements as opposed to occlusion. If the patient has incisal/anterior guidance, the focus will be on establishing a maximum number of bilateral occlusal contacts in maximum intercuspation (ICP). In excursive movements the posterior teeth will disclude and occlusal contacts between posterior teeth will not pose a problem (see Chapter 6). Some authorities suggest that if the patient has incisal/canine/anterior guidance, bodily side shift of the mandible (Bennett movement) is minimized.
• Group function. If the patient demonstrates group function, all excursions must be accommodated by the gold crown. Some consider that refinement of the occlusion will be necessary when fitting the casting. This is because Bennett movement (bodily movement of the mandible) is difficult to accurately transfer to an articulator (see below).
• The occlusal table. Traditionally, the occlusal table of the restoration is punctuated by fissures and is highly polished. There is no evidence that creation of an intricate fissure pattern has any beneficial effect on function. This is not, however, to denigrate the gnathological approach that had its zenith with full mouth rehabilitations placed on natural teeth (these are beyond the scope of this chapter). The most logical approach is one based around function. A sandblasted occlusal surface will pick up articulating paper marks more readily than a polished surface and it is often useful to prescribe this to the dental technician. If the patient prefers a polished surface, however, the casting can be polished once the occlusion has been checked and adjusted if necessary.

Whether or not to remove previous restorations before preparation for the casting?

This will depend to a degree as to why the casting is being prescribed and the predicted future integrity of the restoration. Some would assert it is good practice to remove all previous restorations and bases and then replace them with an adhesive core before preparation for a casting. This would avoid embarrassing loss of the restoration during preparation. Others would consider resources could be more productively spent giving oral health messages and a more pragmatic approach would be to carry out the preparation incorporating the existing restoration(s) as the core. If these remain intact and the dentist’s intuition is that they can support an indirect restoration, then refrain from placing another core. Advocates of this approach highlight the fact that trauma to the pulp is cumulative and that each time a restoration is replaced more tooth tissue is lost. The final decision as to whether to replace the existing restoration and place a new core will need to be made on an individual basis in consultation with the patient.

Where to finish the gold crown preparation with respect to the gingival margin?

There is an enduring tension between engaging as much tooth structure as possible and encroaching on the gingival domain. In the former case this is performed for reasons of retention and resistance; however, the disadvantage of encroaching on the gingival tissues is that an environment is created in an important area that is unfavourable for the patient to maintain plaque free.

Unequivocally, all restorations should be finished on tooth tissue. The reasons for finishing on tooth tissue are to remove any ledges created by the core and to restrict potential leakage to only that between the casting and tooth.

Burs and instruments

In this subsection, only selected areas will be discussed. In the UK it is conventional to prepare teeth for crowns and bridges using medium-grit diamond burs (Figure 8.3). This is in contrast to other countries where tungsten carbide burs are more commonly used. There is no clinical evidence to show that preparations cut with one or another type of bur result in restorations with a superior outcome.

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Figure 8.3 Typical crown preparation bur kit. Finer-grit diamond burs (right two) are used to finish the preparation.

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Related posts:

  1. 3: Endodontic problems in advanced operative dentistry
  2. 2: Periodontal disease
  3. 1: Management of dental caries
  4. 11: All-ceramic crowns
  5. 15: Getting the appearance correct
  6. 6: Occlusion

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Jan 9, 2015 | Posted by in Operative Dentistry | Comments Off on 8: Gold crowns

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