Chapter 8 Gold crowns
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.
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.
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.
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.
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.’
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.
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.
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.
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.