Metal crowns and bridges – is there no alternative?
To make a crown the dentist needs to prepare the tooth, then take moulds of existing teeth, which the laboratory uses to construct the required shape. Crowns are therefore termed indirect restorations, since they are made outside the mouth and fitted at a later appointment.
Traditionally these restorations have always contained metal. To ensure that the crowns look as much like real teeth as possible, non-precious metal base is used and this is then coated with tooth-coloured porcelain to create a solid, durable structure with a convincing appearance. These are called porcelain bonded to metal (PBM) or porcelain fused to metal (PFM) crowns.
A great deal of research has been undertaken to identify metal-free alternatives to traditional PBM crowns and bridges. While porcelain jacket crowns have always been with us, these are prone to fracture under stress and were only used on front teeth in very specific cases. The ceramic materials we use today exhibit up to three to four times more durability than traditional porcelain and are also designed to reduce the risk of cracks developing. There is a huge array of options which have been extensively researched and, as with everything, the dentist needs to make a clinical decision about which material is best, as there are a number of factors apart from strength to consider.
Cost: the newer materials are undoubtedly more expensive. Laboratories require sophisticated machinery to process and shape these types of crown and this price is reflected in the cost of an all- ceramic crown. However, as market demand increases, the basic price falls, so the difference is substantially less than it was 10 years ago. Technological advances have now been adapted further to allow us to make a ceramic crown within the clinic in a single appointment on the same day, making the process far more convenient for the patient despite the additional cost.
Aesthetics: if the preparation and laboratory work has been carried out to a high standard then these crowns can appear almost identical to natural teeth, as they are translucent and reflect light beautifully to mimic the natural tooth. In addition, when compared to traditional PBM crowns, they have the added advantage of not having a metal margin at the gum line. Usually this margin is hidden at the time of fit but over time the gum line does shrink slightly and it has been found that those patients with wide ‘gummy’ smiles can sometimes need to have replacements fitted later, due to poor aesthetics.
Allergies: some patients develop allergies to the metal components and, even if this is not the case, they may have concerns about metallic restorations in their mouths. The all-ceramic materials are bio-compatible and non-allergenic and hence safe to use in every patient.
The best course of action – especially if you are worried about the possibility that metallic crowns and bridges might result in an allergic reaction – is to talk to your dentist about these newer all-ceramic materials to see what might be suitable for you. Due to the incredible advances in material science, there are very few clinical situations today where it is considered that we still require to use metal-crown or bridges.