Preformed Metal Crowns
In this section, we will cover:
- What is a preformed metal crown?
- Why do I need it?
- What does the procedure involve?
- What are the risks?
- How long will it last?
- What other options are there?
What is a preformed metal crown?
A preformed metal crown is a metal cap used to treat decayed or broken down baby molars (back teeth). They are are shiny and silver in colour and they cover the whole of the tooth. It is a great alternative to a dental filling as it usually does not require any drilling or numbing injections. And on top of that, they usually last longer than a normal dental filling!
A preformed metal crown is also known as a stainless steel crown. When explaining it to children, we may refer to it as an "iron man helmet" or a "princess crown" which protects the tooth.
Why do I need it?
Metal caps are usually used to treat decayed baby molars. They are also used for teeth with weak enamel due to developmental defects (i.e. where the tooth has not formed properly).
A metal cap will not be placed on a tooth where the decay has spread into the nerve of the tooth (unless treatment has been carried out on the nerve) or if the tooth is close to falling out naturally. An xray is useful to find out how deep the decay has spread into the tooth and whether the tooth is close to falling out. We expect baby molars to naturally fall out between 8-11 years old but every child is different and some may lose baby teeth earlier or later than others.
What does the procedure involve?
It usually takes two visits to place a metal cap.
Visit 1:
At the first visit, small elastic bands are placed between the teeth using dental floss or special tweezers. This pushes the teeth apart slightly to make space for the metal cap. It feels like a piece of popcorn is stuck between the teeth, but most children will get used to this feeling by the next day.
Visit 2:
A few days later, the elastic bands are removed and the metal cap cemented on. Once the dentist has found the right size, the metal cap is cemented onto the tooth simply by pushing the cap on and asking your child to bite down to make sure it is covering the tooth completely. The excess cement is cleaned up with some cotton wool or gauze. Metal caps come in ready-made shapes and sizes so your dentist may have to try a few out for size before finding the one which fits the tooth best.
Research has shown the success of metal caps with and without removing the decay are very similar. This means decayed teeth can usually be treated reliably without the need for drilling or numbing injections, making it a great option for young children. The metal cap "seals in" the decay and essentially starves the bacteria of any food, causing the decay to slow down and eventually stop. This is known as the "Hall crown" and is named after a Scottish dentist (Dr Norna Hall) who spent 15 years perfecting this technique.
What are the risks?
It can be a bit uncomfortable for the first day or two after the elastic bands and the metal cap are placed. If needed, you can take some painkillers to help with this.
When first put on, the metal cap will look and feel high to bite on. It will normally take just a few days for your child to get used to this feeling and another couple of weeks for the bite to adjust and the teeth to come together again. If your child needs multiple metal caps, your dentist will avoid placing caps on opposing at the same visit as this can be more difficult for your child to get used to. They will choose to do metal caps in the same arch (i.e. top OR bottom teeth) or diagonally opposite (i.e. bottom left and top right or vice versa). This avoids "opening up the bite" so much.
In some cases, the cap may fall out. If this happens, the same cap (or maybe even a slightly smaller one) can usually be cemented back on.
Although metal caps have been shown to be extremely successful, there is still a small chance that decay will continue to spread beneath the cap. If this happens, your child may get toothache or a dental abscess. In the very few cases where this happens, the tooth will need to be removed - you can find out more about dental extractions here.
Occasionally, it won't be possible to find a metal cap which fits your child's tooth. In these cases, there are two options:
- Modified Hall Crown:
The tooth can be adjusted slightly with a dental handpiece (a numbing injection is sometimes needed for this) to make it the right shape for a metal cap. - A dental filling:
The tooth can be cleaned and filled - if the decay extends deep into the tooth, a numbing injection is usually needed to make the cleaning process comfortable.
Metal caps placed on the very back baby molars (second baby molars, or - in dental speak - the "E"s) can sometimes prevent the first adult molar from erupting (pushing through the gum) properly. This tends to be more of a problem for the top teeth. Your dentist will monitor these teeth and if the metal cap is stopping the adult tooth erupting, the metal cap should be removed.
How long will it last?
97% of baby molars treated with a metal cap will last for over 5 years.
What other options are there?
Dental fillings are another option for treating decayed teeth - these fillings are white in colour. Fillings generally require a numbing injection and drilling to remove the decay before placing the filling.
If there is a large hole in the tooth, fillings do not protect the tooth as well as a metal cap. We think of teeth as being made up of 5 surfaces - if more than 2 of these surfaces are affected by decay, metal caps are usually a better option than a dental filling. Decay is more likely to spread beneath a filling and they are more likely to fall out.
Another option to manage holes in baby teeth is silver diamine fluoride (SDF). This is a relatively new treatment in the UK but has been used safely across the world for many decades. It is a very good option for children with limited cooperation at the dentist as it simply involves painting a liquid onto the decayed teeth. The aim of SDF is to prevent holes getting larger.