What is a crown?
A crown is a cap placed onto a heavily broken down or misshapen tooth that has been carefully prepared by a dentist. It acts to restore the function and appearance.
A crown can be made out of a variety of materials. These include:
⦁ Porcelain fused to a metal backing
⦁ Metal (often gold alloys)
Porcelain crowns are very aesthetic and closely resemble a natural tooth. These are often desirable at the front of the mouth on teeth that can readily be seen when speaking or smiling. Metal crowns are commonly found at the back of the mouth, where appearance is less of a concern.
When would a crown be needed?
There are many instances where a crown might be placed.
Heavily broken down teeth may require a crown. This is because the remaining tooth structure may not have enough strength to support a direct filling material, whereas a crown would fit on top of the tooth. This would then restore the original shape of the tooth meaning it can function normally again. A crown would also reestablish the appearance of the broken down tooth.
If a tooth, especially at the back of the mouth, has been root filled a crown may be an appropriate treatment option. Teeth with root fillings are weaker and therefore may require additional protection from fracture, which a crown offers.
As crowns can be very aesthetic and resemble the rest of the teeth, they can also be used to replace discoloured or malformed teeth in some instances.
At the initial appointment the dentist will decide if a crown is an appropriate treatment option. Factors such as active gum disease and poor oral hygiene are contraindications for crowns so it is important to maintain a good cleaning regime to be suitable for the treatment. It is also essential there is no infection present around the root of the tooth so an x-ray is taken prior to the treatment.
How are crowns made?
Having a crown made will require more than one dental appointment.
⦁ The first stage is to prepare the tooth. This involves the dentist carefully drilling the tooth structure so there is:
⦁ Enough space for the crown to fit
⦁ A suitable shape of the tooth to retain the crown in the mouth
⦁ The next stage is to make a copy of the tooth to send to the laboratory technician who will construct the crown – taking an impression does this. A bit of cord (retraction cord) may be placed around the tooth to push away the gums to make sure the impression material captures the entire tooth. This cord is removed before the end of the appointment.
⦁ During the time it takes for the laboratory to construct the final crown, a temporary can be placed over the prepared tooth. This will restore the function and appearance of the tooth as the prep is much smaller than a normal tooth. A temporary can be made at the chair side or already come preformed. It is bonded to the tooth and removed by the dentist at the next appointment.
⦁ Once the crown is made, the final step is to cement the restoration into place. The dentist will decide the most appropriate material to do this based on the shape of the tooth and material of the crown.
Are there any risks?
Preparing a tooth to have a crown fitted is quite an invasive procedure as it involves a lot of drilling. There is therefore a risk of the nerve within the tooth becoming damaged.
Having a porcelain crown rather than an all metal restoration requires a greater amount of tooth to be drilled away so the tooth is left slightly weaker.
Dental work does not last forever and this includes crowns. Although crowns can last for many years it is important to remember the restoration may fail in the future.