A crown is cap placed over the whole visible part of your tooth. With crowns, we can change the shape of a broken or malformed tooth as well as the colour of teeth which have darkened following a root canal or old endodontics treatment, or perhaps due to a metal filling which has darkened your tooth.
Prosthetic crowns also enable us to reconstruct badly damaged teeth, whether or not they have been devitalised. These are caps which cover the remaining part of you tooth to hold it in place, while re-establishing its shape and function
In devitalised teeth, the crown must be anchored to the root with a post or abutment in metal or other materials, such as carbon fibre. Said post is packed in with composite or white filling to form the stump that we will later cover with the crown. Sometimes only the devitalised root is left; in this case, we make a metal crown with its corresponding metal post in a single piece, all covered with a porcelain cap. This is known as a Richmond crown.
The crown process
At the first appointment:
We will start by sculpting your tooth as required to receive the crown, made in a certain shape and to sit at just the right angle. If your tooth has been devitalised and has only a small crown, or if it has an enormous filling, we will insert a post to the root.
There are two ways to fit a crown:
- Directly: we extract part of the devitalisation material from the root and insert the post, cementing it or fixing it in place with adhesive and using composite to reconstruct the stump onto which the crown will be fitted.
- Indirectly: here we also extract part of the devitalisation material and take a silicone impression or mould of the root cavity which is then sent to the laboratory, where they will produce a customised post and stump, known as a false stump, which we will subsequently cement into the root cavity.
Once the tooth stump is ready, we take a silicone impression and send it to the prosthetics laboratory. We also carefully note the colour and shade to ensure that the crown will match the teeth next to it and not look false. Finally, in the surgery, we will prepare a provisional resin crown to protect the sculpted tooth, maintaining the appearance and function of your tooth while the permanent crown is being made at the laboratory.
At the second appointment:
We try the crown to make sure that it fits properly all the way round the stump, checking that the colour and shape match the neighbouring teeth. Its bite against the teeth opposite it must also be perfect, since knocking against one another could cause your crown to become loose with time. Lastly, we cement the crown in place, and you go home happy and satisfied.
Types of crown
Resin or provisional crown
Protects your tooth and maintains its appearance during the two to four weeks required to produce the permanent crown, meaning that you can smile confidently and speak naturally.
You’ll have to be careful not to eat very ‘hard’ food during this time.
These crowns must not be used for more than two to three months, the time sometimes required following a tooth extraction while waiting for the wound to heal.
With time, the provisional crown will become porous, allowing germs to enter, while food pigments will cause it to darken; furthermore, with reabsorption of the temporary cement used to fix it in place, the crown may come loose and even break, meaning that you could swallow it without realising. The tooth beneath the provisional crown could also experience decay in the areas where the cement has come loose. Provisional crowns cannot be used as a permanent crown.
This kind of crown is composed of a metal structure covered with porcelain in the same colour as your surrounding teeth. This is the one we use most often. The metal structure makes it very strong, which is why it is also used in conjunction with other crowns to form a fixed bridge in cases where you are missing one or more teeth.
The interior metal layer gives the crown a degree of opacity to conceal a darkened underlying tooth or metal stump inserted to strengthen the tooth in question. It is very important for the ceramic to be of high quality, to exactly choose the colour we wish to reproduce for a natural result, and to have the crown made in a good laboratory.
This is a variation of the porcelain-fused-to-metal crown. It is used when only the devitalised root of a tooth remains and involves making a metal post which we insert into the cavity, as well as a metal stump and porcelain cap to surround the complete visible part of the tooth.
Full porcelain crown
This is used above all in the front teeth. It is slightly translucent, meaning that it gives your tooth an attractive natural colour. The underlying tooth must have the same colour as those on either side. This crown is rather fragile, and is not recommended for bridges or back molars, unless the bite is highly favourable.
Zirconia is a white and slightly translucent metal, depending on the type and quality of the zirconia used. It is used for front crowns and bridges, when the colour of the underlying tooth is rather pale. It isn’t as strong as the porcelain-fused-to-metal crown, meaning that its use is not advisable for long bridges or back molar crowns.
At our surgery, we will advise you on the type of crown best suited to your aesthetic and functional requirements.