Why Do I Need a Crown?
When teeth break, eg due to trauma or dental decay, there are various options we use to fix them.
If only a small amount of tooth has broken, or there is a small dental cavity, then a filling (direct restoration) can usually be used to fix it. We use materials such as resin composite and amalgam to do this.
However, if a large part of the tooth is missing, or there is a crack in the tooth, it may benefit from a crown or onlay (indirect restoration).
Before (top) and after (bottom) a crown.
Before (top) and after (bottom) a crown.
Crowns and onlays are restorations that are made in the dental laboratory, and then cemented or bonded onto the tooth. In order to fit a crown/onlay, the tooth needs to be carefully prepared into the right size and shape.
These dental models show the tooth prep (top) and the new crown (bottom).
The tooth preparation is different depending on the material used for the restoration (eg gold, porcelain fused to metal, lithium disilicate, zirconia, non precious metal) , and the type of restoration (eg full crown, 3/4 crown, 7/8 crown, onlay). There are so many options! It will depend on the specific tooth/situation as to which design the dentist chooses.
Gold crown
Porcelain fused to metal crowns
Zirconia crowns
During a crown prep appointment, the tooth in question is anaesthetised with local anaesthetic and carefully prepared. Water is used through the drill to keep everything cool, the dental nurses do a great job at aspirating this water away with the dental suction. It can sometimes be a bit noisy during this part.
Sometimes a rubber dam is placed to help isolate the tooth. This is a thin rubber sheet that is placed over the teeth. It is held in place by a small clamp. It can feel like a bit of a mouthful whilst it's being put on, but this only takes a few minutes. Once it's on you don't have to worry about your tongue getting in the way, and a lot of patients find it more comfortable as it keeps the water away and helps keep their mouth open.
The blue sheet is a rubber dam.
Once the tooth is prepared to the correct size and shape, a scan or impression is taken which is then sent to the dental technician. They create a crown that will only fit the particular tooth we have prepared.
Extra measurements can help get the crown fitting just right, such as using a facebow.
I like to take lots of photos before, during and after dental treatments. This is particularly useful for the technician to see the shade and mould of your teeth, so they can match the new crown to your natural teeth.
At the end of the appointment, a temporary crown is placed onto the prepared tooth. As well as protecting the tooth, it stops the adjacent and opposing teeth from moving into the space created, which would cause the final crown not to fit. It is therefore important to let us know if your temporary crown falls off, so we can replace it for you.
Crown prep appointments may seem more lengthy and complicated than you first thought, but all these precise measures we take allows a bespoke dental restoration to be fitted to your tooth.
Two old crowns (top) which weren't fitting properly and allowed decay to develop around the margins. New crowns (bottom) placed to fit better and match the other teeth seamlessly.