Post/Crown
In this section, we will cover:
- What is a post/crown?
- Why would I need one?
- What are the risks?
- What does the procedure involve?
What is a post/crown?
A post/crown is a type of dental restoration consisting of:
- a post which is cemented into the root canal and supports the core
- a core which provides the support for the dental crown, and
- a crown which covers the whole biting surface of the tooth and extends all the way down to the gum line
Why would I need one?
Post/crowns are used for root treated when there is not enough tooth left to hold a "conventional" crown in place.
They are usually used in single rooted teeth at the front of the mouth such as incisors and some premolars.
If your tooth has not been root treated but is too broken down for a filling or crown, your dentist may be able to save the tooth with a post/crown after completing root canal treatment. The other option would be removing the tooth. The gap can be left or replaced with a denture, bridge or implant. You can find out more about these options on your "dental treatments" page.
What are the risks?
Although posts increase retention in broken down teeth (i.e. they hold the restoration in place), they also weaken the tooth. For this reason, post/crowns are only used if there is no other option to successfully restore the tooth.
Other risks include:
- Post/crown falls out
This can be due to failure of the cement (or "glue") which holds the restoration in place. If this is the case, the restoration can be cemented back in without much trouble.
If it is interfering with your bite, the post/crown will need to be adjusted to reduce the chance of it falling out again.
If the reason for failure is decay around the margin, the decay will have to be removed and a new post/crown made if the tooth is still restorable. If the decay is quite extensive, it may not be possible to save the tooth. - Fracture of root
As the forces placed on the crown of your tooth are being passed through the post, there is a higher risk of the root fracturing. Removing the tooth is unfortunately the only option in these cases. - Failed root canal treatment
Sometimes a root canal treatment fails and you get recurrent infections around the tooth. It is much harder to perform a re-root canal treatment on a tooth with a post/crown as they can be difficult to remove. In some cases, surgical endodontic treatment (apicectomy) can be considered. This will require referral to an endodontist or oral surgeon. - Perforation
To place a post, the root canal must be widened using a drill. During this process, a hole (or perforation) can be made in the side of the tooth/root. Sometimes these can be repaired with special materials but the prognosis (outlook) of the tooth is reduced.
What does the procedure involve?
- Root canal treatment if the tooth is not already root treated
- Xray
Your dentist will need an up to date periapical xray (an xray which shows the crown and root of the tooth) to assess how far into the root they need to drill. - Preparing the root canal
Your dentist will first remove most of the root filling material, leaving 4mm at the tip of the root. This ensures there is a good seal preventing bacteria from entering the root canal space.
They will then use a series of special drills to widen the root canal.
The next stage depends on which type of post system is being used - custom made or prefabricated.
- Cementing post and core
A) Custom-made post
For a custom-made post and core, the dentist will place a plastic impression post in the widened canal and take an impression which is sent to the lab. The tooth is then temporised with a temporary post/crown until the labwork is returned.
The post/core is made by the lab and sent back to the dentist to cement into the tooth (this requires an extra appointment).
A custom-made post is often useful for canals which have an unusual shape where a standard post does not fit snugly.
B) Prefabricated post
For a prefabricated post and core, the dentist will cement a metal or fibre post into the widened canal and build up the core themselves, usually in a composite filling material. This means there is one less lab stage but you will spend more time in the dental chair whilst the dentist builds up the core in a filling material. - Preparing for the crown
The core is filed down to make space for the final crown and a new impression is taken and sent to the lab. A temporary crown is made to place over the prepared tooth whilst waiting for the labwork to be returned. - Cementing the crown
The dentist will check the fit of the crown and the appearance before cementing it over the post/core. They will then do a final check to make sure your bite is undisturbed.