Root canal treatment on a tooth that already has a crown
A crowned tooth can usually be root treated through a small opening in the crown. When the crown has to come off instead, and what happens to it afterwards.
Reviewed by Yiğit Bal, dentistWritten in Turkey by a dentist. Klinikle is a clinic directory, not a clinic — no practice pays to appear here, and we do not provide treatment. Where a page compares Turkey with treatment at home, read it knowing where it was written.
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A tooth with a crown on it can have root canal treatment, and the crown does not always have to come off. In most cases the dentist makes a small opening through the biting surface of the crown, or through the back of it on a front tooth, cleans and fills the canals through that opening, and then seals it. Whether the crown stays or goes depends on the state of the crown and of the tooth underneath, and it is a decision worth understanding before the drill starts.
The signs that point to the nerve
On a crowned tooth the warning signs are the same as on any other: sensitivity to heat that lingers after the drink has gone, a throbbing ache that starts on its own and keeps you awake, pain when you bite, or a small pimple-like swelling on the gum near the root. Sometimes there is nothing at all, and the problem shows up as a dark area at the tip of the root on a routine radiograph. A crowned tooth that has gone quiet is not necessarily a healthy one. The decision is made from an examination and an X-ray, never from symptoms alone.
Through the crown, or with it removed
| Opening through the crown | Removing the crown first | |
|---|---|---|
| Usually chosen when | The crown is sound, fits well at the edge and there is no sign of decay under it | The margin is poor, there is decay beneath, or the crown was due for replacement anyway |
| What it gains | The crown is kept; no temporary, no remake | The whole tooth can be seen, so decay and cracks are not missed |
| What it costs | A narrower view of the inside of the tooth | A temporary crown in between, then a new permanent one |
There is a further practical wrinkle. Crowns are sometimes made at a slightly different angle from the root beneath, to line a tooth up with its neighbours, and then the obvious entry point through the crown does not lead straight down the canal. The dentist uses the radiograph to plan the direction. Where the canals are very narrowed, or cannot be located through the crown, removing it may be the safer route.
Removal can also be a finding, not a plan. A dentist who opens through a crown and discovers decay spreading underneath will normally stop and discuss taking the crown off, because root filling a tooth that is decaying under its crown only postpones the problem. How that develops without symptoms is in decay under a crown.
Zirconia is hard to drill through
Zirconia is an extremely tough material, and cutting an access hole through it takes time and specific burs. While that happens, fine cracks can form within the crown, and on layered zirconia or porcelain the outer layer can chip around the opening. Most of the time the crown survives intact. Sometimes it does not, and the dentist should raise that possibility with you beforehand, not afterwards: if the crown is damaged during access, it will need replacing. Lithium disilicate and older metal-ceramic crowns carry their own versions of the same risk.
This is one reason a dentist may prefer to know exactly what the crown is made of before starting. Monolithic and layered zirconia behave differently under a bur, and a crown made abroad is a closed book unless your records say what it is. What your records should include lists the details worth having on file. If the crown does chip, a chipped or cracked crown sets out the repair options.
Sealing the opening
Once the canals are filled, the access hole is closed with a bonded filling material that adheres to both the crown and the tooth. That seal matters more than people expect. Bacteria getting back in through a leaking access filling are one of the main reasons root canal treatment fails, so a well-sealed opening is part of the treatment and not a cosmetic finish. If the work is spread over more than one visit, a temporary filling holds the opening closed in between, and that temporary should not be left for months.
Does the crown need replacing afterwards?
Not always. If the opening is small, the margin of the crown is sound and the access filling is well placed, the same crown can go on doing its job for years. A replacement becomes likely in three situations:
- The crown cracked or chipped while the opening was made.
- Decay or a gap at the margin was found during treatment.
- So much of the tooth had been lost that it needs a new core, sometimes with a post, and a crown made to fit that.
When the crowns were made in Turkey
Two questions come up that would not arise if the crown had been made down the road. The first is the guarantee. Drilling through a crown, or removing it, is exactly the kind of work by another dentist that some guarantees exclude, so if the crown is recent it is worth writing to the original clinic with the radiograph before treatment, asking whether they want to be involved and whether the guarantee survives. In a genuine emergency, though, the tooth comes first and the paperwork second.
The second is why the tooth needed a root filling at all. A nerve that dies a year or two after a healthy tooth was prepared for a crown is a recognised risk of heavy preparation, particularly when many teeth were prepared in one visit, and root canal on a healthy tooth explains why it happens and why it tends to arrive after you are home. If one crowned tooth has lost its nerve, it is reasonable to ask your dentist to check the others on the next radiographs.
If the tooth turns out to be too damaged to keep, even with a root filling, the choice shifts to what replaces it, and keeping a tooth or choosing an implant is where that is weighed up.
This page is general information, not medical advice. Outcomes vary between individuals and suitability can only be established after an in-person examination and imaging by a qualified dentist.
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