Getting a Root Canal Through a Zirconia Crown

Written & Reviewed by Dr David Chen

You were just told that you needed a root canal but the tooth that needs it already has a zirconia crown on it. We can imagine the questions that are running through your mind.

bilayered zirconia crowns
Credit: Glidewell

Could you do the root canal right through the crown? Or do you need to remove it before you can get the treatment done? Lastly, does the entire tooth cap need to be replaced once it is all said and done?

Let us answer all of that for you.

Can you get a root canal through a zirconia crown?

Of course you can get a root canal straight through your zirconia crown and we see this in clinical practice on a daily basis. It is quite easy to spot these because you’ll see a zirconia crown with a filling on the occlusal surface.

Zirconia crown with hole drilled through top for root canal access

The reason there is a dental filling there is because someone drilled through the top of it and repaired it afterwards. Then if you look on the x-ray, you’ll see evidence of a root canal being done. Therefore it is certainly more than possible to get this done, it’s just that having the crown on does make the procedure more difficult.

Root canal through crown - before and after x-rays
Before and after x-rays of root canal through a crown

Increased difficulty and complexity

Your dentist can drill through anything they want, enamel, dentin, fillings, and crowns. The only caveat with trying to do the root canal while the tooth has a zirconia crown on it is that it makes it more difficult. The ceramic material throws off the apex locator’s reading in finding the working length.

working length of tooth diagram
Credit: Garg Nisha, Garg Amit

The purpose of a root canal is to remove the tooth’s nerve but there are steps which need to be completed before it can be done.

  1. Create an access opening. Drill a hole through the top of the tooth until it reaches the pulp chamber. This is how you create an access to the nerve.
  2. Measure working length. Before your dentist can remove the nerve and clean out the canal, they must measure the working length (WL). The WL is basically the distance from the occlusal surface (chewing surface) to the tip of the root. Having a measurement ensures that you clean out the tooth from tip to tip. If your working length is short, you may be leaving a portion of the infection behind.
  3. Remove tooth nerve. Once you’ve the WL you can finally clean out the tooth!

The issue with working through zirconia is that the apex locator which is used to find the WL gives off errors whenever it touches the ceramic. The zirconium dioxide conducts some of the electrical currents and that results in a false reading. In order to get an accurate reading, you must prevent the file which is attached to the locator from touching the ceramic.

Alternatively some dentists also wrap their file in PTFE. That prevents the locator from giving off false readings. Nonetheless, it is something that could be worked around so it isn’t the end of the world.

Do you need a new crown afterwards?

A frequently asked question is if you need a new crown after doing a root canal through it. The answer is that it depends on a couple of factors. You may be able to keep your old one and put a filling in it or you may need to replace it with a new zirconia crown.

Nonetheless, when in doubt the best thing to do is to get a new one but we understand that cost is a factor in the decision making process. Therefore, we’ll try to give you some guidance as to when you may be able to salvage your old tooth cap.

Factors to consider if you need a new crown:

  • How old is it?
  • How big is the access opening?
  • Is tooth decay present?
  • Are finances a consideration?

When did you get that zirconia crown done?

An important factor to consider is how long you’ve had that crown. Is it brand new or has it been in your mouth for a decade already?

  • New. If you’ve only recently had the crown done then that would be a reason to not replace it. The chances of it being defective or decayed are fairly low.
  • Old. If you’ve had it for a long time now, perhaps it is time to get a new one. After all, nothing lasts forever except diamonds right? After a few years, sometimes the color is off or maybe there are chips on the porcelain. Those are all good reasons to have it replaced.

Is the root canal hole big or small?

In order to do a root canal through it, a hole must be drilled through the top of the crown. Was the root canal specialist able to make a small hole or was a big one required?

  • Small hole. A small access opening would mean that most of the structural integrity of the restoration should be intact. The smaller it is the better the prognosis.
  • Big hole. If a big access opening was required it may be better to get a new crown. There is a greater likelihood of the structural integrity being compromised from a large hole.

Is there a cavity underneath the crown?

Sometimes during the root canal, undetected decay can be found. If that is the case it would be prudent to remove the entire crown in order to see what else is going on in there. The presence of decay means that there could be more elsewhere underneath the cap.

It is impossible to visualize the entire tooth underneath simply through the access opening of a root canal. In this case, it would be best to take it off and get a new one once it’s all done.

Is money an issue?

If you never budgeted for emergency medical treatment then our recommendation would be to take the three factors above into your decision. However if money is no issue, the best thing to do would be to get a new zirconia crown.

It’s a no brainer that a fully intact crown is more structurally sound than one with a hole through the top of it. Even though it is filled back in with a composite resin, that access opening does decrease the prognosis.


Yes, it is possible to do a root canal through a tooth with a zirconia crown on it. It does make the procedure a bit more difficult but your dentist can still work around it.

The tough part is deciding what to do afterwards such as whether or not you should replace the crown. We’ve provided a couple of factors to take into consideration in making the decision but you can always discuss with your dentist.

If you need a brand new zirconia crown, the process would be a repeat of what you had to do the first time.


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