Can You Do a Root Canal Through a Crown?

As a busy dentist in private practice, I get some variation of the “can I get a root canal on a tooth with a crown” question quite frequently. The question comes in various forms, but the general summary is something like this:

“I got a crown done about three years ago. Everything was fine until a week ago, and now it feels like it is on fire. I think I need a root canal. Can you do a root canal through a crown?”

The answer to this question is yes (most of the time).

Why Teeth Need Root Canals

Before we describe why/how a root canal is done through a crown, it is important to know why teeth sometimes need root canals.

tooth with cavity needing a root canal

This tooth had a large cavity. The brown spot visible in the photo is the decay. On subsequent removal of the decay, the nerve became inflamed, and the tooth needed a root canal.

A tooth needs a root canal when the nerve inside the tooth becomes inflamed or infected. This can be due to several reasons, including:

  1. Dental decay (a.k.a. cavity) that either comes close to or enters the nerve of the tooth.
  2. A crack or fracture of the tooth where the nerve become exposed.
  3. A large restoration (filling) placed very close to the nerve. The filling is done due to the presence of decay and/or cracks (as talked about in points 1 and 2 above). Note it is not the filling that causes the need for the root canal, but rather the decay and/or fracture.
  4. Trauma to a tooth in which the nerve is injured.
  5. Other more infrequent causes (internal resorption, external resorption, jaw cysts, metastatic malignancies which enter the jawbone, etc.)

Generally speaking, reasons 1, 2, and 3 are the causes for 99% of all root canals.

What is a Root Canal?

Describing a root canal is not the point of this post. But a general summary can be presented.

Root canal access cavity

View of a cleaned out nerve chamber of a lower tooth as seen from directly above the chewing surface. The 3 holes are entry points to 3 separate canls.

In a root canal, the infected and/or inflamed nerve tissue inside the tooth is cleaned out and then filled with a special filling material. We do this by drilling a hole from the top of the chewing surface of the tooth into the nerve chamber. In the photo above, you can see the large hole in the tooth which leads down and exposes 3 smaller openings or orifices. These are the openings to the canals of the tooth.

In a root canal, the roots of the tooth remain. They are not removed. By having a root canal done, you are able to keep a tooth that might otherwise have to be extracted.

How a Root Canal is Done Through a Crown

A crown, often called a cap, is a custom fabricated restoration comprised of metal and/or ceramic that covers the top of portion of the tooth. Crowns are done for many reasons, but they are mostly done to protect a tooth that has been compromised by decay and/or fractures.

When a tooth with a crown needs a root canal, you can expect the following sequence:

  1. You will be given local anesthetic so that your tooth is totally numb (and other parts of your mouth too).
  2. A rubber dam will be placed over the tooth.
  3. A small hole will be drilled through the crown into the tooth and into the nerve chamber.
  4. Then the dentist is ready to begin cleaning out the infected and/or inflammed nerve.

Before and after photos showing a root canal through a crown. In the left photo, you see the procedure in process with the rubber dam and access into the nerve chamber. The right photo shows the completed procedure with a filling sealing the access hole. The crown is saved! Photos and dentistry Dr. Nicholas Calcaterra.

In nearly all cases, the root canal is done through the crown, the access is sealed, and then everything goes back to normal.

When Saving the Crown is not Possible

In some cases, doing a root canal through a crown and keeping that crown is not possible. This can happen for a variety of reasons. Some of them include:

  • The decay – which caused the need for a root canal – is so advanced that a new crown is needed.
  • A large piece of porcelain broke off during the procedure so that the crown is no longer functional.
  • A root fracture of the tooth was discovered during the procedure and the tooth must be extracted.

The above list is not comprehensive but covers many of these situations.

In all cases, your dentist or endodontist should discuss with you the likelihood of you keeping the same crown after the root canal procedure.

What Does a Cavity Under a Crown Look Like?

As this blog approaches nearly 3 years of age and well over 150,000 views, I am able to see what the more popular dental topics are out there. Currently, the fourth most popular post on this site, clocking in with a little more than 19,000 views (as of July 2015), is Dental MythBuster #9: You can’t get a cavity under a crown.

In analyzing what people search for online, many readers – hundreds that is – searched for some variation of: what does a cavity under a dental crown look like?

I had just finished compiling this information when a long time patient of mine – one who I had been telling for several months now about decay under one of her crowns – called to finally schedule her extraction.

Photos and X-rays of Cavities Under a Crown

In this particular case, the decay was so deep that her only option was extraction (see below for why extraction was her only options). Below is a bitewing x-ray:

dental bitewing x-ray showing decay under a crown

The x-ray shows the definite shadow of decay underneath a crown.

I had first diagnosed this nearly a year ago primarily based on the x-ray. In this area of the mouth – the last tooth on the lower left – the cheek drapes up against the tooth – making it very difficult to see – and very difficult to brush!.

I then removed the tooth. And no, I did not put my knee on her chest! The decay was unmistakable. Upon completing the procedure and having the patient go home, the first thing I thought was: “this will make a great photo for my blog!” So here it is:

high quality detailed photo of extracted tooth with decayed cavity under a dental crown

The extracted tooth in all its glory. If you dare, you can click on it to see a larger version!

You can clearly see the decay on this crown when it is out of the mouth. However, when it was in her mouth, it was nearly impossible to see. It could only be “felt” with a dental instrument. But the x-ray showed it.

Why was the tooth extracted?

If you get decay underneath a crown, it doesn’t always mean that the tooth has to be extracted. Before I explain why this was extracted, let’s look at one where the tooth was able to be fixed:

high quality photo of a cavity under an incisor crown

The decay underneath this crown was predictably fixed with a new crown.

The tooth directly above could be saved because the decay was easily accessible and only extended slightly underneath the gum tissue. The tooth had already had a root canal.

For the first tooth, the decay extended deep underneath the gum tissue and went into the furcation (the furcation is where the two roots of two-rooted tooth meet). No amount of modern dental procedures could have saved the tooth. So we extracted it and placed a dental implant.

Please note that I have greatly simplified the criteria for when a tooth can be saved vs. extracted. There are dozens of other factors – all beyond the scope of this post.

So, to summarize:

  • You can get decay or cavities underneath a crown.
  • The extent and location of the decay as well as other factors will dictate the treatment needed to correct the problem.

As always, your dentist should answer all your questions. If he/she doesn’t, it’s time to look for a new one.

I’ll take the dental crown without formaldehyde please

OK. I will admit it. I chose this provocative title to get your attention.

formaldehyde is a toxic chemical and carcinogen

Formaldehyde has not been found in dental crowns but many other toxic chemicals have.

Nearly everyone has heard the news surrounding Lumber Liquidators and the flooring containing elevated levels of the chemical formaldehyde. Formaldehyde, a known carcinogen, was found in flooring manufactured in China and sold by Lumber Liquidators.

Understandably, people do not want to live in a home where there might be elevated levels of formaldehyde. But did you know that tens of thousands of Americans are walking around with crowns and dentures in their mouth that were made in China with possible toxic chemicals?

Toxic Chemicals in Dental Crowns from China

Let’s look at incidents from across the world where toxic chemicals were detected in dental crowns and bridges from China and other Asian countries:

dental crown that contains no lead

Does this crown have lead or cadmium?

  • In Ohio, a woman’s dental bridge that came from a lab in China was tested and found to contain high levels of lead. Additional crowns were then ordered from Chinese labs and some were found to contain lead at a concentration of 490 ppm – nearly five times above the 100 ppm for children’s toys set by the CPSC. Based on this article, the dentistry was performed by Aspen Dental.
  • In this news report out of Australia, they found lead, cadmium and beryllium in many all-ceramic cosmetic dental crowns originating from several Asian countries.
  • This report from the UK talks about the surge of Chinese crowns being brought into Britain and the lack of oversight over the materials used.

This is not just restricted to wood flooring and dental crowns. Remember the lead paint made in China that was used on Mattel toys?

In the United States, the FDA has the authority to inspect and investigate any dental lab. And there are strict laws governing the contents of dental materials. Do you think China has similar safeguards?

You Get What You Pay For

As a dentist in Connecticut, I only use United States based dental labs, and I know my lab fees. From the advertisements I receive from Chinese labs, I could get prosthetics at one fifth the price. So that means if I have to pay a Connecticut based lab $250 for a crown, I could probably have it done in China for around $50 or even less.

dental bridge made in Connecticut

This bridge was made by a Connecticut lab for a patient from Milford, CT

At my office, we will periodically get phone calls from patients asking about our fees for crowns. Since we only do high quality dentistry, our fees are higher than many other offices. How do you think dental offices are able to offer $400 crowns? You guessed it – they’re most likely made in China. In fact, if you believe this post, one large corporate dental chain uses labs in China for their crowns. The use of Chinese labs by this corporate chain owned by a Wall Street Private Equity Form was also noted in this article.

So, if you shop around thinking “all crowns are the same” you will likely end up with an inferior or substandard crown. Remember this famous saying: the bitterness of poor quality is remembered long after the sweetness of low price has faded from memory.

Your Rights as Dental Patients

made in the USA slogan for dental crowns

My office, as well as many other dentists, will only use USA based dental labs.

In the wake of these findings, legislation was introduced in several states regarding dental materials. Laws can and will change. In general:

  • You have the right to ask your dentist where your crown and/or denture was fabricated.
  • You have the right to ask your dentist about the materials used in any dental prosthesis.

In general, if your dental office doesn’t want to give you this information, you should be suspect. As a dentist in private practice, I welcome inquiries from my patients, since I only use dental labs based in my home state.

And lastly, there are no known cases of crowns containing formaldehyde. I only included this given the news surrounding Lumber Liquidators and the Chinese laminate flooring.

Legal disclaimer: the information presented in this article about two large corporations was derived from news reports. Those sources are referenced and linked to. This blog post does not purport to verify the accuracy of those news stories. As always, conduct your own research prior to making conclusions and deciding from whom to receive dental care.