Is It Possible To Get Tooth Decay Under A Crown With Root Canal?

Updated: Aug 18


Crown with decay
Crown with decay

Table of Contents:


Tooth decay under crown with a root canal

Yes, it is possible to get decay underneath a crown even if it had a root canal. The root canal itself does not prevent future decay. As a matter of fact, the root canal procedure does not remove any tooth decay at all. The whole purpose of the procedure is actually to just remove the pulp of the tooth. The root canal specialist will remove the nerve from the tooth and then return the patient to their general dentist for the full cavity removal.


Your general dentist will complete the cavity removal or at least to the best of their ability before putting the crown on for you. Once again, just because the tooth had a root canal and it is dead, it does not make it immune to cavities. Even with the crown put on, it can still get a new cavity.


The only difference is that the crown itself cannot get a cavity but the tooth underneath of it can still get a cavity.



Pictures of tooth decay under crown

Both of these pictures show what the decay looks like underneath of the crown from the very first picture at the top of this article. This is what that crown looks like with it removed.


tooth decay under crown with root canal
tooth decay under crown with root canal

This is a picture of tooth decay under a crown. Yes, it is the same tooth as the very first picture in the article. This is evidence that you can get tooth decay under a crown with a root canal. We will show you another picture of the decay from a different angle.


Tooth decay in root canal
Tooth decay in root canal

Can you see the pink dots in this picture? That is the root canal and look how much the cavity has gotten into the canal. So, what does this tell you?


Even if you have a crown with a root canal, you still need to practice good oral hygiene. Just because your tooth is covered by a porcelain cap, the tooth underneath of it can still get a cavity. Therefore, you must continue to brush for at least 2 minutes twice a day. Floss before you go to bed and use some mouthwash. If you don't like Listerine, you can try some coconut oil pulling.



Why does the porcelain crown not get a cavity?

The porcelain is unable to get a cavity because the acid that the bacteria eats from the sugar in your mouth is unable to melt through the porcelain. The acid from the bacteria is very acidic but is still unable to penetrate through the porcelain. Similar to how you can have very acidic food on your porcelain plate and it won't melt it.


This is the reason why the tooth cap itself is immune but unfortunately you cannot wrap the root of the entire tooth in porcelain. The bacteria can sneak in at the margin of the crown, which is where the porcelain meets your natural tooth structure.



How does decay get under the crown?

There is always a gap somewhere along the gum line where your crown ends that the bacteria can cause a cavity. Most of the time your dentist will place the margin of the crown below the gumline but not everyone brushes at the gumline and thus plaque gets left behind.


Plaque contains a lot of bacteria so if they are left underneath the gumline, they are basically positioned right underneath the crown. If eat a sweet meal and provide the bacteria some sugar, they will produce acid that can lead to decay under the crown.


Decay under crown at gumline
Decay under crown at gumline

This is another picture of tooth decay under a crown but at the gum line. As you can imagine, that is the perfect entry point for a cavity so make sure you brush the gumline!



How to prevent decay under crown?

It is very simple to prevent decay under a crown because all you have to do is be strict with your oral hygiene regime. In addition to the brushing and flossing, make sure you minimize the amount of sugar that you eat throughout the day. If there is no sugar, there is no fuel for the bacteria to cause any tooth decay.


Aside from sugar you should also avoid foods that will cause an acidic environment in your mouth. Cavities don't start forming until the pH gets below 5.5 which is also called the critical pH level.


So just to recap on how to prevent decay underneath a crown:

  • Brush and floss twice a day.

  • Use a fluoride toothpaste.

  • Minimize sweet, sour, and acidic foods in your diet.


Last but not least, don't forget to go in for your 6 month dental check ups and cleaning with your favorite dentist in long island city! If you happen to catch problems early, you can have them treated more conservatively. It'll also be less expensive for you as well.




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About the author: Dr David Chen, DDS

Hello, I'm Dr Chen and I'm an actively practicing dentist in Long Island City, NY. I graduated from Columbia University College of Dental Medicine in 2016 but prior to going to dental school I was already working in the dental field. It's been more than a decade since I first got to know dentistry and let me tell you, time flies by quickly. Since then I've developed a fondness for writing, which is how this all got started!

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Medical Disclaimer:

This blog is purely meant for information purposes and should not be used as medical advice. Each situation in your mouth is unique and complex. It is not possible to give advice nor diagnose any oral conditions based on text nor virtual consultations. The best thing to do is to go in person to see your dentist for an examination and consultation so that you can receive the best care possible.

The purpose of all of this oral health information is to encourage you to see your dentist and to inform you of what you may expect during your visit. Due to the unfortunate nature of dentistry, there isn't really any true home remedies that will get rid of dental problems. Roughly 99.99% of them require in-person intervention by a healthcare professional.

Hint: That is the reason why you can't eliminate seeing dentists in your life!