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Abscess Is Still There After The Root Canal: What To Do?

Updated: Dec 17, 2023

Unfortunately you developed a tooth abscess which was why you had the root canal procedure done in the first place. However, the abscess does not seem to be going away because it is still there.

abscess on root canal tooth
abscess on root canal tooth

We can imagine the questions going through your mind right now.

  • Did something go wrong with the treatment?

  • Was there something else that you should've done?

  • Or perhaps you made the wrong decision...

We will explain what may have happened and also offer you some suggestions as to what your next step may be.

Table of contents:

Why do I still have an abscess despite the root canal?

If the abscess is still there even after the root canal (RCT), it means that the infection did not resolve from the treatment.

Perhaps you were unaware but the success rate for root canals is not 100% which means that it can fail. Historically, the success rate for root canals is about 84.29% and that is according to a five year retrospective study. Typically, if the abscess remains it means that there was a complication.

RCT complications resulting in residual abscess:

  • Curved canals. The roots aren't straight with extreme curvatures.

  • Calcified canals. The canal is not patent.

  • Accessory canals. There are microscopic canals on the side.

Curved canals

If your abscessed tooth has extreme curvatures within the canal, that can certainly decrease the chances of success. Curved canals make it difficult for the root canal files to navigate and clean them out thoroughly.

Molar with curved canals
Curved canals - Credit: Dr Zegar Zegar

Straight canals are more straight forward and permit ease of disinfecting the canal.

straight canal tooth
straight canal

The two x-rays above show what we mean by a tooth having curved canals. Having curves makes it more difficult to physically and mechanically clean out the infection.

Calcified canals

A calcified canal may not permit complete elimination of an infection. Most commonly, the last few millimeters of a tooth may be calcified thus preventing your dentist from clean out that portion. The result of this will be a short obturation where the root canal filling material cannot reach the tip of the root.

x-ray of failed root canal with short obturation
Calcified canal at tip

If you're not able to disinfect the entire canal of the tooth, it's no wonder that the infection persists after treatment.

Accessory canals

Some teeth have accessory canals that go out through the side of the root. These are small branches that are off-shoots of the main canal. These are physically impossible for your dentist to completely disinfect.

root canal - accessory canals
Credit: H. M. A. Ahmed, P. Neelakantan, P. M. H. Dummer

If you have accessory canals, the success rate will be lower than if you didn't have any.


What should I do about it?

There are three treatments available for an abscess that is still there after a root canal.

  • Root canal retreatment. Your dentist can try retreating the tooth by redoing the root canal once more. This redo procedure is called a root canal retreatment. It is similar to the first time you had it done except your dentist will leave antibiotics inside of the canal.

  • Apicoectomy. This is a surgical procedure which cuts off the tip of the root where the infection remains. This is an option if the retreatment has already been done.

  • Extraction. If the infection does not resolve even with a retreat and an apicoectomy, the only option left would be to remove the entire tooth from the mouth. After the extraction, you can consider replacing the missing tooth with an implant.

Which treatment should I do or expect to have done?

If the root canal is not successful and the infection persists, we recommend starting with a retreatment first. If it still does not go away with the retreat then an apicoectomy would be the second choice. The very last option if the first two fails would be tooth removal.

How long does it take for it to finally go away

If the abscess has been successfully treated, you should notice an improvement or complete resolution within 1-2 weeks. That is how long it takes for the signs and symptoms to completely disappear.

What if it doesn't go away?

It is possible for the infection to NOT go away despite numerous treatment attempts. You can try retreating the tooth multiple times and even doing the apico procedure. If all of that fails and the infection persists in your mouth. The only option left would be to do a tooth extraction which will definitely get rid of it.


How can I tell if the infection is still present?

There are four distinct signs and symptoms if you have a non-resolving abscess.

  • Gum boil. There is a pimple on the gums even after the root canal.

  • Periapical radiolucency. X-ray shows a dark spot surrounding the root tip.

  • Swelling. The area is still swollen as if it never went away.

  • Pain. The tooth still hurts when you're chewing or even spontaneously.

Gum boil

If there is a gum boil after a root canal, that is a tell-tale sign that the abscess never went away.

gum boil
gum boil

What it looks like:

  • A pimple on the gums next to the root canal tooth.

  • It may be reddish in color.

  • Can ooze out pus or exudate if you touch or squeeze it.

  • May or may not be painful.

It is a sign of an abscess because a gum boil is actually the orifice of a sinus tract that leads directly to a periapical abscess. In other words, not just a simple pimple but an active infection.

Periapical radiolucency

Alternatively, a residual periapical radiolucency around the root tip of a PA x-ray is potentially indicative of a residual abscess. The x-ray below shows what this failed root canal looks like.

periapical radiolucency around tip of root

What it looks like:

  • There will be a big dark circle that surrounds the tip of your root on an x-ray.

  • The size and shape will differ but it is often near the apex.

  • The black circle is often described as a halo around the root.

Potentially not an infection

However, you should be aware that the periapical lucency could also potentially not be an infection. Sometimes that dark circle could just be residual scar tissue from the procedure. What that means is the bone never healed or filled in the void after the abscess.


Can I leave it untreated?

If the abscess never went away even with the root canal treatment, you should definitely not leave it untreated. It is a sign of an unresolved infection and you don't want it to progress into something really complicated.

Leaving it alone may allow the abscess to grow and make your face swollen which will happen. All abscesses will progress through the stages of a tooth abscess. If the swelling gets very large it will be extremely painful and potentially life threatening.


If your abscess is still there even after doing the root canal treatment, it can only mean one thing. The infection escaped elimination and your tooth is still abscessed. In other words you will need further treatment in order to get rid of it.

That means you shouldn't wait and leave it alone thinking you've already done everything that you could've because you haven't. There are still more treatment options that you have yet to explore.



David Chen 200 x 200.jpg

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!

Association Memberships:

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!

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