Gum Boil After Apicoectomy: Causes & Treatment

Written & Reviewed by Dr David Chen

If a gum boil appears after an apicoectomy, it means that the infection has returned and the procedure was unsuccessful. As a matter of fact, a pimple on the gums is a tell-tale sign of a tooth abscess.

We will explain what all of this means, how it could’ve happened, and what your next steps should be. The short answer is, you will need to return to your dentist once more.

What it means

The appearance of a gum boil (pimple on the gums) on a tooth with an apicoectomy means that there is a recurrent infection. In other words, despite going through all of that treatment, the tooth has become reinfected once again.

Gum boil with sinus tract - drawing
gum boil with sinus tract

Another name for that pimple on the gums is a parulis, which is the opening of a sinus tract that leads directly to a periapical abscess. Yes, you read that correctly, an abscess!

Ultimately, it means that the apicoectomy was unsuccessful because it wasn’t able to completely get rid of the infection since it has somehow returned. What a successful treatment would look like is one that is devoid of a boil on the gums.

What caused it

The precise cause for why your apicoectomy procedure failed may be difficult to pinpoint since it can be due to many reasons. We will list a couple to give you an idea of what it may have been but the only way to know for sure is to revisit your dentist.


  • Infection was too severe. Sometimes a severe abscess can only be treated by extracting the entire tooth. Bacteria can escape detection by hiding in nooks and crannies.
  • Root fracture. If the tooth has sustained a fracture somewhere along its root, it’ll be undetectable to the naked eye. The endodontist may be able to diagnose it by taking a CBCT scan. Fractures often will present with a gum boil.
  • Missed canals. If there was a missed root canal, the apicoectomy will be unsuccessful. The reason is because the source of the infection (the missed canal) can simply keep reproducing new bacteria.
  • Accessory canals. The main root canals which are larger can be adequately disinfected and filled. The smaller accessory canals which are off-shoots may be impossible to be disinfected and filled. If the infection is from one of these, a pimple forming on the gums will be inevitable.
root canal - accessory canals
Credit: H. M. A. Ahmed, P. Neelakantan, P. M. H. Dummer

Typically, if this procedure fails, most dentists recommend against a redo because the success rate for a second attempt is unfavorable. The recommendation is to move onto the next step.

Apicoectomy success rates

The success rate for apicoectomy surgery is about 90% according to the latest study in 2005. That is the result when dental operating microscopes and ultrasonic instruments are used during the procedure.

To give you some perspective, prior to advancement in dental technology the rate of success was lower. According to a 3 year study which followed 93,797 teeth with an apicoectomy, the 3 year survival rate was 81.6%.

  • Anterior teeth = 84%
  • Premolars = 80.4%
  • Molars = 80.2%
  • Success was higher for anterior teeth vs posterior teeth.
  • Younger patients (under 18) was 93.3% vs older patients (over 84) was 75.6%

The odds of the procedure succeeding is pretty good in our opinion but please do keep in mind that it can fail. There is a 10% chance that it can fail and unfortunately it can happen to you even though we often don’t like to believe so. Yes, sometimes you’re the one.

Signs of procedural failure:

  • Presence of a gum boil.
  • Worsening toothache.
  • Facial or mouth swelling.

If you notice any of the above signs, you should see your dentist as soon as possible.

What to do

Unfortunately if your apicoectomy does not succeed, there is typically no second attempt. You will need to return to your dentist to have this condition properly treated.

Don’t forget how you ended up needing it in the first place, which we’ll remind you.

  1. Tooth got infected so you treated it with a root canal.
  2. The root canal got reinfected so you did a root canal retreatment.
  3. Root canal retreated tooth got reinfected again so you did an apicoectomy.
root canal steps diagram
Diagram of a root canal

Essentially, this procedure was your third attempt at trying to eliminate the tooth infection while saving the tooth. However, since the gum boil has presented itself, it means that your tooth has now been infected for the fourth time.

It is time to move onto the next step, which is to extract the tooth.

tooth extraction cartoon

Tooth Extraction

The only treatment that is left available for a failed apicoectomy is a tooth extraction. That means the only way to permanently get rid of that gum boil is by removing the entire tooth from your jaw bone.

Once the tooth has been pulled out, you’ll often see a ball sack attached to the tip of the root. This soft tissue mass is the abscess that created the sinus tract thus forming a pimple on your gums.

After the infection is gone and your socket has healed, you should consider replacement options for the now missing tooth. Our recommendation is to get a dental implant since that is the most conservative way to replace it.

Dental implant crown with screw fixture
Dental implant crown with screw fixture

There are other replacement options as well but you can discuss with your dentist the pros and cons for each. You can decided together which one is the best for your situation which often includes financial considerations as well.


If you have a gum boil after an apicoectomy it means that the tooth infection has come back, meaning that the procedure was not successful. A boil on the gums is a tell-tale sign of a periapical abscess.

Ultimately what this means for you is that you will need further treatment for your tooth so you should schedule a consultation with your dentist. We don’t wish to be the bearer of bad news but you will most likely need to have the tooth removed in order to permanently get rid of the infection.


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