Signs and symptoms of failed root canal treatment –
Signs that your root canalled tooth has problems.
While the root canal therapy that’s been performed for your tooth will hopefully last you a lifetime, complications and treatment failures can and do occur. This may even take place with teeth that have an established history of providing you with years, or even decades, of successful service.
What should you watch out for?
This page outlines clinical signs and symptoms that are frequently associated with failed endodontic therapy.
That includes both indications that you the patient may notice, and also the more subtle hints that are often only obvious to the trained eyes of a dentist.
Following that discussion, this page also explains what your next steps should be if you suspect problems.
More information about root canal failure.
As companion pages to this one, we also discuss the following associated topics:
- Why root canal treatment fails. Reasons. | Examples.
- How common is endodontic failure? Study findings.
- What further treatment or retreatment approaches Possible options. exist for failed cases?
Common Signs and symptoms of root canal failure.
A) How can you tell if your root canalled tooth has a problem?
Many of the signs and symptoms of failed or failing root canal therapy are the same ones as those that originally signaled the tooth’s need for treatment. What to look for. In brief, here are some of the things you may notice:
1) Sensitivity to pressure –
- The discomfort noticed might range from just slight tenderness to outright pain.
- It may be felt when biting/closing your teeth together, tapping on your tooth (sensitivity to percussion) or directing forces to the tooth from the side (pressing, tapping).
(When a dentist evaluates a tooth for this symptom, it’s referred to as a percussion test. How it’s done.)
The cause.
Typically this type of sensitivity is a sign of inflammation in the tissues that surround the tooth’s root.
The general scenario.
- Most cases of root canal treatment failure involve a situation where infection has reestablished itself inside the tooth. (This link explains the types of tooth and/or treatment technical issues that frequently result in endodontic therapy failure. Our list.)
(The microorganisms involved are usually bacteria but in some cases they may be fungi [fungus].)
- Microorganisms and infection byproducts [pus] that leak out of the tooth trigger an inflammation reaction in the tissues surrounding its root. It’s the symptoms associated with this process, in these tissues external to the tooth, that result in its sensitivity to percussion.
▲ Section references – Hargreaves, Tronstad
2) Swelling. –
Since failed endodontic cases typically do involve the presence of infection, swelling is often observed.
- The tissues affected may be limited to just those adjacent to the tooth. Or possibly even just those in the immediate area of its root tip.
At the other extreme, the swelling may be extensive and extend into the patient’s face, or even neck.
- The extent of swelling that’s present at any one point in time will simply correlate with the current level of activity of the infection, which can fluctuate (days, weeks, months).
- While not always noticeable, swollen tissues typically are tender to touch. (For this reason, palpation is an important examination method How it’s done. for a dentist to use.)

A persistent gum boil can be a sign of infection associated with failed root canal therapy.
Variants.
This page provides more detailed coverage about these lesions: What is a sinus tract? Pictures | Diagrams
3) Thermal sensitivity.
This symptom isn’t as characteristic for failed endodontic work as pain and swelling. But experiencing it is a possibility.
Since the tooth’s previous treatment removed its nerve tissue, a response to hot or cold would not be expected. But in cases where one or more of a tooth’s root canals have been overlooked and therefore not treated A common reason for failure., this type of sensitivity is possible. (Hargreaves)
▲ Section references – Hargreaves, Ingle
4) How a tooth’s symptoms may change.
The level or degree to which a person experiences symptoms can fluctuate. The time period involved might be days, weeks or months.
- What’s noticed at any particular point in time will generally correspond with the current level of activity of the infection associated with the tooth.
- With any luck, the person’s immune system can keep the tooth’s infection in check and relatively confined within it. If so, the symptoms they notice may be quite limited.
- However, and as a worst-case scenario, teeth with failed endodontic work have the potential to flare up at any time, resulting in an acute apical abscess. What it’s like.
5) Symptom variability is common.
It must be stated that what we’ve outlined above is not all-inclusive. Your failing tooth may display additional symptoms, or possibly none at all.
Variability is commonplace, and that means that with many cases it will take your dentist’s best efforts in detection and interpretation to be able to definitively conclude that your tooth’s root canal work has failed.
B) Having symptoms doesn’t always indicate endodontic failure.
It’s possible that the symptoms you’ve noticed are not associated with your tooth’s root canal work per se. Here are some possibilities:
1) Referred pain –
The nerve that services a tooth will have the duties of servicing other teeth and structures too. And it’s possible that a dental or medical problem associated with one of them may cause sensations that just happen to feel like they’re coming from your root canalled tooth.
2) Persistent Dentoalveolar Pain disorder (PDAP) –
PDAP disorder is a relatively new term used to label situations characterized by this set of events:
- Pain associated with a tooth signals its need for root canal therapy.
- But following its treatment, the patient continues to experience discomfort with the tooth, for months on end.
- On evaluation, nothing can be found at fault with the tooth or the endodontic treatment it has received.
PDAP cases can be especially problematic, and difficult for a person to endure. For instance, it often takes a dentist some time to finally arrive at this diagnosis. And even then, possibly only after subjecting the tooth, or even neighboring teeth, to dental procedures that have no chance in providing a solution.
And since the underlying cause of PDAP disorder is unknown, treating it is unpredictable. Complete resolution of the patient’s pain may not be possible.
We’ve given our coverage of this condition its own page. You can find it here: Persistent dentoalveolar pain disorder. PDAP
3) Tempromandibular joint disorder (TMJ) –
- While the actual cause of the pain is due to the TMJ condition, it may feel as though it comes from the area of a tooth, such as one that has received endodontic therapy.
- As a separate cause of pain, the excessive forces typically involved with bruxism may get directed primarily to just one or a few teeth, causing them to become sensitive (sensitivity to biting pressure would be characteristic).
When this scenario occurs in association with a tooth that has had root canal therapy, the sensitivity comes from nerve fibers within the ligament that holds the tooth in place, and therefore is not an indication of endodontic treatment failure.
Some signs of endodontic failure can only be detected by your dentist.

The dark spot (radiolucency) at the tip of this tooth’s root suggests that a problem exists.
C) Not all problem teeth display symptoms you can detect.
Usually what the dentist has discovered is referred to as a “radiolucency Why these form.,” like the one shown in our illustration.
The grey area of treatment success.
The point that a tooth’s work might be classified as a failure even though it remains asymptomatic brings up the issue of tooth survival vs. case success.
In endodontic terms, “survival” refers to a lack of symptoms while “success” is associated with the more rigorous standard of both an absence of symptoms and evidence of periradicular (around-the-root) tissue healing (as in no radiolucency is present).
What should you do if you suspect endodontic treatment failure?
a) If your root canalled tooth isn’t symptom-free, it should be evaluated.
For the most part, if you have a tooth that’s had root canal therapy and it continues to have, or has started to show, essentially any type of symptom, it should be examined by your dentist.
What’s normal.
The expectation is that following the completion of a tooth’s endodontic therapy, following an initial period of healing of the tissues that surround the root, the tooth will remain quiet and symptom-free. That’s because:
- The tooth’s nerve has been removed, so there’s no tissue inside the tooth capable of feeling sensation.
- While nerve fibers do lie in the tissues that surround the tooth’s root, successful root canal treatment resolves any issues (like infection, inflammation) that might create an irritating effect on them.
Per these two accomplishments, the tooth should remain asymptomatic (without symptoms). If it doesn’t, it should be evaluated.
b) If something seems wrong, how soon should you have your tooth checked out?
If you notice that something seems amiss with your root canalled tooth you should make contact with your dentist’s office promptly so they can determine the level of urgency associated with your case and schedule you accordingly.
Why is doing so important?
Infection typically plays a role in root canal failure, and how active it may become at any one point in time can’t be predicted. As such, teeth that have an endodontic problem have the potential to flare up at any time.
As a worse case scenario, a long-standing low-grade infection that has only caused minor symptoms may shift into an acute phase, bringing with it intense pain and significant swelling.
Of course, just because this potential exists doesn’t mean that it will happen. But it does mean that there’s absolutely no good reason to delay in contacting your dentist’s office and seeking their attention. Once you’ve done so, they can make a determination about the urgency of your needs.
If scheduling is difficult.
In the case where you can’t be appointed to see your dentist immediately, they may feel that phoning in a prescription for antibiotics for you (either to be started immediately or to have on hand if your situation worsens (a “delayed” prescription)) can provide a means of helping to control your current symptoms and/or risk level.
However, according to current prescribing concepts, the use of an antibiotic in managing endodontic emergencies should typically play a secondary role to direct treatment. So, it is in your best interest to shuffle your schedule however is needed to accommodate whatever appointment your dentist has to offer.
c) Timing your tooth’s corrective treatment.
Once a decision has been made about the type of corrective treatment that’s required for your tooth, it should be performed within the time guidelines recommended by your dentist, for exactly the same reasons just mentioned.
Until that point in time when your tooth’s issues are finally resolved, it still remains unpredictable. And as such, it leaves you at risk for complications and/or acute flare-up.
As a precaution, your dentist may decide to write you a prescription for antibiotics so you already have it on hand if conditions with your tooth worsen before your definitive treatment can be performed. Their decision for a need to do this will simply depend on the conditions associated with your tooth.
Further reading about endodontic case failure:
- Why root canal treatment fails. Reasons. | Examples.
- How common is endodontic failure? Study findings.
- What further treatment or retreatment approaches Possible options. exist for failed cases?
Page references sources:
Hargreaves KM, et al. Cohen’s Pathway of the pulp. Chapter: Nonsurgical retreatment.
Ingle JI, et al. Ingle’s Endodontics. Chapter: Retreatment of Non-Healing Endodontic Therapy and Management of Mishaps
Tronstad L. Clinical Endodontics. Chapter: Oral and Perioral Pain of Endodontic Interest.
All reference sources for topic Root Canals.