Root canal treatment - Complications, Problems, Failures. -

What can go wrong? The signs and symptoms of failed endodontic therapy. | Reasons for failure. Factors and statistics. | Solutions. What options do you have?

Signs of

Link to signs of root canal failure section.

Causes of

Link to why endodontic treatment can fail section.

Common problems with teeth that have had root canal treatment.

Case failures.

While the root canal therapy that's been performed for your tooth will hopefully last you a lifetime, complications and even outright treatment failures can and do occur. In some cases, even after your tooth's work has provided years of successful service.

We've divided our discussion that covers these possibilities into the following subjects:

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 as those that signaled the tooth's original need for treatment. They frequently include:

  • Sensitivity to pressure. - This may range from just slight tenderness to outright pain. The discomfort 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).

    The general idea is that the sensitivity is a sign of inflammation in the tissues that surround the tooth's root, due to the presence of infection associated with the tooth's failed work.

  • Swelling. - Some degree of swelling (and accompanying tenderness) may be present, with its current size corresponding to the rate of pus formation currently being produced by the associated infection.
    Picture of a fistulous tract indicating failed endodontic therapy.

    A persistent gum boil can be a sign of infection associated with failed root canal therapy.

    In some cases a vent may form through which the pus can drain, thus keeping the level of swelling to a minimum.

    This type of lesion (formally referred to as a "fistulous tract") typically takes the form of a persistent gum boil positioned in the region of the tip of the tooth's root.

    Due to the draining pus, a bad taste or odor may be present. Additionally, the tissue around the lesion's opening may be tender. However, in cases where these symptoms are not noticed, the tract may have a history of existing for years.

  • Heat sensitivity. - This symptom isn't as characteristic for failed endodontic work as pain and swelling are. But experiencing it is a possibility.

    Related to possible causes, heat sensitivity is most often noticed in cases where one of a tooth's root canals has been overlooked and therefore remains yet treated. (See below for further explanation.)

  • Symptom characteristics. - The intensity of the symptoms that a person experiences will often wax and wane, with them generally corresponding with the level of activity of the infection that has caused them.

    Their duration can vary too by way of being constant, intermittent or even disappearing completely for much of the time (weeks, months, possibly years).

    In regard to pain and heat sensitivity, as a part of their diagnostic testing the dentist will need to evaluate the duration for which these symptoms persist after the stimulus that has triggered them has been removed.

We discuss this subject further, along with the various forms a person's symptoms may take, here: How can you tell if your tooth needs root canal treatment?

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 treatment 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, after 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?

As a general rule, if you notice that something seems wrong with your root canalled tooth you should have it examined by your dentist sooner rather than later.

That's because teeth that have endodontic problems are unpredictable and have the potential to flare up at any time.


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 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.

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 attention. Once you've done so, they can make a determination about the urgency of your needs.

In the case where you can't be appointed immediately, the simple act of phoning in a prescription for antibiotics for you (either to be started immediately or to have on hand if needed) can reduce your risk for trouble significantly.

Some signs of endodontic failure can only be detected by your dentist.

An x-ray showing evidence of failed root canal treatment.

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.

Some teeth that have failed endodontically won't display any symptoms that the patient really notices.

A common scenario is one where from the patient's point of view their tooth seems perfectly fine. But during x-ray examination (possibly taken as part of a routine dental checkup, or as planned monitoring of the tooth's work) one of the films suggests that a problem exists.

Usually what the dentist has discovered is referred to as a "radiolucency," like the one shown in our illustration.

The grey area of successful treatment.

The point that a tooth's work might be classified as a failure even though it remains quiet brings up the issue of tooth survival vs. case success.

In endodontic terms, survival refers to a lack of symptoms while a classification of 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).

d) Having symptoms doesn't always indicate endodontic failure.

It's possible that the symptoms you have noticed are not associated with your tooth's root canal work at all. Here are some possibilities:

  • Referred pain - The nerve that services a tooth services other teeth and anatomical structures too. It's possible that a dental or medical problem elsewhere along the run of the nerve just happens to create a sensation that feels like it's coming from your root canalled tooth.
  • Phantom pain (deafferentation pain) - This type of tooth sensation is similar to phantom limb pain amputees sometimes experience.

    It stems from some type of traumatic episode that has occurred in relation to the nerve that services the tooth, like when pulp (nerve) tissue is removed from a tooth during its root canal therapy. Possibly phantom pain occurs in as many as 3% of such cases. (Marbach 1993)

(Nixdorf 2010) [page references]

B) Reasons why root canal treatment fails.

The specific cause of any one tooth's endodontic failure usually boils down to some combination of the following factors:

  • The cleaning aspect of the tooth's procedure has been incomplete or ineffectual. If so, infection inside the tooth will persist and ultimately result in case failure.
  • The seal created for the tooth (either during its procedure or by its final restoration) has not been successful in keeping contaminates from seeping into or out of the tooth.

    The seal might have been deficient initially, or has since deteriorated. Either way, the lack of a seal will allow persistent infection to exist within the tooth.

  • Technical shortcomings or complications have prevented the completion of the tooth's work according to the standards needed. Or issues associated with the tooth's preoperative condition have created obstacles.

Specific reasons why root canal treatment may fail.

Listed below are examples of how the above problems may have become a factor in an endodontically treated tooth's failure.

The root canal system of a tooth may branch.

The shape of some canal systems makes them harder to treat.

1) Branched canals (unfilled canals).

Root canals sometimes fork, resulting in one or more offshoots (see picture). In many cases the resulting branches may be very tiny and as a result both hard for the dentist to detect and treat.

If any division of a canal is not identified, the result will be one where one branch is treated while the other is totally overlooked. The untreated portion of the canal will serve as a source of infection that will act as a persistent irritant to the tissues that surround the tooth's root, ultimately leading to case failure.

2) Missed canals.

It's not terribly uncommon for a tooth to have more individual root canals than is normally expected. (Some tooth roots are well known for having, or potentially having, more than one canal. With others, this may be a rare event.)

These additional canals may be very tiny and their presence easily missed when not anticipated. And if a canal is overlooked, it will remain untreated and a locus of persistent infection.

  • A study by Iqbal (2016) determined that missed canals are a major cause of root canal failure (around 18% of failed cases), and most commonly associated with treatment provided by general dentists as opposed to specialists. (It's common for an endodontist to have a surgical microscope that they'll use to search for extra canals.)
  • Hoen (2002) evaluated 337 failed root canal cases and determined that overlooked canals played a role in 42% of them.

A cracked molar.

Some cracked teeth may not be treatable.

3) Root cracks.

Cracks that have formed in a tooth's root can be colonized by bacteria. But unlike root canals that can be cleaned and sealed off, there's no way to treat the minute spaces created by cracks.

That means that once they've been colonized by bacteria the infection that results can't be cleared up. It will be a persistent source of irritation to the tissues that surround the tooth's root.

Compounding this type of situation, when performing endodontic therapy a dentist may be unaware that a crack exists (they can be very difficult to identify), or underestimate the significance of the ones they see. Either way, all of the tooth's problems won't be resolved by its treatment.

In other cases, the crack that has caused the tooth's failure formed after it received its endodontic treatment. (Possibly because an inadequate "final" restoration was placed on the tooth, see below.)

4) Inadequate interior seal.

The integrity of the seal created inside a tooth during its root canal treatment is an important determinant in treatment success. It serves as a barrier to the seepage of bacteria or other contaminates into or from the tooth that would be a constant irritation to the tissues that surround it.

The seal may have deteriorated over time, or been faulty initially (due to underfilling, the presence of voids, etc...). A study of failed cases (Ibqal 2016) determined that 1/3rd involved underfilling the tooth's root canal space.

5) Overextension of the tooth's filling material.

The findings of some studies suggest that if the material that's been used to fill in and seal a tooth's interior extends out beyond its root's tip, the likelihood of endodontic failure is increased. (Tabassum 2016)

Hoen's (2002) evaluation of 337 failed root canal cases reported that overfills were involved in 3% of them.

The ability to properly confine these materials could be expected to be a function of the operator's level of experience and skill (see specialist vs. general dentist discussion below).

6) Inadequate coronal seal.

A defective or inadequate final restoration (the "permanent" one placed after the completion of treatment) can allow bacteria and other contaminates to reenter a tooth. (The x-ray graphic above shows an example of this situation.)

This phenomenon is termed "coronal leakage" and it is a major cause of root canal failure. For more information, use this link: What is Coronal Leakage?

Even the highest quality root canal work can't survive (resist reinfection of the root canal space) if its tooth's permanent restoration doesn't provide an adequate seal. A study by Hoen (2002) reported that 13% of failed cases involved complications with coronal leakage.

7) Other types of technical shortcomings with the tooth's procedure.

Beyond the operator issues mentioned above, other technical complications can effect the outcome of a tooth's procedure. This might include:

  • Problems caused when shaping the canals - A dentist's use of root canal files may inadvertently create contours within the tooth that subsequently makes this space difficult to adequately clean or seal.
  • Perforations - Using drills or files, a dentist may inadvertently create a hole out the side of the tooth's root.
  • Broken instruments - It's not terribly uncommon for a root canal file to break while being used. In some cases the broken portion may be lodged inside the tooth and cannot be retrieved.

A study by Iqbal (2016) determined that about 6% of failed cases could be attributed to problems associated with perforations, and 7% broken instruments. (Note: The sample size of this study was only 90 patients).

8) Lack of clinician expertise.

Research suggests that treatment performed by endodontists (root canal specialists) tends to have a higher success rate than that provided by general dentists. For example, a study by Iqbal (2016) evaluated 90 failed root canal cases and determined that roughly 80% of them had been completed by general dentists. (See additional statistics below.)

Why referral to a specialist may make sense.

Any dentist can tell you, providing endodontic therapy for some teeth will prove to be amazingly straightforward, and then for others surprisingly involved. Unfortunately, a tooth's level of difficulty can't always be predicted.

For this reason, some dentists may feel they can boost their patient's chances of success by referring suspect cases on to an endodontist before complications arise. Per the data in our table below, this might be an especially prudent choice for certain types of teeth (like molars).

Our page "Endodontist vs. General Dentists- Which makes the best choice, and when?" discusses this issue in detail.

A periapical radiolucent lesion.

A tooth with a periapical radiolucency.

Teeth having pre-op radiolucencies may be more likely to fail.

9) Preoperative tooth conditions.

A tooth's initial status may play a role in the ultimate success or failure of its endodontic work. One such concern involves teeth that have a "periapical radiolucent lesion" (see picture).

These types of lesions may continue to harbor bacteria despite the successful completion of the tooth's root canal treatment. If so, this locus of infection will be a persistent irritant to the surrounding tissues.

The success rate of teeth having this initial condition (vs. those without) may be lower on the order of 20% (Iqbal 2016).

C) Contributing / Complicating factors.

It's possible that your tooth's root canal treatment has been successful but the tooth itself has problems due to other factors.

a) The tooth has broken or fractured.

Teeth that have undergone root canal treatment are seldom as structurally sound as they were originally. And for this reason, they often require the placement of a dental crown for strengthening and protection.

If an endodontically treated tooth does break, it's not always a big problem.

  • Assuming that the damage is confined to just the crown portion of the tooth (not its root), it's quite likely that the tooth can be rebuilt. (In some instances, the repair may require the placement of a dental post and core.)
  • If the crack extends into the tooth's root, an evaluation will need to be made to determine if the likelihood of making a successful repair seems possible (see above).

b) The tooth has extensive decay or gum disease.

Just like any other tooth, teeth that have had root canal treatment are at risk for the formation of tooth decay and gum disease. And if allowed to advance, either of these conditions can ultimately lead to the tooth's loss.

How likely is your tooth's root canal therapy to fail?

Overall, research studies suggest that endodontic therapy has a generally high success rate.

a) Treatment success rates.

Chen (2007)

This study monitored over 1.5 million root canalled teeth over a 5 year period. It determined that:

  • Roughly 8% of cases failed and were resolved by extracting the tooth.
  • Of the teeth that survived, 4% had experienced root canal failure but were salvaged by retreating them.

(These findings suggest to us that the overall success rate of a tooth's original treatment lies on the order of 88%.)

Raedel (2015)

This study reviewed a dental insurance database to determine the outcome of over 500,000 root canal cases where the treatment had been provided by general dentists. It calculated a 3-year survival rate of about 84%.

b) Treatment by general dentists vs. endodontists.

It seems logical to speculate that the extra training a root canal specialist (endodontist) receives positively influences the outcome of their work. Research seems to confirm this:

  • Background information included in a paper by Ibqal (2016) states that success rates for root canal work performed by general dentists runs on the order of 65% to 75%. Whereas for specialists, this number lies around 90%.
  • A small study involving just 350 teeth (Alley 2004) found a success rate of 98% for therapy performed by endodontists vs. 90% for cases completed by general practitioners.

Another study (Lazarski 2001) evaluated the outcome of over 100,000 root canal cases (each tooth was followed over a minimum time frame of 2 years).

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It reported a similar success rate for work completed by both specialists and general dentists. But noted that the specialist group treated a substantially greater percentage of molars (multi-rooted teeth often having a very complex canal system) whereas the generalist group more single-rooted, typically easier to treat, teeth. (See our "failure rate by tooth type" table below for a comparison.)

Possibly you could conclude from this study that:

  • The similar success rate achieved by specialists while treating more difficult cases suggests that the extra training and experience they have plays a valuable role in treatment outcome.
  • But this extra experience may not be needed for simple cases.

c) Failure- Retreatment vs. extraction.

The Lazarski (2001) study mentioned above also provided some insight in regard to the ultimate outcome for endodontically treated teeth that had experience failure.

Out of a group of over 4000 failed root canal teeth, 59% of cases were resolved by extraction while the remaining 41% seemed suitable candidates for salvaging via some form of endodontic retreatment.

d) Incidence of root canal failure by tooth type.

We ran across three studies that included data about endodontic failure by tooth type.

Iqbal (2016) - As a part of its evaluation of 90 failed root canal cases, this study reported the following failure rates:

Distribution of failed root canals by tooth type.
4.4% of cases ... Upper incisors
3.3% of cases ... Upper canines (eyeteeth)
15.5% of cases ... Upper premolars (bicuspids)
44.4% of cases ... Upper molars
5.5% of cases ... Lower incisors
1.1% of cases ... Lower canines
5.5% of cases ... Lower premolars
20.0% of cases ... Lower molars

Burry (2016) - As a part of it's investigation of an insurance database, this study evaluated groups of teeth that had been treated by general dentists that had since experienced root canal failure (those that had developed problems at 1, 5 and 10 years after completion, over 338,000 teeth total). The failure rate per tooth type was similar for all three groups.

Distribution of failed root canals by tooth type.
19% to 20% of cases ... Incisors and Canines
32% to 34% of cases ... Premolars
46% to 47% of cases ... Molars

Hoen 2002 - This study evaluated 337 teeth whose initial root canal treatment had failed.

Distribution of failed root canals by tooth type.
20% of cases ... Incisors and Canines
22% of cases ... Premolars
58% of cases ... Molars

Together, these studies seem to suggest that:

  • Anterior teeth (incisors and canines) tend to experience failure less often than premolars and molars.
  • Teeth that most frequently have a single root canal (incisors, canines, lower premolars) tend to have the lowest failure rates.
  • Teeth frequently/typically having multiple canals (upper premolars, upper molars, lower molars) tend to have the highest percentage of failures.
  • Molars in general and possibly upper molars in particular (the type of tooth typically having the greatest number of canals, 3 or more) have the highest failure rate by far.

    (Not only does a larger number of canals present greater challenges but many additional canals are small and curved, thus making them difficult to both identify and treat.)

This data makes it easy to understand why a general dentist might be more inclined to refer the treatment of teeth that have a relatively more complex anatomy (molars, especially upper molars) to a root canal specialist.

What's the fix for failed root canal treatment?

If you have a tooth whose root canal therapy has failed, you really only have two options:

  • Retreatment (performing root canal treatment for the tooth again).
  • Extracting the tooth.
  • (Because failed cases are typically associated with the presence of infection, retaining the tooth without treatment doesn't make an appropriate choice.)

a) Endodontic retreatment.

Failed root canal cases frequently are retreated. A decision to proceed with this option would simply depend upon your dentist's judgment about its chances of success.

What's involved with endodontic retreatment?

In most cases, retreating a tooth simply involves repeating the same procedure that was performed originally, with the exception that additional effort will be required to remove the previously placed canal sealing materials.

  • In some instances, the level of skill and expertise needed to perform this type of conventional retreatment may lie beyond what your general dentist can offer.

    (Potentially difficult tasks: Removing the previously placed materials. If a procedural deficiency has been identified with the previous work, accomplishing a correction or improvement.)

  • Additionally, with some retreatment cases some type of surgical option may be required that falls beyond the services that your dentist wants to provide.

In these situations, the services of an endodontist (root canal specialist) may be required. We discuss issues associated with making this decision here: General dentist vs. Endodontist. We discuss endodontic retreatment costs here.

b) Tooth extraction and replacement.

Besides retreatment, the only other appropriate treatment choice for a tooth whose root canal work has failed is to extract it. This option might be chosen because retreating the tooth is not possible, or only offers a low probability of success.

Timing your next step.

Whichever decision is made, your follow-up treatment should be performed within the time guidelines recommended by your dentist.

Following their examination, they can gauge how much urgency appears to be involved. As a precaution, your dentist might 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.

Why you mustn't delay.

Teeth that have failed endodontic treatment are unpredictable due to the fact that they typically harbor infection, which has the potential to flare up (create pain and/or swelling), possibly significantly so, without warning.



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An old root canal filled tooth that hurts!

Almost 40 years ago I had an abscess on an upper incisor and it was treated with root canal. Over the years it went grey so I had a veneer. Recently (after eating chocolate) it started to hurt, a sharp pain and sensitivity to heat. My dentist has X rayed it and the root canal seems to be intact. My query: I thought this tooth was dead so how can I be experiencing pain?
Thanks (and for your website)


We're not really going to be able to shed any light on your specific situation. In your case, your solution is to continue to monitor your tooth, and continue to document what types of stimuli cause your discomfort. Keep reporting this information to your dentist. They'll ultimately figure things out. Not all diagnoses are quick, easy or one-visit affairs. The diagnostic services of an endodontist is sometimes needed for difficult cases.

The discoloration of your treated tooth that you noticed is commonplace and not necessarily associated with what you are going through now.

Our page about reasons why root canal treatment can fail explains different problems that may crop up. With previously treated, historically successful teeth, some examples are:

1) The seal created by the tooth's original work may have deteriorated and now bacteria are able to reenter the tooth.

2) A previously treated tooth may develop a crack, which can allow an entry point for bacteria.

While an x-ray will often provide valuable information, it may take time for a tooth's condition to advance to a point where the signs associated with its pathology finally show up on one. Hence the need to maintain contact with your dentist and let them to continue to monitor and reevaluate your situation as they feel is indicated.

Beyond what you mention, it's common that a problematic tooth will develop tenderness, swelling and/or a persistent pimple in the region of its root. So watch for that, because if you notice that it will will help in making the diagnosis. Good luck.

Thank you

I'm so grateful to you to have given such a detailed explanation for my strange tooth.
I will indeed keep in close consultation with my dentist and I have taken note of the various factors you have described.
Thanks again

JS Scotland.

Root Canal Retreatment

Thank you for providing the detailed information for this article. It was both informative and helpful. I appreciate the effort.

Thanks SW.

We fear that you wouldn't have read this page unless you're having problems with a tooth, so good luck with getting the difficulty associated with it resolved.

Tooth pain

I had a root canal filling in one of my teeth eight years ago .
About 2 weaks ago it started really to hurt and i went to the dentist and he prescribed antibiotics for me .
The antibiotics did their job perfectly and the pain was gone . The doctor said i don’t need further treatment.
Is that ok ? Can i have another attack of pain in the near future?


Since we know noting about your specific situation, we can only answer in general terms.

As this page discusses, if root canal treatment has failed it frequently involves the situation where bacteria have recolonized (reinfected) the interior of the tooth. (Possibly the seal created by the original root canal treatment has deteriorated, or the tooth's root has developed a crack, or coronal leakage has occurred, etc...)

With this type of situation, taking antibiotics may be able to assist a person's body in controlling the acute flare up of the tooth's infection. But it wouldn't be expected that the bacteria inside the tooth (the source of the infection) would be fully eradicated. (The space far inside the tooth is simply too inaccessible to the body's defense mechanisms.)

So with this scenario, yes there would be risk of another acute flare up sometime in the future, because some of the bacteria still inhabit the interior of the tooth (probably much of the time existing as a chronic, low-grade infection that produces no symptoms).

Textbook treatment usually involves retreating the tooth (performing root canal treatment again), or else extracting it (and replacing it with an artificial one).

Often a dentist will write a patient a second prescription for antibiotics as a precautionary measure. The prescription is then filled if the tooth starts to flare up again before definitive treatment has been performed.

Beyond what we've just stated and as a second scenario, an infection associated with a root canalled tooth might have non-endodontic origins. For example, "gum disease" might be the cause.

With this scenario, an antibiotic might be used to help to get the infection under control. And then if the dentist feels that the gum condition can be prevented from reoccurring (like by performing better oral home care, or more frequent dental cleanings), then the patient would not necessarily be at risk for future problems.

With your case, you'll simply have to ask your dentist for more information about your situation and its expected cause.

Root canal treatment

Very detailed and informative. Thank you for the information.

Root canal

Had root canal 6 months ago it was on the left side next to the canine tooth. First it was sensitive to touch on the top. About 4 months afterwards it was sensitive to chew. Now the whole tooth interior is very sensitive.I have to chew on the right side. No crown just a filing. What is causing this sensitivity to this tooth?


We're simply not going to be able to offer any insight as to the possible cause(s) of what you are experiencing. With some cases, what the patient states is simple to interpret and the problem(s) that probably lies at fault relatively obvious to any dentist.

With your situation, that's not the case. There is no question your tooth needs further examination. But what you describe is confusing and not a standard textbook set of symptoms. It doesn't seem possible to us that anyone could sort through things and arrive at a diagnosis about your tooth without having the opportunity for direct evaluation.

Since endodontic problems have the potential to flare up, you should give making contact with your dentist some priority just to be safe. Best of luck.

Root canal

Should I pay my dentist for redoing my infected root canal? I had it done 2 weeks ago and it got infected . My dentist had to make a small incission in my gum to clean the infected area.


We're assuming there's some information here that we aren't privy to.

Per your statement is seems:

A dentist completed root canal treatment for one of your teeth 2 weeks ago.

Afterward an infection associated with that tooth flared up. (As a part of managing that infection, the dentist aided the drainage of pus by making an incision in the area of the swelling.)

Now 2 weeks after the completion of the tooth's first root canal treatment, and because of the infection scenario that followed, the same dentist has suggested that the same tooth needs to be retreated (the exact same type of root canal treatment performed again), and that involves another fee (the same one as paid for the tooth's first completed root canal treatment).

This seems strange to us, and once again, we're assuming that there's some pertinent information that we're missing.

If a dentist has completed root canal therapy for a tooth, that implies that they were satisfied with the outcome of their treatment (as perceived by them at that time).

It's possible that the act of performing root canal may activate bacteria associated with the tooth and a flare up ensues. In theory, this could be bacteria found in the tissues that surround the tooth's root. So, at least in theory, the infection you experienced might not be associated with outright root canal treatment failure (as in the integrity of the completed work).

For a dentist to recommend retreating a tooth so soon after their providing the tooth's initial treatment, one would assume that they have identified a flaw in the work that they feel they can remedy. One might expect that they could have identified that same flaw previously. But even if not, it seems disappointing that they aren't interested in taking responsibility for correcting it, considering the short time frame.

When dental insurance is involved, it's not uncommon that a policy will limit coverage to a single procedure on a tooth in a given period of time. Our cursory search of the web found two policies that stated such. One provided no coverage for retreatment unless over two years from the tooth's previous treatment, the other had a 3 year limitation. To us, that's a way of stating that it's expected that the work provided by a dentist should have some credibility.

If something transpired after your work that was not common and normal (the tooth broke or cracked since its treatment, the temporary filling that was placed was lost and the dentist not advised promptly, etc... ) then we might envision this situation differently.

infected root canal

I had a root canal about 15 years ago. I just had xray and the dentist says there is an infection. What is the typical treatment?


That's not a terribly uncommon scenario. (We have a page that gives examples of signs on x-rays that suggest root canal is needed.)

Just above on this page we outline what options exist for failed root canal treatment cases.

Root Canal 3 times

I had a root canal in Feb of last year but tooth was still painful after several months. Returned to dentist and he discovered he missed filling the tip of the root so he redid root canal. Another three months passed and tooth was still painful. He sent me to a specialist and the endo found another root that didn't show in dental xray. This endo redid root canal and cut off part of the tip to eliminate root branch. Now, six months later, this tooth area is still sensitive. I decided to get another opinion and went to another dentist. She put antibiotics around the gums but that didn't help. She recommends extraction because of chronic irritation. Does this seem like a failed root canal and does it seem pausible that now I can't save the tooth? I've spent much $ trying to save this tooth.


Sorry to hear about your troubles. You've been through a lot.

The most informed opinion you could seek about your tooth's prognosis is from your endodontist (the specialist).

Diagnosing/interpreting difficult cases is what they do. Since yours has already treated your tooth, they'll have added insight into your current situation. And because they've been your treatment provider before, hopefully they'll have some empathy for your plight.

First off, you never know. Their evaluation may discover that some other type of issue has caused your recent symptoms: gum disease issues, cracked root, something improper about the "bite" of the tooth, or such. But we'd agree, it seems most likely that the 2nd general dentist you consulted with would have discovered these types of issues.

If the problem is determined to be an endodontic one, then you'll end up with 3 options:

Retreating the tooth - And yes we would agree, treating the tooth a 4th time? Only someone directly evaluating your tooth could make this decision. And we would think that in order to make this recommendation that they would need to see something obviously wrong that they could clearly improve upon (like yet another previously undiscovered root canal).

If an endodontic problem exists and retreatment is not chosen, then yes, extraction is the only other appropriate treatment choice. (The hope would be that you would choose to replace the lost tooth with an artificial one.)

As a 3rd possibility, if the tooth has multiple roots, and the tooth's problems clearly seem to be associated with just one of them, then that offending root is sometimes cut off and removed.

This option isn't always possible. When it is, it doesn't always make a good decision. There are definitely case-by-case issues that must be considered. But we mention it here so you can ask whatever dentist provides your treatment if that option exists for you.

Good luck with this. Sorry we didn't have any positive news for you.

Tooth pain after root canal

Had a crown placed on tooth 30. 3 months later had pain between 30 and 31 and more lateral on tooth 30. Pain is above the seat of the crown on the back of tooth 30 especially when pulling the floss out. The gums are not sore . Had root canal done and still have the same pain. Endodontist had me use steroids,special mouthwash and seems to have given up. Dentist says to try baking soda,peroxide salt mix. CT is negative and they both concur that the root canal was successful. The same pain persists. What should i do? I want save the tooth if at all possible. Help!


Sorry but we're not going to have any suggestions as to a cause or solution.

In terms of seeking evaluation or treatment from appropriate people, an endodontist would be the highest authority that dentistry has to offer on this type of situation. So you've done that correctly.

If your endodontist can't come up with a diagnosis or solution, it would seem reasonable to consult with a second one. Doing so might result in a fix, or at the other extreme just a greater realization of how confounding your situation is.

If neither can diagnose your situation, offer a solution, or even offer an appropriate plan for monitoring your tooth to see if any improvement will occur, it would seem time to give up on the tooth. Best of luck with this.

Canine root canal treatment

Two years ago I had my canine root canal treatment. After three / four treatments I felt pain or rather pressure when I place my finger on the tooth. Plus my tooth felt heavy. I told this to the dentist and he said it would go away, but it didn't. I decided to visit another dentist which then he said the last one treated the wrong tooth and this time I had root canal treatment on my tooth next the canine. Still I had pressure on my canine and then the dentist started to treat again the canine. Still no improvement. This went now on for two years. Now I have visited a third dentist after searching thru internet a specialist. She took X-Ray and started with root canal treatment. This time she explained that my root is very long and the former dentists could not reach the end or tip so she shortened my tooth and did the treatment but today I still feel the same pain or pressure.. No improvement . She also explained that maybe the bacteria extended from my root and that treatment from outside might be necessary by making an incision. For this she recommended having CT next time. I don't know whether this would heal or the right method. But now my tooth feels heavy and still have pressure/sensitive up the tooth. What is happening. I am worried and want this situation the finally end. What should I do? Would the incision treatment re rally solve this problem? Help!! Please...


You use the term "specialist." We assume that means a root canal specialist (an endodontist). If so, you should be in good hands.

Root canal files only come in standard lengths and it seems that the longest size still isn't long enough to treat your tooth, hence the need to trim it shorter so the files can extend into it further.

No dentist wants to trim away sound tooth structure. But if otherwise its root canal treatment can't be done properly, then it must be.

Since a part of root canal treatment involves cleaning the entire length of the tooth, what your endodontist has stated about the other dentists not achieving that would likely explain your continued symptoms.

It's disappointing that your symptoms have reappeared this time.
It could be that some of the bacteria from inside your tooth got pushed out into the tissues surrounding the root during this last treatment. If so, that could trigger a flareup (acute infection). With this scenario however, it should be the final event of this sort.

In regard to the need for a surgical approach:

  • Your endodontist's task of cleaning the entire length of the tooth may have been complicated by the previous root canal work the tooth has had. If so, the surgical procedure you mention might be used to trim off the tip of the root (remove that portion of the root that can't be cleaned properly) and a filling placed to seal of the canal. This is referred to as an apicoectomy and retrograde filling.
  • The anatomy of the tooth's previously uncleansed portion may be difficult to clean (for example, the root canal may branch). If so and just like above, a surgical procedure might be used to trim away and seal off this uncleansable portion of the tooth.
  • Your tooth has a long history of being symptomatic, which is probably due to a long standing infection. It may be that the bacteria causing this problem are not just harbored inside your tooth but also have a protected location in the tissues that surround the root's tip. If so, the surgery you mention might be used to remove that nodule of bacteria.

Your endodontist won't be able to guarantee that the surgical procedure will finally solve your problems. But it's their obligation to give you a realistic idea of its chances. They also have an obligation to explain their suggested treatment in comparison to your other options (which would probably only be tooth extraction and replacement. But that might be more attractive if it carried a significantly higher chance of success).
Best of luck with this.

ache under crown / root canal'd tooth

I guess I'm asking more about the symptoms that would lead one to make the choices in this article. I have a tooth (#30) that has had an ache / sensitivity for about 5-6 weeks. Initially, I made an appt with my dentist and they thought it was the made some adjustments. I was back in for a routine cleaning about a week ago, and told her I still had sensitivity to temperature - actually hot more than cold - and pressure. She told me to try sensitive teeth toothpaste for a couple weeks. She took an xray and certainly looked at the tooth. But with the metal crown, I'm guessing it may be difficult to diagnose. Any thoughts on what is going on? And how long should I allow the toothpaste solution to play out? I've been using it for a week. The tooth doesn't ache or barely at all when I'm not eating or drinking. But can be pretty sensitive when I do!


We're not going to be of much help.

The title of your comment states that your tooth has already had root canal treatment (has had its nerve tissue removed). Because of that, it wouldn't be expected that "sensitive teeth toothpaste" would provide a benefit.

Sometimes it's a neighboring (live) tooth that has the thermal sensitivity and it just feels like it's the root canalled tooth (referred sensitivity). If so, using a toothpaste might provide a solution. But as far as the tooth that's been treated itself, no.

In regard to reading x-rays, it's being able to visualize the area around the tip of the tooth's roots that is usually the most informative in regard to diagnosing endodontic problems. Having a crown on the tooth wouldn't interfere with this.

"Sensitive teeth toothpastes" create their effect by way of building up a coating on the tooth's dentin surfaces. If an improvement is noticed, it would typically be a gradual one.

We looked at the directions for one popular brand and it suggested a 4 week time frame for usage. In your case, it makes more sense to go ahead and report to your dentist about what you've noticed and let them decide how long you should try that solution.

It seems your dentist is trying to give your tooth every opportunity to settle down, which is fine as long as you remain under their supervision and follow their directions.

We will mention that sensitivity to hot stimuli and biting pressure can be indicative of continued problems with treated teeth (failing root canal treatment, a missed canal, etc ...). Only your dentist can determine if this applies in your case (how long the discomfort lasts after being set off by the stimuli is often a key indicator).

It seems your dentist is in the process of trying to make this determination. But until a diagnosis is made and treatment provided, you should stay in contact with them in case things take a turn for the worse. Good luck.

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