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 per se. Here are some possibilities:

  • Referred pain - The nerve that services a tooth services other teeth and anatomical structures too. And it's possible that a dental or medical problem elsewhere along the nerve creates sensations that just happen to feel like they're coming from your root canalled tooth.
  • Persistent Dentoalveolar Pain disorder (PDAP) - PDAP might be thought of as a catch-all category used to classify situations where the patient has continued symptoms from their endodontically treated tooth that seem to have an origin that lies beyond the treated tooth itself (the pain has a "nonodontogenic etiology" [non-tooth related cause]).

    Phantom pain is an example of PDAP, and is a phenomenon similar to phantom limb pain that amputees sometimes experience.

    Its underlying cause stems from trauma sustained by the nerve that services the treated tooth (like when the tooth's pulp tissue is removed during root canal therapy). This condition possibly occurs in as many as 3% of cases. (Marbach 1993)

    We discuss PDAP disorder and other nonodontogenic issues in greater detail below.

(Nixdorf 2010, Durham 2014) [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.

1) Missed canals.

Different types of teeth (molars, premolars, canines, incisors) characteristically have differing numbers of roots and root canals. But unfortunately for the treating dentist, there are no hard rules about the configuration that actually exists.

  • Specific roots of some types of teeth are well know for having, or frequently having, multiple canal configurations, and because of this should always be suspected of having more than one.
  • Even beyond what might generally be expected, it's always possible, no matter how rare, that the anatomy of a tooth's root canal system is simply atypical.

The back root (root "a") of a lower molar may have one or two canals.

Picture of an x-ray showing a lower molar's root canal anatomy.

If it has two but both aren't found, its root canal treatment will fail.

A dentist's due diligence.

The problem/question that arises is how much effort a dentist should reasonably expend in searching for these, possibly rare, variations.

As a point of fact, additional canals are frequently tiny in size and as such difficult to identify. Additionally, they may have a location inside the tooth that's strange or unexpected.

  • At minimum, looking for possible variations takes additional time. Although, this should just be a minor consideration for the dentist.
  • Worse, searching a tooth exhaustively can involve trimming away aspects of its interior that can result in structural weakening. Of course, this is especially disappointing when no additional canals are discovered.

For these reasons, it's easy enough to understand why a dentist might not be astoundingly inquisitive if the configuration they have already discovered lies within the parameters of what can be considered normal for the tooth involved.

The underlying problem.

The crux of this issue is simply that any untreated (overlooked, undiscovered) canals, no matter how minute in size, will remain a locus of persistent infection. And as such, will lead to the failure of the tooth's root canal treatment.

Picture of a dentist using a surgical microscope during root canal treatment.

An endodontist using a surgical microscope.

Incidence rates.
  • 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 use a surgical microscope as a visual aid in their search for additional canals. Also, a specialist is more likely to be familiar with what variations might exist, and more likely to be able to adequately treat very tiny canals. See discussion and link below.)

  • Hoen (2002) evaluated 337 failed root canal cases and determined that overlooked canals played a role in 42% of them.
Animation showing lateral and accessory root canals.

Variant root canal anatomies.

2) Unfilled accessory and lateral canals.

The anatomy of the root canals inside a tooth can display variations.

  • An accessory canal is any branch of one of a root's main canals that leads off to an exit point on the root's surface.

    Somewhat arbitrarily, accessory canals are typically defined as canal branching found in the apical end (tip portion) of a tooth's root (last 1/3 of the root or so).

  • A lateral canal is also technically an accessory canal. But, and again arbitrarily, usually defined as branching that occurs in the upper 2/3rds of a tooth's root.

    As a point of difference, lateral canals often run horizontally from the central canal directly to the root's side. In comparison, accessory canals might be considered to have a more split-off/branched configuration (see animation).

The underlying problem.

With both of the above variations, it's common that the division of the canal isn't identified. And even when detected, it may be difficult, or even impossible, for the dentist to adequately treat (clean, shape, fill) the branch.

If that's the case, and just like with missed canals discussed above, the result will be one where some of the tooth's root canal system is left ineffectually treated. As a result, the deficient portion can provide a location where infection can persist and therefore act as a continued irritant to the tissues that surround the tooth's root, ultimately leading to case failure.

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 under filling, the presence of voids, etc...). A study of failed cases (Ibqal 2016) determined that 1/3rd involved under filling 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 an internal configuration that deviates from normal canal anatomy (applicable terms include: canal ledging, apical transportation, zipping).

    This kind of alteration can make the process of cleaning and/or sealing the affected canal(s) difficult or impossible.

  • Perforations - When using drills or files, a dentist may inadvertently create a hole (perforation) that penetrates the side of the tooth's root.

    Depending on the size and location of the perforation, some can be repaired successfully. However, the mere presence of the opening may make it difficult or impossible for the dentist to pass their tools and sealing materials beyond that point, thus inhibiting complete (proper) canal cleaning and sealing.

  • Broken instruments - The files that a dentist uses to clean a tooth's root canal system sometimes break. It's generally attributed to manufacturing defects, fatigue from usage, or with rotary instruments, a situation that creates too much torque.

    As a worst case scenario, the broken piece may be lodged inside the tooth and cannot be retrieved. If so, while leaving the fragment inside the tooth is never the dentist's first choice, the point during the treatment process when the incident occurred may be a mitigating factor.

    If the file separation has occurred after the canal's cleaning process has already been completed, then possibly the canal can still be adequately sealed even with the fragment present. If the incident occurred during the cleaning process and inhibits its completion, the prognosis for the tooth's treatment is much less favorable.


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).

A possibly needed solution.

In cases where the dentist's evaluation of the quality of the tooth's previously performed root canal treatment seems acceptable, the solution for this situation may be a minor surgical procedure referred to as an "apicoectomy with retrograde filling."

During this procedure, the tip of the tooth's root is trimmed away (an apicoectomy is performed). The exposed root canal opening on this trimmed surface is then sealed by placing a filling (a "retrograde" filling).

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.

D) Complications stemming from non-tooth conditions.

While not actually a failure of a tooth's received treatment, the conditions described in this section do represent a failure of root canal treatment to provide a solution for a patient's original symptoms.

a) Persistent Dentoalveolar Pain disorder (PDAP).

PDAP is a relatively new term used to label situations where the patient experiences continued discomfort with their root canalled tooth but an underlying condition associated with the tooth itself or its work doesn't seem to lie at fault. Encompassed terms and conditions include: atypical odontalgia, phantom pain, and deafferentiation pain.

What are the symptoms?

Initially, a tooth displays some version of symptoms similar to those characteristic for needing root canal therapy. After receiving its endodontic treatment, symptoms with the tooth continue to persist (3 to 6 months and longer).

The symptoms that persist are often described as: The sensation of pressure combined with a dull ache. In some cases, the descriptors itching, tingling and/or pricking apply. The discomfort comes from the area of the tooth, deep within the jawbone. The pain is usually present most of the time.

A review of published studies by Sobieh (2013) estimated a 3.4% incidence rate for experiencing PDAP.

(Hargreaves 2015, Warnsinck 2015, Sobieh 2013)

What is the cause?

It's hypothesized that nerve fibers associated with the tooth (peripheral nerves) have been sensitized (transmit signals that pain is felt) due to disease or injury (such as those factors that can instigate the need for root canal treatment). For unknown reasons, these nerves remain sensitized after the tooth's endodontic therapy has been completed.

A complicating issue associated with PDAP disorder is that over time this constant barrage of sensory input (pain) from the sensitized peripheral nerves (those in the area of the tooth) may ultimately induce changes in the patient's central nervous system (meaning the source of the pain is no longer just associated with the region around the tooth but now with the major nerve pathways of the body).

(Hargreaves 2015)

Evaluation for PDAP.

The underlying premise of PDAP disorder is that it does not stem from a deficiency or failure of the root canal work the tooth has received. In most cases, it seems that an endodontist (root canal specialist) and the higher level of expertise and equipment they have to offer would be best able to make this determination (for example the 3D imaging capabilities one typically has might be an asset).

Solutions/treatment for PDAP.

Treating PDAP disorder is unpredictable and enduring this condition frequently places a physical and emotional toll on the patient. Extraction does not provide a solution since the cause of the pain does not lie with the tooth itself.

When this condition is suspected, it frequently serves the patient best if evaluation by the highest authority possible (an endodontist) is sought early on. That's because:

  • A common scenario is one where less knowledgeable authorities are sought first, and on their advice the patient undergoes a number of procedures in an attempt to alleviate their symptoms, although none of them are in fact appropriate measures.
  • Early diagnosis and treatment may help in preventing the condition from transforming from a peripheral to a central one (discussed above).

Once diagnosed, treatment/management of the patient's condition is usually by way of medications vs. an actual procedure (details about treatment lie beyond the scope of our coverage of this subject). Success (absence of pain) can be difficult to achieve.

(Hargreaves 2015, Warnsinck 2015, Sobieh 2013)

b) Tempromandibular joint disorder (TMJ).

TMJ disorder, a condition involving pain and limited function of the jaw joint and the muscles that operate the jaw, is usually precipitated by a person's habit of clenching and grinding their teeth (dentist refer to this activity as bruxism).

  • 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 (tender to biting pressure would be characteristic).

    If the discomfort is associated with a tooth that has had root canal therapy, the sensitivity noticed comes from nerve fibers associated with the ligament that holds the tooth in place. This type of pain is unrelated to the success or failure of the tooth's endodontic treatment.

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.


Written by: Animated-Teeth Dental Staff

Last revision/review: 9/17/2018 - Revision, content added.

Content reference sources.


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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 much 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.

Incisor root canal

I had an incisor crack at the gum line years after root canal because I didn’t get a crown on it. Teeth become more brittle when the nerve is gone since they’re not alive. It was fixed with a post and crown for about 12 years until that, too, cracked the remaining root. It’s now a dental implant which I love!

As Lisa states, the type of

As Lisa states, the type of restoration placed after root canal treatment can play an important role in the tooth's long-term success. We have a page that discusses issues associated with understanding what constitutes an appropriate post-treatment final restoration.

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?


Because 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 filling material has deteriorated, or the tooth's root has developed a crack, or coronal leakage has occurred, etc..., all of these things are discussed above on this page.)

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 tooth).

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 sorry but we're not going to be able to offer any real 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 the description you give doesn't seem to correlate with a standard textbook set of symptoms. To arrive at a diagnosis, a dentist will need direct evaluation of your tooth. They'll also no doubt want better clarification of what some of the terms you have used refer to.

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 that there's some relevant information with your case that we aren't privy to. Per your statement it 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 according to that 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 (referred to as root amputation).

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 possibly find 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 to be a reasonable point 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.

With any one of those scenarios, the procedure might prove to be completely successful.

Of course, 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 that kind of 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.

Failed Root Canal

I had my root canal treatment last year May 2017 in my left canine . At first It was perfectly fine all the pain and sensitivity had gone. But after a year, I noticed that the same symtomps re occur. First when I tap or touch my left canine it feels sensitive, then when I touch it on the top outside near my nose upper lips where the root is located it has the same feeling before the sensitivity and pain. So I decided to visit a Dentist and decided to have a Zirconia Crown on it because I think that maybe It will be needed to put a crown instead of a filling only. I already told the Dentist that I already had a root canal with that particular tooth he took an xray and he told me that there is still a small infection on the top of the root he told me that maybe the last dentist that took the root canal treatment for me had failed. I asked him what should I do, do I need to have a RCT again. He just told that he will do the Zirconia Crown because maybe the infected area will be gone after. Or will lessen its symtomps. I listened to him, he do the crown and cleaning everything was perfect the sentivity is not that much as before but still I have the sensitive feeling on that tooth. My question is, is that posible that the sensitivity or pain will eventually go away by itself or I need to have a retreatment for my root canal? Because as what you have shown at the pictures of failed RCT i have the same case on the top layer of my RC there is a black shadow that indicates an infection as shown on my xray results. Please bear with me I need an answer.


An x-ray isn't necessarily diagnostic by itself. For example, the shadow that is seen might be related to the formation of scar tissue that formed as healing took place.

What's concerning is that with your case you state: "when I tap or touch my left canine it feels sensitive, then when I touch it on the top outside near my nose upper lips where the root is located it has the same feeling before the sensitivity and pain."

Those can be classic signs for a tooth that needs root canal treatment (retreatment). And if that is the case, the shadow at the tooth's root tip on the x-ray is confirmation of that (the shadow area [area of infection/inflammation] would correspond in position with the area of tenderness you touch). Additionally, pain/tenderness persisting for a year suggests that healing didn't occur and that a problem still exists.

If a diagnosis of failure is correct (a diagnosis only a dentist actually evaluating you and your tooth can make, not us), then the only solution is to have endodontic retreatment.

In regard to crown placement as a solution:
A crown can create a superior seal for a tooth, and one that's often needed for root canalled teeth. (Coronal leakage can be a cause of root canal failure.)

But if a tooth already has an existing endodontic problem (meaning an already contaminated root canal system), crown placement will do nothing to resolve that issue (the bacteria are already inside the tooth, they can survive just fine if the tooth has a crown on it or not). What's needed in that case is cleaning and sealing the tooth's root canals by performing endodontic (re)treatment.

Root canal tipped over

I have a very old root canal rear molar that is now so far tipped over that it is almost horizontal due to having the molar in front of it extracted years ago. The tooth in front of the extracted one is also a root canal with the tooth in front of it extracted also. The rear molar seems irritated around the gum from both eating on that side of my mouth and brushing it because I have a failed root canal on the opposite side in the back that my dentist is going to remove this week. it looks like I will need to find an oral surgeon to try to extract the tipped over one. I am wondering how I should be taking care of it until then.


If the situation is simple, the logical assumption is that your now horizontal molar accumulates/traps debris (dental plaque, food particles, etc...) underneath its side that now rests against gum tissue.

This accumulation irritates (inflames) the adjacent gum tissue, the signs of which would be redness, tenderness, swelling and possibly bleeding when provoked.

The solution would be to keep this debris cleaned away, thus allowing the gum tissue to heal.

To do so, possibly the side of the tooth that is face down could still be flossed. If not, possibly rinsing around the tooth with an antiseptic type mouthwash would help. The exposed surfaces of the tooth would need to be kept clean (brushed) as effectively as you can too.

Run all of this past your dentist during your up coming extraction appointment. It should just take them a few moments to confirm that this makes the needed plan.

(While you don't mention it, if perchance the root canal treatment of this tooth has been diagnosed as having failed and that's the cause of what you notice, the only way of controlling it's associated infection over the short-term would be via the use of antibiotics prescribed by your dentist. The same would be true if it was diagnosed that the tooth had advanced gum disease associated with it. If the problem stems from the inability of the tipped tooth to now withstand the level of forces it receives, keeping it cleaner may help but generally there would be no solution other than extraction.)

Possible reoccurence of Route Canal infection in tooth # 3

My guestimate is approx. 9 years ago, in 2009, I had a route canal procedure performed on tooth # 3 by an endodontist, the only one in the city of approx. 65,000 people at the time.

In July of 2017, the crown came off of tooth #3, I sought out a new dentist since my dentist of the past 20 years had retired. Because of the emergency, there was only one dentist open on that Friday. The new (one-time O.V.) dentist took an X-Ray (digital ?) of tooth #3 and showed me the picture of it and pointed out where he said: "one (or two) of the canals was/were missing some filling or sealant". When I queried as to how that could occur I believe he said it was not or may not have been completely filled." He then re-cemented the crown back on tooth #3. He did not offer any additional information, data or instructions indicating there was any problem or possibility of any potential problem (I add this because further evidence and research indicated that he should have).

In August of 2017, tooth #4 fractured because it was incorrectly treated in Nov. of 2015. I found a new dentist and she took out some decay after taking an X-ray which she said showed no shadow and therefore the nerve was not affected. However she warned me that since she had taken out some decay to be aware of any pain and go to an endodontist immediately if there was any pain. She put a temporary crown on tooth #4 and due to delays, she put the permanent crown on tooth #4 in May of 2018, some 9 months later. Since she said the temporary cement had come off during the 9 month interval I requested she put it on with temporary cement in case I needed a route canal . I thought within a month or two if pain showed up I would be able to have the endodontist take the crown off easily. It's important to note that no pain was felt at all for the 9 month interval since she put the temporary crown on.

Back in August of 2017, after the 1st dentist had re-cemented the crown back on tooth #3 I had noticed that there was a space (to me it appeared to be significant) between the crown and my gum line. I initially thought (being a layman and ignorant) that the dentist had not fit the crown back on properly since it was not flush with the gumline. The new dentist said however that that was not the case but that my gum had receded (why only from one tooth is my question). She noted that she could put a new crown on it. 9 months later, in May of 2018, she said there may be additional decay in the tooth. I asked her how she could determine that and she took a dental instrument and began her examination by poking extensively around inside the crown by going through the gap between the crown and the tooth on the interior. She then said she could tell there was decay.

This was done on the same visit I believe that she put the new crown on tooth #4.

Within a week to two weeks, I began experiencing pain in what I initially thought was tooth #4. It would become more painful after eating. But when I flossed & brushed my teeth, the pain stopped. Then after dinner I sensed & felt food matter, pasta and other food matter hanging out of my tooth, stuck there and I could not remove it with my tongue. It actually felt, and I sensed this , that the pasta etc. was hanging out from where it felt it was stuck -- caught the between the crown and the gumline, and extending down over the gum and tooth (crown).

I went to the endodontist that I've been going to since around 1990. He had done R.C. on tooth #3 originally. I told him I had pain and my dentist originally had been emphatic that if I had pain after she treated tooth #4 (which had no shadow on the x-ray) to see an endodontist. I saw him a few days ago on June 28, 2018. He took an x-ray, saw no problem and tested tooth #4 with hot and cold and tapping the tooth -- and the results were no sensitivity to hot or cold or to the tapping w the metal instrument. I sat there and he could not give me a definitive answer to why I was having pain.

A few days after I left his office I ate some rice pudding and could sense, actually feel with my tongue that there was rice pudding blocking (and in ?) the gap (space) between the gumline and the ill-fitting crown on tooth #3!

I went on line to research and found some data/information I was completely ignorant of -- and that is that a tooth that has had a route canal performed upon it can go bad, a canal or more than one canal can become reinfected due to the canal(s) not being completely filled & sealed or perhaps the material that was used to seal the tooth had deterioated.

Putting this all together my logic leads me to believe the pain(s) are possibly actually coming from the re-infection of tooth #3 which had a route canal done on it many years ago.

It is not after hours and I have not had a chance to speak to my dentist or endododist about it but I'm asking you since one would think that given all of the data that I've shared with you, they were both aware of and said nothing. Why do I have to be the one to research all of this and figure this out!?

Please advise. My theory seems logical to me given the facts as outlined above. Why didn't they?


Re the emergency dentist - By stating what he did, in his mind he probably felt he had brought the matter to your attention, however ineptly.
Looking at the situation from his perspective: You presented with a crown that had come off of an asymptomatic tooth, whose work had been performed by a specialist.
This dentist knows that not all treatment turns out as perfectly as the practitioner had hoped (often because of obstacles encountered within the tooth) but the level of care performed was at a specialist's level (implying the best possible).
Short of obvious signs of an active problem, and considering the level of treatment the tooth had originally received, and the evident success of the treatment at that point, we're not so sure how much of an issue they should have raised.

Re the endodontist's evaluation of #4 - We just don't see how it would be possible for an endodontist not to include the evaluation of adjacent teeth when investigating #4. And at least at that point in time, one would have to assume that they honestly felt a diagnosis couldn't be made.
In regard to testing #3, sensitivity to percussion would be characteristic for failed root canal work. In the case of unfilled/missed canals, possibly sensitivity to heat could be a symptom too.

None of your symptoms associated with food accumulation stand out to us as indicating an endodontic problem.

We find it curious that the endodontist didn't make mention of inadequacies of the crown on #3. Beyond missed canals/deteriorated canal system seals, root canal treatment can fail related to coronal leakage. Your crown has an "open margin" (in the location of the decay) and as such no longer creates an intact seal over the tooth.

In regard to the changes you've noticed at the gum line on #3, Google the terms "abfraction" and "abrasion." Of course, the changes could be related to decay formation alone.

It seems everyone involved is simply waiting until your symptoms become characteristic enough that a diagnosis can be made and treatment suggested.

No one wants to treat #4 if it doesn't need it. No one wants to suggest the retreatment of #3 (if it needs it it may not be possible, or may not have a high expectation of success, or might require surgical rather than conventional treatment). No one wants to make a new crown for #3 if there's a possibility that it can't be saved.

Possibly the middle ground here is that a temporary crown should be made for #3 to insure a better seal until things can be figured out and which tooth is at fault is determined. But that would be up to your dentists to decide.

We're sure your situation is frustrating. Stay in close contact with both dentists so they know you still have issues and require attention.

Abcessed tooth/ root canal

A week ago I woke from sleep with an explosive pain in face, I looked in mirror, my right side of my face was extremely swollen, eye was swollen shut, lower part of face drooping. This was at 4am, I went to the ER thinking maybe a sinus infection, I was prescribed antibiotics by the doctor...he did no X-rays, did not look in my nose, didn't look in my mouth. I took the antibiotics for 6 days, still having a great deal of pain, I decided to go to the dentist, after his exam it was determined I have an abcessed tooth, following day he started a root canal, he cleaned the canal, but said I have more infection that didn't drain, he sealed the tooth and has prescribed amoxicillin, and has scheduled root canal part two in 10 days. Is this common?


Yes, the way your dentist is treating you tooth is commonplace, and it sounds like you're in good hands with them.

You said they sealed your tooth back up, meaning they're trying to prevent more bacteria from entering the tooth after cleaning it somewhat.

A sealed tooth might flare up (allow pus to build up like it did before), so they've place you on antibiotics to make that event less likely.

They have appointed you for 10 days out, a point after you'll have stopped taking the antibiotics. That way they'll know if the tooth is staying quiet on its own accord, or only via the assistance of the antibiotics (a diagnostic test helping them to understand when they can complete the tooth's treatment).

If perchance you notice problems, especially those similar to what you had before, starting to brew, let them know promptly. Most likely you'll be fine.

root canal / interventions have not made any difference

My upper right molar became unbearable if I bit down on it. Hoping it would right itself, I started chewing exclusively on the left and I did not go back to my dentist for five months.

My dentist saw nothing on the xray and said my filling had failed and then replaced it. But the pain was just as acute, and therefore sent me to his colleague who specializes in root canals, even though I said the resulting "dead" tooth was as sensitive as ever, he said it would settle down and that the crown would take care of everything. But it did not and the pain got even worse if I accidentally bit down on it. I even had it checked by my dentist in the States when I returned for a visit and she said everything looked excellent and give it a little more time. When I returned to Paris my dentist here said give it a little more time. After two agonizing incidents that lasted half a day after accidentally biting down on that side of the mouth, I went back and the dentist suggested that the plaque built up around the tooth under the gum was causing the difficulty. I was sure that was not the cause of my pain but my dentist said his colleague was the best for root canals so this must be the cause. Viola, we had yet again another intervention (over 2000 Euros spent and a year and a half) where he cut the gum away and probably did a bang up job of needed deep cleaning but he admitted he saw nothing alarming. I am going to see him Monday to get the stitches taken out. There is absolutely no change in the pain from the beginning if I bite down on the tooth. Cold and air blown on and the outside of the tooth are a killer. The teeth before and behind have absolutely no sensitivity at all.
What should I tell, suggest, ask. etc. of him? All I want is the pain to stop but I am extremely frustrated by the money (I am not able to spend more huge sums at present), discomfort. and time already spent for no result.
Many thanks in advance for your much appreciated reply.


We would think that seeking further consult from your endodontist, as opposed to just your general dentists, would be important to do.

By nature of their position in the profession of dentistry (challenging cases are referred to them by general dentists), one would have to assume they would have significantly more experience in making a differential diagnosis with cases that display atypical symptoms than the average dentist.

An endodontist typically has 3D imaging capabilities (Cone Beam Computed Tomography) that a general dentist doesn't that might better help them evaluate your tooth.

If per chance your tooth's root canal treatment hasn't been successful, yet it was performed at expert level (by the endodontist), it just seems that whatever problem exists might be something much more likely to be realized, discovered or interpreted by a specialist, especially one who has a history of providing treatment for your tooth. Good luck.

Pain after recent crown and root canal of molar

Last year I was experiencing some pain with #15 molar, particularly with compression. My dentist took x-rays and said there was nothing conclusive but perhaps either a crown or root canal would fix it; he did also say a cracked root could be the problem but couldn't be sure. I opted for a crown. A couple months later, I was still experiencing pain and was referred to an endodontist for 3D scans and a root canal. The scan didn't show any cracks and a root canal was performed. Now in the last month or so I'm getting headaches from the dull pain, which comes and goes. The tooth hurts more when compressed or when I apply pressure on the sides. Another x-ray at the dentist showed cloudiness above the tooth, and the dentist again mentioned it could be a cracked root. My tooth has never felt right even after all the work and $ spent. Is it safe to assume this tooth needs to be pulled after all? Who can definitively tell me whether the root is cracked or not? I might add the dentist is somewhat new to me and I've never used the endodontist before.


Sorry to hear about your troubles. We would think that you need to let your endodontist evaluate your tooth and its current set of symptoms and make a recommendation about possible solutions.

"Who can definitively tell me whether the root is cracked or not?"
Your endodontist would be in the best position to make this determination, although the word "definitively" may not exactly apply.

We read through some published research papers that evaluated dentists' ability to diagnose cracks in sample groups of teeth using 2d and 3d x-ray imaging. It seems cracks were only identified on the order of 75 to 85% of the time.

One problem with a tooth having a crack is that it gives bacteria a location to live. And over time, their presence (the infection they cause) will tend to trigger changes in the bone that surrounds the tooth (you mention the "cloudiness" seen). So, that may help the endodontist determine if/where a crack lies.

"Is it safe to assume this tooth needs to be pulled after all?"
If the tooth is cracked, yes extraction probably is indicated.

A possible middle ground might be root amputation.
If the tooth has multiple roots (you mention that your problem tooth is #15), and the endodontist can determine which root lies at fault, it may be possible to cut that root off.

This isn't always possible or a good idea, your dentists will have to fill you in. But sometimes this provides a way of salvaging the work you've already had done.

Sensitivity & burning around tooth after root canal

Upon undergoing recent root canal; left upper canine, I am still experiencing a burning sensatsation along with pressure, I revisited my endo, cannot find anything even on ct scan. Could there be nerve damage or anything else lurking causing this issue? I was recently give a course of steroids which corrected the problem for about a week. Any ideas or people with similar issues?


There is neurologic condition that may persist after endodontic therapy. It is sometimes referred to as "phantom tooth pain." We discuss it above on this page as PDAP.

Obviously, we in no way know if this condition is what you are experiencing. But in terms of differential diagnoisis, it seems justifiable enough that it should be considered and discussed with you by your endodontist.

Overall, we think the most important thing you can do is simply stay in continued contact with your endodontist. If they don't know that you're still having problems they may assume you're not, and therefore won't continue to explore possible causes and solutions. Good luck.

Gum tenderness between back lower molars

First of all I have epilepsy and since the onset of seizures - which now are very well controlled, all of my molars have had root canals and crowns. One of the meds I take is Dilantin and I floss faithfully. I noticed gum tenderness between my right lower back molars with flossing 5-7 days ago. No pain with chewing etc. This area remains tender with flossing and this evening I also have discomfort radiating to my right ear. I have also noticed some generalized aching of the area where the gum tissue is tender. I had an infected root canal on the left side 3 years ago which was a nightmare as I had a re-do root canal, new crown, then developed a draining area in my mouth a few months later, this all resulted in extraction of that molar. I am afraid of having the same senario starting again, however I remember how painful that tooth was when the infection was in there and this is not the same. Please advise—thanks!


Obviously it's going to take an evaluation by your dentist to determine what is going on. Considering that there could be infection involved with what you notice, contacting them sooner rather than later would be important. If they feel that infection is an issue, they might prescribe antibiotics for you via telephone to get that started sooner.

You mention your taking Dilantin, so what you notice (as you no doubt know) could be associated with gum tissue enlargement (hyperplasia) related to that. The scenario would be one where the situation keeps you from cleaning the area effectively, hence bacterial accumulation has started an infection. If so, it's likely that the episode could be treated and resolved.

The fact that it's not your tooth that hurts isn't a bad sign. But it's not a definitive one in ruling out the failure of a tooth's root canal treatment as being the source of your problems. (With some failed cases, it's the build up of pus in the jawbone that causes the patient's pain. If conditions exist where some of this pus has found a way to vent off, no pressure/pain may build up, but it is still the tooth's endodontic work that is the source of the problem.)

Only your dentist can make a determination between the two (or other possible causes), and only after physically examining you and likely taking x-rays of the area.


Thank you very much for your assistance! I was able to see my dentist this afternoon. The x-rays looked great which was a great relief. The gum discomfort persists however, they did try to flush the area out with a waterpik/flosser. No debris was in there, Paroex rinse was ordered and I am now using that hoping for complete relief soon. Thanks again!!


That's great

Failed root canal

I have a failed root canal then did a retreat and now I have slight swelling and pus pocket (like the pic u have of a boil) on the gum by that tooth. X-ray shows now that there is a vertical fracture on that tooth. can this tooth be saved or is the best option just to extract it and have implant there?


Generally speaking, the problem with a crack in the root of a tooth is that between the two parts there exists a space that bacteria can colonize yet your dentist can't get at them and clean them out (like they did with your tooth's root canal system).

The consequence of this scenario is that an infection will persist in the crack's space. The fact that you notice swelling associated with your tooth suggests that this is what's going on.

In that case, the tooth can't be successfully treated (the infection can't be cleared out), so extraction (with some type of artificial tooth placed, such as an implant) is the only alternative.

The single exception would be the case were the cracked (infected) root can be trimmed off (root amputation), leaving the remaining successfully root canaled/healthy portion of the tooth.

Obviously this option is only possible with multi-rooted teeth (molars, some premolars). If possible, it doesn't always make that great of a choice but it may. Only your dentist can advise you if pursuing this option makes a reasonable plan.

Failed RCRT attempt Upper Right 1 (Incisor)

Brief history:
2000 - trauma to tooth playing squash - whacked in the faced from opponents backhand racquet. Now a dead tooth.
2004 - Huge Abcess drained + RCT. Evidence of root tip absorption. 2 attempts at RCT over 3 week period.
2017 - Abcess like symptoms returned. Dentist said watch & wait. Acute swelling & mild pain subsided without use of any meds.
2018 - (2 weeks ago) - full on abcess. Drained. Evidence of further root tip absorption. Procedure involved RC re-treatment. Thought was fine but..
Last few days - new swelling. X rays show that Accessory point pushed through beyond end of root tip by a good couple of mm. Most likely from new insertion rod pushing through old debris from first RCT up into cavity. This most likely causing existing bacteria to start brewing again without interruptions!

Have been referred under 'urgent' to local Dental Hospital for Endo-treatment plan and potential Apicoectomy. In the meantime 7 day course of Antibiotics - whilst it may not end infection it'll hopefully stop it spreading further.

Prognosis not great.. Especially with old debris not in cavity space above & beyond root tip...oh dear

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