How to know if your tooth needs root canal.

- Signs and symptoms you may notice (pain, infection, swelling). | Signs dentists look for. | Tooth testing. | What to do if you notice symptoms.

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Gum Boils.

Link to root canal signs and symptoms section.

Signs on

Link to how root canals are diagnosed section.

Does your tooth need root canal?

Figuring out if a tooth requires endodontic therapy isn't always a straightforward or easy task.

Common indications.

As we outline below, there are a number of characteristic signs and symptoms that people who have a tooth that needs treatment frequently do experience. And additionally there are other, sometimes less obvious, signs that dentists know can also suggest that your tooth is in need of attention.

Diagnosis must be based on a complete picture.

The final determination about a tooth's need for root canal must be based on your dentist collecting information from all available sources, and then viewing those findings in light of each other. Only with that complete picture can an accurate diagnosis be made.

We mention this because as eager as we are to share the information on this page with you, it's only your dentist who can provide a proper evaluation and valid diagnosis.

Reading this page can provide valuable background information. But if your tooth has displayed symptoms, you should take that as a sign that you already require the direct attention of your dentist.

Root canal signs, symptoms and testing.

If you have a tooth that's suspect of needing endodontic therapy, here are the type of issues and events that need to be evaluated.

Some of this input needs to come from you the patient. Other factors can only be determined by your dentist.

  1. Symptoms you have noticed. - It's frequently the appearance of pain or signs of infection and/or swelling that first signal to a person that their tooth has a problem.

    Your dentist will quiz you about the symptoms you have experienced: Type, location, onset, triggers, duration, what if anything provides relief.

  2. Signs obvious to your dentist. - Some teeth seem to give little indication that there's a problem within their nerve space. But to the trained eye, there can be subtle hints that are an obvious sign that a problem likely exists.

    Common tip-offs: Dark tooth color, evidence of drainage from infection, soft tissue changes and asymmetry.

  3. Additional testing. - Once a dentist has identified one or more suspect teeth, they'll perform additional testing and evaluation that can help them zero in on the one that lies at fault.

    Types of testing: Thermal (hot and cold), percussion, electric pulp testing and of course x-ray evaluation (conventional and/or cone beam computed tomography).

    Additional evaluation: Dental restoration status (defective, recently placed), periodontal (gum health) status, checking for tenderness, cracked tooth evaluation.

Takeaways from this section.

Since performing endodontic therapy is the needed solution for such a wide variety of problems (acutely inflamed teeth, teeth with dying or dead nerve tissue, cracked teeth, failed initial root canal treatment, etc...), there isn't just a single set of symptoms that appears in every case where it's needed.

It's only after sorting through all of the bits of information they've collected, from all available sources (patient dental and medical history, symptoms experienced, clinical exam, tooth testing), that your dentist can then determine if root canal, or possibly an entirely different dental procedure, seems to be the appropriate solution.

In some cases the data that's been collected may be inconclusive, or even conflicting. If so, the patient may need to wait and be reassessed at a later time, or be referred to a specialist (endodontist) for evaluation.

1) Root canal signs and symptoms that you (the patient) may notice.

Probably the set of symptoms that are most associated (and feared) by patients as an indication that root canal treatment is needed for a tooth are those that occur during an acute tooth flare up (in dental terms, "acute apical abscess").

This condition is characterized by:

  • A quick onset, spontaneous pain, extreme tenderness of the tooth to pressure, pus formation and swelling of surrounding tissues.

Fortunately, having to experience this entire set of events is the exception rather than the rule. Instead, just one or a few symptoms may be experienced, and possibly only vaguely. And possibly only giving a hint that endodontic therapy is needed rather than a clear-cut sign.

For our discussion, we address each type of symptom that a patient may notice individually.

a) Pain.

Tooth pain isn't always one of the signs that a person notices as indication that their tooth requires root canal treatment. Some teeth that require it never hurt at all. Others that do may settle down after an entirely different procedure has been performed.

But when there is an association between the two, one or more of the following scenarios typically plays out.

Type of pain.
  • The discomfort can range from sharp and intense to a dull ache. It's level may range from slight to extreme.


  • The pain may include a throbbing component (feels like it has its own heartbeat).
  • Its character may change (lessen or intensify) as you change your posture (stand up, bend over, lie down, etc...).
  • The discomfort may be severe enough that it wakes you when sleeping.
Onset and duration.
  • Depending on how long the underlying condition has existed, some level of discomfort may have presented itself intermittently before (previous days, weeks, months). In other cases this will be the person's first painful experience.


  • The pain may be spontaneous (hurts on its own, unprovoked) or only triggered in response to a stimulus.
  • In cases where the pain is spontaneous, it may be intermittent or continuous.
  • If a triggering event is involved, it may be: Chewing or biting pressure, the pressure of pressing or tapping on the tooth, thermal insult (like exposure to hot or cold foods and beverages), sweets.

    Once the triggering stimulus has been removed, rather than disappearing immediately the discomfort frequently lingers (often for 30 seconds or longer). It may then finally fade away, or continue for an extended period of time.

    In some cases heat will bother the culprit tooth and cold liquids or ice will settle it down. (Ice application is sometimes used by patients to provide temporary relief.)

  • It's common that over-the-counter analgesics (pain relievers) are ineffective in controlling the pain.
  • It may be quite easy for the patient to identify which tooth hurts. At other times the discomfort may be vague and nondiscript.


  • The person may be able to tell which general area is painful but not which tooth.
  • The pain may be referred, meaning that the tooth or area that hurts the most is not the one that is the actual source of the problem.
Takeaways from this section.
Remember, pain isn't always a sign that root canal is needed.

While each of the above scenarios may be an indication that root canal treatment is needed, there simply isn't a single set of signs that appear in every case that foretell for sure that it is. In fact, many of the symptoms above can also be an indication of more benign tooth conditions.

Beyond just quizzing you about what you have experienced, your dentist may also try to reproduce events that trigger your discomfort so they can evaluate what you are experiencing first hand. (See "testing" section below.)

Even then, while they may have formed a strong opinion about your tooth's condition, they'll still wait until they have collected other information before making a final diagnosis.

So, if you experience some type of pain, be concerned and proceed with seeking assistance. But in regard to it absolutely being a sign that you need root canal, there can be other explanations.

Other dental conditions that may cause tooth pain.

As a part of their differential diagnosis, your dentist will consider additional conditions that may be the cause of your tooth's discomfort. They can include:

  • Tooth decay, tooth fracture, a defective, deep, extensive or new dental restoration, sinus infection, tooth clenching and grinding (bruxism), periodontal (gum) disease, exposed dentin.

If any of these are identified, the dentist will likely initiate treatment aimed at both managing that problem and helping the irritated tooth to settle down. If it doesn't respond positively, or if reevaluation at a later date identifies the need, root canal may still be required.

Swelling associated with a tooth abscess.

This slideshow explains "gumboils."

b) Gum tenderness, swelling, infection.

Obvious signs of infection, like swelling, don't occur in every case where root canal treatment is needed. But when they do display, they will typically show some of the following characteristics.

Degree of enlargement.
  • The swelling can range from being just very slight (a reddish, otherwise normal-looking area that has some tenderness) to quite pronounced (a lump that you can actually feel, or region that has noticeable fullness).
  • In extreme cases, the swelling may extend into your face and/or neck.


  • When the swelling is relatively minor and localized, the area of enlargement usually lies at a level that approximates the tip of the problem tooth's root.
  • Instead of pronounced swelling, a pimple-like drain for pus may form on your gums (a "gum boil").

(See our slide show for details and pictures about both of these points.)


While nothing here is uniquely informative:

  • The swelling may come and go as days, weeks or even months pass, possibly never disappearing completely.
  • It may have presented itself for the first time, with a slow or rapid onset.
Associated symptoms.
  • Swelling may be but isn't always accompanied by the presence of pain.
  • If the pus causing the swelling finds a way to vent off (drain), you may notice a bad taste in your mouth. Draining pus can also be the source of foul breath odor.


  • It's possible that due to infection the tooth feels slightly elevated. (Seems as though it's been pushed out of its socket some and is taller than its neighboring teeth.)
Takeaways from this section.
Swelling isn't always a sign that root canal treatment is needed.

Experiencing swelling doesn't necessarily mean that you have a tooth that needs endodontic therapy but it does indicate that something is wrong somewhere and it's presence should be taken seriously. (While rare, in extreme cases it can become so pronounced as to interfere with your ability to breathe.)

It's a simple matter to contact your dentist's office and report what you have experienced. They can then make a decision about what level of attention you require.

When swelling is present a dentist will frequently have their patient start a regimen of oral antibiotics. Since they typically take about 24 hours to have an effect, when you call your dentist even if they don't feel that you need immediate examination, they may go ahead and prescribe antibiotics for you so you can get started with them.

Ways to distinguish the likely source of your swelling.

In cases where an area of tenderness and swelling is fairly small, the following rules of thumb tend to apply.

  • If caused by periodontal (gum) issues, the area is usually located along side of the tooth or right at its gum line.
  • When caused by infection inside a tooth, it's usually centered in the region of that tooth's root tip. (See picture above and our sideshow.)
Other dental conditions that may cause swelling.

Your dentist will consider other possible sources of infection during their examination. They can include:

  • Periodontal (gum) disease, pericoronitis (most commonly associated with erupting wisdom teeth.

Whatever the source, a dentist will first take steps to manage the swelling so it doesn't get out of hand. Then at a later point diagnose the actual underlying problem and determine what treatment is required to resolve it.

c) Additional signs.

Malaise (a general feeling of illness or uneasiness), fever and/or lymphadenopathy (tender or swollen lymph nodes) may each be noticed in association with a tooth that requires endodontic therapy. And if you have experienced any of them it should be reported to your dentist.

These symptoms on their own however are generally considered to be secondary in nature (they may be present but not directly indicative as to which tooth requires treatment). Other signs will be weighed more heavily by your dentist when making a diagnosis.

d) Frequency of symptoms.

It bears repeating that any of the signs and symptoms discussed above may involve an extended time frame. If so, they may be:

  2. Persistent and continual. - While possibly not always especially noticeable or intense, the symptoms never totally disappear.

e) What you experience can be incredibly varied.

By now it's surely apparent to you why a dentist's level of experience and knowledge is so important in their being able to accurately diagnose a patient's condition.

  • With low-grade chronic cases, the patient may experience almost no symptoms at all (yet always be at risk for an acute flare up).
  • In cases of acute apical abscess, a rapid onset, spontaneous pain, pronounced tissue swelling, and extreme sensitivity to pressure (tapping or biting on the tooth) are all likely to be experienced.
  • With other endodontic cases, it can be almost anything in between.

If you do notice symptoms, don't assume that you can diagnose your situation on your own. For your well being, they need to be checked out by your dentist.

2) Signs of needing root canal that may only be obvious to your dentist.

The death of a tooth's nerve isn't always a big event.

  • In some cases the original events surrounding the nerve's death may have been so mild, or taken place so long ago, that they're not remembered.

With either situation, it may take your dentist's keen eye during their examination to discover that unbeknownst to you endodontic therapy is needed for your tooth.


To a dentist, this is proof positive that endodontic therapy is needed.

a) Identifying teeth that require root canal with x-rays.

In cases where little or no pain or swelling has occurred with a problem tooth, its need for root canal treatment may remain undiscovered, even for some years.

And unearthing these asymptomatic-yet-problematic teeth is one reason why having periodic routine dental x-ray examinations is important.

What dentists look for on x-rays.

Whether your tooth has been asymptomatic or not, there are a number of signs that may be observed on radiographs that may indicate that your tooth does indeed have an endodontic problem.


The classic sign that's seen on x-rays is a dark spot that's centered around the tip of the failed tooth's root (see picture).

Dentists refer to this as a "radiolucency." And when one is found it's typically a sign that changes have occurred with the bone in this area in response to an infection housed inside, and leaking out of, the tooth's root.

Additional changes that may show up on x-rays.

There can be other, frequently more subtle or minute, signs that can sometimes be identified on radiographs that may also indicate a problem with a tooth's nerve.

This includes widening of the ligament space surrounding the tooth's root, or changes in the layer of bone that encapsulates it. Some endodontic conditions result in an increase in bone density in the region around the root.

Note - We have an entire page dedicated to this subject: Diagnosing the need for root canal using dental x-rays.

Takeaways from this section.
X-rays aren't always a clear indicator of endodontic problems.

Unfortunately, the signs that a dentist looks for on an x-ray aren't always obvious or conclusive (because they take some time to develop). Or possibly what looks suspicious on the film has in actuality been caused by unrelated issues (not all of which are pathological in nature).

That means, just as with the other types of testing and evaluation discussed on this page, dental radiographs are simply an individual diagnostic tool. And in most cases simply weigh in as just another piece of the puzzle in forming a diagnosis.

b) Recurring or persistent gum boils.

An active infection inside a tooth may result in the formation of a pimple-like lesion on a person's gum tissue. It will typically form at a level that approximates where the tip of the problem tooth's root lies.

Patients often refer to these lesions as "gum boils." Dentists use the term "fistulous tracts."

What causes them to form?

A fistulous tract is actually a drain for pus. Instead of it building up inside the soft tissues surrounding the tooth and causing tissue enlargement (swelling), the tract provides a way for it to vent off.

  • The size of the boil may rise and fall over time (on a daily, weekly or even monthly basis) as the infection's activity waxes and wanes.
  • Since they function as a drain for pus, a person may detect a bad taste coming from theirs.
  • The lesion is typically tender to touch.
  • If the tract becomes blocked, tissue swelling will form. If it opens back up, drainage can resume, thus bringing down the swelling.

(If you didn't use the link above, this slideshow provides illustrations and further details about these types of lesions.)

Takeaways from this section.
A gum boil may go unnoticed.

In cases where the infection inside a tooth remains low-grade, the boil will tend to be small and only have minimal taste coming from it. If so, it's possible for a person to be totally unaware that it's there.

Often it's their dentist, during a routine dental examination, who is the first to identify it and recognize it as an indication of a problem.

Other dental conditions that may result in a fistulous tract.

This type of lesion is proof positive that a problem exists but not necessarily that root canal treatment is the needed solution. For example, it's possible that the source of the infection is a periodontal (gum disease) issue.


c) Individually darkened teeth.

An individually darkened tooth.

The dark color of this tooth suggests that it needs treatment.

Tooth discoloration can indicate that changes, possibly pathological, have taken place within its nerve space.

This type of color change is frequently the sole reason why a dentist will suspect that a tooth has a problem and requires root canal therapy.


  • It may take place even some years (even 10 years plus) after the original event occurred.
  • The darkening process may not be associated with any noticeable symptoms (pain or swelling).
Takeaways from this section.
Having a tooth darken doesn't always mean that root canal is needed.

This is, yet again, another sign that by itself does not necessarily mean that root canal therapy is required.

This same type of discoloration may take place with teeth that have already had successful endodontic treatment. Or it may indicate that some nerve-space changes have occurred but at this point no attention is necessary.

In other instances the discoloration may be due to the presence of decay, a deteriorated filling or staining caused by a metal filling.

Exposure of a tooth's nerve during dental work.

If nerve exposure occurs, endodontic therapy is usually needed.

d) Exposure of the tooth's nerve.

Performing the dental work that a tooth requires sometimes results in the exposure of its nerve. The term "exposure" means that the dentist's work has made contact with the tooth's pulp tissue.

If this occurs, your dentist will need to advise you that complications have arisen and root canal therapy may be required.


An exposure on its own may be enough to trigger pulp tissue degeneration and the tooth's ultimate need for root canal treatment.

As an added factor, the tooth's potential to make a recovery may be hampered by the condition that lead to the need for the dental work in the first place (such as advanced tooth decay).

For these reasons, if an exposure has occurred during their work the dentist may advise that it's best to go ahead and perform root canal treatment now, so to avoid complications later (such as a painful tooth abscess or a situation that's technically more difficult to treat later on).

Takeaways from this section.
Nerve exposures can be planned or unplanned.


In most cases, an exposure is an unavoidable undesired side effect that has occurred as a dentist attempts to repair a cavity that ideally should have been treated months or years previously.


In a minority of cases (typically involving dental crown placement), the exposure and the subsequent need for root canal is anticipated due to the amount of tooth structure that must be trimmed for the planned dental work.

This section's slideshow provides more details about exposures.

3) Testing your dentist may perform.

Once your dentist has suspicions about a tooth's need for root canal treatment, they'll likely perform additional testing so to get a better idea of its current status. Besides just the suspect tooth, its neighboring teeth and the matching tooth on the other side will probably be evaluated too so a comparison can be made.

Here are some of the tests that are frequently performed.

a) Percussion testing.

Because it's so simple, one of the first evaluations your dentist will most likely perform is a percussion test. It involves their tapping on your tooth using the butt end of one of their dental instruments.

Don't worry. They'll start off by just tapping lightly. Then, if they haven't yet gotten a response from you, they'll tap increasingly harder.

Test findings.

Teeth that require root canal therapy frequently (but not always) respond to this test with tenderness or pain. However, healthy-but-irritated teeth may respond in the same way too.

b) X-ray evaluation.

Your dentist will want to take various x-rays of the suspected tooth (two is the usual minimum), with each one taken at a slightly different angle so what isn't obvious on one may be on another.

The films may reveal evidence of the need for treatment (see "radiolucencies" above). But even if they don't, they can provide subtle hints that may help the dentist to identify which tooth has the problem.

c) Thermal testing.

Testing a tooth with hot and cold extremes can reveal a lot about the health status of its nerve tissue and its potential need for root canal.

  • Problematic teeth frequently respond painfully to both hot and cold stimuli.
  • In some cases, application of a hot stimulus will hurt whereas a cold one will create pain relief. (See this page's "home remedy" section below.)
  • A key factor is how long the tooth's reaction lasts. With healthy teeth the pain usually subsides promptly after removing the stimulus. Pain that lingers (30 seconds or more is usually used as the cut off point) is frequently a sign that a condition exists that will require root canal treatment to resolve.

d) Electric pulp testing.

An electric pulp tester is a device that's held against your tooth and passes a variable electrical current to it.


As horrible as all of this sounds, in practice it isn't. Your dentist will start off with a very low tester setting and then gradually increase the current. At the first sign of a response from you, they'll immediately remove the tester from your tooth.

e) Selective Anesthesia.

There can be times when a patient's endodontic pain is:

  • Vague and diffuse - The situation where it's difficult to tell exactly which tooth the pain is coming from, either because it's nondiscript or else several teeth seem to hurt.
  • Referred - The case where the pain the patient feels is sensed in a healthy tooth that just happens to be serviced by the same nerve as the culprit one, possibly even one that's some distance away. (Such as a problematic lower tooth refers pain to an upper one.)

As a test, the dentist may selectively numb up suspected teeth as a way of identifying which one lies at fault. The idea is that when the culprit tooth is numbed up, the patient's pain will disappear.

f) The Cavity test.

  • If a dentist has been unable to conclusively prove that a suspected tooth is in fact the culprit one ...
  • And they have a high level of suspicion that the pulp tissue inside the tooth in question is necrotic (meaning the tooth's nerve is dead) ...
  • ... a Cavity test may be performed.

This test simply involves the dentist drilling a divot into the suspected tooth, without numbing it first.

The idea is that if the nerve tissue inside the tooth is healthy, at some point during the process sensations will start to be felt. But if the nerve is necrotic as anticipated, no pain will be felt at all, even when the drilling finally penetrates into the tooth's interior nerve space.

What should you do if you suspect that your tooth needs root canal therapy?

Don't delay.

If you notice any of the signs and symptoms mentioned on this page, you should establish contact with your dentist's office and make arrangements to be evaluated and receive treatment in a time frame that they determine is warranted.

Teeth that do require endodontic therapy can be unpredictable, with the consequences of flare up (pain, swelling, etc...) possibly being severe.

Don't make assumptions.

Making a misdiagnosis about their tooth's status (by way of using website information like this) may deter some people from seeking treatment during that stage when another (simpler, cheaper and easier) repair might have been possible.

That's because some people won't seek treatment promptly if in their mind they think it's already too late, will cost too much money or else the idea of having root canal is too unnerving for them.


If root canal is needed ... things you might try.

In the case where you do have a tooth that requires root canal therapy, there's not a lot, unfortunately, that you can do on your own to relieve your symptoms.

  • Within the guidelines of the product you choose, you may find that using an OTC pain reliever provides some degree of relief. However, in severe cases OTC products are typically ineffective.

    Placing an aspirin on the gums next to your tooth makes a poor choice. An aspirin pill (acetylsalicylic acid) is intended to be a systemic drug (absorbed internally after being swallowed) not a topical one (absorbed through the skin). Placing an aspirin next to your tooth will be ineffective in controlling your tooth's pain and will cause a chemical burn on your gum tissue.

  • Since all dentists know that emergencies do happen, they've probably made some type of plan for when their patients experience them. You should call your dentist's office to see if there's a message describing the type of assistance they have to offer.

Home remedy: Try placing ice on your tooth.

In some cases where root canal therapy is needed, during that stage when a tooth has started to produce extended periods of constant pain, chilling it by way of holding a chip of ice against it may provide relief.

This won't work in all cases and in fact may irritate your tooth in some. So, ease into this remedy with testing. But when this solution does work, it can provide much needed relief until you can receive the treatment you require from your dentist.

Takeaways from this section.

If this home remedy works, it's because the chilling effect of the ice lowers the pain-causing pressure inside the tooth's nerve space by way of contracting the gasses and liquids it contains.



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