Root canal tests – Does your tooth need endodontic therapy?

Menu

Tests dentists use to diagnose a tooth’s need for root canal therapy.

If your dentist suspects that you have a tooth that needs endodontic therapy, they’ll then perform some tests that will give them a more complete understanding of the tooth’s current pulpal health (nerve tissue status).

Is this testing always needed?

Yes. Your dentist knows that their ability to formulate an accurate pulpal diagnosis depends on their collecting as much pertinent information as possible.

So, beyond just relying on …

Signs & symptoms you have reported.   What to look for.

Signs they have personally observed.   Clinical signs.

The findings from their x-ray evaluation.   What do x-rays show?

You’ll probably also find that they perform at least a few of the tests we describe below too.

How dentists test if your tooth requires root canal treatment.

This page explains the most common tests that dentists and endodontists (root canal specialists) use to evaluate tooth pulp tissue vitality and therefore the tooth’s need of having root canal treatment.

Dental pulp testing. / Pulpal vitality tests.

• Percussion testing  (Tap testing) – If you’ve ever had a dentist tap around on several of your teeth and wondered why, this section explains. Often, they’re looking for a tooth that stands out and seems different than the others. The degree to which the response of the tooth is different tells them a lot too.
• Thermal testing (Hot/cold/ice testing) – The way a tooth responds to thermal stimulus can tell a dentist a lot about the likely health status of its dental pulp (normal, irritated, compromised, necrotic). As the dentist tests, they’ll not only note if the tooth responded but also the duration and intensity of its response.
• The electric pulp test (EPT) – As terrible as this testing method sounds, it just involves using a device that passes a weak electrical current to your tooth. Healthy nerve tissue will show some sensitivity. And as soon as you notice that, your dentist will stop the test. At the other extreme, a tooth that has a dead nerve (and therefore requires endodontic treatment) won’t respond at all.
• Selective anesthesia testing (Local anesthetic test) – Sometimes teeth that hurt radiate pain to other parts of your mouth. For example, an upper tooth that needs endodontic therapy might cause pain in the lower teeth on the same side (“referred pain”). If your upper tooth is numbed up and your lower pain then disappears, your dentist (likely) has their diagnosis about which tooth to treat.
• The cavity test (Dental drill test) – Your dentist probably won’t use this test unless they’re fairly certain that your tooth’s nerve is dead. Without numbing your tooth up, your dentist will start to drill a hole into it. If you feel anything, they’ll know they’re wrong and will stop immediately.
• Palpation (Feeling your jawbone.) – Infection associated with a tooth can cause tenderness and swelling. In an attempt to discover these symptoms, your dentist will feel the gum and bone tissue alongside your teeth.

As you read on, this page explains in greater detail …

1) What the goal of performing each test is.
2) How the test is performed.
3) What kind of results might be expected under different circumstances.
4) What those results may indicate in regard to the status of your tooth’s pulpal health and therefore its need for root canal treatment.

a) Percussion testing.

Because it’s both so simple and informative, one of the first evaluations of a patient’s teeth usually performed is a percussion test. Sometimes this is referred to as “tap” testing.

How a percussion test is conducted.

This test simply involves your dentist tapping on selected teeth, both in a vertical direction (straight onto their chewing/biting surface) and possibly horizontally too (from the side).

In most cases, the instrument used is just the butt end of the handle of the dentist’s small hand mirror.

The steps.

• Your dentist will start the process off by applying gentle finger pressure on the teeth that will be tested. Then, if they find you can tolerate that OK, they’ll begin the actual process of percussing them.
• As they test each tooth in turn, they’ll just tap lightly at first. Then, as they continue on, they’ll gradually use more force.

  But don’t worry, their goal is to collect information, not to hurt you. They’ll keep your comfort level in mind as they tap.

• As they test each tooth, they’ll evaluate your response. They may need you to clarify things by asking you what you’ve felt (pain, tenderness, nothing unexpected).
• They’ll test the teeth they suspect the most, their neighbors, and even the same teeth on the other side of your mouth, just to see how all of their responses compare.

Test findings.

• One goal of percussion testing is to identify which tooth (or possibly teeth) seems to have some sort of problem, in the sense that it responds differently, or more so, than all of the others.
• A tooth that requires root canal therapy frequently (but not always) responds to percussion testing with tenderness or sharp pain. Typically this tooth displays a greater response than all of the others tested.
• Unfortunately, a positive response (feeling tenderness) doesn’t conclusively prove that a tooth needs root canal treatment.

  Teeth that are healthy but irritated (like those subjected to excessive pressure from teeth clenching and/or grinding) or those that have periodontal (gum) disease may respond in the same way too, thus generating a false positive.

What percussion testing evaluates.

Tapping on a tooth only evaluates the status of its periodontal ligament (the ligament that surrounds the tooth’s root and binds it in its socket), as opposed to directly testing the condition of its nerve.

However, since pathology inside the tooth (like the presence of infection) can lead to the inflammation of its ligament (due to infection byproducts leaking out), tenderness or pain to percussion can be an indication that an endodontic problem in fact exists.

▲ Section references – Torabinejad, Tronstad

b) Thermal testing (hot/cold/ice testing).

Exposing a tooth to hot and cold temperature extremes can give a hint about the status of its nerve tissue and its potential need for root canal treatment.

Possible findings with hot and cold tooth testing.

• Problematic teeth frequently respond painfully to both hot and cold stimuli.

  In some limited cases, the application of a hot stimulus will trigger pain whereas a cold one will create pain relief.

  (Related: See our “home remedy” First aid. section about root canal pain and how this phenomenon might be used to provide emergency relief in some cases.)

• A key factor is how long the tooth’s reaction to the stimulus lasts. With healthy teeth, the pain usually subsides promptly after it’s been removed.

  Pain that lingers (30 seconds or more is usually used as the cutoff criteria) is frequently a sign that a condition exists that will require root canal treatment to resolve.

Testing methods –

How do you perform a cold test on a tooth?

• With cold testing, the dentist will hold ice, dry ice, or a cotton pellet or swab (Q-tip) that’s been soaked in or sprayed with a liquid refrigerant (Endo-ice is one brand of spray) against the surface of the tooth.

How do you perform a hot test on a tooth?

• For hot stimulus testing, a heated object (such as a ball of the rubbery compound gutta percha What’s this?), a metal hand instrument heated in a flame, an electrically-heated instrument/device, or application of hot water (after the tooth has been isolated with a rubber dam What’s this?) might be used, depending on the dentist’s preference.

With both types of testing, the dentist will hold the thermal conducting medium directly against the surface of the tooth to see what response is triggered.

Since it’s possible that a temperature extreme placed against the surface of a healthy tooth might create enough of a temperature gradient to damage its nerve, initially the dentist will be cautious in the level of exposure they create (5 to 15 seconds might be used, depending on the actual temperature of the thermal medium).

What’s being evaluated with hot and cold tooth testing?

In regard to healthy nerve tissue:

• When performing a cold test on a tooth, the stimulus causes fluid in the tooth’s dentin tubules to contract. This fluid movement triggers pain receptors in the tooth’s nerve.
• When performing heat testing on a tooth, the thermal gradient that’s created directly stimulates pain receptors within the tooth’s nerve tissue.
• With both types of testing, it’s expected that the sensation will be felt, and then immediately diminish once the stimulus has been removed. When variant symptoms are observed, nerve tissue pathology is suspected.

It must be stated that even healthy teeth don’t always give a diagnostic response to thermal testing (false negative). And due to deficiencies/difficulties associated with carrying out the testing, false positives are possible too. Additionally, a seemingly normal response isn’t necessarily an indication that the nerve’s status is fully normal.

▲ Section references – Hargreaves, Torabinejad

c) Electric pulp testing (EPT).

As its name implies, with this type of testing the tooth’s nerve is exposed to electrical stimulation and the results are observed.

How a dentist performs electric pulp testing.

For this test, the dentist uses a battery-operated device termed an “electric pulp tester” whose probe can pass a variable low voltage current. The dentist controls the level of the device’s output.

• The dentist will first isolate, and then clean and dry off, the surface of the tooth being tested. (Maintaining moisture control is imperative in performing an accurate test.)
• They’ll then dip the tip of the tester in a conducting medium. (Toothpaste is often used.)
• With the electric tester set to its zero current position, the dentist will place its conductive tip on the tooth’s surface.
• They’ll then gradually increase the level of current that’s passed to the tooth until a point is reached where the patient indicates that they feel (usually a warm or tingling) sensation in their tooth.
• Once a sensation has been felt, the tip of the pulp tester is removed from the surface of the tooth. The device’s current level setting is recorded.

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 its level. At the first sign of a response from you, they’ll immediately remove the tester from your tooth.

Test findings.

The general idea is that healthy nerve tissue will respond to electrical stimulation, as compared to deteriorating or necrotic (dead) tissue which will display a reduced or negative (no sensation) response.

There are a number of tooth-related issues (the presence of a deep metal dental restoration, deep caries (tooth decay), testing an area that has comparatively thicker dental enamel, or the tooth has comparatively smaller pulp chamber or root canals) that can affect the reliability (accuracy, reproducibility, specificity) of electric testing and therefore give false results.

So even a negative response doesn’t necessarily indicate that the tooth requires endodontic treatment. False-positive or negative responses occur in roughly 10 to 20% of cases (Torabinejad).

What’s the underlying basis of electric pulp testing?

Somewhat similar in nature to cold testing, exposure of a tooth to an electrical current creates fluid movements within its dentinal tubules (due to the ionic properties of this fluid). It’s the resulting fluid movement that then triggers receptors associated with the tooth’s nerve. (Hargreaves)

▲ Section references – Hargreaves, Torabinejad

d) 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 nondescript 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 problem tooth is numbed up, the patient’s pain will disappear.

How an anesthesia test is performed.

This type of testing will involve your dentist giving you a series of dental “shots” as they serially numb up each tooth they feel might be a suspect.

In regard to injection technique, infiltration Technique explained. or intraligamentary Technique explained. injections are often used.

▲ Section references – Tronstad

e) 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 pulpal necrosis (nerve tissue death) has occurred as is anticipated, no pain will be felt at all, even when the drilling finally penetrates into the tooth’s interior nerve space.

A test of last resort.

Historically the cavity test has been considered to be one only used when no other means of evaluating the tooth’s condition is available. However, the decision to use it at all is debatable.

While making a repair is possible, performing this test is invasive and irreversible. The patient’s apprehension about the procedure can easily confound their response. And in most cases, it seems what is learned could have been revealed by other testing methods.

f) Palpation.

Endodontic pathology is frequently accompanied by tooth infection. Signs and symptoms of infection can include tenderness and sensitivity in the jawbone and gum tissue in the region near the tooth. Soft tissue swelling may be evident too.

In an attempt to identify these kinds of changes, your dentist will palpate (examine by touch) the hard and soft tissues that surround your teeth. Especially the one(s) they are most suspicious of.

What’s next?

Here’s more information about the ways dentists diagnose the need for root canal therapy –

Comments.

This section contains comments submitted in previous years. Many have been edited so to limit their scope to subjects discussed on this page.