What is root canal treatment (endodontic therapy)?

- What is its purpose? What does it accomplish? Why is having it important and a cure?

What does
root canal

Link to 'What does root canal accomplish?' section.

What does root canal therapy do?

You may find yourself in the situation where you've been told that your tooth needs root canal treatment. And you understand that it offers a way of saving your tooth.

But what you don't get is how it accomplishes this. You don't understand the underlying purpose of having endodontic therapy, and what it changes about your tooth.

These issues are the subject of this page. Below we outline the goals and objectives of this procedure, and explain what's different about your tooth afterward that makes it so it can be retained.

Our website also explains ...

After you've read this page, scroll back to the list below. It contains links to our other pages that provide additional information about having root canal.


1) What is root canal treatment?

Root canal (endodontic) therapy refers to the process where a dentist treats that space inside a tooth originally occupied by its "nerve."


The formal terminology for a tooth's "nerve" is "pulp tissue." On our pages we use all of these terms interchangeably: nerve = nerve tissue = pulp tissue.

Root canal therapy is used to treat conditions involving a tooth's nerve space.

Root canal therapy treats the nerve space inside a tooth.

During treatment, the space is cleansed and sealed off.

2) What does root canal treatment accomplish? / What's its purpose?

Dentists use root canal therapy to treat pathological conditions inside a tooth that involve its nerve tissue.
By completing treatment ...
  • A dentist both resolves the tooth's internal (nerve space) problems (by way of removing dead or dying pulp tissue, clearing up infection, sanitizing the tooth's root canal system, etc...) ...
  • ... and also sets the stage so the person's body's healing process can successfully return those tissues that surround the tooth's root that have been affected by its internal condition, back to a normal healthy state.



The procedure itself is a two-stage process.

Stage 1: Cleansing the tooth's interior.
Necrotic pulp tissue removed from a tooth.

Nerve tissue that's been removed from a tooth.

This portion of the procedure involves removing remnants of the tooth's pulp tissue from within its nerve space (root canal system), along with those tissue breakdown products created during its degenerative process.

Microorganisms (bacteria, fungi) that have invaded this space are removed too, along with the associated debris and contaminants they have formed.

Stage 2: Sealing off the treated area.

The procedure is then completed by sealing off (filling in) the tooth's cleansed internal space (usually with an inert rubbery material), so contaminants and microorganisms can't leak back into or out of it.

Details -

Stage 1: Cleaning the tooth. - What does this step accomplish?


Dentists use the same root canal process to resolve a wide range of nerve-related problems. For example, this fix is the solution when a tooth's pulp tissue is: 1) Irreversibly inflamed, 2) In the process of dying, or 3) Completely necrotic (dead). It's also the solution for when the tooth's interior harbors infection (either chronic or acute).

And although each of these conditions represents a different status, what they all have in common is that they each involve, or ultimately will at some point, a situation where the tooth's nerve space harbors contaminants that will leak out of the tooth's root tip and persistently irritate (inflame) the tissues that surround it.

The goal.

Therefore, as the underlying purpose of the cleaning portion of the root canal procedure The steps., the dentist's goal is to sanitize the interior of the tooth as effectively as possible. So irritants won't exist inside it to ultimately leak out and persistently irritate the tissues that surround its root.

In their attempt to accomplish this goal, they'll remove the remaining remnants of the tooth's pulp tissue (live or dead), the organic debris left over from the breakdown of this tissue, microorganisms (bacteria, fungi) and the toxins and other byproducts they have created.

Stage 2: Sealing off the tooth's interior. - Why is this important?

Diagram showing a tooth's sealed root canal space.

Sealing the root canal space (filling it in) prevents contaminants from entering or exiting it.

The sealing aspect of the root canal procedure The steps. has to do with filling in and sealing off the (now empty and sanitized) nerve space inside the tooth with an inert, biocompatible material (one that will create the most permanent seal possible). Related to this goal, there are two objectives.
  • One of them is for the filling material to create a seal that prevents contaminants from seeping back into the tooth and recontaminating/reinfecting its interior space. (If this occurs, the tooth would again be a persistent leaking source of irritants to the surrounding tissues.)
  • The other goal is just the opposite. The seal prevents any irritants still trapped within the tooth's root canal system from seeping out (we explain in greater detail below). (If this is not prevented, once again, the tooth would be a persistent source of irritants to the tissues that surround its root.)


With the issue of irritants seeping from the tooth now resolved, the tissues surrounding the tooth's root can heal and return to normal. Even without nerve tissue, the tooth will function just like a normal tooth. Since the tissues surrounding its root are healthy, the tooth will be pain-free.

Section references - Torabinejad

How is it that contaminants can seep out of a treated tooth? Hasn't its interior been cleansed?

Root canals don't really have a precise shape like we show in most of our illustrations.

The tooth in the animation shown below is slightly more realistic. It illustrates that the canal inside a tooth's root can be like a river, in the sense that it has a main channel that may give birth to small divisions that wander away and then return. Or else branch off and follow a different route entirely.

Animation showing root canal system cleansing via instrumentation and irrigation.

Complex root canal systems can be impossible to completely disinfect.

This poses a significant challenge for the dentist.
In an attempt to cleanse this type of convoluted anatomy (which must be assumed to exist to some extent with every tooth), a dentist will rely on a two-pronged approach when cleansing a tooth's root canal system.

But despite their best efforts, it's always possible that some amount of debris will still remain. And in fact, the reality of the matter is that studies have shown that the root canal system of a tooth really can't be completely cleaned and disinfected. (Hargreaves)

So, the sealing process ensures that these (hopefully minimal level of) contaminants that remain are entombed within the tooth and therefore can't seep out and persistently irritate the tissues that surround its root.

Section references - Hargreaves

3) Why are contaminants harbored within a tooth such a big issue?

Your body's ability to handle infections inside teeth is different than with other parts of your body. That's because teeth are hard, cavernous objects.

A comparison -

A) Soft-tissue infections.

As an example, imagine that your finger has a cut that's become infected. If so, your body's immune system will kick into gear.
By way of your blood and lymphatic vessels, the area will be flooded with white blood cells that will combat the invading bacteria. And, in most cases, your cells will win. They will kill off the offending microorganisms and clear away their associated debris.

B) Infections inside teeth.

Now, consider the scenario with teeth. Once a tooth's nerve tissue has started to degenerate (die-off), and bacteria have taken up residence inside the tooth's empty nerve space, it's difficult for white blood cells to effectively get at the microorganisms to combat them.

A tooth whose nerve has dies provides a prime location for bacteria to live.

The empty, hollow space inside a necrotic tooth is a difficult location for your body's immune system to fight infection.

There's limited transportation available.
Due to the deteriorated state of the tooth's pulp tissue, the blood and lymphatic vessels inside the tooth that might be used to transport these cells directly to where they are needed, either no longer exist or have been compromised.
That means the nerve space inside a tooth (especially when fully necrotic) can provide a nice cozy cave-like location for bacteria because it's a place where your body's defense mechanisms have a hard time getting at them and being effective. (Ingle)
The consequences.

With this scenario, at best your body will only be able to cordon off the infection stemming from inside your tooth, via setting up a perimeter of defensive tissues and cells around the tooth's root.

As a worst case, the infection will massively overwhelm your body's wall of defenses, resulting in pain and swelling (an acute tooth abscess).

What actually happens is often a mixture of both. One where the tooth's infection remains quite (cordoned off and controlled) most of the time, with periods of (hopefully minor) flare-ups where some level of tenderness, pain or swelling is noticed.

Section references - Ingle

So, here's what root canal treatment accomplishes.

Endodontic therapy provides for a third outcome, one where an infection associated with a tooth is not just cordoned off but instead can actually be cleared up by your body's defense mechanisms.

  • The root canal treatment assists your body's infection-fighting process by removing (disinfecting) and sealing off (entombing) bacteria and contaminants inside your tooth that it would otherwise have difficulty dispensing with.
  • Following the completion of your tooth's treatment, no further leakage of irritants from its root should occur.
  • Any microorganisms and contaminants that have already exited, and as a result have inflamed the tissues that surround your tooth's root, can be dealt with in normal fashion by your body's immune system.
  • The expectation is that this cleanup and healing process will be successful. The result will be an inert tooth root (one that doesn't leak irritants) surrounded by normal healthy tissues.

Section references - Hargreaves

Other things you need to know to understand root canal treatment.

Where precisely in a tooth is its nerve?

A tooth's nerve tissue (pulp) is housed in its canals and pulp chamber.

Total tooth nerve space = Canal(s) + Pulp chamber

Teeth are not solid. Instead, inside every tooth lies a hollow space filled with the tooth's pulp tissue ("nerve"). Dentists use the following terms to refer to various portions of this nerve space:

a) The pulp chamber.

This is a cavern that lies pretty much in the center of a tooth's crown (the portion that is visible above the gum line).

b) Root canals.

Root canals are tiny tunnels that run the length of a tooth's root. (From its pulp chamber down to the root's apex (tip).)

(FYI: Measuring the length of these canals How it's done. is a very important part of the root canal process.)

As a rule, every tooth root (note: some teeth have more than one root) will contain at least one canal. But a root having more than just one canal is possible, and commonplace with some specific kinds of teeth.

(For more in-depth information, visit our page: How many roots and root canals do teeth have? What's normal? | Variations.)

Isn't it important for a tooth to have a nerve?

No, not really. A tooth's pulp tissue plays a role in its formation and development. But once that's been completed, it's not so vitally important. So, having it removed during root canal treatment isn't that big of a deal.

You don't really get much "feeling" input from a tooth's nerve.

Under normal circumstances, the nerve tissue inside our teeth provides us with comparatively little information.

Yes, when subjected to pressure or temperature extremes, or exposed to severe insult (like advancing tooth decay or the formation of a crack), teeth do respond with a painful sensation. But other than that, the nerves inside our teeth remain relatively unresponsive.


You might think that when you push on your teeth, or else close them together, the pressure sensation that you feel (proprioception) is a signal from within your tooth.

Actually, most of this sensation (around 70%) comes from the nerve fibers found in the tissues that surround your tooth's root, with the remainder originating from its pulp tissue (Eliyas). On a practical level however, this loss is not usually noticed.

Section references - Eliyas

You'll never miss your tooth's nerve.

Due to the above, from a standpoint of normal function, the presence of live nerve tissue within a tooth is pretty much optional. If it's present and healthy, then wonderful. But if it's been removed as a part of root canal treatment, then that's fine too. You'll never miss it.


 Page references sources: 

Eliyas S, et al. Restoration of the root canal treated tooth.

Hargreaves KM, et al. Cohen's Pathway of the pulp. Chapter: The core science of endodontics.

Ingle JI, et al. Ingle's Endodontics. Chapter: Irrigants and intracanal medicaments.

Torabinejad M, et al. Endodontics. Principles and Practice. Chapter: Endodontic microbiology.

All reference sources for topic Root Canals.