What is root canal treatment (endodontic therapy)?

- What is its purpose? What does it accomplish?

What is
root canal?

Link to 'What is a root canal?' section.

Where is a
tooth's nerve?

Link to 'Where in a tooth is its nerve?' section.

Goals and objectives.

You may find yourself in the situation where you know your tooth needs root canal treatment, and you do understand that it offers a way of saving your tooth. But you don't really get how it accomplishes this task.

Well, all of that is the topic of this page. It outlines the purpose of having root canal therapy and explains its goals and objectives.

Our website also explains ...

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

Root canal therapy treats the nerve space inside a tooth.

This slide series explains what treatment accomplishes.

1) What is root canal treatment?

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

[Dentists refer to a tooth's "nerve" as its "pulp tissue." On our pages we use both terms interchangeably.]

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

Root canal therapy is used to treat pathological conditions inside a tooth that have affected its nerve tissue, and often the tissues that surround its root too.

By completing a tooth's treatment, a dentist can both resolve its internal problems as well as set the stage so your body's healing process can take place as effectively as possible, thus allowing the tissues surrounding its root to return to and/or maintain a healthy status.

The procedure itself is basically a two-staged process.

  • A) Cleansing the tooth's interior. - The first portion of the procedure removes compromised (infected, necrotic, degenerating) tissues, and associated debris and contaminates, from within a tooth's nerve space.
  • B) Sealing off the treated area. - The procedure is completed by filling in and sealing off the tooth's cleansed internal space, so contaminates can't leak back in, or out.

Details -

A) Cleaning the tooth. - What does this step accomplish?

Dentists use root canal treatment to resolve a wide range of nerve-related problems. For example, this same fix is used when a tooth's nerve tissue is: 1) Acutely inflamed, 2) In the process of dying, or 3) Completely necrotic (dead).

Necrotic pulp tissue removed from a tooth.

This is nerve tissue that's been pulled out of a tooth's canal.

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

So, the underlying goal of the cleaning portion of the root canal procedure is for the dentist to remove as many of these irritants (or items that will degrade into irritants) as possible.

These types of items include pulp (nerve) tissue (live or dead), the organic debris left over from the breakdown of this tissue, bacteria and the toxins and additional byproducts they have created.

B) Sealing off the tooth's interior. - Why is this important?

The sealing aspect of the root canal procedure has to do with filling in and sealing off the (now empty) nerve space inside the tooth. Related to this goal, there are two objectives.

  • One of them is for the filling material to create a seal that prevents contaminates from seeping back into the tooth, so it's not recontaminated.
  • The other goal is just the opposite. The seal prevents any irritants still trapped in the tooth from seeping out.

A tooth's canal system can have many branches.

How a dentist cleanses a tooth.

How is it that things can seep out? Isn't the tooth's interior clean?

Root canals don't really have a precise shape like we show in our illustrations. They're more like a river where the main channel may give birth to small divisions that wander away and then return, or else branch off following a different route.

Due to this convoluted configuration, and despite a dentist's best efforts, it's possible that some debris still remains. So, the sealing process insures that these contaminates remain entombed within the tooth and can't seep out and persistently irritate the tissues that surround its root.

3) Why are contaminates 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 infiltrated by white blood cells that will combat the invading bacteria. And, in most cases, your cells will win. They will kill off the offending bacteria.

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 nerve space, it's difficult for white blood cells to effectively get at these bacteria to combat them.

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

Necrotic (dead) teeth make a nice home for bacteria.

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 a fully necrotic one) 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.

With this scenario, at best your body will only be able to cordon off the infection stemming from inside your tooth. At worst, the infection will massively overwhelm your body's defenses and pain and swelling will ensue (an acute tooth abscess).

So, here's what root canal treatment accomplishes.

Endodontic therapy provides for a third outcome, one where the infection is not just cordoned off but can actually be cleared up. The treatment assists your body's infection-fighting process by removing or sealing off the bacteria and tissue irritants inside your tooth that it has difficulty dispensing with.

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 root. (From the tooth's pulp chamber down to the root's apex (tip).)

Nerve space variations.

An x-ray of a lower first molar.

Teeth always have just one pulp chamber but the number of root canals they have can vary widely.

  • Every tooth will have at least one root, with some frequently having 2 or 3.
  • Each tooth root in turn has at least one canal. The roots of some teeth are well known for usually having 2 or more.


The following comparisons demonstrate how varied the nerve space inside different types of teeth can be:

  • Upper front teeth (incisors) usually just have 1 root and 1 root canal.
  • Lower molars usually have 2 roots and 3 canals (see picture).
  • Most upper molars typically have 3 roots and 3, or frequently more, canals.
  • For more in depth information, visit our page: How many roots and root canals do teeth have?

What does the number of root canals mean to you?

The number of canals that a tooth has will affect you, the patient, in the following ways:

  • The cost of a tooth's treatment is typically based on the number of individual canals that it has. The greater the number, the higher the cost.
  • Appointment length correlates with the number of canals being treated. It's more time consuming for a dentist to treat a tooth with 4 canals as opposed to one that just has 1.
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Isn't a tooth's nerve important?

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 2015). On a practical level however, this loss is not usually noticed.

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.