The root canal procedure. -

An outline of the steps a dentist follows when they perform root canal treatment (endodontic therapy). | Also, what is having each step like for you the patient?

Cleaning
the tooth.

Link to root canal cleaning section.

Sealing
the tooth.

Link to root canal filling and sealing section.

The steps of the root canal procedure.

Step 1 - Placing the rubber dam.

After numbing you up, your dentist will "isolate" your tooth by way of placing a rubber dam.

A dental dam is simply a sheet of "rubber" (latex in most cases) through which your tooth receiving treatment pokes up and through (see picture below).

As explained on our rubber dam page, because your tooth sticking through the sheet lies in a region where its environment can be controlled, it can be washed, dried and kept contaminate-free.

Why is tooth isolation important?

  • One of the fundamental goals of root canal therapy is removing contaminates from within the tooth.
  • Since saliva contains bacteria and other debris, a rubber dam acts as a barrier that helps to keep the tooth isolated (clean, dry, contaminate-free) during its procedure.

Note: Placing a dam is a part of the general "standard of care" that any and every dentist must responsibly provide. If your treatment doesn't involve using one, you should be asking questions.

 

A tooth with a rubber dam in place.

A rubber dam sets the stage so treatment can be successfully performed.

What's this step like?

For you the patient, having a dam should be a non-event. Since you'll be numb by this point, there's no discomfort involved.

We have an entire page that's dedicated to rubber dams, including how they're placed, what it's like to have one, and why the use of a dental dam during your procedure is so important.

 

Step 2 - Creating the access cavity.

As a starting point for performing your tooth's treatment, your dentist will need to gain access to its nerve space. This step is called creating an "access cavity."

An access cavity in the chewing surface of a molar.

The hole through which the dentist performs their work.

  • Your dentist will use their dental drill to make a hole that extends through the surface of your tooth to its pulp chamber.
  • This is the opening through which they will perform their work.
  • With back teeth, the access cavity is made right through the tooth's chewing surface (as shown in our picture).
  • With front ones, it's made on their backside.
  • When creating the access cavity, the dentist will also remove all tooth decay, and any loose or fragile portions of the tooth or its filling.

Related page: Issues involved when treating teeth that have dental crowns.

What's this step like?

By this point, you're numb, the rubber dam is in place, and everything is set for your work to begin.

As mentioned above, dental anesthetic doesn't significantly impair your sensation of pressure. So, when your dentist starts drilling the access cavity, you'll feel the vibrations of the drill. But these mild sensations are really all you should notice.

You shouldn't experience any pain. If you find differently, either at this point or during the remainder of your appointment, just indicate to your dentist so they know. Once they realize there's a problem, they can then determine what steps are needed to control your discomfort.

[Our sideshow contains pictures of access cavities.]

A surgical operating microscope may be used.

Once entrance into the interior of the tooth has been made, it's increasingly becoming the accepted standard of care that the floor of the tooth's pulp chamber is examined using a surgical operating microscope.

These instruments aid the dentist in discovering all of the tooth's root canals by way of helping them to identify the openings of minute canals that might otherwise be overlooked by the naked eye.

Takeaways from this section.

The use of a microscope increases the likelihood that all of the tooth's canals will be found and therefore treated, which generally translates into increased treatment success.

And that means that especially with cases where the need to identify very minute canals might be expected (molars, premolars, lower incisors, teeth with calcified pulp chambers and root canals), the use of one could be considered important.

These instruments have a price tag associated with them. And while it's commonplace that an endodontist (root canal specialist) will have one in their office, it's less likely that your general dentist does.

Step 3 - Measuring the length of the tooth.

Your dentist's goal will be to treat the entire length of your tooth's nerve space but not beyond. Doing so is not only important part of the treatment process but also helps to minimize post-operative pain.

To be able to work within these confines, your dentist must measure the length of each of your tooth's root canals. This measurement is typically calculated to the nearest 1/2 millimeter (about 1/50th of an inch).

Measuring the length of a canal via x-ray.

Slide series - Measuring the length of a canal.

How does a dentist make this calculation?

A dentist has two methods they can use to take measurements.

a) By taking an x-ray.

Traditionally, dentists have established/confirmed/documented length measurements by way of taking an x-ray after a root canal file has been positioned in a tooth's canal. (Since root canal files are metal, they show up distinctly on an x-ray.)

The actual calculation is made by reading markings etched on the file. The x-ray is simply used to confirm that the file is positioned properly (extends the full length of the tooth).

b) Electronic measurements.

In recent decades, the use of electronic length-measuring devices has become commonplace. (Dentists refer to these as "apex locators." The word "apex" refers to the tip of the tooth's root.) Here's how they're used.

  • The dentist will clip one of the unit's wire leads to a root canal file that has been inserted into the tooth. They'll then tuck its second lead inside the patient's lip, so to make a complete electrical circuit.
  • As the dentist slides the file further and further into the root canal (an area insulated by the tooth's root), the unit measures changes in electrical resistance as it's tip passes ever closer to the conductive tissues that lie beyond. A digital readout or a beeping sound indicates when the file has finally reached the canal's end (tip of the root).
  • Once again, the measurement itself is read from the markings on the file. The electronic unit simply indicates when its tip has reached the proper position.

c) Several individual measurements may be needed for a tooth.

A separate length measurement will need to be made for each of the tooth's individual root canals. (Teeth can have several canals and/or roots.)

What's this step like?

The development of electronic devices to aid with this step really has made performing/having root canal treatment quicker and simpler.

If an x-ray measurement is taken, the dentist has to disassemble the rubber dam (so to gain access to your mouth), place the film or sensor next to your tooth, take the picture, and then put everything back together again.

With an electronic unit, a measurement can be taken in less than a minute without disassembling the tooth's rubber dam or anything. And no, even though its measurement of an electrical current is involved, when one of these devices is used you won't feel a thing.

[Our slideshow explains more about taking length measurements.]


Step 4 - Cleaning and shaping the tooth's root canals.

The next step of the root canal process involves "cleaning and shaping" the interior of the tooth (the tooth's pulp chamber and each of its root canals).

In regard to this step:

  • Its cleaning aspect removes nerve tissue (live and/or dead), as well as bacteria, toxins and other debris harbored inside the tooth. (Here's more detailed information about why this is needed.)
  • Shaping refers to a process where the configuration of a tooth's canals are enlarged and flared, so they have a shape that's ideal for the procedure's filling and sealing step.

The whole process is a balancing act. One where the dentist seeks to accomplish the goals above without removing so much internal tooth structure that the integrity of the tooth is compromised.

Endodontic files.

The parts of a root canal file.

a) What tools does a dentist use?

For the most part, a tooth is cleansed and shaped using root canal files.

Files look like tapered straight pins but on close inspection you can see or feel that their surface is rough, not smooth. These instruments literally are miniaturized rasps.

 
Inserting a file into a tooth's canal.

Slide series - Using files inside a tooth.

b) How are files used?

  • A dentist will work a file up and down, with a twisting motion.
  • This action scrubs, scrapes and shaves the sides of the canal, thus cleaning and shaping it.
  • As an adjunct, your dentist will probably coat each file with EDTA paste or gel (ethylenediaminetetra-acetic acid) before it is used.

    EDTA is a chealating agent and as such softens the mineralized (dentin) walls of a canal so the file being used will be more effective. Additionally, its thick, wet consistency serves as a lubricant for the action of the files.

    Both of these functions are especially helpful in aiding the dentist in negotiating and enlarging narrow root canals.

c) Your dentist will use several files.

This same motion will be used with an entire series of files (probably at least six or more), each of which has a slightly larger diameter.

  • The idea is that each of the files, when used in order, slightly increases the dimensions of the root canal.
  • Since some canal contaminates are embedded within a canal's walls, this enlargement process not only produces a shaping effect but a cleaning one too.

d) Your dentist may have a handpiece that can manipulate the files for them.

At least some of the root canal files that your dentist uses in your tooth will be worked by hand. But they may also have a specialized dental drill (handpiece) that files can be placed in which generates the motion for them.

Nickel-titanium files.

Nowadays these endodontic handpieces are usually used with special files made of nickel-titanium alloy and that's a big deal.

The very flexible nature of these files combined with the mechanized motion created by the handpiece typically means that a tooth's root canal system can be cleansed and shaped much more rapidly than in the past.

Tooth irrigation is an important part of the cleaning and shaping process.

While performing their work, your dentist will periodically irrigate (flush out) your tooth. This is a process simply referred to as "irrigation."

  • At minimum, a dentist uses this as a means of removing debris and contaminants from within the tooth. And obviously, doing so enhances the effectiveness of their cleaning efforts.

    However, another important function that irrigation provides is to flush away loose debris that might be compacted by the action of the dentist's files into a plug or blockage.

  • The specific irrigating solution used may be chosen for the additional benefits it can provide. This includes antimicrobial action, or the ability to breakdown organic debris.

a) What kinds of solutions are used?

A number of different types of solutions can be used for this purpose, conceivably even just sterile water or saline solution.

  • By far the one most frequently used is sodium hypochlorite (bleach, Clorox) solution. It's effective in killing bacteria and digesting organic debris.
  • Your dentist may find benefit in using more than one kind of solution during your tooth's treatment.

b) How is tooth irrigation performed?

The process your dentist uses may be as simple as flushing your tooth out using an "irrigating" syringe.

  • This is a normal looking (smallish) syringe that has a bent/curved, blunt-tipped needle.
  • The needle is rested inside your tooth and the solution is gently expressed.

    (There is nothing sharp about the needle, you are not getting a shot. Gently flushing the tooth is the goal here, no solution pressure is generated.)

  • A normal dental suction device is used to catch any excess, or to remove the bulk of the solution from inside the tooth.

As an alternative, some dentists will have a machine with attached handpiece that provides controlled-rate delivery of the irrigant.

c) Why irrigation is such an important part of the root canal procedure.

It's easy to imagine how placing a liquid inside a tooth has the ability to seep into minute nooks and crannies, which are precisely the locations that are impossible for metal root canal files to access.

And especially in the case where the solution itself has cleansing properties, this ability can substantially enhance the effectiveness of the dentist's work.

  • Expect that your dentist will repeatedly irrigate your tooth, seemingly ad infinitum.
  • A minimal goal is to have the tooth's root canal system exposed to the irrigant for a period of 30 minutes or longer. (Darcey 2016)

Generally, this step is so beneficial that sometimes the process of "cleaning and shaping" a tooth is instead referred to as "shaping for cleaning," as in the tooth's root canal system is flared and opened up to enhance the volume and access of the irrigation solution used.

What's this step like?

For the patient, the cleaning and shaping portion of their tooth's treatment is the most boring part. And the time when they're most likely to fall asleep.

The process itself is just continued cycles of: a) use some tools in the tooth, b) wash the tooth out, c) repeat the process again.

During tooth cleaning and shaping.

If your dentist uses a handpiece to manipulate the files, its noise may keep you awake. Or if your tooth is hard to get at, they may have to ask you to open really wide each time they insert a new one into your tooth.

During tooth irrigation.

Your dentist may agitate the irrigating liquid they place in your tooth with an ultrasonic tip. If so, you may hear or feel it's vibrations. Other than that, this whole process should be a non-event.

Bite blocks.

During this step (or anytime during your appointment), if you start to find it hard to stay open, your dentist can put a rubber prop (a "bite block") between your teeth.

[Our slideshow has pictures that illustrate what goes on during this step.]

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Will your tooth's treatment be completed in one or two appointments?

At this point in your tooth's procedure, a potential stopping point has been reached. Its interior has been thoroughly cleansed and properly shaped, and is now ready to be sealed (have its hollow interior filled in).

  • With some cases, the dentist will go ahead and proceed with this process. (One-visit endodontic therapy.)
  • With others, they may feel that it's best to wait about a week before the completion of the tooth's procedure is performed. (Two or more visit treatment.)

For a discussion about how this decision is reached, use this link: How many appointments will your root canal therapy take?

In the case of two-appointment treatment:

  • As a treatment that further disinfects your tooth's root canal system, your dentist may place calcium hydroxide paste inside its canals and let it sit until your next appointment.
  • They will also need to place a temporary filling that seals the access cavity they have performed their work through, so to keep contaminates from reentering your tooth.

    (Related: Precautions you should take with this filling.)


Step 5 - Sealing the tooth.

The gutta percha cone chosen is the same size as the last file used.

Gutta percha points come in sizes that exactly match the dimensions of root canal files.

a) What type of root canal filling material is used?

The most frequently used root canal filling material is a rubber compound called gutta percha.

It comes in preformed cones (often referred to as gutta percha "points") whose sizes exactly match the dimensions (diameter, taper) of root canal files.

b) Placing the gutta percha.

When performing this step:

  • The dentist will select an initial cone of gutta percha to place into each of the tooth's canals. (Remember, different teeth have differing numbers of root canals.)

    For any one canal, the size gutta percha cone chosen will be that one that corresponds with the dimensions of the last (largest) root canal file used to clean and shape it (the "master" file for that canal).

  • They'll then double check how this cone fits by way of taking an x-ray. It's important that this first (master) cone extends the full length of the canal and fits snugly in the region of the tooth's root tip.

    If needed, the cone can be trimmed (shorten). Or the dentist may decide that using a different size one makes a better choice.

  • Accessory cones are then added as needed, to completely fill in the canal's interior space.
Placing gutta percha in a canal.

Slide series - Filling in and sealing the tooth.

In order to create a solid, uniform mass inside the canal:

  • Sealer (a thin paste) is applied to each gutta percha cone before it's placed into the canal, or else applied inside the root canal itself before the cones are inserted. It fills in any voids between pieces of gutta percha, or between them and the canal's walls.
  • The dentist may soften the gutta percha once it's been inserted into the canal by way of touching a hot instrument to it. This way it can be squished and packed down so it closely adapts to the shape of the tooth's interior.
  • As an alternative, a dentist may place gutta percha via the use of a "gun." This apparatus is somewhat similar to a hot-glue gun. It warms a tube of gutta percha. The softened material can then be squeezed out into the tooth.
What's this step like?

There's not really anything that's all that striking about sealing a tooth, other than it means you're getting close to the end of your appointment.

Your dentist may heat the gutta percha so it becomes soft and pliable. So, you may smell that. And you'll feel pressure on your tooth as it's packed in place.

Other than that, this step should be yet another non-event.

[Our slideshow has pictures that illustrate what goes on during this step.]


An x-ray showing a tooth's completed treatment and a temporary filling.

X-ray of a tooth's completed treatment and temporary filling.

Step 6 - Placing a temporary filling.

Once your dentist has finished sealing your tooth, they will place some type of temporary filling. It will seal off the access cavity created at the beginning of your procedure, therefore protecting the work that's just been completed. (Precautions you should take.)


Step 7 - The root canal process has now been completed but your tooth still requires additional work.

At this point, the individual steps of performing the root canal procedure have been finished but your tooth's treatment is not yet complete. A permanent restoration must still be placed.

Choosing an appropriate type of dental restoration, and having it placed promptly, will help to insure the long-term success of your tooth's endodontic therapy.

Takeaways from this section.

Take note of the link in Step 6. It details precautions you should take after you tooth's treatment has been completed. (For the most part, don't look for trouble. Just take it easy with your tooth.)

The link in Step 7 is important to understand too. You must have the right type of permanent restoration placed, within the right time frame. Otherwise you put your tooth and its just completed treatment at risk.


If you have additional questions ...

Use the links below to learn more about the root canal procedure.

 

Written by: Animated-Teeth Dental Staff

Last revision/review: 9/15/2018 - Major update, revision and content added.

Content reference sources.


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