The root canal procedure.

- This page outlines the steps a dentist follows when they perform root canal treatment (endodontic therapy).

Page Graphics | Animations.
Link to canal cleaning slideshow.
Link to filling and sealing slideshow.

The 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 "rubber" dam is really a thin sheet of latex (usually about 6 x 6 inches).
  • Your dentist will punch a tiny hole near its center.
  • They'll then stretch the sheet over your tooth so it alone sticks through the punched hole.
  • A metal clamp is then positioned to hold the dam in place.

As explained in our slideshow, the portion of the tooth that sticks through the dam lies in a region where its environment can be controlled. The tooth can be washed, dried and kept saliva-free.

A tooth with a rubber dam in place.

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

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.

 


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.


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.

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, electronic length-measuring devices have come into common usage.

  • 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.)


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.

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.

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.

Traditionally, root canal files have been used as hand instruments (manipulated by the dentist's fingers). Your dentist may, however, have a specialized dental drill (handpiece) that holds the files and produces the needed filing motion for them.

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

While performing their work, your dentist will also periodically irrigate (flush out) your tooth. This carries off and washes away debris and contaminants.

While a number of different solutions can be used for this purpose, sodium hypochlorite (bleach, Clorox) is the most common one. An added benefit of using bleach is that it's a disinfectant.


Step 5 - Sealing the tooth.

Once the interior of the tooth has been thoroughly cleansed and properly shaped, it's ready to be sealed (have its hollow interior filled in).

  • In some cases, the dentist will want to place the filling material immediately after they've finished cleaning the tooth.
  • With other cases, they may feel that it is best to wait about a week before performing this step.

[ Related content: How many appointments will your root canal therapy take? ]

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

The size of the filling material and file are matched.

If the latter case is chosen, your dentist will need to place a temporary filling in your tooth, so to keep contaminates out during the time period between your appointments. (Precautions you should take with this filling.)

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 whose sizes exactly match the dimensions (diameter, taper) of root canal files.

b) Placing the gutta percha.

When performing this step:

  • The dentist will slip an initial cone of gutta percha into the tooth's canal.
  • It's important that this first cone extends the full length of the canal and fits snugly in the region of the tooth's tip.
  • Additional cones are then added, as needed, to completely fill in the canal's interior.

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.


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.


If you have additional questions ...

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

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