The root canal procedure. -

An outline of the steps a dentist follows when they perform root canal treatment (endodontic therapy). | Cleaning and shaping the canals. | Sealing the root canal system. | What is each step like for 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 endodontic therapy.

The following is an outline of the steps a dentist follows when they provide conventional root canal treatment for a tooth. (The basic procedure most frequently performed for teeth.)

Other terms for this procedure are "non-surgical" and "orthograde" endodontic therapy. Both of these names indicate that the procedure is performed through an opening made in the tooth's crown (the portion that lies above the gum line), as opposed to accessing the root directly via some type of surgical procedure.


Step 1 - Placing the rubber dam.

After numbing you up, your dentist will first "isolate" your tooth by way of placing a rubber dam. A dental dam is simply a sheet of "rubber" (actually, latex in most cases) that's pulled over your tooth so it pokes through (see picture below).

As diagrammed on our What is a rubber dam? page, because the portion of the tooth that sticks through the dam now lies in a region where its environment can be controlled, it can be kept contaminate-free during its procedure.

Why is tooth isolation so important?

  • One of the fundamental goals of root canal therapy is removing contaminates from within the tooth.
  • The barrier created by a dam aids with this goal by preventing saliva (a source of bacteria and debris) from gaining entry into the tooth while its work is being performed.

Note: Placing a dam is part of the "standard of care" that any and every dentist must responsibly provide. If your endodontic procedure doesn't involve using one, you should be asking questions because in the vast majority of cases, it's use is considered absolutely essential. (Ingle)

 

A tooth with a rubber dam in place.

A rubber dam creates a controlled environment where successful endodontic therapy can be performed.

What's this step like?

For you, the patient, wearing a dam should be a non-event.

  • Since you've been numbed up for your procedure, there shouldn't be any discomfort involved as it's placed or while it's worn.
  • What you may feel is the pressure of the clamp that's used to hold the dam in place on your tooth.

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

 

Step 2 - Creating the access cavity.

As a starting point for actually 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 any tooth decay, and all 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?

As alluded above, dental anesthetic doesn't inhibit your sense of pressure. So, when your dentist starts drilling your tooth's access cavity, you'll feel the minor vibrations of their drill. But these mild sensations are really all you should notice.

You shouldn't experience any pain. However, 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 that a problem exists, they can then determine what steps are needed to control your discomfort.

[Our sideshow contains pictures of tooth access cavities.]

Step 3 - Identifying all of the tooth's root canals.

Once the entrance into the interior of your tooth has been made, your dentist will need to identify each of its root canals. (How many canals does your tooth have?)

An important aspect of endodontic therapy is that each one is identified and treated. Falling short of this goal will lead to case failure.

A surgical operating microscope may be used.

It's become increasingly common that the floor of your tooth's pulp chamber will be 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.

Your dentist searching for the openings to your tooth's root canals should be a non-event. Pain should not be a factor. They'll typically use a pointed hand instrument, or root canal file (see below), to feel around inside your tooth until each one is located.

In cases where a canal's location isn't immediately apparent, your dentist may need to trim away additional portions of your tooth's interior to expose them. If so, at most you should just feel the vibrations of your dentist's dental drill as it's being used.


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 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. So while it's commonplace that an endodontist (root canal specialist) will have one in their office, it's less likely that your general dentist will.

Step 4 - Measuring the length of the tooth.

Your dentist's goal will be one of treating the entire length of each of your tooth's root canals but not beyond. Doing so is not only important for creating treatment success but also helps to minimize complications with post-operative pain.

Meeting this goal means that your dentist must measure the length of each of your tooth's root canals. This measurement is typically calculated to a tolerance of/has an accuracy of 1/2 millimeter (about 1/50th of an inch). (Hargreaves)

Setting the parameters for this measurement.

You might be surprised to learn that there's considerable controversy about just where in a canal its endodontic therapy should terminate.

  • Some studies suggest that treatment should extend all of the way to the root's apex (tip). Others seem to have concluded that a point 1 to 2 mm shorter gives a better chance of case success. (Hargreaves)
  • To confuse matters even further, other studies have concluded that the endpoint chosen should be influenced by both the current status of the tooth's pulp tissue (i.e. necrotic, vital, inflamed), and the degree to which the tooth's pathology has affected its surrounding bone tissue. (Hargreaves)

Obviously, choosing the treatment terminus will simply be a judgment call that your dentist will need to make.

Measuring the length of a canal via x-ray.

Slide series - Measuring the length of a canal.

How does a dentist make canal length calculations?

A dentist has two methods they can use to measure a canal.

a) By taking an x-ray.

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

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

b) Electronic measurements.

In recent decades, the use of electronic length-measuring devices has become commonplace. These units are referred to 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 in your tooth. They'll then tuck its second lead inside your lip (this completes the electrical circuit the unit requires).
  • As the dentist slides the file further and further on into the root canal (an electrically insulated space), the unit measures changes in electrical resistance as the file passes ever closer to the conductive tissues that lie beyond the tip of the tooth's root.

    A digital readout or beeping sound indicates when the unit has detected that the file has finally reached the canal's end (tip of the root).

  • Once again, the measurement itself is read from markings on the file. The electronic unit simply indicates when the file's tip has reached the end of the root.

c) Several individual measurements may be needed for a single 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?

Despite the fact that an apex locator is an electrical unit, its use is a non-event for the patient. You won't feel a thing. And, in fact, using one is a plus because it typically makes performing your procedure quicker, simpler and quite possibly more precise.

  • When x-ray measurement is used, 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.
  • In comparison, when an electronic unit is used, minimal preparation is required. A measurement can usually be taken in less than a minute.

The use of an apex locator doesn't mean that no x-rays will be need to be taken. But for steps where it can be applied, it offers advantages.

[Our slideshow explains more about taking length measurements.]


Step 5 - Cleaning and shaping the tooth's root canals.

The next step of the root canal process involves "cleaning and shaping" the tooth's root canal system (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 contours of the tooth's canals are enlarged and flared, so they have a shape that's more ideal for the procedure's filling and sealing step.

The whole process is a delicate balancing act. One where the dentist seeks to accomplish the goals above, without removing internal tooth structure to an extent, or in a fashion, that might compromise the integrity of the tooth, or the outlook for its completed work.

Endodontic files.

The parts of a root canal file.

a) What tools does a dentist use?

For the most part, a tooth is cleaned and shaped (its walls rasped and planed) via the use of root canal files.

What do they look like?

Files look like tapered straight pins but on close inspection you can see, or feel, that their surface is grooved, not smooth.

Although files come in a number of different designs, in general terms, they can mostly just be thought of as miniaturized rasps.

 
Inserting a file into a tooth's canal.

Slide series - Using files inside a tooth.

b) How are the files used?

Filing motion.

A dentist will generally work a file with an up-and-down motion, combined with some type of twisting action (one form is a back-and-forth movement termed "watch winding").

  • The specific way a file is manipulated depends on both its design, and what the dentist is trying to accomplish.

    (For example, are they simply teasing the file down the full length of the canal so a length measurement can be taken vs. actively scraping and rasping the canal's walls to clean and shape them.)

  • The twisting aspect typically engages the file's blades with the canal's walls. And then the up-and-down motion (especially up) rasps and shaves them.
Aids to the filing process.

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 walls of the canal so the file's action will be more effective.
  • Additionally, its thick, wet consistency serves as a lubricant for the filing action.

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

 Reference: 

Ingle JI, et al. Ingle's Endodontics. Chapter: Preparation of coronal and radicular spaces. - Linked above.

c) Your dentist will use several files.

The same general routine will be used with each member of an entire set 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, gradually 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 handpiece (dental drill) that they use to manipulate some of them.

Nickel-titanium.

The specialized files used with endodontic handpieces are usually made of nickel-titanium alloy, and that's a big deal.

Their superior flexibility, combined with the mechanized motion created by the handpiece when they're used, typically means that a tooth's root canal system can be cleansed and shaped much more rapidly than in the past. (That's an important factor in making one-visit root canal treatment possible.)

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.

  • At minimum, they'll use this as a means of flushing debris and contaminants from within it. Doing so enhances the effectiveness of their cleaning efforts.
  • But another important function that irrigation provides is to flush away loose debris before it has a chance of being compacted (by the up and down action of the files) into a plug or blockage.

a) What kinds of irrigating solutions are used?

A number of different types of solutions might be chosen:

  • Conceivably, just sterile water or saline solution could be used to flush out debris.
  • By far, the most frequently used irrigating solution is sodium hypochlorite (bleach, Clorox). That's because it's effective in killing bacteria and digesting organic debris (two functions that can help to disinfect the tooth's root canal system). It also happens to be quite inexpensive.
  • Because different solutions have their own set of advantages, your dentist may consider it optimal to use more than one kind of solution during your tooth's treatment.

(Hargreaves - linked above.)

b) How is tooth irrigation performed?

While your dentist may have a specialized unit they use for this purpose, the process they use 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's nothing sharp about the needle, you are not getting a shot. Gently flushing out 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.

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 root canal files to access.

And especially in the case where the solution itself has properties that help to disinfect the tooth, 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)

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.

 Reference: 

What's this step like?

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

The process itself is just multiple cycles of using files in the tooth ... flushing the tooth out ... and then repeating the process again and 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 the next file into your tooth.

During tooth irrigation.

Your dentist may agitate the solution they place in your tooth with an ultrasonic instrument (its intense vibrations will help to increase the solution's effectiveness). 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 immediately. (One-visit endodontic therapy.)
  • With others, they may feel that it's best to wait about a week, or even two or three, 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 process 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.

    Doing so can be especially effective, and a primary reason why a two-appointment approach is chosen.

  • They will also need to place a temporary filling that seals the access cavity opening they have performed their work through, so to keep contaminates from reentering your tooth.

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


Step 6 - 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 rubbery 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.

One method of gutta percha placement that a dentist might use is referred to as "lateral condensation." When performing this process:

  • 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 chosen will be that one that corresponds with the dimensions of the last (largest) file used to clean and shape its entire length. (This is termed the "master" point 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 root's tip.

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

  • The cone is then removed from the tooth. Sealer (a thin paste) is applied to its sides, or else applied inside the root canal directly, and then the cone is reinserted. (The sealer fills in any voids between the gutta percha and the canal's walls.)
Placing gutta percha in a canal.

Slide series - Filling in and sealing the tooth.

A master point will typically fit snugly (and thus create a satisfactory seal) in the third of the canal (or so) nearest the root's tip.

But higher up in the canal, usually the cleaning process has flared its taper significantly, and this space needs to be filled in with gutta percha too.

In order to create a solid, uniform mass:

  • The dentist will insert a "spreader" in the canal (a tapered/pointed hand instrument that acts as a conically shaped wedge).

    This tool is worked laterally (side to side, hence the term "lateral condensation" for this procedure) to compact the gutta percha that's already been placed.

  • An "accessory point" (a gutta percha point smaller than the master point) is then dipped in sealer and inserted into the space created by the spreader.
  • This process is then repeated until the entire space within the canal has been filled in (sealed). And repeated for each of the tooth's individual root canals.

(Tronstad - linked above.)

Lateral condensation technique is just one of the methods your dentist might use. But all processes are the same in the sense that their goal is simply filling in/sealing the tooth's root canal system with a solid core of material (usually with gutta percha).

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.

  • With some methods, your dentist may heat the gutta percha so it becomes soft and pliable. So, you may smell that.
  • And you'll feel the pressure of the tools being used in your tooth as the gutta percha being placed is packed and condensed.

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

[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 7 - Placing a temporary filling.

Once your dentist has finished sealing your tooth, they'll 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 8 - 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 7. 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 8 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.

 

Last revision/review: 12/16/2018 - Revised. Content added.

 
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