Root Canal Treatment

Root canal treatment / Endodontic therapy: Goals and objectives.

What is the purpose of the root canal procedure?

You could say that the purpose of root canal therapy is to create an end result where the tissues that surround a tooth's root will maintain a healthy status despite the fact that the tooth's nerve has undergone degenerative changes. Specifically, we mean that the tissues surrounding a tooth's root are not affected by bacterial infection and/or irritating substances leaking from those inner aspects of the tooth originally occupied by the tooth's nerve tissue.
Possibly in more scientific terms, our bodies, as a defense mechanism, will initiate an "inflammation reaction" when irritants (such as those that might seep out of a problematic tooth) have injured or destroyed body tissues. So if we choose to incorporate the term "inflammation" into our description we would say, root canal treatment is the treatment of the inner aspects of a tooth (whose nerve has undergone degenerative changes) so to provide an environment where the tissues surrounding a tooth's root are free of, and will likely to continue to be free of, the presence of inflammation.

How does root canal treatment accomplish this goal?

In a nutshell, the process of root canal treatment first removes (as thoroughly as possible) bacteria, nerve tissue, the organic debris left over from the breakdown of nerve tissue, and bacterial toxins from within the inner aspects of a tooth (the area originally occupied by the tooth's nerve tissue). Each of these items can produce tissue irritants that can cause your body to activate an inflammation reaction.
Subsequently, once this space has been cleansed the second half of root canal treatment involves filling in and sealing up the interior of the tooth. This aspect of the treatment is an attempt to minimize the possibility that bacteria will be able to recolonize the inner aspects of the tooth or that tissue fluids can seep inside the tooth, become stagnant, and subsequently break down. (Either of these situations could produce a state of persistent inflammation in the tissues surrounding the tooth's root.) The seal also contains and encapsulates any debris that could not be fully removed during the cleaning aspect of the root canal treatment process so that it can't leak out and trigger an inflammation reaction.

Why go to all of this trouble?

If you get an infection, say from bacteria entering a cut in your skin, your body will transport white blood cells to and from the area (by way of your blood vessels and lymphatic system) so to combat the bacteria that have caused the infection. In most cases your body will win the battle and kill off the offending bacteria.
The problem with teeth and infections is that once a tooth's nerve tissue has started to degenerate and bacteria have taken up residence in the tooth's nerve area, there is no effective way for white blood cells to get at the bacteria to combat them. The dying nerve's blood and lymphatic vessels used to transport white blood cells will have begun to degenerate too.
The net result of all of this is that the nerve space inside a tooth can provide a nice cozy cave-like location for bacteria to persist because it's a place where your body's defense mechanisms can't get at them effectively. With this scenario, at best your body will only be able to cordon off the infection caused by the bacteria living inside your tooth. At worst, this bacterial infection will overwhelm your body's defense mechanisms and pain and swelling will ensue (an acute tooth abscess).
The idea behind having root canal treatment is that it provides the bulk of the clean up work for your body. It removes bacteria and tissue irritants that are present inside the tooth, especially those in the locations where your body would have the most trouble combating them. As an end result, once root canal treatment has been completed it provides your body with an environment where its mechanisms are able to clear away any residual bacteria and tissue irritants that may still be present, thus allowing complete healing (resolution of the inflammation) to occur.

The root canal treatment procedure: What steps are involved with endodontic therapy?

What are the individual steps of the root canal treatment process?

A) Placing a rubber dam around your tooth.

After numbing your tooth but before beginning the actual process of performing the root canal treatment, your dentist will stretch a sheet of rubber around your tooth. Dentists call this sheet of rubber a "rubber dam." It is held in place by a small clamp that grasps your tooth.
The purpose of a rubber dam is as follows. Since one of the fundamental goals of root canal therapy is to clean bacteria out of a tooth, and since saliva does have bacteria in it, the placement of a rubber dam allows the dentist to keep your tooth saliva free so it doesn't get recontaminated with bacteria while your root canal treatment is being performed.

B) Gaining access to the nerve area of the tooth.

As a starting point for the process of performing your root canal treatment your dentist must first gain access to that area inside the tooth where the nerve tissue resides. This is accomplished by using a dental drill and making an access cavity that extends down to the pulp chamber of the tooth. On posterior teeth this hole is made on the chewing surface of the tooth. On front teeth the access hole is made on the tooth's backside.

C) Cleaning the tooth out.

The next step of the root canal treatment process is for your dentist to clean out the interior of your tooth (the pulp chamber and all root canals). As we discussed previously, this cleaning process removes any bacteria, toxins, nerve tissue, and related debris that are harbored inside your tooth.
For the most part the cleaning process is accomplished by way of using "root canal files" and copious irrigation. Root canal files look like straight pins but on closer inspection you would find that their surface is rough, not smooth. These instruments literally are files and are used as such. Your dentist will work a series of root canal files, each of increasing diameter, up and down in your tooth while simultaneously using a twisting motion. This action will scrape and scrub the sides of the tooth's root canal(s), thus cleaning it out.
As an additional part of the cleaning process, your dentist will wash your tooth out periodically ("irrigate" the tooth) so to help flush away any debris that is present. Traditionally, a number of different solutions have been used for this purpose. Nowadays, sodium hypochlorite (bleach, Clorox) is commonly used. An added benefit of bleach is that it is a disinfectant.
The goal is for your dentist to clean the entire length of the tooth's root canal(s), but not beyond. As a means of determining the length of a canal your dentist may place a root canal file in your tooth and then take an x-ray. Once developed the x-ray picture will reveal if the file extends the full length of the canal or not. Alternatively, your dentist may have an electronic device that can make this same determination when it is touched to a file that has been positioned in a canal.
 
Traditionally the filing action of root canal files has been created by way of the dentist manipulating them with their fingers. There are, however, special dental drills (dental drills are called "handpieces") which can hold and twist these files, and your dentist may choose to use one. As a variation on this same theme, there is yet another type of dental handpiece that produces a cleaning motion by way of holding a root canal file and vibrating it vigorously.

Restoring a tooth after root canal treatment has been completed.

What additional dental work is needed for a tooth that has had root canal treatment?

After your tooth's root canal treatment has been completed your dentist will need to discuss with you what additional dental work will be required so to make the tooth fully functional again.


Many times a tooth that has required root canal treatment is one that has a big filling or else has large portions missing due to decay or breakage. These teeth, in this state, are not as sturdy as they once were and for this reason it is commonplace that a dentist will recommend that a tooth that has had root canal treatment should be restored with either a dental crown or else a dental crown in combination with a dental post. Of course your dentist will need to determine what treatment is appropriate in your situation.

The dental restoration that is chosen for rebuilding a tooth that has had root canal treatment provides another function also. It provides a seal protecting the interior of the tooth. This barrier helps to prevent seepage of bacteria and contaminates from the oral cavity into the interior aspects of the tooth (a phenomenon termed "coronal leakage"). Your dentist will need to advise you as to what they think is best for your situation but, in general, the sooner arrangements can be made to have the permanent dental restoration placed (thus creating the best possible seal) the better.

Placing a post in a tooth that has had root canal treatment.

A "post" is a rod that a dentist has positioned and then cemented in the canal space in a tooth's root. Typically, but not always, dental posts are made out of metal.
Posts are usually only placed in those teeth which have extensive portions of their natural tooth structure missing. Dentists know, in general, that the greater the amount of a tooth that can extend up into the center of the dental crown, the more stable the crown will be. In those cases where a great deal of tooth structure is missing a dentist will "build up" the height of the tooth using dental filling material. A dental post provides a way for the dentist to securely anchor this filling material core to the tooth.
 

How does a dentist place a post in a tooth?

When placing a post a dentist will first use a drill and remove some of the gutta percha filling material that was placed during the tooth's root canal treatment. They will then cement the post and subsequently place a core of filling material around the post's upper portion, so to increase the overall amount of structure that will extend up into the crown.

Placing a dental crown on a tooth that has had root canal treatment.

Crowns are dental restorations that cup over the portion of a tooth that lies above the gum line. People sometimes refer to dental crowns as “caps." Dental crowns can either be gold or else have a porcelain surface so they look white like a tooth's neighboring teeth.

A dentist will use a dental crown as a means of improving the appearance of a tooth, restoring a broken tooth to its original shape, and/or strengthening a tooth. Additionally, and very importantly, dental crowns create an excellent seal over a tooth. By this we mean that a crown cemented in place provides a barrier that is helpful in preventing bacteria and contaminates from seeping back into those inner aspects of a tooth where the root canal treatment has been performed. After a tooth has had its root canal treatment completed, any or all of these qualities which a crown can provide may be needed.

What steps are needed to make a dental crown?

Before a dental crown can be placed the tooth must first be trimmed so it is tapered in shape. This tapered aspect of the tooth will extend up into the dental crown's center and is a very important factor in the crown's stability. After the needed shape has been achieved your dentist will take an impression of the tooth, which in turn is sent to a dental laboratory which will create the crown. Once the dental lab has completed your crown your dentist will cement it in place.

Root canal treatment complications, problems and reasons for failure and retreatment.

How long will a tooth that has had root canal treatment last?

No doubt it is the hope of your dentist that the root canal treatment they provide for you will allow your tooth to last a lifetime. This can certainly be the case and hopefully the outcome you will experience.

What can cause root canal treatment to fail?

Previously we described some of the goals of root canal treatment:

It removes bacteria, toxins, unhealthy nerve tissue, and irritants that are present in a tooth. It fills in and seals off the nerve space inside a tooth so physically there is no location where bacteria and tissue irritants can exist and be out of effective reach of your body's defense mechanisms.

If after root canal treatment has been performed a tooth still harbors bacteria or irritants which keep the tissues surrounding the root of the tooth from being healthy (inflamed), then the treatment has not been successful. Some signs of failed root canal treatment can include tooth pain (ranging from very mild to extreme) and tenderness or swelling in the gums in the area near the tooth (ranging from very slight to pronounced). These signs can either:

Persist from the time of the root canal treatment. Be transient (varying week to week or month to month). Appear even though the tooth has been asymptomatic for years.

In other cases a tooth may have been, and continues to be, without symptoms but the tissues surrounding the tooth are identified as having the presence of persistent inflammation by way of a x-ray examination by a dentist.
In general, the presence of problems indicates that, despite your dentist's best efforts to clean and seal up the tooth, bacteria or tissue irritants have found some location in which to persist beyond the reach of your body's defense mechanisms. As a result there is persistent inflammation in the tissues that surround the tooth's root. Here are some of the reasons why this scenario might occur:

The shape of any tooth's root canals can vary greatly. As an example, there can be root canals that have branches or forks in them. This branching can be hard for a dentist to detect and, as a result, one branch may be cleansed and sealed while the other branch is left untreated. A tooth may have more root canals than is normally anticipated. In these cases, especially when the unexpected root canals are very tiny, your dentist may not discover them and as a result not clean and seal them. There is a crack in the root of the tooth. These cracks can be very small or else in a location in which your dentist cannot detect them. The tooth has a defective or inadequate dental restoration and as a result bacteria have been able to seep past this restoration on into the inner aspects of the tooth and recontaminate that area originally cleansed and sealed off by the root canal treatment. This phenomenon is termed "coronal leakage." Even though a tooth has been expertly cleaned and sealed, with the passage of time the integrity of this seal can degrade, thus allowing bacteria to recontaminate the interior aspects of the tooth.

Your dentist will have to evaluate your specific situation and advise you as to if they think the retreatment of your tooth is likely to resolve your problems. They may offer to perform this treatment themselves or they may feel that the expertise of an endodontist is warranted for your case. If retreatment is not a possibility then the tooth should be extracted.