Root canal treatment failure: Coronal leakage.

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Link to diagram of dental restoration leakage.
Link to picture of failed root canal.

Dentists have become increasingly aware of a phenomenon referred to as "coronal leakage." This process involves a situation where bacteria and debris find a way to recontaminate a tooth that has previously had root canal therapy.

Current thought is that this process likely plays a significant role in the failure of many endodontically treated teeth.

As this page explains, it's prevented by way of placing a proper permanent dental restoration on a tooth promptly after its root canal work has been completed.

A description of the problem.

One of the goals of root canal therapy is the elimination of bacteria and other contaminates from within a tooth.

Bacteria seeping past an endodontically treated tooth's filling.

Now, imagine the situation where a tooth's treatment has been successful in accomplishing this task. But, over time, the same types of contaminates are able to leak back into the inner confines of the tooth.

If this occurs, the conditions inside the tooth will revert to those similar to what likely existed before its treatment was initiated. And as a result, what was successful treatment will ultimately fail.

That's what coronal leakage is.

This type of recontamination process is precisely what the term "coronal leakage" refers to.

An x-ray showing failed endodontic therapy as a result of coronal leakage.

It's the phenomenon where oral debris and bacteria seep from the mouth, past a tooth's dental restoration, and penetrate into the tooth's treated root canal space.

The term "coronal" refers to the fact that the pathway of this seepage is via the "crown" portion of the tooth (the part of the tooth that lies above the gum line).

What research has found.

While the concept of coronal leakage has been known for over 100 years, it's only since the 1990's that it's received wide-spread attention and study.

Nowadays it's considered a significant factor in endodontic failure. But only one factor of several that may be involved. Here's an explanation.

Gillen (2011) [reference sources] applied statistical analysis to data collected from published studies. The findings of the report were:

  • Teeth having both adequate-quality root canal treatment and final dental restorations had a 2.8 greater success rate than teeth having adequate treatment and inadequate restorations.

But the study also determined that:

  • Teeth having both adequate-quality root canal treatment and final dental restorations had a 2.7 greater success rate than teeth having inadequate treatment and adequate restorations.

Together, these findings imply that:

  • Placing a suitable restoration can play an important role in protecting the outcome of a tooth's therapy.
  • But a well-sealing restoration alone can't overcome problems created by low-quality endodontic work (which only makes sense).

Recontamination can occur fairly rapidly.

Although a tooth's root canal system is sealed during its procedure (by way of placing gutta percha and sealer), the integrity of this seal can't resist the assault allowed by coronal leakage indefinitely.

Studies suggest that recontamination of the entire canal system may occur in as little as 3 to 6 weeks. (Torabinejad 1990)

Understanding what this means for you.

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

A) Coronal leakage as it pertains to temporary dental restorations:

Once your root canal therapy has been completed, your dentist will need to place some type of temporary restoration that will create a seal that protects your tooth's work until that point in time when a permanent one can be placed.

You need to be aware of the temporary nature of this restoration and the time frame over which it can be expected to maintain its seal. You'll need to ask your dentist for details but it may be as little as 3 weeks. (AAE 2002)

B) Coronal leakage as it pertains to permanent dental restorations:

Generally speaking, your tooth's permanent restoration should be placed as soon as is reasonably convenient (in other words, don't drag your feet on scheduling this procedure).

The seal of a dental crown helps to prevent coronal leakage.

It will need to:

  • Be capable of creating a barrier to seepage.
  • Be durable enough that this seal is maintained, even as the tooth functions under extreme conditions.
  • Offer protection for the tooth so the seal is not compromised due to tooth fracture.

After an evaluation, your dentist will make a recommendation as to what type of restoration will do. For some teeth, a dental filling may suffice. In other cases, a dental crown may be required.

We discuss factors related to this decision in greater detail here: Rebuilding teeth after root canal treatment.


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