Coronal leakage - A cause of root canal treatment failure. -

Coronal leakage: What is it?

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

Why is it a problem?

Coronal leakage causes root canal treatment failure. Once it has occurred, the tooth will require endodontic retreatment so to once again clean/disinfect and then reseal the tooth's root canal system.

How is coronal leakage prevented?

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

A description of the phenomenon of coronal leakage.

The scenario.

If the filling's seal is compromised, bacteria can recolonize the tooth's root canal system.

That scenario describes what coronal leakage is.

Coronal leakage is the phenomenon where oral debris and bacteria seep from the patient's mouth, past an endodontically treated tooth's dental restoration, and ultimately penetrate into and recontaminates its interior root canal space.

The term "coronal" refers to the fact that the entry of the seepage is via the "crown" portion of the tooth. (The part of the tooth that's visible 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.

Bacteria seeping past this tooth's defective filling has caused its root canal treatment to fail.

How big of a problem is it?

But with cases in general, it may be only one factor of several that are involved. Here's an explanation.

• 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. (Inadequate restorations allow coronal leakage to occur.)

• 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.

▲ Section references - Hoen, Gillen

Recontamination can occur fairly rapidly.

Although a tooth's root canal system does receive an "endodontic" seal during its procedure (by way of the dentist placing gutta percha inside the tooth), the integrity of this seal isn't able to resist the continued assault of contaminants that takes place when coronal leakage occurs.

Research findings.

• A study by Torabinejad determined that the recontamination of a tooth's entire root canal system may occur in as little as 2.5 to 6 weeks.
  
• A more recent study by Eliyas found that bacteria can physically recolonize the full length of a tooth's sealed root canal system in as little as a few days.
  

  Even worse, this same study determined that endotoxins, irritating molecular compounds produced by bacteria, can cause recontamination at an even faster rate than the microorganisms themselves.

▲ Section references - Torabinejad, Eliyas

Understanding how the potential for coronal leakage might affect your tooth's treatment.

Replacing a temporary filling promptly helps to protect your root canal work.

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

▲ Section references - AAE

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

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

It's important to adhere to your dentist's instructions on this matter. Their recommendation will be based on the type of interim restoration they have placed in your tooth's access cavity and the time frame they feel they can rely on the seal it creates.

The restoration they place 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.

What types of restorations can meet these requirements?

After an evaluation, your dentist will make a recommendation as to what type of restoration they feel should be placed. (We discuss factors related to making this decision here: Rebuilding teeth after root canal treatment.)

Generally speaking, there are three alternatives that might be utilized.

A dental crown can establish an excellent seal but not all root canalled teeth require one.

1. Placing a dental crown. - Without question, the fit of a dental crown over its tooth typically creates a superior, lasting seal. And for teeth that require strengthening/protection from fracture, placing one makes the right choice.
2. Placing a filling. - Not all root canalled teeth require the protection of a crown. If after its endodontic treatment has been completed the tooth remains primarily intact, the placement of a dental filling (dental bonding or amalgam) has been shown to create an adequate seal. (Eliyas 2015)
   

   In most cases, the type of teeth that meet this criterion would be those that previously had no, or just a minimal, dental restoration.

3. Patch the tooth's existing crown. - In the case where a tooth's root canal work has been performed through an opening drilled through its (existing) crown, it's possible that a satisfactory seal can be created by filling the tooth's access cavity with dental restorative (amalgam or bonding).

Which makes the best choice toward preventing coronal leakage?

In terms of creating a predictable, lasting seal, there is no question that placing a brand new dental crown makes an excellent choice. But this procedure is too aggressive for teeth that don't otherwise require this type of restoration (see "rebuilding" link above).

Choosing to patch an existing crown through which the tooth's root canal treatment has been performed makes the least predictable choice. We explain the reasons why here.

Update log -

12/27/2018 - Revised with content added.

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Topic Menu ▶  Root Canal Treatment

• Root canal (endodontic therapy) basics.
• What is it? / What does it do? - Treatment goals and objectives.
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• Diagnosing a need for root canal therapy -
  
  • Signs and symptoms of needing treatment.
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    • Appointment details - How many visits, how long?
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  • Statistics / Incident rates of endodontic success and failure.
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  • Failure due to coronal leakage.
  • Persistent Dentoalveolar Pain disorder (PDAP).
• Overview: Root canal treatment alternatives.
  
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