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All topics.  »All Root Canal pages.  »Treatment failure – Coronal leakage.

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

What is it? | What causes it? | Symptoms to watch for. | How can coronal leaking be prevented? | Which type of dental restoration creates the best seal for a tooth? – Crown vs. filling.

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Coronal
leakage
diagram.

Link to diagram of dental restoration leakage.

Evidence of
coronal
leakage.

Link to picture of failed root canal.

Coronal leakage: What is it?

Dentists, especially endodontists, have become increasingly aware of a process termed “coronal leakage.” This phenomenon involves the situation where oral bacteria and debris find a way of leaking into and recontaminating and infecting the interior of a tooth that has previously had root canal therapy.

Why is it a problem?

Coronal leakage leads to root canal treatment failure and associated symptoms. Once it has occurred, the tooth will require endodontic retreatment so to once again clean/disinfect and then reseal Procedure steps the tooth’s root canal system.

How is coronal leakage prevented?

As this page explains, it’s prevented by way of placing an appropriate final dental restoration for a tooth promptly after its root canal work has been completed. (Frequently a permanent crown, in some cases a filling may suffice.)


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A description of the phenomenon of coronal leakage.

The scenario.
Bacteria seeping past an endodontically treated tooth's filling.

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

One of the primary goals of root canal therapy is the elimination of bacteria and other contaminants from within the tooth. Why? | How?
Now, imagine the situation where a tooth’s endodontic treatment has been successful in accomplishing this task. But, over time, the same kinds of contaminants that were originally responsible for its problems once again find a way of leaking back into its interior space (pulp chamber and root canals).

If this occurs, the conditions inside the tooth will revert back to those that existed before its therapy was performed. The tooth’s previously successful work will now need to be considered failed root canal treatment. (Leaking root canal symptoms.)

As a solution for this change of events, conventional root canal retreatment, apicoectomy, or else tooth extraction will be required. (For more information about these options, use this link: Endodontic retreatment How successful is this? )

And 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 recontaminate and infect 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 1990s that it’s received widespread attention and study.

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

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

How big of a problem is it?
Nowadays it’s considered a significant factor in the process of root canal failure. For example, a study by Hoen evaluated 337 failed endodontic cases and determined that 13% of them involved complications with coronal leakage.

However, with any one case, coronal leakage may be only one factor of several that are involved. Here’s an explanation.

A study by Gillen applied statistical analysis to data collected from published research. 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. (Inadequate restorations allow coronal leakage to occur.)

 

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.
That conclusion isn’t necessarily surprising. But it does reinforce the fact that each and every step of a tooth’s treatment is important and interrelated.

▲ 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 packing gutta percha inside the tooth How this is done.), the integrity of this seal isn’t able to resist the continued assault of contaminants that takes place when coronal leakage occurs.

Root Canal Failure

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Coronal Leakage
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Statistics
Research findings.
The following two studies investigated how quickly a tooth’s endodontic seal is compromised when it doesn’t have the protection of any type of coronal restoration (like a filling or dental crown). This would be similar to the situation where a (failed, defective, or inadequate) restoration was allowing coronal leakage to occur.
  • 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 chemical compounds produced by bacteria, can cause contamination of the tooth’s root canal space even more quickly than the microorganisms themselves.

▲ Section references – Torabinejad, Eliyas


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

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

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

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 without leaking.
You’ll need to ask your dentist for details (that will be based on the type of temporary filling material that has been placed) but it may be as little as 3 weeks. (AAE)

▲ Section references – AAE

Related Page

Restoring root canal teeth.

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 (temporary) 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 final restoration they place will need to:
  • Be capable of creating a barrier to seepage/leaking.
  • 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. Options.)

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

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

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 permanent crown over its tooth typically creates a superior and lasting seal. And for teeth that require strengthening/protection from fracture, placing this kind of restoration 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 permanent crown Explained, it may be possible that a satisfactory seal can be created by filling the tooth’s access cavity with dental restorative (amalgam or bonding).

 

Series of x-rays showing before and after root canal treatment and then signs of root canal failure due to coronal leakage.

Coronal leakage due to an inadequate final restoration (a filling in this case) could explain this case’s treatment failure.

Which makes the best choice for preventing coronal leakage?

In terms of creating a predictable, lasting seal, there is no question that placing a brand-new dental crown following a tooth’s treatment makes an excellent choice, especially in the case of molars.

But this procedure may be judged too aggressive (in terms of the amount of tooth structure lost) for teeth that don’t otherwise require the benefits that a crown can provide (see “rebuilding” link above). If so, placing a filling may be considered appropriate.

Choosing to patch the hole in an existing crown (through which the tooth’s root canal treatment has been performed) with a filling makes the least predictable choice. We explain the reasons why here. Pros / Cons


What symptoms can you expect with coronal leakage?

Once contaminants leaking into your tooth’s root canal system has occurred, you have the potential to experience any of the wide range of symptoms normally associated with endodontic infection.

Common leaking root canal symptoms.

  • Tooth sensitivity or discomfort. – Intermittent or persistent pain, either triggered or spontaneous. Throbbing pain. Sensitivity to pressure (like biting on the tooth).
  • Tooth abscess. – The presence of swelling (intermittent or persistent). Development of a pus pimple (gum boil) next to your tooth (formally termed a fistulous tract).
  • Additional symptoms of tooth infection. – Noticing a bad taste in your mouth or having a bad breath odor.

This link covers the topic of failed root canal symptoms What to look for. in greater detail.

 
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Page details –Last update:  October 07, 2023Authored by  Animated-Teeth Staff Dentist

What's next?

Full menu for topic:  Root Canal Treatment

  • Root canal (endodontic therapy) basics.
    • What is it? / What does it do? - Treatment goals and objectives.
  • Diagnosing a need for root canal therapy -
    • Signs and symptoms of needing treatment.
      • Covid-19 (Coronavirus) and seeking assistance.
    • Diagnostic testing your dentist performs.
    • X-ray diagnosis.
    • Sinus tracts (fistulous tracts, gum boils).
  • Having root canal treatment -
    • The steps of the procedure. / What will you experience?
      • Appointment details - How many visits, how long?
      • Rubber dam - Why is it needed? / Placement & usage.
      • All about root canal files.
      • Making the procedure's access cavity.
      • How many roots and canals does your tooth have?
      • How and why a canal's length is measured.
      • Does having root canal hurt?
    • Endodontist vs. General Dentist - Pros and cons.
  • Post-procedure considerations -
    • What to expect after having root canal.
    • What kind of final restoration will be needed?
      • What is a post & core? - The basics.
      • The post & core procedure.
      • Can a tooth's existing crown be reused after root canal?
  • Complications & treatment failures -
    • Signs and symptoms of endodontic failure.
    • Technical and procedural issues that lead to case failure.
    • Failure due to coronal leakage.
    • Retreating failed root canals - What options exist?
  • Overview: Root canal treatment alternatives.
    • Root canal vs. Implant placement.
  • Root canal treatment costs - (By tooth type.) / Details about insurance coverage.
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 Page references sources: 

American Association of Endodontists (AAE). Coronal Leakage.

Eliyas S, et al. Restoration of the root canal treated tooth.

Gillen B. et al. Impact of the Quality of Coronal Restoration versus the Quality of Root Canal Fillings on Success of Root Canal Treatment: A Systematic Review and Meta-analysis.

Hoen MM, et al. Contemporary Endodontic Retreatments: An Analysis based on Clinical Treatment Findings.

Torabinejad M. et al. In vitro bacterial penetration of coronally unsealed endodontically treated teeth.

All reference sources for topic Root Canals.

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