Root canal therapy failure: Coronal leakage.

As you have already learned from our pages, one goal of root canal treatment is the elimination of bacteria and irritating substances harbored within a tooth that are capable of causing inflammation in the tissues that surround it. Now, imagine a situation where root canal therapy has been successful in accomplishing this task initially but over time contaminates are allowed to seep back into the inner confines of the tooth. If this type of reinfection of the tooth is allowed to occur, the success of the root canal treatment will falter.

This recontamination phenomenon is exactly what the term "coronal leakage" means. Coronal leakage refers to the ability of contaminates to migrate from the mouth (past a tooth's dental restoration) and on into the tooth's treated root canal space. The term "coronal" references 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), as opposed to a pathway involving the root portion of the tooth (the portion of the tooth encased in the jawbone).

Coronal leakage can lead to root canal treatment failure.

Over the past several decades, coronal leakage has increasingly been hypothesized as being a primary cause of endodontic failure. Studies have shown that reinfection of the root canal space can occur quite rapidly if the root filling materials that have been placed are not adequately protected from contaminates found in the oral environment by way of a well sealing dental restoration.

Understanding coronal seepage is important on a number of fronts, both for the treating dentist and patient alike.

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

At the completion of their treatment, the treating dentist or endodontist will need to place some type of provisional dental restoration that can create a seal that protects the tooth's root canal filling materials until that point in time when a permanent restoration can be positioned. The dentist must, of course, choose a dental restorative that can be expected to create an adequate seal. The dental patient must understand the temporary nature of this restoration and the time frame over which it can be expected to maintain its seal.

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

In regards to preventing coronal leakage, the type of permanent dental restoration that might be suitable for a tooth after its root canal treatment has been completed will depend on a couple of factors. The restoration, by nature, needs to be a type that is capable of creating an appropriate seal (barrier to coronal leakage) for the tooth. The restoration must also be durable enough that this seal will be maintained, even as the tooth functions under extreme conditions. The type of dental restoration chosen must also offer protection for the tooth so the tooth's coronal seal is not compromised by tooth fracture or breakage.

After evaluating these, and any other salient considerations, the dentist will make their treatment recommendation. Some teeth, such as an anterior tooth that has required root canal treatment but otherwise has never had need for a dental restoration, might be adequately restored with a white filling (dental bonding). In comparison, a molar (a type of tooth that will need to withstand heavy chewing forces), especially one that already housed a large filling before its root canal therapy was performed, would probably be best restored with a dental crown.