Root canal retreatment - What options exist for your tooth if its endodontic therapy has failed? -

Explanations about Non-surgical retreatment, Apical surgery, Intentional Replantation, Extraction. | When is retreatment possible? | What success rates do these procedures offer?

What can be done for a tooth whose root canal treatment has been unsuccessful?

This page explains what options exist if your dentist determines that your tooth's primary (initial) endodontic therapy has failed. (Related: Signs and symptoms of root canal failure.)

In a nutshell, you only have two options ...

a) Making an attempt to salvage your tooth.

This approach involves performing some type of endodontic retreatment procedure.

The rationale.

Since the underlying problem that currently exists with your tooth is that its root canal system is contaminated (with microorganisms, debris, irritants, etc...), the only dental procedure that can remedy its situation is additional root canal therapy (retreatment).

b) Having the tooth extracted.

If conditions within the tooth's root canal system can't be, or won't be, resolved by performing some type of retreatment procedure, then the only other way to rid your body of the problematic conditions associated with it is to have it taken out.

Of course, ideal treatment would normally include replacing the tooth with an artificial one.

c) Not choosing is not a valid option.

As an FYI point, due to the unpredictable nature of teeth that harbor infection, not making a decision about which approach will be pursued leaves you at perpetual risk for the development of complications.

If a tooth has no potential to be a healthy contributing member of your dentition (set of teeth), it should be removed before its condition affects surrounding tissues, neighboring teeth, or causes an emergency situation.


What treatment options exist for failed root canal treatment?

Your dentist generally has four basic approaches that they can offer as a solution for your tooth's failed root canal status. Three of them involve performing some type of endodontic retreatment procedure.

  • Conventional retreatment - This is the situation where the tooth's root canal therapy is performed again, much like it was the first time.

    In more formal terms, this approach is referred to as orthograde or non-surgical endodontic retreatment.

  • Surgical retreatment - This option involves performing a minor surgical procedure where the tip of the problematic tooth's root is accessed and corrections/improvements are made with it.

    The formal term for this type of work is apical surgery. (FYI: The tip portion of a root is referred to as its "apex.")

  • Extraction with replantation - This procedure, as strange as it seems, involves extracting the problematic tooth. Then, some type of endodontic procedure is performed as a remedy for its failed endodontic status (like apical surgery). The repaired tooth is then placed back into its socket to heal.

    The formal term for this procedure is intentional replantation.

  • Extracting the tooth - Since retaining a tooth that shows evidence of pathology without performing some type of corrective procedure doesn't make an appropriate choice, its extraction is indicated.

    Afterward, ideal treatment usually involves replacing the missing tooth with some type of artificial one, like an implant or via dental bridge placement.

Section references - Ingle

Which option should be used?

If your dentist feels that it offers a good chance for success, they'll usually lean toward an approach of retreating the tooth, either conventionally or surgically.

But estimating those odds can only be determined on a case-by-case basis, based on the exact situation/deficiency that exists. (Related: This page offers general rules of thumb about which treatment approaches typically offer a potential solution for different causes of endodontic failure.)

Root canal vs. implant placement.

In regard to the extraction option, people frequently have questions about implant placement. We discuss that issue here: Implants vs. root canal treatment, which makes the better choice?

Note: The success-rate statistics stated in the discussion on that page are in reference to primary (initial) root canal treatment. As you'll read below, retreatment cases may offer a lower success rate, and this difference must be kept in mind.

Possible retreatment approaches -

Conventional / Orthograde retreatment.

A picture showing conventional (orthograde) root canal retreatment.

Non-surgical retreatment is performed via an opening in the crown of the tooth.

A) Non-surgical endodontic retreatment.

The approach taken with most failed root canal cases is non-surgical retreatment.

What does it entail?

This process involves repeating the same basic procedure (conventional / orthograde endodontic therapy) that was performed for your tooth originally, with the exception that additional effort will be required to remove the previously placed root canal filling materials.

A decision to proceed with this option simply depends on your dentist's judgment about its chances for success.

Why is this approach usually the preferred one?

Most root canal failures are due to microorganisms living within the tooth's root canal system. (They either survived the tooth's primary treatment, or invaded its filled root canal space after its work had been completed.) (Friedman)

  • Since orthograde endodontic therapy offers the least restricted access to the tooth's entire root canal system (which is needed in order to thoroughly disinfect and seal off the tooth's interior space), it makes the preferred choice.
  • Additionally, it's non-surgical nature makes it the least aggressive option (in terms of creating tissue trauma, patient tolerance for the procedure, etc...).

Section references - Friedman, Ingle

When isn't conventional retreatment chosen?

a) Difficulties with accessing the tooth's root canal system.

In order to perform retreatment work, the dentist must be able to make access to the tooth's root canal space. And in some situations this may be difficult to achieve due to the manner in which the tooth was rebuilt following its original treatment.

As an example, the tooth may have required post placement in one if its canals (see picture below). In some cases, post removal can prove challenging (difficult to accomplish, doing so may place the root at risk for fracture).

b) Difficulties in instrumenting the tooth's individual root canals.

If some type of situation exists that prevents the dentist from being able to use their instruments (root canal files) throughout all regions of the tooth's root canal space, the chances of retreatment success are reduced.

  • A tooth may have anatomical issues that impede the dentist's efforts, like canals that have an extreme curvature, heavy calcification, are exceptionally tiny in size, etc... (These issues may be the same ones associated with the original work's failure.)
  • Previously treated teeth may now be found to have issues associated with procedural errors or mishaps that occurred when performing that original work.

    This can include obstacles that are now present, like broken files or clogged canals. Or unfavorable changes in canal geometry (intra canal ledges, irregular/inappropriate canal enlargement, root perforations, etc...).

  • In some cases, the type of material used to fill in and seal the tooth's canals during its previous work may be difficult to remove.

In providing conventional retreatment, the dentist must feel that they have a reasonable chance of being able to overcome these challenges. If not, other approaches will need to be considered.

Section references - Ingle

Success rates for non-surgical endodontic retreatment.

As an example of what might be expected, a study by Gorni evaluated the 2-year outcome of 452 retreated teeth.

  • It found that cases that posed what the investigators categorized as relatively straightforward retreatment challenges were found to have a 87% success rate.
  • Those categorized as posing a higher level of difficulty (specifically, unfavorable changes in their original root canal anatomy caused by their previous work), were found to have just a 47% rate of success.

These numbers are in comparison to the 90% and above success rate typically associated with primary root canal treatment.

Section references - Gorni

Note: The wide range in treatment outcomes determined by this study simply demonstrates the importance of your dentist's abilities in creating a successful retreatment outcome.

  • They must be able to form a valid opinion about what went wrong with the tooth's original work.
  • Understand how the tooth's previous work may affect their retreatment attempts.
  • And have the skills needed to be able to successfully overcome the difficulties that they expect to encounter.

Is referral to a specialist needed?

In some instances, the level of skill and expertise needed to perform conventional root canal retreatment may lie beyond what your dentist feels they can offer. If so, the services of an endodontist (root canal specialist) will be required.

We discuss some of the considerations associated with making this decision here: General dentist vs. Endodontist. We discuss endodontic retreatment costs here.

B) Surgical retreatment.

Background.

As mentioned above, most cases of root canal therapy failure are due to microorganisms harbored within the tooth's root canal system.

And as they, and the waste products they create, leak out of the tooth's root the surrounding tissues are perpetually irritated.

a) With non-surgical endodontic retreatment ...

The focus of the procedure is on disinfection. It is an attempt to eliminate the offending agents from within the tooth (then followed by filling in and sealing off this now re-cleansed space).

Surgical endodontic retreatment.

An x-ray showing a root's retrograde filling.

Apical surgery has been performed, including retrograde filling placement.

b) With surgical retreatment ...
  • One goal may be irritant containment.

    The procedure is used to create a better seal of the root's canal opening (often by placing a filling), so the irritating substances still harbored inside the tooth can't leak out and continue to irritate the surrounding tissues.

  • Another goal can be removing locations harboring infection.

    This can include scraping away the tissues that have been affected by the disease process occurring around the root's tip. Or trimming away parts of the root itself that contain portions of its canal(s) that can't be properly cleansed.

When is a surgical retreatment approach needed?

Generally, the use of a surgical procedure is indicated when there is some reason why conventional (orthograde) root canal therapy would not be expected to be successful.

This might be due to complications associated with the tooth's original root canal anatomy, or ways it has been altered by previous treatment attempts. Or the dentist's access to the canals via a conventional approach is impeded (like with the post example given above, see picture).

 

What does the procedure entail?

Accessing a tooth's root end requires a (minor) surgical procedure. In brief ...

An incision is made in the gum tissue in the region of the root's end, and it is flapped back. Bone tissue is then trimmed away, to the extent that the tooth's root tip (apex) is revealed.

At this point, the precise steps that are carried out will vary according to the needs of the case.

  • The apex of the root may be trimmed away (termed root-end resection). The amount is often on the order of 1/8th of an inch or so but varies according to the precise needs of the case.

    The goal of the trimming may be to remove a problematic portion of the canal's anatomy, or to provide a suitable site to place a filling (or both). Doing so also allows the dentist an opportunity to evaluate the canal's seal that was created by its previous treatment.

  • The diseased tissues that surround the root's tip are scraped away (along with the microorganisms and debris they contain).
  • In some cases, root canal treatment may be performed for the exposed root, in an attempt to remove the bacteria and irritants harbored in it as best as possible. (Performing root canal treatment via its root end is termed "retrograde" endodontic therapy.)
  • A filling (termed a "retrograde" filling) may be placed in the root's end, so to create an improved seal for its exposed root canal opening.

Once all of the needed steps have been performed, the surgical site is closed and stitches are placed to stabilize the gum tissue during the healing process that follows.

Related to the fact that all of these steps involve the root's end (its apex), this procedure is sometimes referred to as apical surgery or an apicoectomy.

How extensive is the process?

This procedure is generally categorized as minor dental surgery. It falls on the same order as having a medium-sized tooth extracted, or gum surgery performed in an isolated area.

Some general dentists may feel that providing this procedure lies beyond their level of skill and training. If so, referral to an endodontist is indicated.

Success rates.

Research studies suggest that success rates for surgical retreatment cases range from 62% to 98% (Ingle).

But other than noticing that the lower end of that range lies substantially below what's generally expected for a tooth's primary (original) root canal therapy (see link above), those numbers are fairly meaningless due to the fact that individual case factors play such an important role in treatment outcome.

Section references - Ingle

Non-surgical retreatment may be needed first.

Your dentist may feel that performing orthograde (conventional) retreatment prior to your apical surgery will benefit your case's outcome.

A study by Grung evaluated 477 teeth that were treated with apical surgery procedures and found that cases where conventional retreatment had been performed first had a 24% higher success rate. (Ingle)

Section references - Ingle


C) Tooth extraction, retreatment and replantation.

This option is usually referred to as "intentional replantation."

What does this procedure involve?

As you might deduce from this section's title, this procedure is composed of the following steps:

  • The tooth is extracted. - This step must be performed as gently as possible because doing so helps to insure that the tissues attached to the tooth's root surface (that will be important in promoting its reattachment during the healing process) aren't excessively traumatized.
  • Some kind of endodontic retreatment procedure is performed. - This is usually some type of step similar to what is performed during apical surgery (discussed above).

    Since most endodontic failures are associated with microorganisms inside the tooth, retrograde endodontic therapy (root canal retreatment performed from the root end of the tooth), is common, as is retrograde filling placement.

    The care the dentist takes in handling the tooth is vital in preserving the tissues attached to its roots(s). For example, the tooth must be kept moist at all times. Touching root surfaces avoided. Procedure time is ideally kept to 15 minutes or less.

  • The tooth is then gently replanted back into its socket. - Some type of splinting will be required to stabilize the tooth during the next 7 to 14 days of its healing process.

When is intentional replantation considered?

This technique is generally only utilized with cases where conventional or surgical retreatment (both described above) are not feasible.

For example, intentional replantation might make the better choice for a tooth whose root tip lies in close proximity to a major nerve that might be damaged during apical surgery.

Success rates.

Of all of the different endodontic retreatment options, this is the one least studied. In his textbook, Ingle states that studies have suggested success rates ranging from 34% to 93%. But also states that the exact criteria used to determine those numbers has varied among researchers.

Section references - Ingle

Complications.

A problem sometimes associated with intentional replantation is progressive root resorption (the loss of root structure due to bodily processes).

The potential for the tooth to experience this complication generally correlates with procedural factors, such as how gently it was extracted, how it was handled and maintained while out of the mouth, and for how long.

Under ideal conditions, root resorption is thought to occur in just a minimum of cases (possibly 5% or less). The first signs of damage are usually apparent during the first year after the procedure.

Section references - Ingle


D) Tooth extraction.

Besides performing some type of case retreatment, the only other appropriate choice for a tooth whose root canal work has failed is to extract it. This option might be the only one suitable for cases where retreating the tooth is not possible, or only offers a low probability of success.


Timing your next step.

Whatever decision is made, your corrective treatment should be performed within the time guidelines recommended by your dentist.

Following their examination, they can gauge how much urgency appears to be involved. As a precaution, your dentist might write you a prescription for antibiotics so you already have it on hand if conditions with your tooth worsen before your definitive treatment can be performed.

Why you mustn't delay.
  • Teeth that have failed endodontic treatment are unpredictable due to the fact that they typically harbor infection, which has the potential to flare up (create pain and/or swelling), possibly significantly so, without warning.
  • Infections that are allowed to persist can result in complications associated with the tissues that surround the problem tooth (possibly even affecting neighboring teeth). Also, teeth that harbor chronic endodontic infections can be more problematic to successfully retreat.

Further reading about root canal failure:

 
 
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