Root Canal Retreatment – Guide

Written & Reviewed by Dr David Chen

When a root canal fails, endodontic retreatment is a dental procedure that redos the root canal thus giving the tooth a second chance. There are many causes for failure but retreating can save your tooth from extraction.

x-ray - four nerve molar root canal

We’re going to explain everything that you’d ever want to know about root canal retreatment.


Root canal retreatment is essentially a second root canal that is done on a tooth which already had one completed.

  • For the patient, it will feel like dejavu because the entire process repeats once more.
  • For the dentist, there will be slight differences in the steps but the ultimate goal remains the same, to eliminate infection.

Despite the best efforts of the dental community, the success rate for initial root canal therapy is not 100% which means it can fail. Studies have shown that it has a 85.1% survival rate over a period of ten years.

If the procedure fails the first time around, can you guess what the next step would be? That’s right, it would be to retreat the tooth once more and hopefully there’ll be a better outcome.

Who does it?

An endodontist (root canal specialist) will do endodontic retreatments. They specialize in endodontic procedures and that is what they do all day long. They are the type dentist to see if you need this procedure done.

Some general dentists may do it as well but it would depend on their personal expertise. Many of them would do initial therapy but retreating the teeth are often referred out to the specialists. You’d have to call them and ask but if they can’t help you, they certainly do have an endodontist that they can refer you to.

When is endodontic retreatment needed?

There are many conditions which may cause the initial endodontic treatment to fail, thus requiring the tooth to be retreated.

x-ray of tooth with halo around root after root canal - outlined

Causes for root canal retreatment:

  • Missed canals. Canals or nerves can be missed and what that means for you is an untreated infection.
    • Extra nerve – entire roots that were hidden could be missed such as MB2 (maxillary buccal root #2) in maxillary molars. Studies show 69.6% of these molars have it.
    • Curved canals – the curvature of the root may make it very difficult to disinfect.
    • Accessory canals – these are lateral canals are difficult to clean and shape.
  • Delayed permanent restoration. After a root canal, some patients delay returning to their dentist for a crown. Even worse, some never return at all and that is how it gets re-infected.
  • Saliva contamination. If isolation is not perfect, saliva which has a lot of bacteria can introduce them into the root canal system.
  • Tooth decay. The tooth cap covering the tooth may be immune to cavities but not the natural tooth underneath of it. The crown margin is where cavities develop.
  • Broken restoration. If the crown which is protecting the tooth breaks, bacteria can seep in and cause an infection.
  • Recurrent infection. After finishing treatment, it does not make the tooth immune to future infections. It can happen once again if you don’t take care of the tooth. Other times, the abscess can still be there even after the root canal.

The x-rays above are just to show you how the canals can curve. Navigating these are difficult and can be next to impossible sometimes. That is why you should see an endodontist.

Signs and symptoms

If your tooth requires a retreatment, it’ll often present with a certain set of clinical signs and symptoms.

When to see a dentist

If you’re experiencing any of the symptoms above you should schedule a consultation with your dentist. You should have them checked out because if you need a retreatment, only your dentist can do it. Home remedies are ineffective are fixing the source of the problem.

Don’t wait. Delaying the consultation may make it worse and more complicated.

What to expect during root canal retreatment

There is nothing to be afraid of for endodontic retreatment because it’s very similar to a root canal and you can think of it as a redo. If you managed to survive through the first one, you’ll make it through this one as well.

It’ll just feel like dejavu but just in case, we’ll remind you of the steps involved so you know what to expect for the procedure.

Procedure steps

The entire retreatment procedure will take about two hours but they’ll be spread out over two separate visits.

  • First visit – removing old root canal, disinfecting, and placing antibiotic medication in the canal.
  • Second visit – finish disinfecting and filling in the canals with gutta percha.

After all of that, you may return to your general dentist to get a permanent restoration.

First appointment

  1. Administer local anesthesia.
  2. Place rubber dam.
  3. Create access opening. Drill a hole through the top of the tooth to reach the pulp.
  4. Excavate old root canal filling. Remove all of the old gutta percha.
  5. Disinfection with sodium hypochlorite.
  6. Clean and shape canals.
  7. Place calcium hydroxide (antibiotic medication) inside canals.
  8. Place temporary filling.
what the temporary filling looks like after it has been adapted
Example of what the temporary filling looks like

Second appointment

  1. Administer local anesthesia.
  2. Place rubber dam.
  3. Remove temporary filling.
  4. Clean and shape the canals.
  5. Disinfect entire tooth.
  6. Fill canals with gutta percha.
  7. Place temporary.

Before and After

Below are before and after x-rays of what a root canal retreatment looks like.

As you can see in the before x-ray, the root canal filling was short of the apex which is why the patient needed it. However, in the after x-ray, you can see a very nice distinct filling in the canal all the way to the apex.

Does it hurt?

The entire procedure should not hurt because you’ll be adequately numb the whole time. If it hurts it simply means you need more local anesthesia. Most dentists will ask you to raise your left hand if it hurts and they’ll give you more numbing.

Risks, benefits, and alternatives


All procedures will have a chance for complications to arise and this one is of no exception.

  • Retreatment failure. Despite redoing the root canal once more, sometimes the infection does not dissipate. Bacteria seem to escape elimination and persist in the tooth.
  • Tooth fracture. Doing the procedure too often will eventually remove too much sound tooth structure. If there is not enough structural support the tooth can fracture and become non-restorable.
  • Swelling. Flare ups are possible in between the first and second visit.
  • Pain. Intra-op and post-op pain are to be expected.


The main benefit of retreating the tooth instead of simply extracting it is that you’re giving it a second chance and also saving yourself on total treatment time.

  • Saving your tooth. If you retreat it, you don’t need to extract it which means you get to keep your natural tooth.
  • Shorter treatment time. A root canal retreatment with a crown will take about a month to complete at most. That is in comparison to an extraction and implant which can take 8-12 months to finish. Essentially it takes less time to finish.


There are two alternatives to doing a retreatment, an apicoectomy or extraction with an implant.

  • Apicoectomy. A surgical procedure which cuts off the end piece of the root tip. Typically the abscess or infection will aggregate around the apices.
  • Extraction with implant. Alternatively, you can have the entire tooth removed and then replaced with an implant. It is a drastic measure but will eliminate the source of the infection which stems from the tooth itself.


The average cost for root canal retreatment is $1158.55 without dental insurance. The exact cost will differ depending on the tooth type that needs retreatment and also the cost of living in your area.

Tooth typeAverage costRange
Anterior teeth$1009.41$720-1485
Root canal retreatment cost by tooth type

Although if you have insurance, you can lower your out of pocket cost significantly.

Cost with insurance

With dental insurance the cost would be significantly less because coverage for it may be 50-80% on average. On average, you can expect to pay between $231.71 (80% coverage) and $579.28 (50% coverage) with insurance.

Recovery and outlook

The aftercare and recovery from endodontic retreatment is usually uneventful. You don’t have to do anything special to take care of it aside from your routine oral hygiene regime. Brush it twice a day, floss before bed, and minimize sugar intake as much as possible.

However you should be aware that there may be the possibility of flare ups, which is severe inflammation accompanied by pain in between appointments. It is rare but may occur. If that happens, you may need additional antibiotics and disinfection of the canals.

Success rate

According to International Endodontic Journal, the estimated success rate for root canal retreatments is 77%. That makes it less than the success rate of initial therapy which was at 85.1% as listed in the beginning of our article.

Therefore, doing it again the second time around does have a lower success rate.

How many times can you do a retreat?

There isn’t a limit to the amount that you can retreat a root canal tooth. However, most dentists and endodontists would probably agree that one time is the most reasonable.

Basically if it fails the first time, you can give it a second try to see if the results are different. However, if it fails a third time its not likely that a third try would change the outcome.

More often than not, if it fails the second time the next step or recommended treatment option would be to remove the tooth and replace it with an implant. You can discuss with your dentist what they recommend but we’re just telling you what they’re most likely to tell you.


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