What if Root Canal Treatment Fails

Root canal treatment is done when infection reaches the pulp portion of the tooth. During root canal treatment, necrotic and infected portion of the tooth is removed and is then sealed with a filling material. If done with great precision and complete care, a root canal treated tooth can last lifelong. But in cases where root canal continues to harbor bacteria or irritants which keep the tissues surrounding the root of the teeth from being healthy (inflamed)even after the completion of the root canal treatment then the root canal treatment is taken to be a failure. Root canal failure signs and symptoms can occur month or years after root canal treatment. Pain occurs in root canal treated tooth in case of failure of root canal treatment.

Signs and symptoms of root canal failure include:

  1. Mild to severe tooth pain
  2. Slight to severe pain or edema in the gums neighboring the tooth involved can either be in a continuous or intermittent mode after the root canal treatment.

These signs can be persistent from the time of root canal treatment, be transient varying week to months or even be dormant for years making the tooth appear completely asymptomatic during this dormant period. In cases where the tooth is completely asymptomatic, the signs of root canal failure which show as persistent inflammation surrounding the infected tooth, can be identified by the dentist through the medium of x-rays.

Causes of Failure of Root Canal Treatment

1.    Shape of the Tooth’s Root Canals:  Sometimes the tooth may have root canal branches which are difficult to detect. The canals which are curved and branch out often go undetected at times. These undetected branches might be missed in the root canal treatment leading to its failure.

2.    Unexpected Number of Root Canals: There can be variation in number of canals which are present in the tooth. A tooth might have many small root canals also called as the accessory root canals which may be missed during the treatment. If a canal is missed during root canal treatment, then tooth can become infectious months or years after treatment and in such cases, root canal re-treatment is required.

3.    Bacteria in root canal:  Certain bacteria are very resistant in nature and no matter what it’s very hard to remove them therefore they easily escape the disinfection by root canal and infection persists.

4.    Cracked root: By root canal therapy, roots of the tooth become bit brittle and can fracture on chewing which can further cause failure of root canal treatment. Dental crown after root canal treatment prevents fracture of tooth on chewing. Fracture of the root may occur during root canal treatment procedure and cause root canal treatment failure. It is difficult to diagnose these cracks and these cracks can lead to pain later on.

5.    Breakage of file during root canal procedure: Accidental breakage of file during cleaning and shaping of canal during root canal treatment can cause infection in root canal treated tooth and failure of root canal treatment. If canals are sterilized and clean before breakage of file in tooth, then it doesn’t cause any symptom otherwise broken file in canal can lead to pain and infection later on. If file remains in canal before removing the necrotic pulp, then it has to be removed. File in unsterilized canals is to be removed before sealing the root canal treated tooth.  

6.    Defective or Incomplete Restoration: Defective or incomplete restoration at the end of root canal treatment fails to maintain a proper seal and this may lead to bacteria to penetrate back into the cleaned canal causing re-infection.

Inadequate filled canals and broken instrument in left lower incisor

7.    Gum Disease: The treated teeth are not completely resistant to tooth decay or gum disease so the tooth might be lost if proper oral hygiene is not maintained. If patient doesn’t maintain good oral hygiene, then abscess can occur years after root canal treatment and dental crown.

8.    Tooth Structure: The tooth structure which is damaged or broken as a result of treatment and which require restoration for stability which if not done can cause failure of root canal treatment.
The tooth filling even if accurately done at the time of treatment might break down with time due to some reason like high biting force which will again lead to seepage of bacteria into the canal and re-contaminate it

Success rate of root canal treatment is 95%. In about 5% of cases, complications may occur after root canal procedure which can lead to failure of root canal treatment.   
To avoid further infections after getting root canal treatment and dental crown, it is important that patient maintains good oral hygiene and get regular dental check ups done.

Treatment after Failed Root Canal Therapy

In case of root canal failure, re-root canal treatment, Apicoectomy or tooth extraction may also be required to remove the infection from the tooth. Dentist will evaluate the condition of the tooth and will decide that whether tooth can be saved or not. If he thinks that prognosis of tooth after root canal treatment or Apicoectomy is not good, then he will pull the tooth out. If tooth extraction is required, then missing tooth can be replaced with dental implants, dental bridges or partial dentures. Dental implants are the best option for replacement of missing tooth.   

Dental Implants after Tooth Extraction   

Root canal retreatment can be done to save the tooth and tooth and remove the infection in root canal treated tooth. Procedure of root canal re-treatment is somewhat similar to root canal treatment and is mainly performed by an endodontist who is specialist in performing root canal procedure.

Apicoectomy that is surgical removal of root apex may be required to remove the infection from the tooth. To seal the root, small filling (retrofill) is used.

Bone Removal for Apicoectomy

Success rate of root canal treatment is not as high as root canal treatment done for the first time. Root canal treatment success rate is 50%-75%. If re-infection occurs after root canal re-treatment, then tooth extraction may also be required.


 User Comments on -  What if Root Canal Treatment Fails

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Posted By : keith stevens on 22-Aug-2015 01:23 PM
I had my semi-annual cleaning and this is the time they take x-rays but this time they decide to take one of the front lower teeth. I have gone to the same dentist for 10 years and they are awesome but this is first time they did an x-ray in the front. They noticed a shadow below a lower front tooth. I had a root canal 30 years ago and have not had any pain or swelling. They tapped the tooth and checked the gum area but I did not feel any pain. I was referred to another doctor and he told me the pin they used was too long and would break the tooth if taken out. The doctor told me the tooth was in good condition. He told me I needed to get a re-treatment to get the rest of the root out and then back fill the tooth. Will this solve the chronic infection below the root?

Posted By : dr apinder on 25-Jun-2014 06:32 AM
hello tony this is also the method of rct so dont worry...

Posted By : Erik on 20-Feb-2014 10:49 PM
If a Root Canal Treatment isn't successful, due to a portion to the root being left behind, is the re-treatment of the affected tooth normally the responsibility of the the Doctor who initially did the root canal? I had a root canal done on #7, and approximately 4 months later I had symptoms of an abscess(I've had half a dozen of them, so by now I can usually tell when the abscesses are just beginning) and upon consultation with my Endo an apicoectomy was performed on said tooth. My question is would it be reasonable or off base for the doctor who perform the failed RCT to pay for the apicoectomy or at least a portion of it? The RCT was performed by a doc(not the Endo), and my Endo hinted at the fact that the retreat should be at least partially paid for by the original Dr. The Dr from the original treatment does not believe that he should be responsible for the failure of the RCT. I do understand that things go wrong and they can't always be avoided, but with any other service if there was a mistake then the person who messed up should help rectify the situation. Between the $1000 for the original RCT, and the $1400 I had to pay to fix the RCT failure, I feel like this is ridiculous. If a mechanic messed up on fixing something on my car, then I would expect him to fix it or at least not charge me for the cost of fixing the mistake.

Posted By : Rita on 27-Dec-2013 09:12 AM
my boyfriend had a root canal #14 for chronic pain in the tooth, not for an infection. it was not successful and the dentist recommends a cap? is this a good solution

Posted By : Dr. Rtiz on 02-May-2013 08:14 PM
Hi Dennis, Re Root Canal treatment is a normal procedure done for infected tooth which is already root canal treated. However the prognosis is not that good as it is with first time root canal treatment. For the success of re treatment the case selection is good. If your Endodontist say that you need it then you should go ahead with this.

Posted By : Dennis on 01-May-2013 09:52 AM
I had a root canal about 2 years ago & now need a Re-Tx by Endodontics. Does this procedure help correct the issue. Starting have some infection & some pain in crown tooth.

Posted By : Katie on 26-Dec-2012 02:38 PM
I had a root canal done 4 years ago and a crown placed. This is what I was told. Is there anybody who willing and confident enough to try the retreatment for me? I can send you my x-ray. Tooth #4 Xray shows that it has an infection at the root tip. The infection has caused some bone loss at the root tip. Also, the tooth has some widening of periodontal ligament(PDL) space. This space act as a shock absorber and will increase in response to biting force. Is the tooth loose? This will eventually cause bone loss around the tooth if not fixed. I see a lot of respond like this when the crown is too high. How long has the crown been placed? The root of this tooth has been shortened by ortho treatment. Short root, bone loss around the tooth(not sure at this point need to check pocket depth and mobility) with failing endo is a bad combination to this tooth. Procedure needed to save this tooth if no money is concerned 1. Adjust crown to lower the biting force on this tooth. Remove crown if needed. Access/removal of old root canal material and determine if retreatment if possible. These two steps will help heal the infection at the root tip and fix the trauma caused by the biting force. 2. After retreatment is completed and crown lowered. Tooth will need to be observed for healing for couple months. Xray every month. Check healing of pimple at the top of the tooth. It should close and will not return. Check for tooth mobility and PDL space improvement. 3. If healing is observed after couple months, new crown is needed. If no healing observed, then you need to get extraction and implant. 4. This approach is less predictable and time comsuming but it will be what I prefer to do to my tooth before extracting it. 5. This approach might not be practical because of the current liability and insurance issue. Not a lot of dentist will attempt this approach.

Posted By : Dr.Ritz on 20-Nov-2012 12:03 AM

Hi ROSE,An infection can sometimes still occur under a crown,for reasons that were unforeseeable at the time.A crown requires the preparation of a tooth,changing the structure of the tooth itself so a new crown can be cemented on permanently.In the cases where there is infection under the crown, it's usually because hygiene hasn't been adhered to by the patient.Decay can easily form around the margins of the crown,therefore making it STILL important for the patient to continue getting their regular exams and cleanings on a routine basis.My suggestion for you would be to go in for rct as saving natural tooth is always the best option.But nothing can be said for sure without looking at the tooth and x rays of the involved tooth.If you are in doubt,visit an endodontist(specialist in Rct) for expert opinion.Hope that helped.


Posted By : Rose on 19-Nov-2012 06:00 PM
Dear Dr.Ritz, One of my healthy teeth cracked and lost about 1/3 of it, with no pain. X-rays were taken with a healthy result, clear of any infection, still with no pain. My dentist built a core and placed a crown. Two weeks after this replacement, I chewed some soft food on this tooth, I felt an intense toothache a few hours later at bedtime. Another few short episodes of toothache occurred after this. I have not used this tooth ever since and no pain is currently experienced. I returned for another x-ray. This time my dentist declared the x-ray now shows an infection under this tooth. He recommended a tooth extraction and a dental implant. Root canal is another option, but not with assurance. I wonder how could an infection developed within 2 weeks, after the crown replacement? What is your opinion about the permanent fix for this tooth, about root canal or implant? Thank you for your time, and attention. Rose

Posted By : Dr.Ritz on 31-Aug-2012 01:23 AM

Dear CATHY, Nothing can be said unless Xray of the region isnt taken. So, you case requires a clinical examination. If possible, send us the scanned copies of your xrays so that we can diagnose the case. And for which tooth you underwent Xray. If it was of upper tooth then there are chances of sinus infection. You start doing warm saline gargles and take ibuprofen.


Posted By : Cathy on 29-Aug-2012 09:33 AM
I had RCT done approx. 2 weeks ago and haven't felt well since. Now experiencing pressure in that area, nausea, and chills. Went to the dentist who found no problem but commented that maybe lactic acid build-up was cause since mouth was open so long. Went to endodontist this morning who found nothing and sent me to my medical doctor. Med doc couldn't find anything and suggested an ENT. Is there possibly something everyone is overlooking? Thanks for your expedient advice.

Posted By : JR on 28-Aug-2012 02:54 PM
Thank you, Dr. Rita. No additional xray, then. It's not a matter of concern about having the root canal itself, but if the infection has cleared, and all tissue appears healthy, isn't it even remotely feasible that decay might be removed and the tooth resealed? Even if there is a small chance that the way would be clear to do this, it would seem a better option if possible to save the integrity of the tooth?Thank you, again.

Posted By : Dr.Ritz on 28-Aug-2012 02:12 AM

Dear JR You can request your dentist to shoot an Xray but the finding will still be same. If their is pulp infection then second Xray will also show the same but for your satisfaction you can ask for that. And i would suggest you to start the treatment as early as possible because this will prevent the further spreading of infection.


Posted By : JR on 27-Aug-2012 07:59 PM
Having no pain, but intermittent, mild discomfort with hot or cold on upper molar. Xray shows cracked filling with infected pulp. Antibiotics given. Root canal recommended. Shouldn't another xray be taken to get a clearer picture of the tooth? Thank you.

Posted By : Dr.Ritz on 19-Aug-2012 10:17 PM

Dear COSTAS, Dont delay the treatment as there can be infection developing and delaying would further cause the spread of infection. So, visit the dentist asap and get an Xray done to find the root cause of the treatment.


Posted By : Costas on 18-Aug-2012 06:30 PM
Dear doctor, I had a root canal 2 months ago. This past week,, my mouth felt strange. My gums were dry and sensitive throughout. When i tried to stretch them they felt unflexible. Today the gum right below the rct'ed tooth is having some pain/discomfort. Monday,i will call my dentist but the rct consumed all of dental insurance for 2012. Could I postpone further treatment until 2013? Thx

Posted By : Dr.Ritz on 17-Aug-2012 11:32 PM

Dear LISA, Tooth discoloration, no pain, abscess formation , all are indicative of tooth going dead. So, RCT is a good option. Blockage of root canal in medical terminology is ledge formation and there are specially designed instruments to overcome it. So, you don't need to worry and consult an endodontist and i am sure you don't have to get your tooth extracted.


Posted By : lisa on 17-Aug-2012 01:54 PM
10 yrs ago I had experienced throbbing pain in my lower front teeth. I visited my dentist who took xrays and did a deep cleanse and I think gave me antibiotics or pain pills. I didn't experience any pain thereafter but the tooth did discolor. A few weeks ago I noticed a abcess form at the root of this tooth inside my gum. There was no pain so I left it for 2 wks and then decided to chek it out. After xrays the dentist prescribed antibiotics and said I needed rct. The abcess did not subside even after taking the antibiotics. A week later I went in for rct but the dentist could not get to the root as the canal had closed off. Now the abcess is still there and there is not pain. The dentist said I have to extract the tooth which I am nt happy about as it is my front lower tooth in the centre of my jaw! He also said he wud do a bridge which is also not apealing to me :(. I just want to save this tooth! Is there any other way?

Posted By : Dr.Ritz on 16-Aug-2012 11:07 PM

Dear MARCI, Without clinical examinations of your case along with Xrays it is really quite difficult to come up to the conclusion. If it is possible, could you send us your Xrays that were taken. From your description what it seems is that you are having a sinus infection (not sure without any examination) As you said that your sinus in Xray had cloudy appearance, this means that there is mucous filled instead of air.


Posted By : Dr.Ritz on 16-Aug-2012 10:58 PM

Dear CARYN, You dont need to worry as most of the dental materials including gutta percha are inert and well below the toxicity levels. They donot react with the body and gets absorbed. All the dental products passes the quality tests before coming into the market.


Posted By : Marci on 16-Aug-2012 08:35 PM
Thank goodness for this site. I had two root canals + crowns done 2 1/2 years ago, both on top molars next to each other. For the past six months I have been having some pretty serious pain, to the point where my jaw swelled up and I couldn't really open it much at all. I was put on antibiotics (from the E.R.) and the swelling went down, and the pain went away for the most part. Now it's back, and it's worse. I'm on amoxicillin now (almost a week) and it's had no effect on the pain. I had x-rays done and they said they "can't figure it out" -- although I noticed a gap in the fake-root rubber thing they put in. They noticed that part of my sinus around the area was cloudy. I do tend to get more stuffed up on that side than the other lately. What does a cloudy sinus have to do with tooth pain?

Posted By : Caryn on 16-Aug-2012 02:03 PM
While having my root canal done, Dentist pushed gutta percha thru the root can and a piece of it broke off outside the canal. They gave me antibiotics and said they hoped my body would absorb the gutta percha but I may have trouble in the future. Should I be concerned?

Posted By : Dr.Ritz on 07-Aug-2012 02:11 AM

Dear RUCHI, After undergoing an RCT you can have pain but there shouldn't be any sensation as the tooth is already dead. Now having tooth sensation means that the Root canal finishing wasn't done properly and the nerves are still active in the canals. So, it is advised to get an X ray done to know the exact cause of pain.


Posted By : ruchi on 06-Aug-2012 10:39 AM
Dear Dr. I had had a root canal treatment 2 years ago. Now when i press the gum near my tooth its slightly sensitive.It isnt very painful but just a sensation. My dentist told me to massage that area and that it would go away. But its persistent. Sometimes i feel that maybe i pay it too much attention or touch it too much which is why it is sensitive.Also a couple of months back i tripped and broke two lower front teeth. One of them needs a root canal treatment for sure. I want to get another opinion. But im really concerned since its a front tooth. Also I'm only 20 and already have so may teeth issues. I dont want to b a toothless/fake-toootheld old lady. Its a mind block.

Posted By : Dr.Ritz on 05-Aug-2012 11:51 PM

Dear TONY, You dont need to worry as the procedure done to you will definitely make your teeth healthy. When the infection is still there after RCT and the part of infection is not accessible then the only way out is to take out the tooth, do the treatment and put it back in the socket. It tremendously decreases the chances failure and also gums will gradually develop a grip on your avulsed out tooth.


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