8 Signs Your Root Canal Failed

8 Signs Your Root Canal Failed

 Whitney DiFoggio MA, RDH
Written by Whitney DiFoggio MA, RDH
Medical Reviewed on Nov 8, 2022
byDr. Matthew Hannan DDS
🔬 Evidence Based
8 Signs Your Root Canal Failed

For anyone who has completed endodontic treatment, a failed root canal is their worst dental “nightmare.” Considering that many people have to psych themselves up to get a root canal to begin with (they aren’t as scary as you think) the idea of having to re-treat one can be extremely upsetting. Recognizing failed root canal symptoms can help you intercept the problem as quickly as possible before you risk the complete loss of your tooth.

What Is A Root Canal Failure?

A failed root canal is when your treated tooth experiences some type of complication. Such as re-infection, pain, or breakage in the tooth. There are several different reasons why a root canal can fail (more on that in a bit). Not only is endodontic failure painful in most cases, but it also puts you at a high risk of tooth loss.

Fortunately, there are dental experts out there called endodontists who specialize in root canal treatment and retreatment. Their offices are equipped with state-of-the-art technology designed precisely for root canal procedures. On top of that, endodontists have 2-3 years of training in addition to 4 years of dental school. So, if you were to experience failed root canal symptoms, they’re the dental specialist you’ll want to see.

Root Canal Procedure Recovery Period

Every restorative or therapeutic dental treatment has some type of recovery time. Sometimes it’s a matter of hours and other times it’s weeks or months. With root canal therapy, you don’t have anything surgical that you need to recover from. The actual procedure is more like getting a dental filling, so you’ll need to wait a few hours for the anesthetic to wear off. That being said, your jaw could feel sore for a few days depending on how long your procedure took.

Every restorative or therapeutic dental treatment has some type of recovery time. Sometimes it’s a matter of hours and other times it’s weeks or months. With root canal therapy, you don’t have anything surgical that you need to recover from. The actual procedure is more like getting a dental filling, so you’ll need to wait a few hours for the anesthetic to wear off. That being said, your jaw could feel sore for a few days depending on how long your procedure took.

Even though it’s not a “recovery period” per se, you’ll also want to wait a couple of weeks to eat on your root canal tooth. Once your dentist puts a permanent crown over it, you should be back to normal. Anything like gum irritation or tooth sensitivity past that point isn’t usually normal.

If for any reason you’re experiencing tooth pain or chewing on your tooth too early, there’s a chance you’ll experience discomfort or a root canal complication. Take it easy and always communicate with your dentist or endodontist about your symptoms.

8 Signs Your Root Canal Failed

How can you tell if something is wrong with your tooth after a root canal? Here are the most common warning signs to look for.

1) Pain

One of the most obvious failed root canal symptoms is pain or discomfort coming from that part of your mouth. It could be a sharp pain or more of a dull, throbbing ache. It might not even hurt except when you’re biting down or releasing pressure in that area. The pain could be as soon as your numbing medication wears off or it might not develop until the days and weeks following your appointment.

2) Tooth Sensitivity

Your teeth are extremely delicate structures that can pick up on things before other symptoms become noticeable. Tooth sensitivity after a root canal is not normal. If temperature changes or stimulation (from something like a toothbrush) bothers your tooth, something is going on. Theoretically, your tooth shouldn’t feel anything after a root canal because all of the nerves have been removed. But sensitivity is one of many failed root canal symptoms that can tie back to secondary nerve canals that go unnoticed the first time around.

3) Swelling

Is there any inflammation in your gums, jaw, or side of the mouth that your root canal is on? You shouldn’t experience anything more than some minor gum irritation after a root canal (usually where the injection is administered.) Swollen gums could indicate a cyst or infection down inside of your bone. If there is a crack in your tooth, bacteria can still enter down into the root and affect the tissues around it. Be sure to check with your dentist, but if the swelling starts to spread through your face or interfere with your airway, you need to head straight to the emergency room.

4) Discharge

Dental abscesses have to drain somehow, which is why some of them create sores on the gums next to the roots. The discharge can also come up through cavities or cracks in teeth. You might also notice it along the gums if you press down on the tooth. Normally this discharge has a salty or metallic taste to it.

5) Tooth Discoloration

Teeth tend to turn darker in color when there is nerve tissue dying inside of them. Usually, the tooth shifts to a brown or bluish shade. When you smile, it stands out from the teeth next to it. The discoloration isn’t something that you can bleach away, but your dentist might be able to go in and perform some internal bleaching to help lighten the shade of your enamel. Be sure to rule out a failed root canal or internal resorption by having your dentist take an X-ray.

6) Boil Or Pimple On The Jaw

Active abscesses create cysts inside of the bone and gum tissues, creating a “fistula” or fluid-filled pimple on your gums. These fistulas can range from small, tiny sores to large boils. On your X-ray, there may even be a hollow-looking cyst inside of the bone next to your tooth root. A fistula can come and go, depending on whether the pus drains out of it or the infection goes down. But the source of the swelling won’t heal itself, so don’t make the mistake of thinking that the problem has resolved itself.

7) Sinus Problems

If you seem to have sinus problems like congestion or a runny nose, has it been going on since your root canal? The pressure from a sinus infection, inflammation, or allergies often mimics toothaches. But sometimes your upper tooth roots reach so far that the lining of your sinus cavity drapes over them. If the root canal treatment penetrates your sinus lining, you run the risk of bacteria entering your sinuses and a host of other complications after that.

8) No Physical Symptoms

Maybe your tooth doesn’t hurt at all. You’re sitting in the dentist’s office for a checkup getting routine X-rays and, unbeknownst to you, one of them shows up with something irregular on it. Upon further inspection, your dentist finds something wrong with the root (such as resorption) or a recurring cyst from an abscess near the root tip. The absence of pain doesn’t mean you’re in the clear, it just means the main pain receptors have been removed from the tooth. Any existing infection still needs to be treated.

5 Likely Reasons Why It Failed

What causes a root canal to fail? Between the anatomy of your tooth and any damage it incurred, it’s usually because of one of the following reasons:

1) Coronal Seal Breakdown

Your tooth has a protective cap/crown over it after the root canal is completed. But if there’s isn’t a good seal between the tooth and restorative crown, bacteria can leak up under the restoration and into the tooth. Usually, if there’s a breakdown of the seal, your crown will start to feel loose or come off completely.

2) Crown Breakdown

Your tooth’s natural crown is the portion of the anatomy that extends above the gum lines. At a certain point, it will be covered with a porcelain crown or other restoration. But if the treatment is delayed or falls off, you could potentially break your anatomical crown during everyday activities. Crown breakage exposes weaker areas of your tooth, which can cause it to completely deteriorate. Without enough crown in place, your tooth can’t function normally.

3) Failure To Clean The Canal

If your dentist doesn’t clean out the nerve canal entirely, there will be bacteria left inside of your tooth that can cause a reinfection. Even though lack of experience or the wrong equipment can contribute to this problem, it might not actually be your dentist’s fault. For example, if your tooth has a secondary nerve canal coming off of it somewhere, your dentist may have no idea. And if that nerve tissue gets left behind, the tooth can stay infected. That’s one reason why endodontists may use special microscopes that go down inside of your tooth.

4) New Decay

Your tooth isn’t immune to cavities after root canal treatment. You still need to brush along the gums and floss daily. Otherwise, plaque will accumulate and cause new areas of decay along the gumline and underneath your fixed crown.

5) Trauma

If you’re an athlete or get injured in a fall, traumatic injuries to your mouth can cause major dental concerns. Broken teeth are a great example. But sometimes trauma isn’t so obvious. Something as simple as biting down on a tooth the wrong way or chewing on it before you get your crown may provide all the force necessary to cause something to break.

What To Do About A Failed Root Canal

There are only two options if you have a failed root canal: re-treat the tooth or have it extracted.

Root canal retreatment (endodontic retreatment) is almost always performed by an endodontist. Even more experienced general dentists typically refer their patients to an endodontic office because of the resources they have on hand. Retreatment can help you avoid an extraction, manage pain, and preserve as much tooth structure as possible.

Ideally, your dentist and endodontist will want to try to maintain your natural tooth. But sometimes a dental extraction can’t be avoided. Such as severe fractures extending through the root tips or aggressive decay that has worked its way well into the majority of the tooth. In some instances, the inside of the tooth will begin to resorb (essentially dissolve) leaving little to nothing left to repair. An extraction is usually recommended in any of these scenarios. But at that point, you’ll also need to plan for replacing your tooth with something like a bridge or dental implant.

Root Canal Retreatment

Retreating a tooth with a root canal consists of opening up the tooth and removing the filling material inside of it. This process can be quite tedious and difficult to perform with everyday dental instruments, so your endodontist will use special equipment to reach these tight spaces. Some endodontic offices even have microscopes that reach down inside of the tooth to see everything inside of it.

Since your tooth is no longer vital, you shouldn’t have to worry about irritation while it’s being treated. However, there could still be secondary nerve canals or sensitivity from teeth or gums next to it, so the dentist will want to be sure to numb that area of your mouth.

Even though the need for retreatments is fairly rare, they’re quite successful procedures. Especially if you’re seeing an endodontic specialist. Investing in re-treatment will help you save your smile for the long haul, minimizing the impact that tooth loss or pain will have on the rest of your teeth.

Is root canal retreatment the standard of care? Yes. The same can be said for any restoration that needs to be redone. Such as a filling with new decay around it, or a crown where the seal isn’t tight enough. You don’t want to avoid retreatment because the issue won’t fix itself or improve over time. Delaying care will only put you at risk of additional complications, discomfort, and ultimately tooth loss.

Briefly put, a root canal treatment usually includes:

  • Numbing the tooth
  • Re-opening the area at the top of the tooth
  • Using tools to clean out the filling material
  • Inspecting the tooth for any infection or secondary nerve canals
  • Cleaning out and re-shaping the canals
  • Filling the hollow nerve canals with new material
  • Putting a temporary filling or crown over the tooth

After monitoring the tooth to make sure you recover, the endodontist or your general dentist will fit you with a permanent crown.

In some scenarios, an apicoectomy is performed instead of an entirely new root canal (where the root tip is removed.)

Retreatment Cost

An average root canal cost can easily range between $600 to $1,500 or more, depending on where you’re located and which dentist you’re using (that’s before insurance kicks in.) Root canal retreatments usually cost more than the original root canal. The good news is that your insurance might help cover some or all of the procedure. Some specialists list the pricing on their website, with retreatments anywhere from $200 to $500 more than original root canals, depending on which tooth it is that’s being treated. Since teeth further back in your mouth have more roots than your front teeth and some of them are challenging to reach, they take longer and cost more to treat. Your endodontist or dentist can provide you with an estimate before you schedule the treatment so that there are no surprise bills in your mail the next month.

How To Prevent Failures

The most important thing you can do to avoid a failed root canal is to follow your home care instructions. Specifically, not eating or chewing on that tooth after your endodontic procedure. If you’re biting down on it and there isn’t a permanent crown yet, you could potentially crack the tooth or cause parts of it to break off. When that happens, it can cause pain or root canal failure.

Recurrent tooth decay—that’s the term we use for a new cavity in a place where you had an old cavity repaired—can also cause root canal failure. Even though the tooth is no longer “alive” and has a crown over it, the remaining enamel can still develop cavities. You need to practice good oral hygiene around the tooth and its crown to prevent any recurrent decay from developing along the gum lines.

Another thing you can do to avoid a failed root canal is to see an endodontist from the get-go. Not that dentists aren’t trained to perform root canals, because they are, but more challenging cases might better be handled by a specialist. Such as teeth with narrow canals or curved and twisted roots. Root canal specialists have extra equipment and training on hand to properly treat those teeth, whereas a general dentist usually doesn’t. No matter how much you love your dentist, if they refer you to a specialist, trust them.

Root Canal Alternatives

There are only limited options when it comes to treating an abscessed tooth. Realistically, the best alternative is to focus on preventative home care to avoid decay or infections from the start. So, if you already have one tooth with a root canal, get ahead of the game so that you can prevent needing endodontic therapy on other teeth. Daily brushing, flossing, and regular checkups are crucial. You’ll also want to limit your intake of natural sugars, artificial sweeteners, and processed carbs.

For children who have a large cavity, a “pulp cap” is a great root canal alternative. Pulp capping helps limit the pain and the spread of infection, allowing the child to preserve their tooth until it’s closer to the normal time for it to fall out (reducing side-effects to adult teeth.) Unfortunately, pulp capping isn’t typically used on adults.

In some situations, a dentist may try to avoid performing a root canal on adult teeth by placing a desensitizing agent before large fillings or crowns are installed. If a cavity is too close to the nerve of a tooth, root canals are always a possibility. But if the dentist thinks they can get just close enough to the nerve (to remove the cavity) without actually touching it, the desensitizer could help prevent nerve hypersensitivity. Otherwise, a root canal would probably be necessary.

One other root canal alternative is an “apicoectomy” or what some people call “root end surgery.” During an apicoectomy, the endodontist creates a small opening in the gums and bone next to the tip of the tooth root. Then the bottom portion of the root is removed and the surgical site is sealed up.

When To Talk To A Dentist

As a general rule of thumb, you should speak to your dentist any time a tooth “just doesn’t feel right.” Pain, pressure, or swelling are obvious reasons to schedule a dental appointment, but even those unsuspecting odd feelings can also mean something is going on. The best thing to do is to rule out any concerns before they have the chance to get any worse. Even if that just means making a phone call to your dental office to make sure what you’re feeling is completely normal.

If you feel any type of pain or throbbing when you bite down on your root canal tooth, schedule a dental appointment ASAP. It could be that the tooth is abscessed again or that the root has cracked. Even if you don’t have a major nerve feeding your tooth anymore, there are still other tissues and nerve endings around it that won’t feel right if there’s a problem.

Call your dentist if you’re in pain after your appointment, can’t eat anything, or there’s any type of swelling. If you catch a failed root canal early enough, you can prevent losing your tooth. But if you try to put it off, you may run out of options.

Overcoming Failed Root Canals

If you notice failed root canal symptoms in the days, weeks, or months after your endodontic procedure, make sure you tell your dentist. Even though failed root canal therapy is rare, it does happen from time to time. Your dentist will probably refer you to an endodontist (root canal specialist) to have the tooth evaluated and retreated. Besides retreatment, there aren’t a lot of options available; retreating the tooth is the best way to avoid an extraction. You can usually expect to spend a few hundred dollars more on retreating a failed root canal than you did the initial endodontic procedure.

 Whitney DiFoggio MA, RDH
Written by Whitney DiFoggio MA, RDH"Teeth Talk Girl," is a registered dental hygienist. She started her dental health journey on YouTube, educating the public through videos.
Dr. Matthew  Hannan DDS
Medical Reviewed byDr. Matthew Hannan DDSDr. Matthew Hannan is a board-certified dentist and graduate of UT Health San Antonio School of Dentistry.
Last updated onNovember 19, 2022Here is our process

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