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Why Do You Have A Toothache After A Root Canal?

Why Do You Have A Toothache After A Root Canal?

Author: Donald Tanenbaum DDS MPH - Board-Certified Orofacial Pain Specialist at New York TMJ & Orofacial Pain

Date: January 25, 2024


As a board-certified Orofacial Pain specialist, I focus entirely on caring for patients who suffer from facial and unexplained tooth pain. Every week, I see someone in our office seeking our help. Sometimes, the problem is they still have a toothache after a root canal, and the reason why has been unclear.

Before I get into what can cause a toothache after a root canal, let’s discuss what a root canal is in the first place. A root canal is a dental procedure to remove inflamed or infected nerve tissue on the inside of a tooth. The compromised nerve tissue or pulp is removed, the space occupied by the pulp (the canal) is carefully cleaned and disinfected, and then the empty canal space is filled and sealed.

Root canal treatment is designed to eliminate inflamed or infected pulp tissue, removing bacteria at the same time. When accomplished properly, reinfection is unlikely, and the tooth will remain asymptomatic and stable.

Around 95% of patients who have a root canal never again feel pain in the treated tooth. But what happens to the 5% of people who still have a toothache after a root canal? If that’s you, you’re in the right place.

Did This Happen To You?

One day, you woke up with a terrible toothache. You took some Ibuprofen and powered through your day. But you were still in pain a few days later. So you see your dentist, who tells you, “You need a root canal.”

You weren’t excited about having a root canal, but you were looking forward to your tooth pain being a thing of the past. But that’s not what happened.

Your pain persisted for another week, so you went back to your dentist, who told you: “Everything looks good. Try to be patient while it heals.” But the pain never went away. What’s going on?

Before I go any further, I want to emphasize this:

If your dentist recommends a root canal after a thorough examination and x-rays, don’t resist! Remember, 95% of root canals are completely successful. In the rare cases when they’re not, one of these three scenarios likely holds the explanation:

3 Common Causes Of Persistent Toothache After A Root Canal

Scenario 1:  The root canal was necessary, but it didn’t get rid of your toothache

Under this scenario, your dentist accurately diagnosed the cause of your toothache and appropriately recommended root canal therapy. However, your pain persists.

At this point, your dentist may send you to an endodontist to take a look. Endodontists are root canal specialists who typically have advanced diagnostic tools in their offices, such as 3D cone beam imaging and highly magnifying operating microscopes.

The endodontist will look for clues to explain why you still have a toothache. They may detect a crack in your tooth that wasn’t visible in the x-rays at your dentist’s office. Or they find a lingering infection that needs to be removed in a curved part of the root that wasn’t fully cleaned the first time. Or, there may be another canal that needs to be treated that hadn’t been detected.

If this is your scenario, you’re in luck! You may have to endure a bit more time in the dental chair,  but your pain will resolve, and your life will go on.

Scenario 2:  The root canal was necessary, but a different kind of pain emerged

You may have heard about a strange phenomenon called phantom limb pain. Phantom limb pain is when someone who has lost a limb still feels pain in the limb, even though it’s gone! A similar thing can happen in dentistry when pain continues to be experienced in a tooth after the nerve tissue and pulp that we mentioned above are removed.

Fortunately, the incidence of phantom tooth pain after a root canal is much lower than that of phantom limb pain after an amputation. In both cases, however, research has suggested that, at times, removal of dental pulp can cause a nerve injury that leads to persistent pain. The formal term for phantom tooth pain is Post Traumatic Trigeminal Nerve Pain or PTTNP. The trigeminal nerve is the cranial nerve responsible for sensations in teeth.

Unfortunately, there can be a delay in making this diagnosis because your previous exams and x-rays suggest there’s nothing wrong despite your pain. Your frustration understandably grows as you can end up feeling that, somehow, it’s your fault.

At this point, your dentist or endodontist might refer you to an Orofacial Pain specialist like the doctors at our practice. Orofacial Pain specialists have advanced training in diagnosing and treating unexplained toothaches and fully understand the complexities of trigeminal nerve pain. The education and care they can provide with oral and topical medications are often the first steps toward pain relief.

If a referral to an Orofacial Pain specialist isn’t suggested – ask!

Scenario 3: It turns out your root canal wasn’t necessary

Before you read on, I can’t express this enough: 95% of root canals are necessary and successful!

But occasionally, a non-tooth-related condition can cause pain that mimics a bad toothache, and no amount of root canal therapy will help. It may be hard to appreciate, but your toothache from day one may have been caused by something that didn’t originate in your tooth. As a result, the root canal failed to get rid of the pain.

Less obvious causes for a lingering toothache after a root canal is referred pain from your jaw muscles. When these muscles become fatigued from constant bruxism or fatiguing head posture, it can actually cause pain in a tooth. As Orofacial Pain specialists, we commonly see patients who were diagnosed with a TMJ problem or a chronic neck problem and report persistent tooth pain. Nearly 18% of the population suffers from a TMJ disorder, so this scenario is commonly seen in our practice.

Thankfully, we have strategies to get rid of that lingering tooth pain. Treatment can be a combination of strategies that include changing daytime jaw overuse behaviors and fatiguing head postures, exercises, medications, muscle injections, and custom oral appliances.

There can be other medical causes of persistent toothaches. They are rare but should be mentioned: Lyme disease, cardiovascular problems,  sinus infections, salivary gland pathology, trigeminal neuralgia, and intracranial diseases inclusive of brain tumors. Orofacial Pain specialists have been trained in very specific ways to listen to the symptoms and stories of pain, looking for clues to make alternative diagnoses or referrals to medical colleagues to broaden out the evaluation process.

In Conclusion

If you have a lingering toothache after a root canal and neither your dentist nor an endodontist can figure out why, request a referral to an Orofacial Pain specialist.
If you’re located in the NYC metro area, we have offices in Manhattan, White Plains, Long Island, and New Jersey. Click here for exact locations and contact info.

Outside our area? Check the directory of the American Board of Orofacial Pain for a specialist in your area with Diplomate designation.

You may also be interested in:
What Is A Root Canal?
What Is Referred Pain?
More About Persistent Toothaches

Dr. John E. Dinan is a Diplomate of the American Board of Orofacial Pain and the American Board of Dental Sleep Medicine. He is part of the team at New York TMJ and Orofacial Pain team, practicing in our Manhattan and Springfield, NJ offices.


DISCLAIMER: The advice offered in response to your questions is intended to be informational only and generic in nature. Namely, we in no way offer a definitive diagnosis or specific treatment recommendation for your particular situation. Our intent is solely educational and our responses to your actual questions serve as a springboard to discussion of a variety of dental topics that come up in a day-to-day dental practice. Any advice offered is no substitute for proper evaluation and care by a qualified professional.

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