Common Signs Of A Failed Root Canal

If you are experiencing pain or discomfort in your natural teeth. In that case, it may signify that the nerve inside is dying and needs to be removed. The only way to stop this from happening is by having a root canal treatment

A root canal is a restoration procedure to save your original tooth from extraction. It is typically done as a last resort for teeth with extreme decay or trauma.

For most people, root canals last their entire lives without any problems or complications. However, it’s possible to have a failed root canal. It can be challenging to identify if you’ve had one because the symptoms are often similar to other dental problems.

In this blog post, we’ll look at some common types of symptoms that may be indicators of a failed root canal. 

What Is a Root Canal?

 A root canal is a dental procedure that preserves severely damaged teeth. Although tooth decay, dental disease, and injury often result in tooth loss, advancements in dentistry can more likely save the teeth. This dental treatment becomes necessary when the tooth pulp, which contains blood vessels and nerves, gets inflamed due to deep cavities, cracks or fractures in its enamel. Also, this method is referred to as endodontics, endodontic treatment or endodontic therapy.

A conventional root canal procedure involves removing your infected tissue, cleaning and sealing the dental canal to protect against future root canal infections. The dental professional will temporarily fill the access hole while waiting for the permanent crown to be fitted on your next dental visit. However, a dentist may place a permanent filling, so there is no need to use a dental crown.

Why Do I Need a Root Canal?

Severe pain or swelling may be experienced if the tooth nerve has died. In other cases, there is no pain and no sign of a problem until x-rays are taken at the dental clinic. Root canal therapy is necessary when the nerve tissue inside a tooth dies. If untreated, a severe infection can spread through the tooth root, causing extreme discomfort and further damage around the surrounding gum tissue and adjacent teeth. Eventually, an abscess may form that will need to be drained by your dentist. Leaving this problem untreated can lead to tooth loss. Root canal surgery is almost always successful in saving teeth. 

If you notice any signs of infection in your mouth, you should get treatment as soon as possible. It will help you recover more quickly and increase your chance of avoiding complications in the future.

Learn More: Common Signs I Need a Root Canal Treatment

Signs of A Failed Root Canal

  Many symptoms can arise when you have a failed root canal. It’s important not to jump to conclusions since most of these signs could also point towards other problems. Suppose you experience any or all of the following side effects. In that case, it is best for your health and safety if you schedule an appointment with your dental office:


The root canal procedure should relieve any discomfort, but if it becomes more painful when pressure is applied, there is probably something wrong. There is a possibility that the pain is caused by inflammation of the tissue around a treated tooth that results from pus leakage or infection.

Usually, dentists use a percussion test to spot this symptom. Still, you can do it yourself if you feel comfortable doing so.

Test the tenderness of a tooth by gently pressing down with your finger. If there’s no discomfort, try biting onto a Q-tip with that tooth. If nothing hurts or causes pain in your mouth, take something made of plastic, and tap it gently against its surface.


After a full recovery process, there should not be any swelling in the area around your affected tooth. If you notice even a little bit of swelling, call your doctor immediately because it can mean serious re-infection.

When a tooth infection progresses, it can cause symptoms like swollen tissues that are tender. If it becomes severe enough to reach the surface of the gums, it manifests as an open abscess that leaks pus into your mouth. This drainage hole is called the sinus tract. Thus, early detection is key to preventing serious complications. If left untreated, the infection could spread to other mouth or jawbone areas. Never ignore this issue because it could get worse over time if not treated quickly and adequately.

Sensitivity to heat or cold

Tooth sensitivity caused by a failed root canal can be very problematic as it is usually conditional; that means specific circumstances cause intense pain. When your teeth are exposed to extreme temperatures, such as sipping hot coffee or a cold beverage, it will immediately cause sharp pain.

It may be an indication of root canal treatment failure if this symptom occurs. Since the nerves in your pulp chamber have been removed, it is hard to feel anything in your tooth after the endodontic procedure. Suppose a patient is sensitive to extreme temperatures in a specific tooth. In that case, it means the infected nerve hasn’t been completely removed. Thus, high thermal sensitivity is a sign of re-infection.


It is essential to recognise root canal symptoms for a successful procedure. One such symptom is discolouration of the teeth. When your endodontist drills into your teeth, they remove all the necrotic pulp in the chamber and replace it with a biocompatible plant material called gutta-percha. If everything went properly and all the infected nerve was pulled out from the roots, it would cause no problems for years.

Sometimes some bleeding occurs as the dentist scrapes off the pulp. The blood will seep into the dentist’s filling to fill up the canal, and it turns brown when it dries up. Thus, it is expected to have a tooth discolouration after a root canal treatment.

Teeth whitening is a great way to deal with discoloured teeth, but it doesn’t always work for those who have undergone root canal surgery. In some cases, the filler material will re-discolour the tooth.

If your dentist successfully removed the infected tissue without removing any healthy tissue, there shouldn’t be much bleeding. However, dental practitioners can prevent this from occurring by applying a bonding agent. 

Persistent Pain

If you suffer from prolonged pain after the root canal procedure is complete, it may signify that something went wrong. There are various options to relieve the toothache. Still, it is best to see a dentist immediately if it’s persistent or getting worse. Moreover, it may be comforting to know that many patients do not experience this root canal failure symptom.

Learn More: Root Canal Alternatives: What Options Do You Have

Common Causes of A Failed Root Canal

  A root canal is usually required when you have an infected tooth. The goal is to get rid of any trace of the infection to preserve the tooth. However, with any dental or medical procedures, there is a risk of failure. In cases where there is re-infection, patients have no other treatment option but to have a root canal retreatment.


One of the biggest causes would have to be inadequate sanitation. Sanitation is vital for keeping everything clean and sterile. Still, even if your dentist tries their best, it’s not always enough.

The dentist has to be extra careful not to contaminate the access holes with saliva during the procedure. Saliva contains a lot of bacteria, so any contamination could potentially ruin an operation. Yet, it is challenging to drill someone’s teeth without allowing some saliva to enter those areas.

Broken root tip

A root tip that separates from the tooth dies and begins to rot, which causes a severe infection that dentists can remove. A dentist can remove the broken root tip. However, they typically need to extract the entire tooth first. Unfortunately, this means you will lose a tooth that may have cost you time and money to save. 

Soft sealant

Another reason for a failed root canal is the sealant used to fill the pulp chamber. Sealing material helps isolate harmful bacteria from other parts of your tooth. The seal may become compromised if it does not harden quickly enough. If this occurs, further complications may occur.

Crack or fissure

  Cracks in your tooth are usually the leading cause of root canal discomfort. When this happens, you must act fast because it reduces the strength and health of your teeth.

Sometimes, the fissures in your teeth are so minuscule that you don’t even realise they exist. During drilling, when they are sufficiently deep and damage the tooth’s root, you will experience severe root canal pain.

Final Thoughts

It can be challenging to tell when a root canal has gone wrong. Suppose you are experiencing any of the symptoms of root canal failure. In that case, it may be time to schedule endodontic surgery. You must contact your dentist immediately if there is pain or sensitivity in your teeth. Endodontic treatments should not be put off for too long.

Make sure you are getting the best treatment possible, so don’t hesitate to get in touch with us if you have any questions about your oral health. We offer comprehensive dental care services at our dental office. We look forward to hearing from you soon. 

Avatar photo

Peel Dental Studio

Dr. Bailey formerly served on the Australian Dental Association as President, Vice President Treasurer and Country Councillor. He was on the Australian Dental Association Federal Council and has always been keen to give back to the profession that has been his life. He has tutored student dentists at the Oral Health Centre in Perth.