Why does my tooth that’s had a root canal hurt?

It is a common misconception that teeth that have had a root canal will never give you pain again. It is certainly untrue.

It is true that the dental pulp (nerve) has been removed, but the bone and gums around the tooth are still present and can cause pain. It is also possible to have remnants of pulp tissue left inside a tooth that is inadequately cleaned.

These are the most common reasons why a tooth that has had a root canal can hurt.

Reinfection

The ultimate aim of a root canal therapy is to remove infection inside the tooth. However, it can get reinfected. This can happen if there are remaining microorganisms inside the root canal system or leakage of the restoration and root canal filling. Untreated tooth decay will also lead to leakage to the root canal system.

Missed canal

Not all teeth are the same and there is variation in the number of roots and canals in teeth. Some cases will have extra canals to what is normal and these out of the ordinary situations are more complex to treat.

Cracked root

This is an unsalvageable situation, which results in the tooth needing to be extracted. A cracked root is much more likely in root treated teeth, as you tend to bite harder on the tooth and it is physically weaker. Also, many teeth that need root canals are due to cracks. To prevent this, be careful with biting hard foods and consider getting an occlusal splint from your dentist.

Gum infection

Root canal treated teeth tend to accumulate more tartar, which increases the likelihood of gum infections. Regular flossing and brushing will help prevent this.

Inadequate quality of root canal therapy

There are lots of important factors that need to be met for successful root canal therapy. The entire root canal system needs to be treated.

For example, if the treatment is too short of the canal, there will be remaining microbes. If the treatment is too long, there will be trauma and potentially chronic irritation of the tissues outside past the tip of the root into the surrounding bone.

Periodontal disease

This is really unrelated to the tooth canal, but it can cause pain in a tooth that has had a root canal.