A female patient rubs her jaw, which still hurts after a root canal.

Patients sometimes ask, “Why does my tooth hurt after a root canal?” It is a reasonable question. Today, root canal procedures are virtually painless. It can be a little disarming to undergo such a comfortable and effective root canal treatment, only to encounter discomfort afterwards. The majority of patients enjoy a pain-free recuperative period. However, for the small percentage that experiences some pain, this fact offers little solace. When your endodontist removes the nerve within your tooth, the hope is that the pain it once caused will immediately subside. When it does not, frustration is completely understandable.

Why Does My Tooth Hurt?

In most cases, tooth pain after a root canal is due to tissue inflammation, but not indicative of an active infection. The most common source of pain after a root canal is the inflammation of tissues around the tooth’s root. This is “periradicular inflammation.” Depending on severity, it does take some time for such swelling to go down and the tissue to fully heal.

A wide variety of events can inflame these tissues. It is possible that the infection that necessitated a root canal previously caused these ligaments to swell. The problem could also be linked to “overinstrumentation.” When removing the infected tissue, endodontists are careful to diligently clean out the full length of the root canals. It is possible, however, to unfortunately extract or otherwise potentially irritate tissue beyond the end of the tooth.

The tool endodontists use to clean out root canals is a file. If it pushes past the end of the root during the cleaning process, you will be sore until that damage can heal. This also exacerbates the risk of bacteria and debris from the root’s tip escaping into the surrounding tissues. The same risk applies to the leakage of solutions and medicaments. For example, the sealer (a material used to “seal off” the inside of the tooth during treatment) might push beyond the end of the root. The consequent aggravation to the tissue can cause even more tenderness.

Other Potential Causes of Tooth Pain

There are a handful of other potential culprits to consider. Some patients suffer gum tissue trauma from the rubber dam clamp used in the procedure. This may be the source of your pain, which some people incorrectly attribute to the tooth itself. One of the final steps of a root canal is to add a filling. If this filling is a too tall, you will exert disproportionate pressure on it, which makes it sore. Even a slight miscalculation in the height of your filling can create noticeable, sustained discomfort. Fortunately, the endodontist (or a dentist) simply needs to adjust the filling, and the soreness will rapidly dissipate.

Very rarely, certain patients experience “phantom pain.” The nerve that leads into the tooth does remain sensitive for some time, which may create the sensation that it is still attached to the tooth’s formerly diseased nerve (even after the root canal removed it).

Another rare but possible cause of your tooth pain is that, during root canal therapy, the procedure triggered the activation of bacteria within the root canals. This can lead to an acute infection.

Does My Tooth Pain Mean the Root Canal Failed?

Discomfort immediately following your root canal is not reflective of the procedure’s success. Most often, pain that follows a root canal directly correlates to both the level of pain prior to treatment and the intensity of tissue irritation required to complete the endodontic treatment thoroughly.

It is important to remember that, with proper endodontic treatment and restoration, you can save your previously infected tooth. This will allow it to serve you just as well as your natural teeth for a long time to come. It will only require the same great oral hygiene regimen at home and regular dental care as the rest of your teeth. Be sure to follow-up with your dentist or endodontist, who will likely X-ray the tooth to check on its healing process. Should your tooth truly fail to heal (and thus the pain continue indefinitely), repeating the endodontic procedure is typically the best strategy to save the tooth.

Prevent Tooth Pain After a Root Canal

Follow these simple steps to prevent pain after a root canal:

  • Do not eat until your mouth is regains feeling, in order to prevent accidentally biting your cheek or tongue while numb.
  • Use over-the-counter pain medication. Be sure to follow the provided instructions.
  • Do not use the treated tooth to chew until it has been fully restored.
  • Brush and floss your teeth regularly.
  • Be patient with temporary filling materials, which can partially wear down between appointments. If the entire filling comes out, contact the endodontist immediately.

Every patient must accept that some tenderness in the area in which treatment took place is completely normal for a few days after the root canal. Some people even experience tenderness in their jaw. This can temporarily prevent them from comfortably opening their mouths up wide. These kinds of symptoms do not remain for very long and are effectively alleviated by consuming over-the-counter pain medications. Additionally, your tooth may simply feel different for a little while, as the your body’s normal healing processes run their course.