In 2014, my dentist did a root canal on an upper right molar. Two months ago, the tooth started hurting, and it’s getting worse. Will I need an extraction and dental implant, or if I see a specialist, can they try a root canal treatment again and prevent an extraction? – Thanks. Noble R. from CT

Noble,

Root canal treatment is one of the least predictable treatments in dentistry. Even if a dentist performs the procedure correctly, it has a 5-15% failure rate.

Can Root Canal Treatment Be Repeated?

Root canal treatment can be repeated multiple times. But it doesn’t always make sense to do it. Still, there is an option before extracting a tooth and replacing it with a dental implant.

Why Causes Root Canal Failure?

Sometimes root canal treatment fails because the dentist could not completely remove the infection from a tooth. Canals in a tooth can twist and turn and make it difficult or impossible for a dentist to clean out the infection and seal out bacteria fully.

The pulp in your tooth contains living tissue, nerves, and blood vessels. A pulp chamber is in the crown of a tooth, and a pulp canal conducts blood supply and nerve in the chamber. If tooth pulp is infected, a dentist will clean out the chamber and canal and seal them to prevent bacteria from entering the tooth.

Molar teeth usually have three canals for each tooth root. But sometimes a tooth has a fourth canal that’s difficult to find and clean. Some canals have branches at right angles. A dentist has tiny, highly flexible files to insert in the tooth and remove the infected tissue, but the files cannot enter a side branch with a right angle. Although a minority of teeth have fourth canals and challenging angles, sometimes fourth canals exist and retreatment is needed. Retreatment has a 50 to 75% success rate. But if retreatment is completed by a dentist who is skilled in root canal treatment and it fails, a third treatment is likely to fail.

Root Canal Surgery

Root canal surgery is a procedure that enters the tooth through the root instead of the crown. A root canal specialist, or endodontist, performs root canal surgery, or an apicoectomy. The treatment is 50 to 75% successful. The specialist will take the following steps:

• Make an opening in the bone
• Cut off the root tip of the infected tooth
• Place a small filling at the end of the tooth to seal it

But even with an apicoectomy, a specialist sometimes can’t access tooth roots, or a root’s location—such as near a nerve in the lower jaw and lip—makes surgery risky.

Extraction Instead of Repeat Root Canal Treatment?

An extraction is an alternative to repeat root canal treatment. Although it’s not the first choice, sometimes even a specialist can’t save a tooth, and you’ll need an extraction and dental implant.

Schedule a follow-up appointment with your dentist to discuss your options. You can compare your dentist’s recommendation with a second opinion from a root canal specialist.

Michael Szarek, DMD, a Lowell, MA, cosmetic dentist, sponsors this post.