What are some complications of root canal treated teeth?

Some of the possible complications of root canal treated teeth can be:

• Root fracture or crown fracture
• Post-op infection
• Instrument breakage within the canal
• Perforating the side of the root
• Potential for re-treatment
• Recurrent decay
• Tooth color changes
• Post-op pain or swelling

Most of these happen rarely, but they are still possible complications that you should be aware of and discuss with your dentist if you are considering root canal therapy.  In most cases, with the aid of a good radiograph, your dentist can inform you of which of these might be more likely to occur.

Once the nerves and blood vessels have been removed by having a root canal, the tooth is no longer vital/alive. That means no pain, however, it becomes more brittle. This means it should have a crown placed to protect it from fracturing.

If the tooth had not previously had any fillings and the endodontist was able to treat it by accessing the nerve with a small opening, a crown may not be necessary. However, since it is no longer alive, the tooth may become darker. If the tooth is in the cosmetic/smile zone, internal bleaching may resolve this. Sometimes it will not and if the color change is objectionable, a veneer or crown might be necessary for cosmetic reasons.

Root canal therapy is a very predictable and successful dental procedure. However, due to the anatomical complexity of the nerve canals inside a tooth, complications can and do arise. 

1) Separated instruments : the instruments used to clean the canals are very thin and although they are remarkably strong, they can break ... even in the most gifted clinician's hands. Depending upon where the instrument has broken it may be possible to safely remove it. In other cases it may be left inside the tooth where it may pose a risk for future infection.

2) Perforation - when cleaning the inside of the tooth, a perforation or hole may be created in the floor or side of the root. In most cases, this hole can be repaired successfully. In other cases, it may lead to reinfection of the tooth or supporting bone and gums.

3) Infection - Many teeth that require root canal therapy are already infected. If some of the infected tissue is forced out the end of the root during root canal therapy, it may cause pain and swelling. In addition, infected tooth structure or tissue that remains inside the tooth after treatment can cause a failure of the treatment and a need to redo it.

4) Root fracture - A root fracture is typically a death sentence for a tooth in which there is no remedy. A fractured root can exist before the root canal has been started, can be caused by the root canal therapy itself, or can occur after the root canal has been completed. Crowns are highly recommended to protect teeth (especially molars and premolars) after root canal therapy.

5) Numbness or Paresthesia - Root canal filling material that extrudes out of the normal confines of the tooth can cause inflammation of nerves in the jaw, resulting in tingling or numbness which may be temporary or permanent.

6) Weakening of the tooth - depending upon how much of the inner tooth is removed to complete the root canal treatment, the tooth and root may be more brittle and susceptible to breakage. In addition, if the root canal was done through an existing crown, the underlying tooth structure supporting the crown may be weakened as well.

7) Color change - Although not common, teeth that have undergone root canal therapy can experience color change.

Although many of these complications cannot be avoided entirely, proper treatment planning and imaging prior to the root canal procedure will reduce the risks significantly.

Every situation is unique, but for the most part endodontic (root canal) treatment has a high probability of success. Routine complications include incomplete healing of the supporting bone accompanied by symptoms such as pain and infection, re-decay and breakdown of the crown--usually several months or years after the completion of the root canal filling and fracture of the tooth especially the root under heavy chewing forces or trauma.

Typically, patients neglect the restoration portion of the root canal treatment. After an otherwise successful root canal filling, if the tooth is not adequately restored with a cap or crown the remaining tooth structure will be very prone to breakdown with the result that the entire tooth may have to be removed. I stress to my patients that the root canal treatment must include the ultimate restoration of the crown otherwise the entire tooth should be sacrificed at the outset thus avoiding the expense and trouble of the endodontic therapy.

The incomplete healing of the supporting bone around the tooth can be caused by general health complications such as diabetes or radiation and chemotherapy side effects during cancer treatment. Unless the actual root canal filling was poorly done, the most likely cause of incomplete healing is periodontal (gum) disease. Almost all adult teeth show some signs of periodontal disease. If the disease progresses and eventually undermines the support of the root canal treated tooth, then the tooth will be lost in most cases.

As in all dental care, prevention, early detection and complete treatment when needed are the best tools for long-term success.

The vast majority of teeth having root canals (95%+) have no complications following treatment. In rare cases continued post-operative pain and discomfort can be present. This is often a sign of continued infection and need for further treatment. If a tooth is not properly restored with final restoration such as a crown, following root canal treatment, then tooth breakage can occur. Some root canal teeth, especially front teeth, can darken over time.

There are many things that may occur to a tooth that has had root canal therapy. Many of the risks or unwanted complications can happen whether or not a tooth has had endo therapy. These include, but are not limited to, root or crown fracture, recurrent decay and reaction to medication or anesthesia.

Other complications include conditions that require retreatment or surgical treatment to allow for improved healing, post-op tingling, swelling, pain or infection. Problems can also occur during access for treatment and instrumentation.

As with any treatment, dental or other, it is important to discuss the benefits and risks of treatment with your healthcare practitioner, and to review the potential problems that may be more specific to your case.

I have personally performed thousands of root canals and you can get many different results. The problem usually is not the procedure itself. If you see a dentist that has had some experience in performing root canals, the result is usually predictable. Problems usually start when a root canal is done on a tooth that was already compromised due to different problems such as bone loss or extensive decay and then once the procedure is performed and final restoration is placed, ideal results cannot be achieved since those results were not possible to begin with before the procedure was done. So it is very important to get the procedure done by a dentist that has enough knowledge about the procedure itself and the restoration after the procedure so complications can be kept to a minimum. A second opinion is always a good idea in these situations.

The most common complication of a tooth that has had root canal is that the tooth will break. This happens for two reasons; the first is that during root canal, the tooth is hollowed out, like taking the core out of an apple. This makes the tooth structurally weak. The second reason is that the process of root canal removes the tiny nerves and blood vessels within the tooth's roots which make it brittle. This is why most teeth that have had a root canal will also require a crown (aka cap) shortly after the root canal is completed. The crown protects the tooth and rebuilds it. See also: http://www.dentalcomfortzone.com/template.php?aid=290.

In general terms, root canals are almost always successful, and will cause no further complications. However, everyone is different, so there could be some after-effects, depending on the individual. This can range from chronic discomfort (which usually clears up after a week or two) to the tooth eventually cracking (after all, a root canal hollows out the tooth). A crown will help strengthen things. If you are experiencing pain in a root-canaled tooth – especially if the root canal is more than a few weeks old – you should definitely contact your dentist.