Most root canal-treated teeth last for many years. But occasionally a treated tooth starts to hurt again, sometimes months later and sometimes a decade or more. When that happens, it is easy to assume the only option left is an extraction. Often it is not.
Why a root canal fails
The American Association of Endodontists describes two groups of causes.
Problems from the original treatment:
- narrow or curved canals that were not treated,
- complicated canal anatomy that went undetected,
- a crown or other restoration placed too late,
- a restoration that did not keep saliva out.
New problems after a successful treatment:
- new decay that exposes the root canal filling to bacteria,
- a loose, cracked or broken crown or filling,
- a fracture of the tooth.
Finding the cause is the most important step, because it decides which fix makes sense. Dr. Hirose looks for missed canals, leaks and cracks under the surgical microscope before recommending anything. A Penn study of 3D scans found that teeth with a missed canal were 4.4 times more likely to have infection at the root tip, so this step matters.
Option 1: Retreatment
In retreatment, the tooth is reopened, the old filling material is removed, and the canals are cleaned, examined for anything missed, and sealed again.
Option 2: Microsurgery
Sometimes the problem is best reached from the root tip instead of through the crown, for example when a tooth has a well-made crown or a post that would be risky to remove. In an apicoectomy, a small opening in the gum gives access to the root tip, which is cleaned and sealed from below.
How they compare
A systematic review of the research compared the two:
- At two to four years, surgery had the higher success rate: 77.8 percent versus 70.9 percent for retreatment.
- At four to six years, the order reversed: retreatment 83.0 percent, surgery 71.8 percent.
How surgery is done matters a great deal. A meta-analysis comparing older techniques with modern endodontic microsurgery, which uses a surgical microscope and precise instruments, found success rates of 59 percent for the traditional approach and 94 percent for microsurgery.
Option 3: Extraction
Some teeth cannot be saved predictably. A crack running down the length of the root is a common reason. In that case, removing the tooth and replacing it, usually with an implant, is the better investment, and a systematic review found that restored root canal-treated teeth and single implants survive at similar rates, so both are sound choices when the tooth itself calls for one or the other.
How we help you decide
At your consultation, Dr. Hirose reviews your history and your x-rays with you, explains what he thinks went wrong, and lays out the options that fit your tooth. If saving it is not a good bet, he will say so. Learn more about retreatment and microsurgery.