When the nerve (pulp) of a tooth becomes inflamed (pulpitis) due to tooth decay or trauma to a tooth, a root canal is often the only way to save the tooth. Once a dentist removes the infected nerve, they then fill the tooth with composite resin and place a crown on it to protect it and allow you to use it as normal. The only other issue you may have to deal with in future is crown replacement in 10–15 years.
However, although 90% of root canals are successful, on occasion, an endodontically treated tooth might become re-infected within a few months or even years after the root canal. When this happens, a second root canal is necessary.
The Tooth May Still Harbour Bacteria
When an endodontist treats a tooth, they remove all of the diseased nerve before filling in the root canal to prevent bacteria from gaining access. However, if even a tiny amount of tissue remains in the tooth, down near the root tip for example, it likely contains bacteria that will infect the bone surrounding the tooth and possibly cause an abscess.
Decay or Trauma May Have Exposed the Tooth
A tooth can also be re-infected when the filling layer inside the tooth is exposed to the millions of bacteria in the human mouth. This may be because of tooth decay under or near the crown, or trauma that caused the crown to become loose or displaced. Either way, bacteria will re-enter the tooth and cause another infection.
You May Not Have Replaced Your Crown in Time
Dental patients should aim to replace their crowns every 10–15 years. Over time, due to wear and tear, crowns deteriorate along with the glue binding them to the tooth. Bacteria are then able to slip between the crown and tooth, causing another infection. Talk with a dentist if you're concerned about your crown's strength.
Is it Worth it to Re-Treat the Tooth?
Although extraction is cheaper, consider the future without that tooth. If you extract the tooth and don't replace it, your teeth will move into the space and cause overcrowding. This does not make for a very appealing smile. It will also cause your bite to become misaligned. If you do replace the tooth with a denture, be aware that your body will resorb the bone in that area, shrinking your face over time. Dental implants are an option but this is even more expensive than a root canal.
If your tooth becomes re-infected, your best and cheapest course of action—in the long run—is to have a second root canal on that tooth. At least then you'll still have most of your natural tooth, and nothing a dentist can prepare can compare to the power of nature
