A root canal can fail due to several reasons. If the infection was not completely removed from the canals, they can multiply and cause pain. Bacteria can also reinfect a tooth if a permanent filling was not placed very soon after the root canal treatment. Temporary fillings or poorly placed permanent fillings can break down or leak. This allows bacteria back into the canal.
Sometimes the dentist does not locate all the canals in a tooth. This can occur if a tooth has more than the typical number of canals for the type of tooth. The bacteria in the unfilled canal will multiply and start to cause pain.
A repeat root canal treatment tends to be more involved and take more time than the first one. Your dentist must remove the crown, post and core, and filling material before doing the second root canal. Some people who need another treatment may have infections that are difficult to control.
Sometimes a second root canal can be hard to do. In this case your dentist may decide to do endodontic surgery.
This surgery allows the dentist to get inside a tooth’s root from the bottom of the tooth, rather than from the top.
Endodontic surgery is done in the dentist’s office under local anesthesia. Your dentist will make a small cut in the gum near the base of the tooth. He or she will clean out the infected tissue around the tip (apex) of the root and shave off the tip. This procedure is called an apicoectomy. The dentist will clean the inside of the canal from the root end, and then put a filling in the end of the root. The incision is then stitched.
Endodontic surgery is successful about 85% of the time. It is typically done only on premolars and front teeth. If the surgery does not get rid of the infection, the tooth will have to be extracted.