Can a Root Canal Fail?

The answer is yes - it is common for a small percentage of root canals to fail or re-abscess.  Usually when this happens it is due to bacteria finding a vent and escaping and this causes toxins to deteriorate bone.  The hard part about this situation is the dental patient won't even know it is happening as the nerve endings  were removed.  This is why it is important to have your root canal inspected several times as sever bone destruction to the maxilla or mandible and cause the tooth to become loose.

If a tooth is re-infected, a procedure called 'apicoectomy' is performed and a bone augmentation may need to be done. This surgical procedure involves making an incision in the gum near the tip of the root and deriding the infected area.  Typically, the tip of the patients root will be removed and the tooth is retro-filled. This means a filling is placed into the tip of the root, essentially filling it from the bottom up.  The material used to fill this area by dentists is called Silver Amalgam.  This needs to be done as quickly as possible to seal the bacteria inside the tooth.
 
It seems that an extraction is suitable option instead of the root canal being performed in the first place.  One must consider the patient's philosophy on health.  Do they want to outlive their teeth of have their teeth outlive them.