"You need a root canal" is never something you want to hear coming from your dentist's lips. However, if the dentist is going to save the tooth instead of extracting it completely, a root canal is really the only way to go. There are also medical and health-related issues that can occur before a root canal is performed and sometimes after the procedure is complete. You should know what those conditions and possible complications are as you go forward with the procedure. 

Infections Before and After

A dead or dying tooth root can become very infected. It can lead to a buildup of pus in your gum tissue in and around the tooth with the dead/dying root. The pus, when left in this swollen state, causes high fevers and eventually hospitalization. Historically, people died from this type of infection because medical science was not far enough along to know what the problem was (i.e., an abscess) or how to treat it. 

Likewise, you may encounter an infection after the root canal. It is quite uncommon, but it could happen. Since the tooth root is exposed and connected to other roots in the same area, part of a developing infection in the root that is being repaired can travel to other roots. If and when that happens, it may be possible to head it off with antibiotics, which is why your dentist will prescribe a post-procedure antibiotic. If your dentist gets into the tooth root and sees that a small abscess was already forming and appears to be moving toward infecting another tooth root, the dentist will attempt to remove all of the pus before completing the root canal. Then he/she will not only prescribe the antibiotic, but also insist that you take it to avoid any post-procedural complications. 

Dead Roots Before and After

A root canal is performed to save a tooth from total loss. The root with the problem is either already dead, or it is dying. Not much can be done to revive the root, and it will affect the other roots of that same tooth. Worse still, if left untreated, it can cause roots of neighboring teeth to begin dying as the problem will spread along the blood vessels and nerves that feed into the neighboring teeth. 

Dead tooth roots that occur after a root canal is performed is an unusual event. What happens is that the dentist completes the root canal, but something goes awry with the procedure. The nerves or the blood vessels that feed into neighboring roots are damaged, and other roots die in the process. Sometimes unusual patient anatomy in the patient's mouth can contribute to this rare occurrence. Your dentist may or may not be able to spot this during the procedure, but because you will be awake, he/she will discuss the matter with you before proceeding.