Why do I need a crown over a root canal tooth?

Almost always when a posterior (back) tooth has to receive a root canal for whatever reason (cavity, broken, infected), a crown is typically recommended following completion of root canal therapy. The reason is that the tooth is compromised from previous factors such as cavity, fracture lines, big filling, etc. The foundation of the tooth has been greatly compromised not to mention a root canal is essentially creating a hole down the middle of the tooth further weakening an already compromised tooth. A root canal also involves removing the nerve from the teeth which cuts away some of the blood and nerve supplies which can lead to desiccation or "drying out" of the tooth. Put this all together and a tooth with previous work + root canal= a tooth that will potentially fracture.

Unfortunately when these teeth fracture, they tend to do it catastrophically and sometimes to the point where they are not fixable and need to be extracted. A crown provides additional protection to the tooth as it helps splint the remaining tooth structure together and offsets some of the stresses that occur while eating, chewing, grinding, clenching etc. Depending on the situation, there are different kinds of crowns that can be used and will be discussed at a later date. Ultimately, a crown is very important following root canal therapy to minimize the changes of breaking and fracturing.