When the pulp tissue becomes infected or irreparably damaged, there are two options other than root canal treatment:

1) Do nothing. If the inflamed pulp or infection is left untreated, it can cause severe pain, lead to abscess and/or spread, possibly leading to life-threatening infection.

2) Extract the tooth. If the extracted tooth is not replaced, related side effects may include shifting of teeth, disruption of one's bite, loss of chewing function, affected speech and loss of support leading to premature aging of one's facial appearance.
  
Generally, replacing an extracted tooth with a bridge or implant can be more expensive and time-consuming than endodontic treatment and restoration of the natural tooth.