Root canal treatment is the removal of the tooth's pulp, a small, thread-like tissue in the center of the tooth. Once the damaged, diseased or dead pulp is removed, the remaining space is cleaned, shaped and filled.This procedure seals off the root canal. Years ago, teeth with diseased or injured pulps were removed.he common causes affecting the pulp are a cracked tooth, a deep cavity, repeated dental treatment to the tooth or trauma. The term root canal comes from cleaning of the canals inside the tooth's root. What to Expect During a ROOT CANAL. If you think you need a root canal, consult your dentist.