Root Canal Treatment is a process which involves removing the nerves from the inside of the root canals. By doing this you are removing any sensation from the tooth. This treatment is carried when a tooth is heavily decayed, and they decay has reached the nerve (causing the pain) or when a tooth experiences repeat infections.
Once the nerves and infection has been removed the canals are filled and a restoration can be placed.
Root canal treatment can take up 1-2 appointments to complete, possibly more depending on the restoration type that has been chosen. Your dentist will discuss with you the timeframe for the treatment and the expected finish date.
Your dentist may suggest that a crown is the best restoration type to give better longevity.