The process of root canal treatment involves the removal of the nerve within the root of a tooth. This is a serious type of treatment and usually involves multiple sessions to properly remove the patient from pain and attend to the remaining pulp to stop it from becoming infected.
Root canal therapy is done for the benefit of the tooth but the procedure inherently weakens the tooth. Often a crown is placed over the tooth to ensure it doesn't break in the future. This also prevents bacteria from re-entering the tooth, since the crown forms an extremely tight microscopic seal around the tooth.
How do I know if I need a root canal?
Unfortunately, this is practically impossible for the untrained individual to find out by themselves. A dentist is the first port of call in this regard. A clinical examination followed by a number of tests including but not limited to "pulp tests", x-rays and clinical photos are required to establish a clear diagnosis.
More information on root canal treatment