My tooth is dying. how do dentists normally treat this?

Root Canal Therapy: Root canal therapy is the treatment for a dead or dying nerve in a tooth.

Root canal treatment: Root canal treatment is the cleaning out of all the dying / dead tissue in the canal space inside the tooth. A small access hole is made in the tooth to allow tiny instruments to clean the canal(s) out. After disinfecting with solutions, the space is sealed and either a filling or a build-up (maybe with a post) and crown will be placed to protect and rebuild the tooth. Sooner the better.