How effective is a root canal for treating a cavity?

Root Canal for?: Root Canal Therapy treats the nerve and tissues within the tooth. Although a cavity can lead to the need for RCT, the RCT treats the result of trauma, caries, etc. and not the cavity directly. The tooth still needs the decay removed and the tooth restored. RCT can also relieve the pain from an infected pulp as the result of dental caries. Your own dentist can better explain these issues in person

Root canal: A root canal does not treat a cavity. A root canal removes the nerve that is irreversibly damaged by the cavity. Typically before the root canal is completed or during the root canal procedure, your dentist should remove all of the tooth decay to ensure your tooth can be fixed.

Root canal: An untreated cavity will progress and get bigger and deeper. If the decay gets into the nerve you will need a root canal. The root canal will treat the infected pupal tissue, the decay will need to be removed and the tooth restored. Don't wait until the decay has progressed, the sooner it is treated the better.