What are the most common causes for needing a root canal?

The most common causes that necessitate a root canal are irritation and inflammation of the tooth's nerve and pulp, according to WebMD. These irritations are caused by repeated dental procedures, deep decay, a crack or chip in the tooth, or facial trauma.

Signs an individual may need a root canal are severe toothache pain upon applying pressure or chewing; prolonged sensitivity to color or hot temperatures; darkening or discoloration of the tooth; tenderness and swelling to nearby gums; or a recurring and persistent pimple on the gums, states WebMD. Sometimes there are no symptoms present to indicate the need for a root canal.