One of my front teeth is darker than my other teeth and my dentist said the tooth needs a root canal.  If my tooth does not hurt, why do I still need a root canal?

Discoloration of a single front tooth usually indicates the tooth was injured at some point in your life. Injuries to front teeth are very common, especially in children, and the bleeding inside the tooth will cause the tooth to change color. Although your tooth does not hurt, the nerve inside the tooth is probably dead and the tooth will require root canal therapy in the future. After the root canal is completed, your dentist can bleach the inside of your tooth to lighten the shade.