No. One of my patients told me that a dentist said a root canal must always be done before a crown is placed. This doesn't make sense. They are 2 separate treatments that are commonly done together but not requirements of each other.
Root Canal Therapy
Root canal therapy is treatment involving the nerve inside a tooth. It is required when the nerve is infected or dead. The main purpose is to prevent or treat an infection.
A crown is a type of restoration on a tooth, to restore it to a strong and functional shape. The main purpose is to make the tooth functional, esthetic and comfortable.
In back teeth, a crown is commonly required after a root canal therapy. This is because back teeth are subjected to heavy forces when biting and is prone to fracture after a root canal. The crown will provide extra strength and protection to the tooth. It would be a shame for a tooth to fracture after you have spent much money and time on a root canal.
Sometimes a root canal is performed on a tooth that requires a crown. This is not a common situation. The reason why this would be done is that there is a high risk of the tooth dying or becoming infected. It is troublesome to have to perform a root canal after a crown has been placed.