These three treatments solve different problems. A filling replaces a limited amount of missing tooth. A crown covers a tooth that needs full protection. A root canal treats the nerve and blood supply inside the tooth when they are inflamed or infected. One tooth can need more than one of them.
How the decision is made
The dentist looks at the tooth, tests it, and reads an X-ray. A small cavity with plenty of tooth left often stays a filling. A crack, a very large filling, or a tooth that has already had a root canal often needs a crown. Swelling, pain on biting, or hot and cold that lingers can mean the nerve is involved. Those signs do not prove a root canal is required. They mean the tooth needs the exam before anyone quotes a crown alone.
Price before you commit
You cannot know from home whether a tooth needs a root canal. At this office the first visit is the exam and X-ray, and the written price comes before payment. If a root canal is recommended, that fee is separate from the $799 crown and is shown before you accept it. You can decline.
A root canal treats infection or irreversible inflammation inside the tooth. A crown after a root canal protects what is left. They are not substitutes for each other.