How can i tell if i need a root canal or a filling?

See your dentist.: Your dentist will be able to examine your tooth and x-rays to determine whether or not your tooth requires a filling, root canal, or some other sort of restoration.

Duration of symptoms: Typically the duration and intensity of pain symptoms is much more significant when a root canal might be indicated compared to a filling.

Depends: If you have severe pain and swelling the need may be obvious. Otherwise it depends on the amount of decay present in the cavity, its's nearness to the pulp (nerve) of the tooth (if it's into the nerve you usually need rct) and the kind of symptoms you have (heat sensitivity usually means rct). It's up to your tooth, not the dentist or you!