What could cause pain in teeth from hot food?

Inflamed nerve: A tooth in which the nerve is unhealthy may resond painfully to heat stimulus. Heat increases blood flow which puts additional pressure on the nerve.

Tooth decay: Usually when hot effects a tooth it is quite possible a nerve in a tooth is of need of a root canal. The cause of the condition could be from tooth decay or past trauma to the area which damaged the nerve.

Pain from hot: Generally sensitivity to hot foods can be serious. This may mean a tooth is dying and could become infected or get an abscess. See your dentist asap.