If the metal filling was replaced with another metal filling, and the opposing tooth has some sort of metal restoration, you may get the strange sensation when the two metals coming into contact. If your filling was replaced with a composite (white) filling, and the dentist checked to make sure it wasn't too high at the last visit, it could have been placed close enough to the nerve to cause sensitivity.

This does not mean you need a root canal. You may just need some time for the tooth to "settle down" after the procedure. Sometimes air is trapped or a there is a tiny opening between the tooth and the filling. These can cause discomfort when biting down. If the feeling continues, the filling should be removed and redone to see if that will fix the problem.