Dentist here. I'm afraid your post doesn't make 100% sense to me, which suggests that your dentist has not really communicated what is going on to you very well.
Neither bridge work nor crowns are usually cures for tooth ache, and bridges are to replace missing teeth, not to cure tooth ache.
Oh, and it is 100% possible to get pain from a root filled tooth. I agree that in an ideal world, and the intention always is for, there never to be any pain again from that tooth. Life ain't like that I'm afraid. If the treatment was inadequate, or the anatomy unusual, or a crack was present, or the seal on the filling / crown on top was poor you can definitely get pain from the tooth.
And that assumes that the pain you had was a pain that can be sorted by root canal treatment. Some need something else, some are misdiagnosed entirely, and are from a different tooth, or from the gum, or jaw, or neuralgia, or angina.
Second opinion time....