If a root canal didn't fix the tooth, which literally removes the "root" or nerve ending from the tooth, and didn't stop the pain, removing your teeth might be the only viable option. I am not a dentist though. However, a lot of tooth pain is not actually caused by teeth. While on deployment, the entire right side of my body slammed into a windshield at 30 MPH. I found out when I got home, all the teeth on that side had fractured. All needed crowns, a lot had root canals. I have a small mouth and the pressure from the crowns caused constant pain. Or at least I thought it was the pressure. But my cheekbone apparently also collapsed a little, messing with my sinus passages. This made them more prone to infection. I kept going back to the dentist because of the pain, when really it was a sinus infection. It's really hard to tell the difference. It doesn't help that sometimes it's both. That was $6k worth of work. Sorry for the long response and probably TMI, but it might be helpful to check into the sinus thing, it's more common than I knew.

This sounds really weird OP, but have you ever had your sinuses checked up on? I have chronic sinusitis and because of all of the connected nerves, I normally get frequent tooth aches and nerve pain associated with teeth. I thought for a long time it was my teeth, but it's actually due to my sinuses being inflamed. I'm sorry you have found no relief in your pain. :( Try to think of things you wouldn't though! You'd be surprised that one visit to check your sinuses or anything else could help with (presumed) unrelated pain. Good luck!