I can't comment on the TN...

But oral demerol is not a good choice for chronic pain. It is toxic over time and can cause seizures!

Most doctors don't use it anymore orally, or for chronic issues.
It is reserved for acute temporary pain, or post surgical pain.

I have had 2 teeth over the past 20 yrs that started dying and causing horrible face pain. Neither showed up on Xrays as being abnormal. I had root canals in both finally which corrected the problem. The first one was the back upper molar, and I suffered for about 4 yrs with that one. The recent one was the first upper bicuspid on the right, which was giving me sinus pain.

The first one I consulted 1) my reg dentist, 2) oral surgeon -when my jaw locked up, 3) TMJ specialist dentist, and finally the endodontist my dentist referred me to was unsure, but did finally root canal it and it fixed it finally...took 6mos to calm down the pain tho.

You should never rule out a tooth. That is my motto now!