Hi. My TMJ started as a complication of orthodontic treatment.
I did visit a functional orthodontist. He did seem to know more about the jaw function than my orthodontist, who continues to insist that the TMJ is caused by a bad bite - which he is correcting, so the symptoms should not be getting worse. My orthodontist actually never checked the jaw function and bases his treatment strictly on the visual things he sees in my mouth. (Needless to say, he is a very bad orthodontist!)
The functional orthdontist I saw wanted to give me a full mouth splint made from a hard, clear acrylic that would completely cover the bottom teeth and have little indentations for the top teeth. It would not have allowed eating solid foods, and talking would be difficult. I did not end up going this route.
I don't know if this helps - I hope so. Please be aware that orthdontic treatment can CAUSE TMJ. It would not be wise to undergo orthodontic treatment to correct your TMJ, since moving the teeth will really make the TMJ symptoms worse. Address the TMJ first, then do orthodontic treatment if you need to.