What kind of doctor treats tmj?
An oral surgeon, I think.
Dentists can often help with this too. There are usually both that specialize in TMJ related problems.
Pretty much all the treatments are unproven and contested, according to the National Institute of Health: http://www.nidcr.nih.gov/oralhealth/topics/tmj/lessisbest.htm
If you are a chronic bruxer, a thin custom mouthguard will reduce damage to your teeth and dental work. All the invasive, bite changing splints, NTI's, ortho work, and surgeries are unproven. Botoxing your masseters gives you temporary relief at best, and signifcant long term jaw bone loss, meaning don't do this unapproved, best selling treatment. Since we all brux occasionally, stress reduction can prevent it from becoming chronic. But once it is a chronic, subconscious, neuromuscular disorder, don't let anyone sell you massage or P.T. as a cure.
Unfortunately, the NIDCR has decided to defer a study of jsut how much TMJoint related pain is caused by chronic bruxing. I think before you let anyone diagnose by structural analyses, or diagnose by trying on treatments, you should rule out chronic bruxism, or get an ironclad diagnosis.
EMG home sleep studies are the effective diagnostic, and will also tell you if a treatment is working or not. Note that lots of treatments can temporarily interrupt chronic bruxism, whether silent clenching or teeth grinding (this can buy you some very expensive false hope).
If you have the obviously worn teeth of a bruxer, be very suspicious of any TMJ specialist who doesn't want to use non-invasive EMG home sleep studies (rent a unit from a dentist) - these guys get a big, "Why?" from me. Cosmetic dentistry and bite changing really can make your smile beautiful, but it's completely unproven and contested for TMJoint related pain. I love cosmetic dentistry's effects.
I have spent a house worth of money on all the contested treatments and surgeries for TMJD related pain, with occasional temporary relief, and sometimes more damage. My topos/scans/etc. are ugly, one ball is a raggedy D shape, what little discs I have are displaced, but the real problem was the chronic bruxing, so I function fine now. The one treatment I skipped is the titanium ball and/or socket replacement, since the Mayo Clinic is honest enough to point out right on their website that it rarely reduces pain.
And if it's chronic, don't let anyone sell you stress reduction or massage as appropriate treatment. Good living can prevent a passing bout of bruxism from becoming chronic. We all brux sometimes. But a chronic, neuromuscular disorder will not respond to being told to chill out.