Cyclobenzaprine
"It's not a miracle cure, but it definitely helps.  First time I was prescribed it, my jaw had been locked for a little over three weeks.  Needless to say, I was pretty desperate to have any kind of fix.  After yet another failed appointment with the TMJ specialists, I went to my primary doctor hoping that she had been able to find something new.  This time, she prescribed Cyclobenzaprine.  No joke, four hours later I could open my jaw.  Works like a charm.  The pain goes away with it too (no more tension).  Only downside, is it makes me sleepy and a little loopy.  No driving on this stuff (for me anyways)."