Most splint therapies work on the basis of bringing your lower jaw down a bit and forward a bit (try putting your front upper two and lower two teeth tips together and this is about the change you get). This works by creating more space in the jaw joint to hopefully allow the discs to pop back in, relaxes tightened and shortened muscles and releases pressure on the trigemenial (sp?) nerve and inner ear nerves. Anything that pushes the lower jaw backwards unless it is unaturally forward to start with - is a bad idea as if creates the opposite of these benefits. I am currently in down/forward treatment with a gelb type splint and am starting to feel an improvement in my symptoms. All splints make it difficult to eat/talk until you get used to them as your mouth and tongue will be in a different position, but it only takes a few days.

I forgot to add that if splint therapy works you normally need orthodontic treatment to stabilise your new bite or your teeth just push the jaw back to the old bad position and they symptoms may return.

http://www.healthboards.com/boards/tmj-disorder-temporomandibular-joint/592923-2-different-splint-therapies-do.html