Grinding of teeth cause immense pressure and muscle spasms in your jaw, thus causeing pain
. I know, you wonder how can my jaw
influence my back, right? Your jaw
muscle tire out, and recruit other muscle groups to help carry some of the work. Its that same thing with any muscle group, as you notice as you are working out and get to the end of a set, your form is off, as your body subconsciously recruits other muscles when in need.