I have bad bruxism. i wear a guard at night. when i get an ex ray done to my jaw, what will it show if something is wrong? does it show fluid?

Structural damage: Sleep bruxism is a parafunctional activity that occurs in nearly all people. It is simply night-time clenching or grinding of the teeth. Bruxism can cause significant damage to the teeth and tmj. It can be reponsible for tension type headache pain. It is best managed with a custom fitted nightime splint that if designed well can minimize or eliminate all of these effects.

Hard to say: Length of time, severity and other symptoms may dictate what an x-ray will show. But as far as a more definitive imaging, a MRI is the best source of info.