L.B.
He is grinding because his jaws are growing and he is unconsciously trying to find the right fit. If you get a mouthguard, it will fit for such a short time before he grows out of it, or loses a tooth, that it is not practical. Stress is the usual reason adults grind, and then a mouthguard is recommended. His teeth will probably show a little wear, but he should lose them before it becomes a problem with sensitivity.