Hopefully it fixes things! My gelding was like that for ages but just stopped one day, before I had his teeth done.
What sort of bridle and bit does dusty have? Just thinking as I changed mitchs bridle and bit and he changed quickly.
Good luck tomorrow! If it does turn out that he has teeth issues and they were the root of the problem, he may still exhibit some of that behavior afterwards for awhile out of habit until he realizes he's no longer in pain.