head tossing

Is there any way of getting 7yr old thouroughbred gelding out of head tossing? As everything about him is beautiful except his head tossing...does anyone have any ideas?
Thankyou

When does he head toss?

I'd need more information than this to be sure, but my TB tosses his head when I hold his mouth too tightly. Make sure he's got some rein.

It may be caused from some discomfort. When did he last have his teeth checked?