I have always had this problem, ever since an incident about five or six years ago, in which I caught a baseball with my front teeth. (I lost it on the exhange.
)
I also use the classic Fox 40 with the cushioned tip, which I like, but I think the biggest difference can be seen, if you simply loosen your bite, release your whistle, or take it in your hand, as you run the floor. Especially if there is little or no backcourt pressure, the majority of your whistles will be when you have gotten to your position, and are only moving to adjust to ball movement in the half-court game. I have found that this helps alot, since alot of the jarring impact occurs with the quick hard steps that occur when you are running in transition.