I know darn near nothing about horses. This, and Google fu provided some interesting reading. How often does this become a problem, and can you ever address this with an unsedated stallion.
Like I posted above, this is usually taken care of when teeth are floated. the horses are anesthetized for that.
I think horses handled a lot will allow some of the tender areas to be touched. For this gelding, I was quick and he appreciated the speed with which I accomplished the task.