My 3yr old (m) dog chews on my 6month old (f) pup's ears -dominance? how do i stop this?

I am a veterinary technician, and non of my doctors know what to do with this situation.... I've tried using bitter apple spray on her ears... i've tried catching him in the act and stopping him. He doens't hurt her- just gently gnaws enough to slobber on her. no matter what i have done, he continues- i need suggestions!!!