Teach your dog that his teeth are never allowed to touch a person, even when playing! Playing tug-of-war and other games with dog toys is fine, but I recommend winning (showing that you’re the leader) and teaching the dog to release the toy on command. It is very natural for a dog to play with other dogs with their teeth. Some dogs will give others massages with their teeth. Typically, the firmer the grip the more aggressive the dog is being, and some play very aggressively. I teach dogs that they are not to be aggressive even during play with other dogs. Remember, never let a dog put their teeth on you or others, ever.