I'm not sure if it's bad for their teeth & gums. I would think it depends on the individual dog & how good their breeding is. Dogs are meant to clamp down & bite. smaller & weaker dogs are because man chose to mess with nature.
Still, I am not an expert. So consult one before doing something.
As far as temperament, I am a bit more knowledgeable there then with vet stuff.
It depends on factors that are more about is the dog already vicious.
I guess most people want to cuddle with their yorkie & play games, like fetch or rope, rather than supposed big dog activities. However, rope, fetch, or stuff toys (that look like animals) can bring out aggressiveness in some dogs.
I don't see how
Schutzhund would be any different.
https://k9trainer.wordpress.com/2008...a-vicious-dog/