Dogs who like to chew rocks - knew a Labrador, Jake, once who loved to chew rocks - do not have pointy teeth like that. To the contrary, it wears them down and can break them badly. Jake's "boys" were made to to clear their yard of rocks, because he was doing such a job on this teeth - he could have a yard full of toys and bones and sticks and would instead root around the landscaping to find a rock to munch. Once they did a thorough job of clearing their own yard, he'd simply lope over to a neighbor's yard to find munchable rocks. Jake was not the brightest bulb on the tree, needless to say, and would "sneak" a rock into the house, go under my buddy Pete's bed to munch it on the sly, but the sound of teeth grinding against stone would wake the dead, and he never figured out how they knew!