You can only get botulism if the dent has caused a tiny pinhole in the can. If you open a dented can and foam or liquid spurts out of it don't eat it. Also if the food is discolored, moldy or smells horrible don't eat it. A small dent in a can is ok, but if it's a big deep dent don't eat it. I've eaten lots of food from dented cans and have never gotten sick.