They are only dangerous if you don't brush or floss. With respect to ancient cultures a little twig is a damn effective dental cleaner and about as good as a modern toothbrush.
People today who brush regularly still have way more rotted-out teeth than people who didn't eat significant quantities of carbohydrates. They are dangerous even if you brush.
Growing up, my dad often said that raw carrots are "nature's toothbrush" and he would encourage us to end any picnic lunch with carrot sticks, not with a sugary dessert. Can carrot sticks function like a little twig in terms of knocking undesirable food gunk off teeth?