What would chewing your nails actually do to your teeth?

See answer: It can cause your teeth to eventually chip or crack. Please try to stop or use another stress reduction activity.

Can hurt gums: Nail biting is more of a problem for your fingers and gums than for your teeth. Your finger nails are hard and sharp, your gums are soft. It is very easy to accidentally cut or damage your gums while biting. I have also had several patients get pieces of fingernail stuck between their teeth that they can not dislodge on their own. Biting dirty fingernails also adds lots of bacteria to your mouth.