Biting your nails doesn’t just harm the appearance of your hands — it can also damage your teeth and become an oral hygiene issue. Chronic nail biting can cause your teeth to move out of place. In addition, nail biting could potentially cause teeth to break or tooth enamel to splinter. Some people have a habit of holding objects — such as pens, pencils, or eyeglasses — between their teeth when concentrating on a difficult task. But what many might not realize is how much pressure they’re placing on their teeth as they bite down on a non-food object. Similar to nail biting, biting on a pen or a similar object can cause your teeth to shift or crack.