Biting our nails is one of the habits that the body seems to do when it’s stressed. Some don’t realize they’re biting their nails until somebody else points out to them. The causes of nail-biting haven’t been specified yet but most people believe that is due to preoccupation, boredom, tiredness or anxiety. It may be a hard habit to break, but it is necessary for the health of your teeth and of course – your manicure. So, what does nail-biting do to your teeth? It can cause teeth to crack, chip or wear down their front. It can also tear or damage your gum tissue.