What are dog grinding teeth? Why do dogs grind their teeth? Bruxism or teeth grinding is common among humans, but it can also appear in your dog. Teeth grinding in dogs happens when they rub their upper and lower teeth together over and over. This action can damage your dog’s healthy set of teeth, causing a fractured tooth, exposed pulp, tooth infections, and painful teeth and gums. Learn more about the different reasons why dogs grind their teeth and what to do to deal with this issue.