Having a slight overbite is normal because the shape of the human skull naturally allows for the upper teeth to extend beyond the lower teeth. An overlap of more than 2-3 mm is considered an excessive overbite and should be treated. If you do have an overbite, you will notice that your bottom teeth bite very close to the roof of your mouth. In some cases, your bottom teeth may even touch the roof of your mouth when you bite naturally. During checkups, your dentist should measure your overbite and underbite and consult with you if they suspect any issues.