Upper front teeth protrude excessively over the lower teeth Upper front teeth cover the majority of the lower teeth when biting together (deep bite) Upper front teeth are behind or inside the lower front teeth (underbite) The upper and lower front teeth do not touch when biting together (open bite) Crowded or overlapped teeth The center of the upper and lower teeth do not line up Finger- or thumb-sucking habits which continue after six or seven years old Difficulty chewing Teeth wearing unevenly or excessively The lower jaw shifts to one side or the other when biting together Spaces between the teeth