It can take two to three years of schooling to become a dental hygienist. You will need to take pre-requisite classes and then take core classes. You will most likely be required to do an internship in a dentist's office so that you can get hands on experience. You will go to school between 2 and 3 years to get all of your course work and experience before you are granted a license. The classes vary by state but are typically very similar.