It can take you 8 or more years after high school to become a practicing dentist. Initially, you will be required to get a 4 year bachelor's degree in natural sciences. After this, you must sit for the Dental Admission Test (DAT). The scores of your DAT will help you to enroll in an accredited dental school. In a dental school, you will further spend four or more years studying basic oral sciences and covering subjects such as oral anatomy, physiology, pathology and histology. After the first two years at the dental school, your choice of specialization will determine how much longer it will take for you to become a dentist. Once you've graduated from the dental school, you will be required to pass a licensure exam.
(Source: The Bureau of Labor Statistics)