Patients will often ask this question. I chose to write this answer for that reason but also because I love educating and mentoring our youth as my very own dentist did when I was younger.
The amount of time from start to finish will vary from dentist to dentist but on average, after high school, there are four years of college and undergraduate coursework, generally in a technical and science background, although that’s not required as long as you make time for your pre-dental requirements; then four years of dental school with two board examinations and you become a dentist. You’ll need to pass your licensure exam or be credentialed in with a portfolio or a residency at completion to legally practice dentistry, and some will pursue post-graduate work in an area of interest for 1+ years after all this, with some more exams to come.
For me, after high school I studied engineering in college for four years, then went to dental school for four more, interning for more experience during my times off; took my two board examinations then my licensure examination, did a one-year post doctoral training program called a residency (my field was termed Advanced Education in General Dentistry) and went on to complete 500 hours of additional continuing education. I then took my Fellowship exam to work towards becoming a Fellow with the Academy of General Dentistry. With all this, I still have many options to further my education even more with Mastership awards and Life Long Learning awards. It takes years to develop the skill set and knowledge required to become a dentist, and there are years of education, even after you walk across the stage and receive your diploma. It is not for the faint at heart.