In the U.S., unless things have changed, both medical and dental school education is studied after one graduates from a University with a BA or BS degree, and they both are called doctors when they finish the additional schooling, 4 years for medicine and 4 for dentistry.
Medical doctors have an additional internship and often residencies after getting their m.d.s. Re dentistry here:
Dental education in U.S. re wiki -
In order to be accepted to an American dental school, most candidates must possess at least a Bachelor's degree as well as the pre-requisite courses.
The first 2 years of dental school consist mostly of didactic education as well as simulation courses. The last two years generally involve direct patient care under supervision. There tends to be much overlap in most schools' curricula; the didactic years may have some clinical components while the last two years still have significant didactic coursework. During dental school, students must take and successfully pass Part I and Part II of the National Board Dental Examination (also known as "the Boards"), which are administered by the ADA. Part I is usually taken after the second year of dental school, while Part II is usually taken sometime in the fourth year.
So that's eight years of school to get to be called doctors.