how long does it take and do l have to take extra courses in advance to normal classes?

It takes at least six years. Maybe 8. l know you need at least a four year degree before you can apply for Dental School. l am not sure if it is 2 or 4 years before you graduate Dental School. You should go to the website of a Dental School in your area. It should list all the requirements.

In the US, it works like this:

~Go to high school
~go to a 4-year university or college
~get a bachelor is & take a certain number of prerequisites (calculus, bio, organic chem, general chem, english, etc.).
~Take the Dental Admissions Test (and ideally get above 20)
~Apply to dental school using AADSAS (https://portal.aadsasweb.org/) & get ur letters of req sent in & do ur essay & all that
~Interviews/acceptances
~Dental school is 4 years
~If u want a general residency afterwards, that is 1 year. If u want a specialty, that is 2-6 more years.

So after high school, a minimum of 8 years. 14 if u want oral surgery!