How many years Of school to be a dentist and orthodontist?

Typically it takes 4 years of college followed by 4 years of dental school followed by 2 to 3 years of orthodontic residency training.

However a college degree is not strictly required to enter dental school so you could conceivably just do the prerequisites and then apply to dental school after 2 or 3 years of college.

Also there is one dental school in the US that is only 3 years. University of the Pacific. It also has a 2 plus 3 program that lets you do 2 years of college followed by 3 years of dental school. Thus cutting the 8 years of school down to 5.