It is not mutually exclusive to be a dental hygienist and orthodontist. You can start with an UG degree in dental hygienist and decide later whether you want to attend dental school, and after become a dentist, you can later on go back to orthodontist school to learn how become a orthodontist.
I once took my D to a very successful orthodontist office to get first evaluation, he has 10 chairs full of patients and about a dozen nurse running around, plus several doctors. I believe he makes more than 200K a year, more like a million+.