Can Fast Braces be used to close tooth gaps? (photos)

I am 18 years old and have found out that I have two permanent teeth missing on my lower jaw. These are 2 molars (circled). My dentist told me i must have to baby teeth removed and close the spaces with braces. Ive been looking into fastbraces as I am very concsious of cost and the time it will take for the dental work to be complete, and fastbraces seems to be the most appealing for me. My other teeth are pretty okay, i have some minor crowding but my main concern is closing the gaps.