The number of clear aligners needed varies depending on WHAT YOU’RE TRYING TO ACCOMPLISH, how crooked your teeth are and how quickly they move into proper alignment. IT COULD TAKE AS FEW AS 6 ALIGNERS AND AS MANY AS 40 ALIGNERS BUT Most patients use between 20 and 30 aligners during treatment, switching them every two weeks. As a certified Invisalign Dentist, Dr. Makhoul can accurately estimate how many trays you will need at your first appointment.