A retainer of any type is not meant for realigning teeth. If the amount of correction is not a great deal, Invisalign Express with 5 or 10 aligners may do the job well. Everyone's teeth lean towards the front of the mouth and therefore crowding of your front teeth is normal without good retention. Once the teeth have moved out of alignment only orthodontic treatment with realign them. Invisalign is the fastest, healthiest, most esthetic, and most comfortable way to straighten teeth.