The "U" means Upper, as in your upper teeth, and the "L" means Lower, as in your lower teeth. Each aligner set comes in its own little sealed bag, with information about the aligner (U or L) and step number. Many people have equal numbers of Upper and Lower trays, but some may be finished with treatment on either upper or lower first. In these cases, you will have an unequal number of upper and lowers. Either way, once your upper or lower is finished with the aligners, start wearing the retainer on that arch, as per instructions in the booklet.
Modified on: Tue, 9 Oct, 2018 at 11:51 AM
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