What happens is that the teeth move into position within a few days of putting the aligners in. The rest of the time is allotted to allow the bone to remodel around the new tooth position. If you don't give it that rest time and move your teeth too quickly, your teeth will become loose.

Is it normal for your Invisalign to be loose?

“Too loose” is more of a concern for your treatment. There should be no gaps between the trays and the incisal edges of the teeth. Gaps typically indicate that the trays are too big or too little, and are usually caused by inaccurate impressions or the teeth's inability to expand or move at the expected rate.

Why is my aligner loose at the back?

Another common problem with aligners fitting improperly is on the back teeth. If you feel a gap in the back of your teeth, remove the aligner, and bend it and squeeze it with your fingers to close the opening tighter, so it fits more snugly over your teeth.