I did not wear my top Invisalign tray for too long and now will not fit. How can I get it back on?

Unfortunately once the teeth move it’s not that easy to get
them back. You will have to consult with your orthodontist. You might be able
to go back few trays to realign them or
they might have to order some additional trays at this time.

Sometimes when teeth have moved from not wearing the aligners, you can go back a few aligners to a set that fits and then go forward again using the same time frame as originally done. You would have to have your dentist make the decision on which set to start with. This will only work if your teeth have migrated back to a similar position they were in before. Otherwise, a revision will have to be done by your dentist taking new impressions and having the lab make new aligners from the place you are at now to getting them straight again. There may or may not be a fee for this.