Can I wear my plastic retainers after not wearing them for 5 years? My bonded wire broke while flossing.

You are running in to a common problem we are seeing with patients at this time.  Lost, broken, or missing retainers happen everyday. It doesn't stop with a pandemic!  Wearing an old retainer is better than nothing...if it (sort of) fits. If it is too painful to wear or if you notice any shifting because of it, certainly stop. Even with bonded retainers, teeth can shift enough that the teeth may not be exactly as they were when your braces were removed.  Also if there is still glue left on your teeth from the bonded retainer, it may make the retainer not fit all the way down and even push teeth out of position if your retainer is forced in.  A decent alternative is to go to the drug store or sporting good store and get a "boil and bite" mouthguard you can wear just at night time in an attempt to keep things straight until your orthodontist opens back up.