Is it safe to use crest whitening strips with lingual braces on?

It might be : Difficult to keep the white strips on - i'm not that familiar with their design. If they just stick to the facial aspect (frontside) of the teeth then i don't anticipate a problem - sensitivity maybe? If they slip on the teeth (covering both front and back) then you might have a problem getting them to stay.

Yes: The only problem you might run into is making sure the strips stay in place. Make sure you have consulted with your dentist/orthodontist before doing this, and if you experience any sensitivity, bring it to their attention.

Yes: Should not be a problem at all.

Would not: while most whitening toothpaste is very mild, you may cause a shade difference between the exposed tooth and the part covered by the braces. I would wait until after the braces come off and ask your orthodontist about using your retainer as a tray to employ professional grade whitening (we sell this for only an extra $25 after braces)