How do the orthodontists adjust the retainer if they move after your braces are off?

Yes: For minor movements and corrections the retainers can be adjusted, depending on the type of retainer used, wire and plate kind or the clear type. If the teeth have moved a lot, a recorrective phase of treatment might be required. Please do not wait for your condition to get worse and see your orthodontist as soon as possible and if you have moved , ask him to recommend someone in your area.

Tighten the Wire: If your teeth have shifted because you haven't worn your retainer, they need to be moved back into straight alignment. If your retainer has a wire on it, often tightening this wire can put pressure on your teeth & straighten them again. This movement must be slight, however. If the retainer doesn't have a wire, then it usually can't move teeth...It's just meant to hold them. The orthodontist knows.

Depends: Sometimes you can adjust a wire to re rotate just cutting the plastic will sometimes allow a tooth to move. An aligner can be made which can re treat the tooth and then the retainer adjusted to the corrected relation.