Retainers can . Modified retainers can be used to move your teeth. There are limitations with how much movement can be accomplished with retainers. Invisalign is a form of retainers that can make much larger changes.
Nt really. Retainers retain, they hold things where they are. Active removable appliances are capable of some corrective movement, but only some. Invisalign is less than half as effective as braces in moving teeth. Unfortunately once teeth shift they often mov e off of bone support, making pretreatment less effective. Best to where retainers as directed when braces removed. See an orthodontist.
No. A retainer does just what the word means. It retains. It retains the teeth in the position that they are currently in, and stops them from getting more crooked.;.