Can a crown that has been in my mouth for years be taken out and repositioned?

Thank you for your inquiry. Generally speaking, when a crown is removed it likely can only be removed by sectioning it off in pieces, so you'll need a new crown. Even if a crown can be removed in one piece, cementing it back into place will not do much. If you think your crown needs to be shifted, you'll likely need a new crown or possibly treatment done to adjacent teeth since crowns aren't typically "re-positioned." If the crown is not fitting properly, a new crown is recommended. Your dentist who placed your crown should be able to work with you since it was placed not too long ago, but again it depends on what has caused this crown to not fit properly (and/or adjacent teeth) and what your dentist recommends at this point. We hope this helps and we wish you all the best!

The way crowns are fabricated and the teeth are prepared is designed to only allow for the crown to fully seat in one specific alignment.  Properly made crowns will only seat to one exact position so the margins are sealed, the contacts between the teeth are correct and the bite fits comfortably.