That is possible.  Obviously the dentist placing the restoration felt
it may be somewhat fragile considering the precautions given by your
dentist.
    Was the entire tooth knocked out, root and all?  Or was it fractured
and repaired?  Re-implanted teeth sometimes ankylose (ie: fuse to the
bone).  More frequently they suffer root resorption.  If the tooth was
re-implanted, orthodontic treatment may somewhat increase the risks of
root resorption, which usually leads ultimately to loss of the tooth.  I
would make sure the dentist who re-implanted the tooth consult with the
orthodontist before braces are placed.
    OTOH, if it was simply a repair of (for example) the corner of the
tooth, it is possible that braces could somewhat increase the chance of
failure of the filling.  But these are simple enough to repair, and I
wouldn't let that alone dissuade you from having orthodontic treatment
if needed.

Steve