Technically you are supposed to report any change to your medical status, (any change to answers you filled out on your DODMERB questionnaire) to DoDMERB after your exam. As far as Orthodontia goes, you have to be completed with all orthodontic treatment prior to reporting for I-day, so if treatment for new invisabraces will be on going after this June, then you may have an issue. If all treatment will be done prior to I-day, then you don't have any worries. There is an orthodontia form on the DODMERB website that your orthodontist would fill out and send to DODMERB showing date treatment will end.
Your best bet is to contact DODMERB and ask them, as nobody on this forum is a DODMERB expert.