X-rays can give us valuable information not only before treatment starts, but also during treatment and at the end of it. Your orthodontist may ask you to have a panoramic X-ray, and possibly a cephalometric X-ray, before booking the appointment to remove your braces, in order to check that the roots of the teeth are parallel and how the front teeth are inclined in profile. These X-rays may show that some teeth are not yet in the right position and that treatment needs to continue.
This answer is for general information. Your own case needs an examination by an orthodontist.