Are you talking about the x-ray that goes around your head?
I cracked a tooth eating something and had to have a crown done (so expensive! But he has a process similar to 3d printing which was cool to see and no more impression material in the mouth and the crown was ready in about 30 minutes!). They have a digital camera now too to take the x-rays and the radiation exposure is much less then the old style. I had the panorex ( full mouth xray) transferred over from my other dentist. If you had the full mouth one and go to a different dentist within 3-5 years you can ask to get the xray transferred. It's good as a base line to see the roots and the bone level and if you have any hidden teeth in your jaw.