I've been with my dentist for a while and in the last 10 years or so I think they've updated their X-ray machines twice. It used to be a massive machine that was in a special room, which they'd use to take multiple photos of your face by wheeling around. Then they got a smaller one that could be right next to your chair, and they'd make you bite down on some film while they moved an arm around with the source on it. Recently they have a new machine that you put your head in and it just seems to do the whole thing in one pass.
The head thing might not be doing the same x-ray as the bite thing.
I'm impressed they only got the bedside one recently. My dentist just recently upgraded to direct digital sensors for their x-rays (wires to the computer in the room instead of digital plates), but the X-ray source shows decades of battle scars.
I did ask a dentist once about why the roots of my wisdom teeth were so strangely distorted in an X-ray and they carefully explained that there was no distortion and they really were that shape...