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.