we know these are not "drywall" screws due to the shape of the screw head and the pitch of the threads. they may be wood screws which would have the more conical head and steep threading. now, why would we be seeing wood screws?
well, this is just an image i found on reddit with no context so everything's speculation; its possible this was a dummy whose max/mand had been screwed to the dummy using these screws, and the technician was practicing the xray. its possible this was a practice placement in a replica model.
its not super likely that there was a patient with wood screws holding his bridge in place, though that might be why they came to the dentist in the first place.