The appropriate code for taking two bitewing images on a panoramic machine, where the image is split down the middle to create bitewing images, is D0251.
Code D0251: This code is specifically for intraoral posterior dental radiographic images captured using extraoral imaging, such as a panoramic machine.
Code D0272: This code is for bitewings, specifically two radiographic images captured intraorally using traditional intraoral techniques.
Since the images were taken using a panoramic machine, which is an extraoral imaging technique, D0251 is the appropriate code.