Abstract: A first photographic image (1) in the form of a hologram of the tooth (2) and location points (3) near the tooth taken on the occasion of the first examination is placed alongside a second photographic image (4') in the form of a hologram of the tooth (2') and location points (3') near the tooth taken on the occasion of the second examination. Adjusting devices (5, 6, 7) are provided to permit the displacement of the first photographic image (1) relative to the second photographic image (4'). This will bring the location points (3) on the first photographic image into line with the location points (3') on the second photographic image (4'), whereupon the displacement of the tooth (2) may be determined as the difference between the position of the tooth in the first photographic image (1) and the position of the tooth in the second photographic image (4').