The invention relates to an orthodontic diagnostic method wherein at least one initial two-dimensional X-ray image (1) of a first zone (2) of a head (3) is taken. Then at least one three-dimensional X-ray image (4) of a second zone (5) of a dental situation is taken, and the three-dimensional X-ray image (4) is combined with the initial two-dimensional X-ray image (1) using a registration process in order to obtain a full image (8).