Two methods are frequently used to obtain three dimensional information
- Examine two films projected at right angles to each other. Mostly used in mandible. In maxillary projection superimposition occurs.
- Employ tube shift technique/buccal object rule/clark’s rule
The buccal-object rule relates to the manner in which the relative position of radiographic images of two separate objects changes when the projection angle at which the images were made is changed. The principle states that the object closest to the buccal surface appears to move in the direction opposite the movement of the cone or tube head, when compared with a second film. Objects closest to the lingual surface appear to move (on a film) in the same direction that the cone moved.