The paralleling technique is the most accurate intraoral radiographic technique, meeting four of the five shadow-casting principles. The paralleling technique does not allow for a short as possible object-to-receptor distance (Principle Three). This technique produces truer images that are preferred for diagnostic quality. Due to the use of film-holding devices, the paralleling technique is also easy to standardize and execute.
The paralleling technique is accomplished by placing the receptor parallel to the long axis of the tooth. After this parallel relationship has been established, the central ray must be directed perpendicular to both the tooth and receptor. Because the receptor cannot always be placed as close as possible to the tooth due to the film-holding device, image magnification may occur. However, this can be compensated for by using an increased source-object distance, which decreases magnification and unsharpness. The paralleling technique, when performed correctly, is superior to the bisecting angle technique by producing an image with both linear and dimensional accuracy.