The place of rotational tomography in dentistry. 2. Orthodontics

The OPG view is the radiograph that gives the most information to the orthodontist. If an OPG cannot be taken the alternative is: Two oblique laterals (Figure 11) These views must show from upper canine to lower third molar. Frequently this is not possible and additional intra-oral views have to be taken to show the upper canines. As the oblique lateral views are difficult to position, the OPG is preferred. However, it must be noted that the oblique lateral, at its best, is clearer and has a greater depth of field. Upper standard occlusal and vertex occlusal: Figures 12a and 12b show the difference in technique between the two occlusal views. As can be seen the vertex occlusal is a true view of the shape of the upper arch and the relative positions of the teeth. A cassette is required to take this view. Cephalometric lateral skull is a lateral view of the jaws and facial bones taken with the patient in a craniostat (Figure 13). Subsequent films can then be taken in the same position. A lead shield must be used down the front of the face or placed on the source of radiation so that the soft tissues can be seen.