Читать книгу Orthodontic Treatment of Impacted Teeth - Adrian Becker - Страница 74

Radiographic views may be taken at right angles to one another in various ways but, for the method to be of value, it must be possible to determine the exact orientation in space of both the receptor and the central ray [1, 2]. The observer must be in a position to deduce these from observation of other structures on the radiograph whose locations are known. Thus, if one begins with a periapical view, it becomes necessary to provide another view that is at 90° to it, in order to satisfy the minimum geometric conditions. However, having done this, it must be possible to mentally reconstruct the exact orientation of this second view at a later date, by looking at the radiograph alone and without necessarily having prior knowledge of exactly how the tube and receptor were placed. This is obviously very confusing and completely impractical.