A determination of the minimum radiopacification necessary for radiographic detection of an aspirated or swallowed object.

It was hoped that it might be possible to establish some standard or starting point which could be used by future investigators to judge adequate levels of radiopacity of radiopaque denture-base materials. Aluminum and copper were used to define a suitable radiopacity scale. The scale was represented by two sets of specimens--one of regular outline and uniform thickness, the other of irregular shape and tapering thickness. Radiographs of the chest and abdominal regions of a cadaver were exposed, with the specimens placed on the film side and then on the opposite side of the cadaver. The results showed that it was more difficult to locate the beveled irregular specimens, that there was little difference between the chest and the abdomen with respect to ease of locating the same objects, and that the closer an object is to the film the easier it is to locate. For 95 per cent observability, an object should have a level of radiopacity at least equal to that produced by 0.20 mm. of copper.