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An in vitro study of the influence of X-ray beam angulation on the radiographic images of the amelocemental junction and simulated alveolar crest.

The aim of this in vitro study was to determine the effect of X-ray beam angulation on the radiographic images and relative positions of the amelocemental junction and alveolar crest. Using an artificial model to represent the tooth/bone relationship, radiographs were taken of a total of 15 extracted premolar teeth which had been divided into three distinct groups on the basis of the contour (configuration) of their approximal amelocemental junction. Radiographs of the tooth/bone units were taken at baseline and with a range of horizontal and vertical X-ray beam angulations from 5 degrees to 20 degrees. Analysis of the radiographs revealed that when using the ideal horizontal angulation the radiographic image of the amelocemental junction was dependent upon its contour and was not always represented by its mid-point bucco-lingually. Changing the horizontal angulation of the X-ray beam altered substantially that part of the junction visible on the film regardless of contour. Variation in the vertical angulation of the X-ray beam had little influence on the distance between the radiographic images of the amelocemental junction and a point representative of the approximal crest of the alveolar bone. It is concluded that the contour of the approximal amelocemental junction has an influence on its radiographic appearance and that films taken with an inappropriate horizontal angulation never provide an image of its mid-point bucco-lingually.