Again, missing teeth in this region can create a positioning error. It is important to check on both sides that the position of the beam is on the same teeth. In the newer machines this problem occurs because the vertical beam of light is positioned on a tooth anterior to the position recommended by the manufacturer. To correct the problem when using older machines, the patient must be positioned further forward so the operator does not feel the skin anterior to the tragus. The further back the patient is positioned in the focal trough, the progressively wider the images of the anterior teeth will become until they are so wide that the outlines of the crowns of the teeth cannot be discerned. If the patient is positioned too far back (posteriorly), the skin anterior to the tragus can be felt immediately posterior to the head support. Missing teeth in this region may make it difficult to correctly position the patient (Figure 2). To avoid this problem with older units, one should check that the correct amount of tragus is felt bilaterally on newer machines the correct patient position is assured by the vertical indication beams positioned on anterior teeth. The appearance of periapical pathology may be similarly affected. In these cases, interproximal caries may not appear or may appear much smaller. It is important to stress that a positioning error of only 3 to 4 mm in the horizontal plane can make a dramatic difference to the width of the images. Fuzzy images of the incisor teeth will appear when the patient is seated too far forward in the focal trough. When exposing a panoramic radiograph, the patient must be positioned with the incisor teeth in the middle of the focal trough. NARROW, “FUZZY,” ANTERIOR TEETH (FIGURES 1, 2, 3, AND 6) Several panoramic radiographs shown have been cropped so that the technical errors can be visualized more clearly. If the skin anterior to the tragus can also be felt, the patient is seated too far back. If the whole of the tragus cannot be felt, the patient is seated too far forward. However, in the horizontal plane, particularly in the anterior region of the mouth, there can be magnification or demagnification, depending on the horizontal positioning of the patient.įor older machines the correct patient position in the horizontal plane is such that the whole of the tragus (the prominence anterior to the external opening of the ear) must be able to be felt immediately behind the head support. If requested, several panoramic machine companies will supply a ruler that takes this magnification into consideration. This also applies to measuring the amount of alveolar tooth support. Thus, when determining the height of the alveolar bone above the mandibular canal in the body of the mandible during the planning of implant surgery, this magnification must be included in the calculations. On a correctly taken panoramic radiograph with the patient correctly positioned, and with all the images of the anterior region clearly outlined, there is always a magnification of 15% to 20% in the vertical dimension. When taking a periapical radiograph, the size of the object and the image should ideally be the same. Whether the panoramic machine uses conventional films or is digital, the same principles apply. This will allow the clinician or technician to improve the quality of panoramic radiographs. In this article we show examples of the more common technical errors that often occur when taking panoramic radiographs and explain how these errors can be avoided and/or corrected. This will result in higher diagnostic yields that in turn will result in better patient management and treatment. The overall quality of panoramic radiographs can be greatly improved when particular attention is paid to initial patient preparation and positioning.
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