Bone height measurements on panoramic radiographs - The effect of shape and position of edentulous mandibles

Objective. The aim of this study was to quantify the effect of mandibular angulation, position, and shape of an edentulous mandible on the distortion of its image in panoramic radiographs.Study design. Five edentulous dry mandibles varying in size from small to wide and equipped with metal bars in and on top of the mandible were used. The mandibles were radiographed at nine different positions by tilting the mandible posteriorly around a transversal axis, using an orthopantomograph.Results. The length of the images of the bars on top of the mandible increased significantly by tilting the mandibles from +20 degrees to -20 degrees. The magnification factor of the images of the intrabony bars in the mandible was the largest at 0 degrees and decreased significantly by both decreasing or increasing the inclination. The size of the mandible was not related to the magnification factor.Conclusion. For both diagnostic and evaluation purposes of the edentulous mandible, the panoramic radiograph is not a reliable radiographic technique unless meticulous precautions are taken for reproducible positioning of the patient in the apparatus.