The validity of superimposing oblique cephalometric radiographs to assess tooth movement: an implant study

Assessment of the exact position of the posterior teeth on lateral headfilms is of limited validity because of the superimposition of the 2 sides. Lateral headfilms are also of limited use for evaluating orthodontic tooth movement, especially in cases of asymmetric mechanics. To solve this problem, the oblique cephalometric radiograph, which brings only 1 side of the image into focus, was introduced. We evaluated whether the projection of the cranial base could be used for evaluating facial growth and whether structures that were stable relative to the implants could be identified and thus replace the implants in future evaluations. Thirty sets of headfilms from growing patients with metallic implants were analyzed. Three types of superimpositions were performed. Displacement of the metallic implants in the maxillary complex and the mandible with respect to the superimposed structures of the cranial base was evaluated. When the development of the lateral parts of the facial skeleton was evaluated in relation to the cranial base, the reproducibility of the superimpositioning was significantly better in the vertical-S(e) = 0.41-than in the horizontal plane of space-S(e) = 1.35). The error of the method when superimposed on the stable structures in the maxillary complex varied between 0.31 and 0.72 and did not differ in the vertical and sagittal directions. In the mandible, the stable structures suggested for superimposition of the lateral headfilms were applicable on the oblique cephalometric radiograph-S(e) = 0.33-0.57. Oblique projection is recommended when individual analysis of the 2 sides is needed.