[Incisor roots in the mandibular symphysis in the computed tomogram and in the lateral teleradiogram]

On the basis of lateral cephalograms and computer tomograms (CT) the position of the incisor roots and the bone structure surrounding them were studied. Nine patients each had an axial CT of the mandibular symphysis area and, in addition, 6 of these patients had lateral cephalograms. In order to compare both images, we defined a classification scheme as follows: Class 1 = the incisor roots are projected into the midst of the oral corticalis of the symphysis; class 2 = the roots are in contact with the oral corticalis; class 3 = the incisor roots are at a distance to the oral corticalis. The results from the 2 types of visualization were then compared. When looking at the bone structures surrounding the incisor roots, the lateral cephalograms failed to yield an exact differentiation. Such details can be best examined in the axial CT layers, because in the lateral cephalogram the 4 incisor roots are over projected to 1 root. The space for movement of the incisors is narrow. The root of each and every patient showed a different position in oro-buccal direction. This fact must be taken into consideration in clinical practice, especially when employing fixed appliances with 3-dimensional root control.