Interrelationship between cross-sectional and sagittal imaging in computer-assisted dental implant tomography

To determine what changes may occur in computer-assisted dental tomography to cross-sectional and sagittal slices when the positions of one or both slices are adjusted.

A human skull with a ball bearing attached to the mandibular first molar was positioned off-centre in a CommCAT (Imaging Sciences International, Hatfield, PA, USA) tomographic machine. An occlusal projection of the mandibular dental arch was scanned into the computer. Correction measurements obtained from scout cross-sectional and sagittal slices were used to 'customize' cross-sectional and sagittal slices simultaneously and also individually.

The resulting changes in position and blur of the ball bearing were analysed. When simultaneously and correctly customized, the resultant slices were at the correct locations with a sharp image of the marker. When the sagittal slice only was adjusted, the blur of the marker changed, but its position remained unchanged; at the same time, the blur of the marker in the cross-sectional slice remained unchanged, but its position changed. When the cross-sectional slice only was adjusted, the blur changed, but its position remained unchanged; at the same time, the blur of the marker in the sagittal slice remained unchanged, but its position changed.

It is important for dentists evaluating tomograms for implant placement to be aware that with the CommCAT tomographic machine an interrelationship exists between cross-sectional and sagittal slices and that adjustment in one type of slice produces changes in either the blur or position of the marker in the adjusted and unadjusted slices.