Diagnosis of external root resorption using TACT (tuned-aperture computed tomography).

This study compared the ability of the TACT system of imaging and conventional D-speed film to detect simulated resorptive defects in cadaver teeth and jaws. Mandibular human jaw blocks were prepared and then split through the teeth in a mesial to distal direction so that the mandibular halves could be opened and reassembled when necessary. One half of each of 42 teeth was extracted, and areas on the tooth and corresponding bone identified to be studied. The jaws were opened and reassembled after no defects or after defects of different sizes (0.25, 0.5, 1.0, 2.0 mm) were placed in the tooth and the corresponding bone at predetermined evaluation areas. The teeth were imaged after each stage with conventional D-speed film using a standard paralleling technique, and with a modified orthopantomograph OP100 machine using a Schick #2 size CCD sensor as the image receptor. The source images were registered and TACT slices were generated using TACT Workbench Software. Three observers were asked to identify the presence of resorptive defects in the conventional film group and the TACT image group using specific criteria. TACT imaging was statistically superior to conventional radiographs in detecting defects that were present (Wilcoxon matched pairs signed ranks test P = 0.003). This was true for all sizes of defects examined. There was no difference between the two modalities when a defect was not present.