Three-dimensional visualization of composite fillings for dental identification using CT images.

OBJECTIVES: This study aimed to discriminate between enamel and composite resins by differences in Hounsfield units shown on 16 section multidetector CT (MDCT) images taken of unidentified bodies. METHODS: First, we determined the Hounsfield units of composite resins in 15 extracted human teeth. We then filled a single cavity prepared in each of the teeth with one of five different types of composite resins, and scanned the teeth using our routine post-mortem CT protocol for the head and neck. Obtained data were transferred to a radiological workstation and reconstructed. Furthermore, post-mortem CT images of the head of three unidentified bodies were reconstructed in the same manner. RESULTS: Four types of composite resins containing radio-opaque fillers showed a constant value of 4000 HU, and one radiolucent composite resin showed values in the range of 660-800 HU in the extracted teeth. Pixels at 4000 HU indicated that the composite resins were selected and visualized as three-dimensional colour images. Composite resins could be visualized on reconstructed images of the three unidentified bodies, and the sites visualized matched those noted on the forensic dental charts. CONCLUSIONS: Discriminating enamel and composite resins containing radio-opaque materials was difficult because of their similar Hounsfield unit values. However, we did succeed in visualizing the composite resins despite limitations of the CT scale. CT reconstructed images can contribute to dental identification, particularly in cases where it is difficult to detect composite resins on external investigation, and these images can be prepared during routine dental identification work.