Detection of simulated internal tooth resorption using conventional radiography and subtraction imaging

OBJECTIVES: To compare the diagnostic accuracy of conventional radiography with digital subtraction imaging in the detection of simulated internal resorption. METHODS: Simulated resorption cavities were created by the sequential use of progressively larger round burs (ISO size range 006-016) in the labial wall of the coronal or apical thirds of the pulp chamber of the maxillary incisors of two cadavers. Five viewers examined 120 pairs of radiographs, one of each pair being baseline (no lesion) and the other with or without a lesion. The process was then repeated with subtraction images of the pairs of radiographs. Receiver Operating Characteristic (ROC) analysis was used to compare the diagnostic accuracy of the two imaging modalities. RESULTS: Using conventional radiography, the minimum lesion size detectable coronally was in the 'medium' range (ISO size 010 and 012 round burs), but only 'large' lesions (ISO size 014 and 016) could be detected in the apical region. The overall diagnostic accuracy of subtraction imaging was superior to conventional radiography but only significant (P<0.05) for coronal lesions. CONCLUSION: Subtraction radiography may be a useful tool for detecting and monitoring the progress of internal root resorption.