Comparative Evaluation of the Artefacts Index of Dental Materials on Two-Dimensional Cone-beam Computed Tomography

The aim of the study was to propose the artefact index on cone-beam computed tomography (CBCT) images of clinical prosthodontics materials and to compare the effect of the artefacts on CBCT image clarity of normal oral tissues. Seven spheres of different materials were secured on the centre of a resin baseboard, respectively and four human molars in vitro were placed at 10 mm front, back, left and right of the sphere. The board was scanned using CBCT with the same setting. 10 tomographic images from each of the seven data sets with clear artefacts was selected. The grayscale measuring tool of Photoshop software was used to measure the grayscale (G0) within the boundary of tomographic image and the grayscales of the streaky artefacts that were 1 mm and 20 mm outside the circular boundary (G1 and G2). The arc length, L1, of the circular boundary with artefacts was measured; the circumference, L2, was calculated. The artefact index, A, was determined as (G1/G0) × 0.5 + (G2/G1) × 0.4 + (L2/L1) × 0.1. The artefact index A can comprehensively represent the effect of artefacts on CBCT image clarity for oral tissue.