Noninvasive cross-sectional imaging of incomplete crown fractures (cracks) using swept-source optical coherence tomography.

AIM: To investigate the ability of swept-source optical coherence tomography (SS-OCT) to detect incomplete crown fractures (cracks) in extracted teeth. METHODOLOGY: Cracks were created by subjecting 30 porcine premolars to impaction by a steel rod plunging from the occlusal tip. SS-OCT images and stereomicroscopic photographs of the surface were acquired for each specimen before and after impaction. For evaluation, the focused light beam of SS-OCT was projected from three directions on the same plane: buccal or lingual, 45° to the mesial, and 45° to the distal. Histological sections were prepared after impaction, and length and width of cracks and lamellae were evaluated using the corresponding SS-OCT image. The values were analysed using Pearson's correlation coefficient. RESULTS: Through SS-OCT, cracks and lamellae were clearly detected as intensified scattering signals at the same position on the corresponding microphotographs and histological sections. Amongst the three scanning angles, the greatest lengths and widths were considered the corresponding values of SS-OCT and were used for analysis. Significant correlations regarding line length and width were observed between SS-OCT and histological sections (length: r = 0.65, P < 0.001; width: r = 0.60, P < 0.001). CONCLUSIONS: SS-OCT can clearly discriminate cracks, which appear as highlighted lines due to the scattering of light. The results obtained from the three scanning directions were correlated well with those of the histological sections.