Method: Ninety extracted human teeth with NCCL were used. Cross-sectional images of NCCL were obtained by SS-OCT to measure the depth (D: μm) and axial length (L: μm) of NCCL using image software (Image J). The morphology of NCCL was characterized by D✕L size parameter. Cervical crack along DEJ and the remaining enamel thickness (RET) under the occlusal or incisal attrition surface were also evaluated using SS-OCT. The teeth were then sectioned and directly observed using confocal laser microscope to confirm the presence of cracks. Relationships between D✕L, crack, and RET were evaluated by Pearson’s correlation at significance level of α = 0.05.
Result: Cross-sectional views of NCCLs were readily obtained by SS-OCT for morphological assessment in real time. In the grayscale SS-OCT images, cracks were detected as highlighted bright lines, since the signal intensity increased at the crack borders. Significant correlations were detected between crack length and RET; with attrition resulting in small RET, more extensive cervical cracks were found. There were no statistical correlation between crack length and D✕L, and D✕L and RET; however when D✕L was limited up to 0.4 mm², statistical correlation was found with RET; larger NCCLs were found in tooth with small RET.
Conclusion: SS-OCT showed the potential to obtain the cross-sectional images for studying the structural morphology of NCCL and enamel crack noninvasively. The results of the current study showed the possible association of enamel attrition and NCCL formation.