Optical Assessment of Bleached Enamel Surface using SS-OCT

Abstract

 Purpose: Tooth bleaching has been reported to have side effects on the morphology of enamel, such as change of enamel crystal structure and decalcification at the microscopic level. Previous studies using swept-source optical coherence tomography (SS-OCT) demonstrated that demineralized enamel resulted in an exponential decline of backscatter signal with depth due to the increased porosity of the tissue. Since the signal intensity and attenuation patterns of SS-OCT images are influenced by demineralization, attempts were made to utilize the signal intensity and attenuation coefficient as quantitative parameters for the detection of demineralization. In this study, we assessed the influence of bleaching on the enamel surface using optical parameters obtained from the SS-OCT signal.

 Methods: Ten human anterior teeth were collected and their enamel surfaces were bleached 27 times using SHOFU Hi-Lite. SS-OCT scanning was performed on bleached and non-bleached enamel surfaces. SS-OCT signal analysis was performed using Image J software. The area of interest of 1,000 nm in width and 400 nm in optical depth was then selected from the SS-OCT image for the enamel surface. The integrated value of signal intensity (AUC400) and attenuation coefficient (μ_t) were calculated and statistically analyzed at the significance level of p=0.05.

 Results: μ_t showed significant attenuation of the SS-OCT signal for the bleached enamel (mean±SD; non-bleached enamel: 0.59±0.19, bleached enamel: 0.87±0.23). From the results of AUC400, the bleached enamel also showed significantly higher scattering of the SS-OCT signal than the non-bleached enamel (mean±SD; non-bleached enamel: 96.66±9.26, bleached enamel: 102.93±7.16). However, four enamel surfaces out of the 10 samples showed no significant change of AUC400 or μ_t even after 27 times of bleaching.

 Conclusion: It is suggested that the effect of tooth bleaching on the optical properties of enamel may vary depending on the individual’s tooth characteristics and response.