A Preliminary Study on Remaining Enamel Thickness Measurement Using Time-domain Optical Coherence Tomography

Purpose: We evaluated the ability of optical coherent tomography (OCT) to detect remaining enamel thickness (RET). Methods: The labial surfaces of extracted bovine teeth were ground with wet silicon carbide papers ranging from #240-grit to #1,200-grit to create different RETs. A time-domain (TD)-OCT imaging system was projected onto the specimen surface, and scanning was performed across the areas of interest using a probe attached to a mounting device. A depth profile of backscattering along a line perpendicular to the object surface was generated (A-scan), and the RET was obtained. Following the OCT measurement, the specimens were sectioned along the tooth axis in the vertical direction (labial-lingual), and the thicknesses of the specimens were measured using scanning laser microscopy. The data obtained from the different measurements were subsequently compared. The Bland-Altman comparison and the paired t-test were used at a significance level of 0.05. Results: The agreement among the different measurement methods was analyzed to assess inter-methodology variation, with strong and positive correlations found for each group of measurements. The results indicated that the mean difference between the OCT measurement and the direct measurement was −16.333±7.997 μm, with the 95% Bland-Altman limits of agreement ranging from −32.001 to −0.659 μm. Conclusion: While this preliminary study involved several limitations, the OCT method is a promising non-destructive method for evaluating RET under the conditions applied in this in vitro study.