Correlation of OCT, Micro-CT, and SEM in Measuring Enamel Demineralization

Objectives: This study aimed to compare the outcome measures of swept-source Optical Coherence Tomography (ss-OCT), Micro-Computed Tomography (micro-CT) and SEM for demineralized enamel of various severity.
Methods: Ten bovine incisors were covered with an acid-resistant varnish except for a 5mm-by-5mm square on the facial surface. For four weeks, the samples were subjected to daily cycles of demineralization and remineralization. After each week, the samples were imaged with ss-OCT, four consistent samples were imaged via micro-CT, and two samples were removed from the pH cycling protocol. The depth and percentage of demineralization in the intra- and interrod space were determined from the B-frames of the ss-OCT images. The depth of the lesions from the micro-CT frames were also measured, and the correlation between lesion depths in the two scanning methods was found. Two of the micro-CT samples were analyzed using Scanning Electron Microscopy (SEM) as well.
Results: After four weeks, ss-OCT scans showed an average inter-rod demineralization depth (D_Ie) of 156.42µm and an average intra-rod demineralization depth (D_Ia) of 59.22µm, while micro-CT scans showed an average lesion depth (D_mct) of 177.00µm. Linear correlation was evaluated using Microsoft Excel and the R² value between D_Ie and D_mct after the four weeks was found to be 0.2174, and 0.1136 between D_Ia and D_mct. After four weeks of pH cycling, three of the four samples exhibited significant surface cavitation. SEM images showed significant surface loss on one sample, and there was predominantly more intra-rod demineralization than inter-rod demineralization.
Conclusions: While the correlation in the depths of the lesions between ss-OCT and micro-CT was not particularly strong, both methods proved adept at showing the degree of demineralization, albeit in different portions, of the enamel.