Micro-CT and OCT-Based Analysis of Demineralization Depths of Artificial Enamel Caries

Objectives: The aim of the study was to assess demineralization depth formed by a chemical pH-cycling model as measured with micro-computed tomography (Micro-CT) against demineralization depth measured by optical coherence tomography (OCT).
Methods: Nine bovine incisors were used and a 6.5×6.5 mm² area of enamel was subjected to demineralization using a pH-cycling model, with 6 and 16-hours of daily de- and remineralization respectively. After 4 weeks, the demineralized surface was assessed using Micro-CT and OCT. Four corresponding MCT and OCT scans were extracted from each sample. They were further divided into Surface intact (SI) and Surface loss (SL) groups. Using a bespoke Matlab script, demineralization depth from Micro-CT scans (D_m) and from OCT (D_o) [HPC1] were computed for both groups. Additionally, linear surface loss from Micro-CT scans (D_sl) and percentage of demineralization area of from OCT scans (A_o) were computed for the SL group. In both groups, one-sample T-test were used to compare D_o-D_m. Additionally, Pearsons correlation were used to explore correlations between D_o-D_m (in both groups), D_o-D_sl and A_o-D_sl.
Results: In the SI group, D_o and D_m were significantly different, with D_o being deeper than D_m by 0.032 ± 0.0021 mm. In the SL group, D_o and D_m were not significantly different. Bland-Altman plot showed more than half of the differences lies within the upper and lower CI. Pearsons correlation showed significant (P<0.001) linear correlations between D_o-D_m in the SI group and A_o-D_sl with the R² value of 0.684 and 0.507 respectively.
Conclusions: Although demineralization depths measured by Micro-CT and OCT for lesions with intact surface were significantly different, there were good linear correlation between them. In lesions with surface loss, they are not significantly different. These finding enables the projection and comparison of OCT results especially in clinical setting with Micro-CT data.