In vitro longitudinal evaluation of enamel wear by cross-polarization optical coherence tomography

Enamel thickness determination by Cross-Polarization Optical Coherence Tomography (CP-OCT) is a promising approach for quantitative monitoring of tooth wear progression. This study evaluated the ability of CP-OCT to quantify the thickness of natural enamel before, during and after tooth wear simulation.

Natural, unpolished human dental enamel slabs were submitted to five wear stages (Wear 1: to level the surfaces; Wear 2 to Wear 5: 0.05±0.02mm reduction each) simulated by an automatic grinding/polishing machine. Enamel thickness was evaluated with CP-OCT and a gold-standard method (micro-CT) at baseline and after every wear stage. Data were analyzed using ANOVA with pairwise comparisons for wear stages' impact on the thickness and wear depth measurements. The inter-method agreement was analyzed using intra-class correlation coefficients, the difference between means, and Bland-Altman plots.

Enamel thickness measurements (mean±standard error, in mm) with natural (1.40±0.05) and worn surfaces (1.08±0.02) by CP-OCT did not differ significantly from those measured by micro-CT (natural=1.39±0.05; worn=1.09±0.02; p-values=0.30 and 0.39, respectively). CP-OCT and micro-CT showed excellent agreement on natural (ICC=0.98) and worn surfaces (ICC=0.98) enamel thickness measurements. Among and between wear stages, there were significant differences in enamel thickness and wear depth measurements for both methods (p-value <0.0001 for all). Both methods yielded similar measurements' mean (0.14±0.01; p-value=0.87) and were in good agreement (ICC=0.77) for wear depth estimation.

CP-OCT allows accurate measurement of enamel thickness on natural tooth surfaces. Enamel thickness measurement by CP-OCT allows quantitative monitoring of enamel thickness changes and wear depth following progressive wear.