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

OBJECTIVES

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.

MATERIALS AND METHODS

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.

RESULTS

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.

SIGNIFICANCE

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.