Validation of Quantitative Light-Induced Fluorescence Digital Analysis for Assessing Early Dental Caries Depth: A Micro-Computed Tomography-Based In Vitro Study

<b>Background/Objectives:</b> This study aimed to evaluate the analytical validity of micro-computed tomography (µCT) and compare it with quantitative light-induced fluorescence digital (QLFD) for assessing early dental caries (EDC) lesion depth (LD). This study was conducted in a destructive <i>in vitro</i> setting. <b>Methods:</b> EDC lesions were artificially induced in 28 bovine tooth specimens for 10, 20, 30, 40, 50, 60, and 70 days, respectively. The lesions were analyzed using µCT and QLFD, with grayscale intensity thresholds set at 90% and 95%. A Pearson correlation analysis was performed to evaluate the relationship between lesion depths measured using micro-computed tomography (LD_µCT) and quantitative light-induced fluorescence digital (LD_QLFD) across different demineralization periods. Additionally, a Bland-Altman analysis was conducted to assess agreement between the two methods and identify systematic differences and potential bias. A regression analysis was further conducted with LD_QLFD as the independent variable and LD_µCT as the dependent variable. <b>Results:</b> LD_µCT was consistently lower than LD_QLFD across all demineralization periods. The Pearson correlation analysis demonstrated a strong correlation between LD_µCT and LD_QLFD (r = 0.898-0.977, <i>p</i> < 0.001). The Bland-Altman analysis demonstrated a high level of agreement, with most data points falling within the 95% limit of agreement. Furthermore, the regression analysis suggested that QLFD may serve as a reliable complementary tool for lesion depth assessment. <b>Conclusions:</b> Although µCT and QLFD operate based on different principles, the findings of this study, along with the cost-effectiveness and ease of use of QLFD, suggest that QLFD may serve as a complementary tool to µCT in experimental research.