Radiomics on 2D Profilometry Images to Evaluate Dental Enamel Modified by Nd:YAG Laser Irradiation and Acidulated Phosphate Fluoride (APF)

Nd:YAG laser irradiation can alter dental enamel's surface morphology, where the number of consecutive irradiations is an importante variable to be considered. This study used radiomics on 2D profilometry images to quantitatively evaluate topographical changes in human enamel irradiated with varying numbers of Nd:YAG laser irradiations, with or without subsequent Acidulated Phosphate Fluoride (APF) gel application.

A total of 148 2D profilometer images (from 150 enamel specimens, 15 images/group, except for group CN: 13 images) were analyzed across 10 groups: negative control (CN), positive control with APF (CF), and Nd:YAG laser (1064nm, 65mJ/pulse, 10Hz, 100μs, 400μm fiber diameter, 51.7J/cm²) applied as one to four consecutive motorized scans over a coal photoabsorber, without (L1 to L4) or with subsequent APF (L1F to L4F). Radiomic features were extracted using PyRadiomics to capture textural patterns. After removing highly correlated variables, features were submitted to Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). The first components and top features were analyzed using Kruskall-Wallis and Mann-Whitney tests with Holm correction (p<0.05).

PCA explained 68.8% of the variance, with PC1 opposing uniformity to disorder and localized abrupt transitions. LDA separated all irradiated groups from controls (p<0.001). Topographical responses to APF were strictly dependent on the number of prior laser irradiations. Specifically, after three irradiations, APF (L3F) acted as a surface homogenizer, significantly decreasing median JointEntropy (5.75 to 5.35) and Contrast (0.031 to 0.023) compared to L3 (p<0.01). On the other hand, following four irradiations, APF (L4F) significantly exacerbated topographical chaos, increasing JointEntropy (5.11 to 5.71) and Contrast (0.018 to 0.031) compared to L4 (p<0.001).

The topographical impact of APF was substrate dependent: it statistically homogenized surfaces treated with three irradiations, but increased structural disorder after four irradiations. 2D radiomics effectively quantified morphological alterations induced by the Nd:YAG laser and APF.