SEM-Based Evaluation and Quantitative Validation of ICON Resin Infiltration in Sound Enamel: A Microinvasive Preventive Strategy in Orthodontics

Background: Resin infiltration has emerged as a micro-invasive strategy for managing enamel porosities, offering both therapeutic and aesthetic benefits. ICON® (DMG, Hamburg, Germany) is the most widely used system; however, evidence on its penetration behavior in sound enamel remains limited. Objectives: This in vitro study aimed to evaluate the penetration depth and morphological pattern of ICON resin infiltration in sound human enamel, using quantitative morphometric analysis and scanning electron microscopy (SEM). Methods: Fourteen freshly extracted, caries-free anterior teeth were sectioned longitudinally. ICON® resin infiltrate was applied to the buccal enamel surfaces according to the manufacturer’s protocol, while the lingual/palatal surfaces served as internal controls. Penetration depth was measured quantitatively on both mesial (surface A) and distal (surface B) halves, and SEM was used to assess resin–enamel interface morphology. Statistical analysis included the Shapiro–Wilk test, paired t-test, Pearson correlation, and percentage difference calculation. Results: The mean difference in penetration depth between surfaces A and B was −21.29 µm (p = 0.525), indicating no statistically significant variation. A strong positive correlation was observed between surfaces (r = 0.783, p = 0.001). The mean percentage difference was −3.57% (SD = 18.61%), suggesting minimal directional bias. SEM images confirmed continuous and homogeneous resin infiltration within enamel prisms. Post-hoc power analysis indicated 15.2% power, reflecting the impact of the limited sample size typical for SEM-based exploratory studies. Conclusions: Within the limitations of this in vitro investigation, ICON resin infiltration demonstrated uniform and consistent penetration in sound enamel, supported by both quantitative and SEM analyses. These findings validate its potential as a reliable preventive and micro-invasive biomaterial in dental practice, particularly for protecting enamel surfaces prior to orthodontic bracket bonding. Further clinical research with larger cohorts is recommended to confirm its long-term stability and prophylactic performance.