Optical Coherence Tomography for Dynamic Monitoring of Resin Infiltration Kinetics: An Exploratory Ex Vivo Study.

OBJECTIVE: This study aimed to investigate the relationships between etching and infiltration durations and their corresponding depths using optical coherence tomography (OCT), develop preliminary time-depth predictive models, and evaluate the ex vivo performance of OCT-optimized individualized resin infiltration (OCT-IRI) for enamel specimens with varying depths of demineralization. METHODS: Enamel specimens were subjected to acid etching and resin infiltration for varying durations, and OCT-derived mean gray value (MGV) changes were used to construct time-depth curves. Natural enamel specimens exhibiting non-cavitated subsurface alterations (lesions < 300 μm) and artificially demineralized teeth (lesions ≥ 300 μm) were divided into four subgroups: Untreated Control (UC), Fluoride Varnish (Duraphat), Conventional Resin Infiltration (CRI), and OCT-IRI. Following an acid challenge, resistance to secondary demineralization was evaluated. RESULTS: Both etching and infiltration depths increased nonlinearly with treatment duration, gradually approaching a plateau. For lesions < 300 μm, OCT-IRI showed significantly lower secondary demineralization than CRI and Fluoride Varnish (P < 0.05). For lesions ≥ 300 μm, CRI and OCT-IRI showed similar ex vivo performance (P > 0.05), with both performing better than Fluoride Varnish (P < 0.05), which showed no significant difference compared with the control (P > 0.05). CONCLUSION: Under these ex vivo conditions, OCT provided a non-invasive, depth-resolved quantitative assessment of enamel alterations and monitored kinetic changes over time. The observed time-depth relationships may provide preliminary reference data for future studies investigating etching and resin infiltration durations in enamel lesions of varying depths. CLINICAL SIGNIFICANCE: These preliminary findings suggest that OCT-IRI may have potential for non-invasive assessment and longitudinal monitoring of subsurface enamel changes following RI. The observed time-depth relationships provide preliminary insights toward the future development of individualized treatment protocols. However, given the exploratory ex vivo design and small sample size of this study, further in vivo and clinical studies are strictly warranted to confirm the potential clinical applicability of OCT-IRI.