Quantitative in vivo monitoring of early erosion-associated enamel optical changes using swept-source optical coherence tomography (SS-OCT)

To evaluate the capability of swept-source optical coherence tomography (SS-OCT) to detect early erosion-associated enamel optical changes in vivo following repeated erosive challenges under standardized intraoral conditions and to assess the influence of salivary stimulation through chewing gum. Twenty-two healthy adults participated in a two-phase longitudinal study involving repeated orange juice erosive challenges over three consecutive days. Participants underwent both phases sequentially using a fixed-order design. In Phase A, no post-exposure chewing gum stimulation was performed, whereas in Phase B, chewing gum stimulation was introduced following each erosive challenge. SS-OCT imaging was performed at six daily time points (t1–t6). Integrated reflectivity (IR), derived from A-scan analysis, was used to quantify changes in enamel backscattering. Statistical analyses included paired t-tests and linear mixed-effects modelling (α = 0.05). Paired comparisons demonstrated a significant increase in IR on Day 3 of Phase B ( p = 0.012), whereas no significant differences were observed for other individual comparisons. However, longitudinal mixed-effects modelling incorporating all repeated measurements demonstrated significantly higher IR values on Day 2 (β = 4.52 × 10 9 , p = 0.006) and Day 3 (β = 5.83 × 10 9 , p < 0.001) compared with Day 1. No significant overall phase effect was identified; however, because Phase A always preceded Phase B, phase-related findings cannot be separated from potential order or carryover effects. SS-OCT detected progressive changes in enamel integrated reflectivity following repeated erosive challenges in vivo. Although direct paired comparisons demonstrated limited statistical significance, longitudinal analysis identified progressive enamel optical alterations over time. These findings support the potential utility of SS-OCT as a non-invasive tool for monitoring early erosion-associated enamel changes. Further studies incorporating direct mineral validation, repeatability assessment, and longer-term clinical evaluation are warranted to establish its clinical applicability. ClinicalTrials.gov, NCT07690644, 1 July 2026 (first submitted). Retrospectively registered.