Multimodal non-ionizing quantitative characterization of enamel hypomineralization

Enamel hypomineralization is clinically graded but difficult to quantify with visual and radiographic assessment. We evaluated whether optical coherence tomography (OCT) and lock-in thermography imaging (LITI) provide non-ionizing, quantitative lesion localization and phenotyping, using clinical mDDE classification as a practical benchmark and micro-CT ({micro}CT) mineral density as an in vitro reference in a subset. Twenty-five extracted first permanent molars were classified as control, hypomineralized (Type 1 white-cream; Type 2 yellow-brown), or other enamel defects. Co-localized OCT A-scan decay slopes and LITI lock-in phase-contrast were measured in predefined ROIs; six teeth underwent {micro}CT with hydroxyapatite calibration. Clinical scoring showed substantial agreement (inter-rater {kappa}=0.61; intra-rater {kappa}=0.70). OCT decay slopes differed across clinical groups (Kruskal-Wallis p=0.00028), separating controls from defect groups, while separation between hypomineralization and other defects was limited. LITI detected thermophotonic "hot spots" at many clinically identified sites (sensitivity 80%) but showed low specificity (20%) at a single modulation frequency, consistent with high anomaly sensitivity but limited etiologic discrimination. In the {micro}CT subset, hypomineralized ROIs showed reduced mineral density relative to adjacent enamel and spatial concordance with OCT and LITI contrast. Together, OCT+LITI support objective lesion mapping and motivate multi-frequency thermophotonics and expanded reference sampling to improve specificity for chairside translation.