Intermethod Association in Orthodontic White Spot Lesion Assessment: A Multimodal-Assessment

AIMS: To evaluate stage-specific intermethod association among DIAGNOdent, quantitative light-induced fluorescence (QLF), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and colourimetry in white spot lesion (WSL) assessment, and to compare alternative explanatory model structures for QLF-derived lesion volume (ΔQ). METHODS: This secondary in vitro matched-block analysis included 20 bovine incisors sectioned into four enamel surfaces (80 surfaces). Within each tooth, surfaces were allocated to one of four groups. Measurements were obtained at baseline (T0), postdemineralization (T1), day 7 (T2), and day 30 post-treatment (T3). DIAGNOdent, QLF metrics (ΔF, lesion area [LA], and ΔQ), colourimetry, and SEM-EDS values were recorded. Statistical analyses included Spearman correlation and mixed-effects models. RESULTS: At T1, intermethod association was limited, with weak associations among QLF, SEM-EDS, and DIAGNOdent. At T3, stronger associations were observed, particularly between intensity-based QLF metrics and mineral-related parameters. Ca/P showed positive associations with ΔF and ΔQ, while LA was inversely associated with Ca/P. DIAGNOdent scores were inversely associated with Ca/P and ΔF and positively associated with LA. Mixed-effects analyses identified a limited number of significant predictors of ΔQ, and the combined model demonstrated better relative in-sample fit than the clinical and compositional models at both T1 and T3. CONCLUSIONS: WSL assessment methods provided complementary rather than interchangeable information. Cross-method associations were limited after lesion induction, whereas stronger associations were observed after treatment, particularly between intensity-based QLF parameters and mineral-related measures. No single metric fully characterized WSL change, and the combined model showed modest explanatory performance. CLINICAL RELEVANCE: No single chairside measure appears sufficient for all aspects of WSL assessment. Within the limits of this in vitro study, intensity-based QLF measures were more closely aligned with mineral-related changes after treatment, whereas LA and colour-based indices provided complementary information on lesion extent and visible appearance.