In vivo comparison of DIAGNOdent Pen and QrayCam Pro quantitative fluorescence for occlusal caries detection and lesion depth staging in permanent posterior teeth

Background Early detection of occlusal caries in posterior teeth is essential to avoid unnecessary operative treatment and enable non-invasive management. Visual systems such as the International Caries Detection and Assessment System (ICDAS II) improve diagnostic sensitivity but remain examiner-dependent. Laser fluorescence and quantitative light-induced fluorescence (QLF) devices provide objective numeric outputs, yet their comparative performance for lesion staging in vivo is not fully established. This study compared DIAGNOdent Pen and QrayCam Pro quantitative fluorescence (ΔF_max and ΔR_max) against ICDAS II-based lesion depth categories in permanent posterior teeth. Methods In this cross-sectional study, 64 adult patients contributed 145 posterior permanent teeth (mean age 26.3 ± 5.2 years; 36 females, 28 males). Occlusal surfaces with ICDAS II codes 0–5 were included; code 6 and teeth with restorations or sealants were excluded. Two calibrated examiners recorded ICDAS II scores (inter- and intra-examiner reliability 0.96 and 0.88). DIAGNOdent Pen measurements and QrayCam Pro images were obtained at identical sites and analysed to derive maximum percentage fluorescence loss (ΔF_max) and maximum red fluorescence (ΔR_max). For analysis, ICDAS II scores were grouped as E0 (0), E1 (1), E2 (2–3) and D1 (4–5) as a surrogate for lesion depth. Descriptive statistics, Spearman rank correlations, and ROC curves (AUC, 95% CI) were used. Results Of 145 teeth, 30 were sound (ICDAS II 0), 39 had code 1, 12 code 2, 36 code 3, 23 code 4 and 5 code 5. Median DIAGNOdent values rose from 10.5 (2–16) in ICDAS II 0 to 99.0 (67–99) in ICDAS II 5. ΔF_max became more negative with severity (0.0% in ICDAS II 0 to − 65.0% in ICDAS II 5), while ΔR_max increased from 0.0 to 281.0 a.u. ICDAS II correlated very strongly with DIAGNOdent (ρ = 0.91, p < 0.001) and ΔF_max (ρ = −0.80, p < 0.001), and moderately-strongly with ΔR_max (ρ = 0.67, p < 0.001). AUCs for discriminating E0 vs (E1 + E2 + D1) were 0.94 (0.91–0.98) for DIAGNOdent, 0.97 (0.94–1.00) for ΔF_max and 0.74 (0.66–0.82) for ΔR_max. For E2 vs D1, AUCs were 0.93 (0.89–0.97), 0.85 (0.76–0.93) and 0.80 (0.71–0.90), respectively. Conclusions DIAGNOdent and QrayCam Pro metrics showed strong agreement with ICDAS II-based lesion depth. ΔF_max best discriminated sound from carious surfaces, whereas DIAGNOdent pen performed best for detecting dentin-level involvement. ΔR_max reflected lesion severity but was less accurate alone. Combining visual scoring with ΔF-based fluorescence may support minimally invasive, stage-specific management of occlusal caries.