Microscope-Integrated Quantitative Fluorescence Imaging for Assessing Crack Severity in Teeth

Background: This study investigated the fluorescence characteristics associated with cracks and evaluated the relationship between crack depth and fluorescence-derived variables using quantitative light-induced fluorescence-digital (QLF-D) and microscope-QLF hybrid techniques.Agreement between maximum fluorescence loss (Fmax) values obtained from the two modalities was also assessed.Methods: Extracted teeth with confirmed cracks were examined using QLF-D and a microscope-QLF hybrid technique integrating a fluorescence light source with an operating microscope.Fluorescence-derived variables, including Fmax and red fluorescence (R) and maximum red fluorescece (Rmax) variables, were quantified using dedicated analysis software.The crack depth was measured using micro-computed tomography as the reference standard.Associations between the crack depth and fluorescence-derived variables were analyzed using Spearman's rank correlation analysis.Agreement between Fmax values obtained from the two imaging modalities was evaluated using Bland-Altman analysis.Results: Cracks displayed characteristic fluorescence loss and red fluorescence patterns in both imaging modalities.Among the fluorescence-derived variables, Fmax demonstrated the strongest correlation with crack depth for both the QLF-D and the microscope-QLF hybrid techniques (p0.01).The corresponding Fmax values obtained from the two modalities were strongly correlated.Bland-Altman analysis indicated a small systematic bias, with the microscope-QLF hybrid technique slightly overestimating Fmax; however, all measurements remained within the 95% limits of agreement.Conclusion: The microscope-QLF hybrid technique showed a measurable and consistent relationship with QLF-D for quantitative fluorescence assessment.Although systematic differences were observed, the hybrid technique may serve as a supportive tool for assessing relative crack severity during endodontic procedures.