Occlusal discoloration due to staining frequently occurs on the pits and fissures of teeth. Noncariogenic discoloration (non-CD) refers to the attachment of staining chromogens to sound surfaces, whereas cariogenic discoloration (CD) represents the discoloration of porous structures due to bacterial metabolites and mineral loss from the enamel surface. This study evaluated whether it is possible to distinguish between non-CD and CD on stained occlusal surfaces with fluorescence assessed by the quantitative light-induced fluorescence (QLF) technology. Sixty-two extracted human permanent teeth with suspected discolorations on the pit and fissure were examined. The maximum values of fluorescence loss (ΔFmax) and red fluorescence gain (ΔRmax) were calculated using QLF images. Using histology as the gold standard, it was found that 12 teeth were sound (non-CD), while 50 teeth had enamel and dentine caries (CD). The validity tests at the enamel histological caries level, ΔRmax (ρ = 0.80) were strongly correlated with the histology (P < 0.001). At the optimum threshold (105.0) of ΔRmax, it showed high levels of sensitivity and specificity (0.96 and 0.83, respectively). Therefore, QLF can be used to distinguish non-CD from CD on occlusal surfaces using red fluorescence values with high validity.
The study aimed to determine whether the red fluorescence (RF) of a dental microcosm biofilm as measured with quantitative light-induced fluorescence (QLF) technology is useful for assessing the efficacy of antimicrobials. Dental microcosm biofilms were formed on bovine enamel discs and grown under 0.3% sucrose challenge and treated with chlorhexidine (CHX) solutions at different concentrations (0.05%, 0.1%, and 0.5%) plus a negative control [sterile distilled water (DW)] twice daily for 7 days. The biofilms were photographed using a QLF-digital system to evaluate the RF by calculating the red/green ratio, and pH values of the medium were measured daily. After 7 days, the bacterial viability of the biofilm was assessed by measuring the counts of viable total bacteria and aciduric bacteria, and the percentage surface microhardness changes (%SHC) was evaluated. The RF and cariogenic properties were compared for the different concentrations of CHX, and their correlations were examined. The RF and its increase rate were much lower for CHX-treated biofilms than for DW-treated biofilms. The RF after 7 days of maturation decreased significantly with increasing CHX concentrations (p<0.001) and was from 31% (for 0.05% CHX) to 46% (for 0.5% CHX) lower than that of the DW group. Strong correlations were reported between the RF of the 7-day-maturation biofilms and cariogenic properties, such as the number of total bacteria (r=0.93), number of aciduric bacteria (r=0.97), supernatant pH (r=0.43), and %SHC (r=0.98). In conclusion, the RF of dental biofilms as measured with QLF technology can be used to nondestructively assess and monitor the effect of antimicrobials against biofilm.
Various technologies used to objectively determine enamel thickness or dentin exposure have been suggested. However, most methods have clinical limitations. This study was conducted to confirm the potential of quantitative light-induced fluorescence (QLF) using autofluorescence intensity of occlusal surfaces of worn teeth according to enamel grinding depth in vitro. Sixteen permanent premolars were used. Each tooth was gradationally ground down at the occlusal surface in the apical direction. QLF-digital and swept-source optical coherence tomography images were acquired at each grinding depth (in steps of 100 μm). All QLF images were converted to 8-bit grayscale images to calculate the fluorescence intensity. The maximum brightness (MB) values of the same sound regions in grayscale images before (MBbaseline) and phased values after (MBworn) the grinding process were calculated. Finally, 13 samples were evaluated. MBworn increased over the grinding depth range with a strong correlation (r=0.994, P<0.001). In conclusion, the fluorescence intensity of the teeth and grinding depth was strongly correlated in the QLF images. Therefore, QLF technology may be a useful noninvasive tool used to monitor the progression of tooth wear and to conveniently estimate enamel thickness.