Eun-Song Lee

Association between the cariogenicity of a dental microcosm biofilm and its red fluorescence detected by Quantitative Light-induced Fluorescence-Digital (QLF-D)

OBJECTIVE This study evaluated whether Quantitative Light-induced Fluorescence-Digital (QLF-D) can detect the levels of cariogenicity of dental microcosm biofilms by assessing the red fluorescence intensity. METHODS Dental microcosm biofilms were initiated from human saliva on bovine enamel discs. Biofilms with various levels of cariogenicity were then grown in artificial saliva supplemented with sucrose at different concentrations (0.05%, 0.1%, 0.2%, and 0.5%) in 24-well microplates. After 10 days, fluorescence images of the biofilms were captured by the QLF-D to analyse the red fluorescence intensity, which was quantified as the red/green ratio (R/G value). The supernatant pH was also measured, as well as the total and aciduric bacteria counts of the collected biofilms. Mineral loss in enamel was also evaluated by calculating the percentage of surface microhardness changes (%SHC). RESULTS The R/G values of the biofilms differed significantly with the sucrose concentration (p<0.0001), increasing consistently as the sucrose concentration increased from 0.05% (=0.91) to 0.5% (=2.56). Strong correlation was identified between the R/G value and the number of aciduric bacteria (r=0.83, p<0.0001), supernatant pH (r=-0.95, p<0.0001), and %SHC (r=0.90, p<0.0001). CONCLUSIONS The red fluorescence as observed by the QLF-D was correlated with the cariogenic properties of dental microcosm biofilms in vitro, which indicates that this device can be used to detect the levels of cariogenicity of a dental biofilm. CLINICAL SIGNIFICANCE The QLF-D is able to assess the cariogenic levels of dental plaque based on the intensity of red fluorescence.

Monitoring the maturation process of a dental microcosm biofilm using the Quantitative Light-induced Fluorescence-Digital (QLF-D)

OBJECTIVE The aim of this study was to investigate whether Quantitative Light-induced Fluorescence-Digital (QLF-D) could monitor the degree of maturation of dental microcosm biofilms by observing the red fluorescence emitted from the biofilms. METHODS Dental microcosm the biofilms were grown on bovine enamel discs. They were initiated from human saliva, and then grown in 0.5% sucrose growth media for 10 days. On days 1, 2, 3, 7, and 10 after the inoculation, fluorescence images of the biofilms were captured using the QLF-D and the red fluorescence intensity was quantified by calculating the red/green ratio (R/G value). Total and aciduric bacteria within the biofilms were counted, and the degree of demineralization was evaluated by measuring the percentage of surface microhardness change (ΔVHN) and lesion depth in the enamel. RESULTS The R/G values of the biofilms assessed by the QLF-D increased significantly over time up to 7 days after inoculation (p<0.0001). The R/G values showed significant positive correlations with the total bacterial CFUs (r=0.74, p=0.001), aciduric bacterial CFUs (r=0.85, p=0.001), ΔVHN (r=0.65, p=0.001), and lesion depth in the enamel (r=0.82, p=0.001) according to the maturation time. CONCLUSIONS The red fluorescence detected by the QLF-D increased according to biofilm maturation and was significantly associated with the cariogenicity of the biofilm. Therefore, this device could be used to monitor the degree of biofilm maturation by observing the red fluorescence emitted from cariogenic biofilms. CLINICAL SIGNIFICANCE The QLF-D enables the detection of a mature dental plaque and monitoring of its cariogenic status by observing the plaque fluorescence non-destructively, in real time.

La2O3 interface modification of mesoporous TiO2 nanostructures enabling highly efficient perovskite solar cells

Perovskite solar cell performance is critically dependent on the characteristics of the electron transporting layer (ETL) and its interface. This work demonstrates the importance of interface modification in which the charge transport kinetics is improved through band gap engineering of the interfaces in perovskite solar cells with La2O3. The surface of a mesoporous TiO2 ETL (mp-TiO2) on CH3NH3PbI3-based solar cells is modified using a simple dip-coating method involving a lanthanum salt solution. The layer thickness of La2O3 was optimized, and its effects on the conduction band position, interfacial charge recombination, and photovoltaic performance were investigated. Modifying the mp-TiO2 ETL with La2O3 resulted in a nearly 46% enhancement of the power conversion efficiency because of the energetically favourable band gap engineering, which allowed the fast transfer of photo-generated electrons from the perovskite absorber layer to the ETL. Our simple interfacial control approach uses a new efficient interface-modifying material, demonstrating that interface engineering could be a key strategy for improving the performance of perovskite solar cells.

Comparison of various subjective video quality assessment methods

In this paper, we present comparison of three subjective testing methods: the double stimulus continuous quality scale (DSCQS) method, the single stimulus continuous quality evaluation (SSCQE) method and the absolute category rating (ACR) method. The DSCQS method was used for validate objective models in the VQEG Phase II FRTV test. The SSCQE method is chosen to be used in the VQEG RRTV test. The ACR method is chosen to be used in the VQEG Multimedia test. Since a different subjective test method is used in each test, analyses of the three methods will provide helpful information in understanding human perception of video quality.

A new class of chiral semiconductors: chiral-organic-molecule-incorporating organic–inorganic hybrid perovskites

An organic–inorganic hybrid perovskite incorporating chiral organic molecules is demonstrated as a new class of chiral semiconductors. Chiral perovskites exhibit oppositely-signed circular dichroism (CD) according to the S- and R-configurations of chiral organics. The CD signals can be also varied by changing the crystalline orientation and thickness of the chiral perovskite films.

Ecological changes in oral microcosm biofilm during maturation.

Abstract. The aim of this study was to evaluate the ecological changes in the biofilm at different stages of maturation using 16S rDNA gene amplicon sequencing and to identify correlations between red/green (R/G) fluorescence ratio and ecological changes. An oral microcosm biofilm was initiated from the saliva of a single donor and grown anaerobically for up to 10 days in basal medium mucin. Quantitative light-induced fluorescence analysis was shown that the R/G ratio of the biofilm increased consistently, but the slope rapidly decreased after six days. The bacterial compositions of 10 species also consistently changed over time. However, there was no significant correlation between each bacteria and red fluorescence. The monitoring of the maturation process of oral microcosm biofilm over 10 days revealed that the R/G ratio and the bacterial composition within biofilm consistently changed. Therefore, the R/G fluorescence ratio of biofilm may be related with its ecological change rather than specific bacteria.

Clinical assessment of oral malodor using autofluorescence of tongue coating

OBJECTIVES The aim of this study was to evaluate whether a new method using quantitative light-induced fluorescence-digital (QLF-D) was appropriate for the diagnosis of oral malodor by quantifying the fluorescence of tongue coating. METHODS This study examined 103 healthy subjects who have an oral malodor as a main complaint. The levels of oral malodor were measured by organoleptic scores (OLS) and volatile sulfur compound (VSC) levels. The fluorescent tongue coating images captured by QLF-D were quantified as the integrated fluorescence score (IF score) by multiplying the intensity and area of fluorescence. The correlations between the fluorescence parameters and OLS as well as VSC levels and the diagnostic accuracy of the IF score were evaluated. RESULTS The IF score of tongue coating showed a significant positive correlation with the OLS (r=0.54, p<0.01) and the VSC levels (r=0.49, p<0.01). This score was significantly differed with the level of oral malodor (p<0.001), and its AUC was 0.72 in identifying the patient with definite oral malodor (≥OLS 2). CONCLUSIONS A new method quantifying tongue coating fluorescence detected by QLF-D can be used to diagnose oral malodor and assess its severity in the clinical practice.

A new screening method to detect proximal dental caries using fluorescence imaging

OBJECTIVES This study aimed to assess the screening performance of the quantitative light-induced fluorescence (QLF) technology to detect proximal caries using both fluorescence loss and red fluorescence in a clinical situation. Moreover, a new simplified QLF score for the proximal caries (QS-Proximal) is proposed and its validity for detecting proximal caries was evaluated as well. METHODS This clinical study included 280 proximal surfaces, which were assessed by visual-tactile and radiographic examinations and scored by each scoring system according to lesion severity. The occlusal QLF images were analysed in two different ways: (1) a quantitative analysis producing fluorescence loss (ΔF) and red fluorescence (ΔR) parameters; and (2) a new QLF scoring index. For both quantitative parameters and QS-Proximal, the sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) were calculated as a function of the radiographic scoring index at the enamel and dentine caries levels. RESULTS Both ΔF and ΔR showed excellent AUROC values at the dentine caries level (ΔF=0.860, ΔR=0.902) whereas a relatively lower value was observed at the enamel caries level (ΔF=0.655, ΔR=0.686). The QS-Proximal also showed excellent AUROC ranged from 0.826 to 0.864 for detecting proximal caries at the dentine level. CONCLUSION The QS-Proximal, which represents fluorescence changes, showed excellent performance in detecting proximal caries using the radiographic score as the gold standard.

Bactericidal effect of the photocatalystic reaction of titanium dioxide using visible wavelengths on Streptococcus mutans biofilm

BACKGROUND The aim of this study was to determine the effect of titanium dioxide (TiO2) photocatalysis induced by the application of clinically acceptable visible light at 405nm on the growth of Streptococcus mutans biofilms. METHODS S. mutans biofilms were grown on a hydroxyapatite (HA) disk and deposited in a rutile-type TiO2 solution at a concentration of 0.1mg/mL. TiO2 photocatalysis was measured for exposure to visible light (405nm) and ultraviolet (UV) light (254nm) produced by light-emitting diodes for 10, 20, 30, and 40min. After two treatments, the number of colonies formed in the final S. mutans biofilm on the HA disk were measured to confirm their viability, and the morphological changes of S. mutans were evaluated using scanning electronic microscopy. RESULTS The bactericidal effects of 254- and 405-nm light resulted in > 5-log and 4-log reductions, respectively (p<0.05), after 20min of treatment and a>7-log reduction after 40min of treatment in both treatment groups relative to the control group. CONCLUSION It was confirmed that the antibacterial effect could be shown by causing the photocatalytic reaction of TiO2 in S. mutans biofilm even at the wavelength of visible light (405nm) as at the wavelength of ultraviolet light (254nm).

Plaque autofluorescence as potential diagnostic targets for oral malodor

Abstract. The aim of this study was to determine whether the degree of tongue and interdental plaque can be used to assess oral malodor by quantifying their fluorescence as detected using quantitative light-induced fluorescence (QLF) technology. Ninety-nine subjects who complained of oral malodor were included. The level of oral malodor was quantified using the organoleptic score (OLS) and the concentration of volatile sulfur compounds (VSCs). The fluorescence properties of tongue and interdental plaque were quantified as scores calculated by multiplying the intensity and area of fluorescence in QLF-digital images, and the combined plaque fluorescence (CPF) score was obtained by summing the scores for the two regions. The associations of the scores with malodor levels and the diagnostic accuracy of the CPF score were analyzed. The two plaque fluorescence scores and their combined score differed significantly with the level of oral malodor (p<0.001). The CPF score was moderately correlated with OLS (r=0.64) and VSC levels (r=0.54), and its area under the receiver operating characteristic curve was 0.77 for identifying subjects with definite oral malodor (OLS≥2). In conclusion, plaque fluorescence from tongue and interdental sites as detected using QLF technology can be used to assess the level of oral malodor.