Si-Mook Kang

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.

Validation of quantitative light-induced fluorescence-digital (QLF-D) for the detection of approximal caries in vitro

OBJECTIVES Detection of approximal caries lesions can be difficult due to their anatomical position. This study aimed to assess the ability of the quantitative light-induced fluorescence-digital (QLF-D) in detecting approximal caries, and to compare the performance with those of the International Caries Detection and Assessment System II (ICDAS II) and digital radiography (DR). METHODS Extracted permanent teeth (n=100) were selected and mounted in pairs. The simulation pairs were assessed by one calibrated dentist using each detection method. After all the examinations, the teeth (n=95) were sectioned and examined histologically as gold standard. The modalities were compared in terms of sensitivity, specificity, areas under receiver operating characteristic curves (AUROC) for enamel (D1) and dentine (D3) levels. The intra-examiner reliability was assessed for all modalities. RESULTS At D1 threshold, the ICDAS II presented the highest sensitivity (0.80) while the DR showed the highest specificity (0.89); however, the methods with the greatest AUC values at D1 threshold were DR and QLF-D (0.80 and 0.80 respectively). At D3 threshold, the methods with the highest sensitivity were ICDAS II and QLF-D (0.64 and 0.64 respectively) while the method with the lowest sensitivity was DR (0.50). However, with regard to the AUC values at D3 threshold, the QLF-D presented the highest value (0.76). All modalities showed to have excellent intra-examiner reliability. CONCLUSIONS The newly developed QLF-D was not only able to detect proximal caries, but also showed to have comparable performance to the visual inspection and radiography in detecting proximal caries. CLINICAL SIGNIFICANCE QLF-D has the potential to be a useful detection method for proximal caries.

Objective and subjective assessment of masticatory function for patients with temporomandibular disorder in Korea.

This study examined the differences in the masticatory function of patients with temporomandibular disorder (TMD) in Korea. The experimental groups were as follows: 23 patients with painful arthralgia classified as pain group according to the research diagnostic criteria for temporomandibular disorder (RDC/TMC) and 28 patients with pain-free disc displacement and reduction classified as clicking group. The subjects were obtained from those who had visited Yonsei University Dental Hospital from 2007 to 2008. Twenty dental students without TMD symptoms were enroled as the normal control group. The Mixing Ability Index (MAI) was used as the objective index, and the Food Intake Ability (FIA) Index, Visual Analogue Scale (VAS) and oral health impact profile (OHIP) were used as the subjective indices. The MAI, FIA and VAS were significantly lower in the pain group than in the normal and clicking groups (P<0·05). The pain group showed a MAI, FIA and VAS of 16%, 81% and 67%, respectively, compared to that of the normal group. However, there were no significant differences in the MAI, FIA and VAS between the clicking and normal groups. The pain and clicking groups showed a 1·7 and 1·4 times higher OHIP value than the normal group (P<0·05). The MAI and subjective indices, such as the FIA (r=0·40) and VAS (r=0·48), showed a moderate correlation (P<0·01). In conclusion, pain is the main factor for the reduced masticatory function in patients with TMD in Korea, and the joint sound, not the masticatory function, affects the declining OHIP.

Subjective food intake ability in relation to the Mixing Ability Index in Korean adults

This study examined the association between the subjective food intake ability (FIA) using a questionnaire with 30 types of foods and the objective Mixing Ability Index (MAI) using a two-coloured wax cube. A total of 147 subjects (32 males, 115 females, mean age: 54.9 +/- 20.7) were enrolled in this study. The FIA for 30 food types and the key food intake ability (KFIA) for five key food types were obtained using a self-assessed questionnaire to evaluate the subjective chewing ability. The objective chewing ability was evaluated by asking the subjects to chew a wax cube for 10 strokes. The MAI was calculated by image analysis of the chewed wax cube. The Pearsons correlation between the subjective FIA and objective MAI was analysed according to age and number of post-canine teeth lost. The FIA for the 30 foods and five key food types showed a moderate correlation with the MAI (r = 0.51, 0.55, respectively, P < 0.01). The KFIA of the denture wearing group (r = 0.44, P < 0.01) and over 60-year-old group (r = 0.49, P < 0.01) showed a significantly higher correlation with the MAI than the other groups. In conclusion, there was a moderate correlation between the subjective FIA and objective MAI in Korean adults.

Validity of Screening Methods for Periodontitis Using Salivary Hemoglobin Level and Self-Report Questionnaires in People with Disabilities

BACKGROUND The aim of this study is to evaluate the validity of screening methods in predicting periodontitis in people with disabilities using the objective salivary hemoglobin level, a subjective self-report questionnaire, and a combined model of the two methods with demographic characteristics. METHODS The participants were 195 patients with disabilities aged >18 years who were examined using the community periodontal index (CPI), salivary hemoglobin level, and answers to 10 self-report questions (n = 192). Multivariable logistic regression and receiver operating characteristic (ROC) curve analysis were performed to evaluate the validity of the methods and the combined model in predicting the prevalence of ≥CPI 3 (probing depth [PD] ≥4 mm) or CPI 4 (PD ≥6 mm). RESULTS Overall, 75.9% of the study group (148 of 195) were diagnosed with ≥CPI 3, and 38.5% of the study group (75 of 195) were diagnosed with CPI 4. The areas under the ROC curve (AUCs) of the salivary hemoglobin level were 0.578 (sensitivity of 41% and specificity of 77%) and 0.662 (sensitivity of 53% and specificity of 75%) for predicting the prevalence of ≥CPI 3 and CPI 4, respectively. Multivariable modeling incorporating four different questions for predicting ≥CPI 3 or CPI 4 indicated higher AUCs of 0.710 and 0.732, respectively, yielding higher sensitivity (55% for ≥CPI 3 and 69% for CPI 4) than that of salivary hemoglobin level. The most useful prediction models for ≥CPI 3 or CPI 4 were combined models, which yielded AUCs of 0.773 and 0.807, respectively, with sensitivity values of 70% and specificity values >75%. CONCLUSION The salivary hemoglobin level, self-report questionnaire, and the combined method demonstrated screening potential that could predict the population prevalence of ≥CPI 3 or CPI 4.

Differences in the intensity of light-induced fluorescence emitted by resin composites

BACKGROUND The aims of this study were to compare the intensities of fluorescence emitted by different resin composites as detected using quantitative light-induced fluorescence (QLF) technology, and to compare the fluorescence intensity contrast with the color contrast between a restored composite and the adjacent region of the tooth. METHODS Six brands of light-cured resin composites (shade A2) were investigated. The composites were used to prepare composite discs, and fill holes that had been prepared in extracted human teeth. White-light and fluorescence images of all specimens were obtained using a fluorescence camera based on QLF technology (QLF-D) and converted into 8-bit grayscale images. The fluorescence intensity of the discs as well as the fluorescence intensity contrast and the color contrast between the composite restoration and adjacent tooth region were calculated as grayscale levels. RESULTS The grayscale levels for the composite discs differed significantly with the brand (p<0.001): DenFil (10.84±0.35, mean±SD), Filtek Z350 (58.28±1.37), Premisa (156.94±1.58), Grandio (177.20±0.81), Charisma (207.05±0.77), and Gradia direct posterior (211.52±1.66). The difference in grayscale levels between a resin restoration and the adjacent tooth was significantly greater in fluorescence images for each brand than in white-light images, except for the Filtek Z350 (p<0.05). However, the Filtek Z350 restoration was distinguishable from the adjacent tooth in a fluorescence image. CONCLUSIONS The intensities of fluorescence detected from the resin composites varied. The differences between the composite and adjacent tooth were greater for the fluorescence intensity contrast than for the colors observed in the white-light images.

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.

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).

Antibacterial photodynamic therapy with curcumin and Curcuma xanthorrhiza extract against Streptococcus mutans

BACKGROUND Bacteria are becoming increasingly resistant to conventional antibacterial chemotherapy. This has prompted the application of antibacterial photodynamic therapy (aPDT) in bacteria-related diseases due to its excellent biocide effects. However, few studies have attempted to develop a novel photosensitizer based on natural components. The aim of the present study was to compare the aPDT effects of curcumin and Curcuma xanthorrhiza extract (CXE) against Streptococcus mutans. METHODS A planktonic suspension containing an S. mutans strain was treated in three separate groups: aPDT with curcumin, CXE, and a mixture of curcumin and CXE (ratio= 1:1) at concentrations of 0, 10, 102, 103, and 104ng/ml. Light irradiation with a center wavelength of 405nm was applied using an LED (power density of 84.5mW for 300s at an energy density of 25.3J/cm2). The phototoxicity of photosensitizers against S. mutans was investigated using a colony-forming-unit assay. Percentage logarithmic reductions [log10(CFU/ml) values] were analyzed using one-way ANOVA followed by the Tukey test (p<0.05) and Students independent t-test. RESULTS The viability of S. mutans in the presence of curcumin, CXE, and a mixture of these two components was substantially reduced during irradiation with 405nm light. The phototoxicity of the photosensitizer varied with its solubility and concentration. CONCLUSION These preliminary in vitro findings imply that combining curcumin and CXE with a 405nm LED may be a novel method of applying aPDT. This could be advantageous in preventing and treating dental caries using devices that are readily available in clinics.