Validity assessment of quantitative light-induced fluorescence-digital (QLF-D) for the dental plaque scoring system: a cross-sectional study.

BACKGROUND: The aim of this study was to analyze the correlation between the dental plaque indices measured using quantitative light-induced fluorescence-digital (QLF-D) and conventional clinical indices that assess gingival status. METHODS: From among the patients who visited Ewha Womans University Mokdong Hospital, 33 adults in their 20s who had relatively even teeth were selected for full-mouth QLF-D imaging. The images were used to analyze the QLF-D score and the QLF-D ΔR score. As clinical indices, the gingival index (GI), bleeding on probing (BOP), probing pocket depth (PPD), and patient hygiene performance (PHP) index were measured. The correlations between the QLF-D score and QLF-D ΔR score and each clinical index were analyzed. Analyses were performed comparing the indices of maxillary and mandibular teeth, the teeth on right and left sides of the mouth, anterior and posterior teeth, and buccal and lingual surfaces of each tooth. Pearson's correlation analysis was conducted (p < 0.05). RESULTS: The mean full-mouth QLF-D score was highly correlated with the GI, BOP, PPD, PHP index (p < 0.01). The mean full-mouth QLF-D score showed the highest correlation with GI (r = 0.749) and the lowest correlation with PPD (r = 0.683). The correlations between the QLF-D score were higher in the mandible than in the maxilla and in the anterior teeth than in the posterior teeth, while no significant differences were seen between the buccal and lingual surfaces of tooth. CONCLUSIONS: This study concluded that the correlations between the plaque indices measured for each tooth surface area using QLF-D and the clinical indices assessed were significantly high, and it allowed objective determination of the gingival status. Therefore, the plaque index measured using QLF-D may be used as an alternative to supplement the shortcomings of conventional clinical indices for educating patients about plaque control and continued patient oral care.

Development of a novel in vitro model for non-cavitated carious lesion formation reflecting carious lesion activity.

BACKGROUND: Oral biofilms are a critical component in dental caries formation. However, current remineralization studies often overlook the impact of microbial factors. Therefore, a comprehensive clinically relevant assessment of caries is needed. This study aimed to develop a novel in vitro model capable of generating non-cavitated carious lesions that incorporates both mineral loss and microbial activity using quantitative light-induced fluorescence-digital (QLF-D) technology. METHODS: A total of 44 artificial early carious lesions were formed using bovine incisors. The extent of fluorescence loss (ΔF) was analyzed using a QLF-D camera. Oral microcosm biofilms were then employed to construct 22 active and 22 inactive carious lesions. The red fluorescence emission rate (ΔR) and bacterial viability (RatioG/G+R) was measured using QLF-D camera and a live-dead bacterial assay, respectively. Independent t-tests were performed to compare ΔF, ΔR, and bacterial viability of artificial carious lesions according to their activity status. RESULTS: No significant difference in ΔF between the lesions was found based on activity status (p = 0.361). However, the ΔR of active lesions was 1.82 times higher than that of inactive lesions, and the RatioG/G+R was 1.49 times higher in active lesions than in inactive lesions (both p < 0.001). CONCLUSIONS: The significant differences observed in ΔR and RatioG/G+R between active and inactive lesions emphasize the importance of considering lesion activity status when evaluating the potential efficacy of remineralization agents. This study presents a novel in vitro remineralization assessment model that reflects carious lesion activity while controlling baseline mineral distributions of lesions.

Red fluorescence intensity as a criterion for assessing remineralization efficacy in early carious lesions.

OBJECTIVES: Evaluating early carious lesion activity with an objective and clinically valid approach is crucial for developing effective treatment plans. Therefore, we here assessed the activity of non-cavitated carious lesions using a quantitative light-induced fluorescence-digital (QLF-D) camera and compared the remineralization efficiency after fluoride treatment according to the lesion's activity level. METHODS: Red fluorescence emission rate (ΔR) and fluorescence loss (ΔF) were evaluated in 44 non-cavitated carious lesions by using a QLF-D camera. Based on the ΔR level, the lesions were classified into 22 active (ΔR ≥37.55) and 22 inactive carious lesions (ΔR <37.55). Each lesion was treated with 1.23 % fluoride gel for 60 s and then immersed into artificial saliva for 7 days. Subsequently, ΔR and ΔF changes in the lesions were measured. RESULTS: Significant interactions between lesion activity and time were found for both ΔR and ΔF (p < 0.001). ΔR of active lesions declined faster and ΔF increased more steeply than did inactive lesions. Specifically, on day 7 post-fluoride treatment, the ΔR reduction rate was 1.40-times higher in active lesions, and the ΔF recovery rate was 2.50-times higher, indicating that active lesions respond more markedly to fluoride application. CONCLUSIONS: This study highlighted the significance of ΔR in predicting remineralization efficiency in non-cavitated carious lesions after fluoride application. It underscored the importance of accurately assessing caries activity when formulating effective treatment plans. Lesion activity, as determined by ΔR, not only influences the outcome of remineralization treatments but also provides a more objective measure for tailoring caries management strategies.

Red fluorescence threshold for assessing the lesion activity of early caries.

PURPOSE: The aim of this study was to determine a red fluorescence threshold for differentiating active from inactive non-cavitated carious lesions. METHODS: Using the Nyvad criteria, 30 human teeth with non-cavitated carious lesions were divided into active lesions (15 teeth) and inactive lesions (15 teeth). Using the blue light of a quantitative light-induced fluorescence-digital camera, the red fluorescence of the lesions was measured as the ΔR value. By live/dead bacterial staining, bacterial viability was calculated as the RatioG/G+R. The ΔR and RatioG/G+R of active and inactive lesions were compared. The relationship between ΔR and RatioG/G+R was also analyzed. The ΔR threshold was determined for the classification of lesion activity, and its validity was tested. RESULTS: The mean ΔR of active lesions was 1.85 fold higher than that of inactive lesions (p < 0.001), and the RatioG/G+R of active lesions was 1.97 fold higher than that of inactive lesions (p < 0.001). There was a significant positive correlation between the ΔR and the RatioG/G+R in non-cavitated carious lesions (p < 0.05). The ΔR threshold for the differentiating non-cavitated carious lesions by activity status was 37.55, and the sensitivity and specificity were both 83.33 %. CONCLUSIONS: A red fluorescence threshold for categorizing non-cavitated carious lesion activity based on microbial metabolic activity was determined. Accurate evaluation of the activity status of non-cavitated carious lesions will assist in diagnosis and treatment planning for patients with dental caries.

Manual dexterity and dental biofilm accumulation in independent older adults without hand disabilities: A cross-sectional study.

BACKGROUND: This study investigated the relationship between manual dexterity and dental biofilm accumulation in independent older Koreans using Quantitative Light-Induced Fluorescence-Digital (QLF-D). METHODS: This cross-sectional study included 44 participants recruited from senior welfare facilities in South Korea and aged ≥65 years. Participants were surveyed using face-to-face structured interviews; manual dexterity was assessed using the Box and Blocks Test. To evaluate dental biofilm accumulation, the 528 surfaces of six index teeth were imaged using QLF-D and then quantified into Simple Plaque Scores (SPS) and ΔR20 values. The t-test and one-way analysis of variance were used to analyze differences in SPS and ΔR20 according to general characteristics and manual dexterity. RESULTS: Those who brushed their teeth ≤2 times per day had higher SPS and ΔR20 values on the lingual surface of tooth #24 than those who brushed ≥3 times per day (p < 0.05). The low manual dexterity group had higher SPS on lingual surfaces of teeth #12, #24, and #32, as well as higher ΔR20 values on the lingual surfaces of teeth #12, #24, #32, and #44 (p < 0.05) than the normal group. CONCLUSIONS: The low manual dexterity group had more dental biofilm-particularly on the lingual surfaces of teeth-and more mature biofilm than the normal group. These findings indicate that reduced manual dexterity could be a predictor of poor oral hygiene in independent older adults without hand disabilities. Therefore, we suggest manual dexterity be assessed in advance of dental biofilm assessment and tooth brushing instruction.

Inter-rater agreement among multiple examiners for the assessment of plaque scores between quantitative light-induced fluorescence-digital and two-tone disclosing solution-stained digital images.

BACKGROUND: To utilize plaque scoring indices as objective measures, a certain standard of intra-rater and inter-rater agreement must be met. Achievement of high consistency among several examiners in the assessment of images from Q-ray cam (for quantitative light-induced fluorescence-digital imaging) and digital single-lens reflex camera of stained tooth surfaces might enable more efficient undertaking of large epidemiological studies and oral tests. METHODS: Second-year dental hygiene students and registered dental hygienists 40 examiners were randomly selected, all of whom provided informed consent. Multiple examiners assessed plaque scoring indices from the two types of images of the same 30 patients. The images were observed on a computer monitor, and the area with dental plaque was assessed using the Patient Hygiene Performance Index. The intra-class correlation coefficient was determined to evaluate the agreement among examiners and test methods for dental plaque Q-ray cam and digital single-lens reflex camera measurements were compared using a Bland-Altman plot. The intra-class correlation coefficient was analyzed using SPSS version 24 software (SPSS Inc., Chicago, IL, USA), and the exploratory graph was analyzed with MedCalc. RESULTS: Agreement among 40 examiners was excellent with an intra-class correlation coefficient of 0.990 when the Q-ray cam was used. The intra-class correlation coefficient for the registered dental hygienists group was 0.987 and that for the dental hygiene students group was 0.980. CONCLUSIONS: The study was high agreement in the assessment of Q-ray cam images and digital single-lens reflex camera images of stained dental plaque by multiple examiners, confirming that the two methods are validated both independently and with high mutual agreement.

Hand motor functions on the presence of red fluorescent dental biofilm in older community-dwelling Koreans.

BACKGROUND: The Quantitative Light-induced Fluorescence-Digital (QLF-D) system visualizes old and mature dental biofilm as red fluorescence. Risk factors for poor oral hygiene have been identified, however, few studies have evaluated the relationship between mature dental biofilm and hand motor functions. This study aimed to investigate the effects of two important manual motor functions for object manipulation -handgrip strength and manual dexterity- on the presence of red fluorescent dental biofilm in older community-dwelling Koreans using QLF-D, an optical device that reveals dental biofilm. METHODS: This cross-sectional study included 70 Korean participants aged ≥65 years, all of whom completed questionnaires and were tested for handgrip strength and manual dexterity. In total, 840 dental surfaces were photographed using QLF-D, and ΔR20 values, which reflect mature dental biofilm accumulation, were calculated. The t-test was performed to analyze the differences in the ∆R20 values according to sociodemographic characteristics, health-related characteristics and hand motor functions, while multiple linear regression analysis was used to investigate the effects of hand motor functions on the ∆R20 values. RESULTS: Multivariate regression analysis revealed that handgrip strength (ß = -0.294) was the factor most strongly affecting mature dental biofilm accumulation (ΔR20), followed by tooth-brushing time (ß = -0.262) and manual dexterity (ß = -0.241). CONCLUSIONS: Reductions in handgrip strength and manual dexterity were independent risk factors for pathogenic dental biofilm accumulation. The results of this investigation suggest that programs designed to prevent the decline, as well as improve, handgrip strength and manual dexterity might improve the oral hygiene of older adults.

The effects of 8DSS peptide on remineralization in a rat model of enamel caries evaluated by two nondestructive techniques.

Nowadays, dental caries is one of the most common oral health problems, affecting most individuals. It has been found that, by remineralizing enamel at an early stage in the formation of enamel caries, teeth can be effectively protected from dental caries. In this work, a peptide with eight repetitive sequences of aspartate-serine-serine (8DSS) is applied as the bio-mineralizer in an in-vivo rat enamel caries model. Nondestructive quantitative light-induced fluorescence-digital (QLF-D) imaging and micro-computed tomography (micro-CT) are used to evaluate the remineralization of enamel carious lesions by measuring the total fluorescence radiance loss of the molar area (Δ QTotal), acquired using QLF-D imaging, and the mineral density and residual molar enamel volume, acquired using micro-CT. Correlations are explored between Δ QTotal and mineral density (strong correlation, r = 0.8000, p < 0.001) and Δ QTotal and residual molar enamel volume (moderate correlation, r = 0.6375, p < 0.001). Our results demonstrate that 8DSS is a promising in-vivo remineralization agent that exhibits comparable effects to NaF ( p < 0.05), which has been verified using the classical Keyes method. Moreover, the nondestructive QLF-D and micro-CT methods can be combined to quantify the remineralization of enamel carious lesions three-dimensionally in vivo, making them broadly applicable in quantifying hard tissues.

Cutoff fluorescence loss for the recovery of incipient carious lesions after fluoride application in primary teeth: A clinical study.

PURPOSE: Early detection and diagnosis of incipient caries are the keys to achieving a favorable prognosis. Monitoring of pathological changes based on clinical evidence leads to an accurate prognosis. Therefore, this clinical study investigated changes in minerals of incipient carious lesions using quantitative light-induced fluorescence-digital (QLF-D) after applying professional fluoride treatment to children, with improvement of the lesion severity assessed based on the fluorescence loss (ΔF) value obtained using QLF-D. METHODS: This study examined 90 incipient enamel lesions on the primary teeth of 27 children aged between 4 and 10 years. QLF-D images were obtained before and after the application of 1.23% acidulated phosphate fluoride gel for 1 min, and the ΔF values at 0 and 4 weeks (ΔF(0) and ΔF(4), respectively) and the recovery rates (RΔF) of the lesions were evaluated. Receiver operating characteristic curve analysis was used to calculate the cutoff ΔF(0) value at which recovery of the lesion with fluoride treatment remained feasible. RESULTS AND CONCLUSION: The recovery patterns of ΔF 4 weeks after fluoride application differed depending on the ΔF(0) values. The incipient lesions with ΔF(0) values of less than -13.00 recovered 4 weeks after fluoride application (P <  0.001) and had an average RΔF value of 19.27%. The results indicate that a ΔF(0) cutoff value can be determined for predicting the effects of remineralization after fluoride application and quantitative prognostic data can be provided to patients.

Improving the competency of dental hygiene students in detecting dental restorations using quantitative light-induced fluorescence technology.

OBJECTIVES: The purpose of this study was to determine the usefulness of a quantitative light-induced fluorescence (QLF) technology in detecting dental restorations by comparing the detection ability of dental hygiene students between using conventional visual inspection alone and visual inspection combined with QLF technology. METHODS: The subjects of this study comprised 92 dental hygiene students. The students assigned to the control group only used white-light images to visually assess the mouth environment, while those in the experimental group additionally used fluorescence images. Using the test results of an experienced inspector as a reference value, the agreement between the reference value and the evaluation results of the students in the experimental and control groups was evaluated using Cohen's kappa and the percentage agreement. The subjects were then classified into groups covering three percentage ranges according to the score distribution and agreement values of the three groups were compared. The percentage agreement was calculated according to the type of dental restorations. RESULTS: The mean kappa value was significantly higher in the experimental group than the control group (0.70 vs 0.60, p<0.001), as was the percentage agreement (80.06% vs 72.64%, p<0.001). The agreement rate when using QLF technology increased by 8% more in the middle and bottom percentage groups than in the top percentage group (p<0.001). The agreement rate also varied with the type of restoration, being significantly higher for a sound tooth or tooth-colored restoration in the experimental group (p<0.001). CONCLUSIONS: Combining QLF technology with conventional visual inspections could improve the ability to detect dental restorations and distinguish sound teeth from aesthetic restorations.

Detection of proximal caries using quantitative light-induced fluorescence-digital and laser fluorescence: a comparative study.

PURPOSE: The purpose of this study was to evaluate the in vitro validity of quantitative light-induced fluorescence-digital (QLF-D) and laser fluorescence (DIAGNOdent) for assessing proximal caries in extracted premolars, using digital radiography as reference method. MATERIALS AND METHODS: A total of 102 extracted premolars with similar lengths and shapes were used. A single operator conducted all the examinations using three different detection methods (bitewing radiography, QLF-D, and DIAGNOdent). The bitewing x-ray scale, QLF-D fluorescence loss (ΔF), and DIAGNOdent peak readings were compared and statistically analyzed. RESULTS: Each method showed an excellent reliability. The correlation coefficient between bitewing radiography and QLF-D, DIAGNOdent were -0.644 and 0.448, respectively, while the value between QLF-D and DIAGNOdent was -0.382. The kappa statistics for bitewing radiography and QLF-D had a higher diagnosis consensus than those for bitewing radiography and DIAGNOdent. The QLF-D was moderately to highly accurate (AUC = 0.753 - 0.908), while DIAGNOdent was moderately to less accurate (AUC = 0.622 - 0.784). All detection methods showed statistically significant correlation and high correlation between the bitewing radiography and QLF-D. CONCLUSION: QLF-D was found to be a valid and reliable alternative diagnostic method to digital bitewing radiography for in vitro detection of proximal caries.

Evaluation of resin infiltration using quantitative light-induced fluorescence technology.

OBJECTIVES: To determine whether quantitative light-induced fluorescence (QLF) technology can be used to classify the colour of teeth specimens before and after resin infiltration (RI) treatment, and calculate the correlation between the ΔF value and colour difference (ΔE) in fluorescence images of the specimens obtained using a QLF-digital (QLF-D) device. METHODS: Sixty sound bovine permanent teeth specimens were immersed in demineralized solution. Two exposed windows were formed in each specimen, and RI treatment was applied to one of them. The ΔE values were obtained for the differences between a sound tooth surface (SS), an early dental caries surface (ECS) and an ECS treated with RI (RS) in white-light and fluorescence images obtained using QLF-D, respectively. The ΔF value was obtained from fluorescence images using dedicated software for QLF-D. The mean differences between the ΔE values obtained from the white-light and fluorescence images were analyzed by paired t-test. Pearson correlation analysis and Bland-Altman plots were applied to the differences between the ΔF value for ECS (ΔFSS-ECS) and the ΔE value between SS and ECS (ΔESS-ECS), and between the ΔF value for RS (ΔFSS-RS) and the ΔE value between SS and RS (ΔESS-RS) in fluorescence images. RESULTS: The ΔE values obtained from fluorescence images were three times higher than the ΔE values obtained from white-light images (p<0.001). Significant correlations were confirmed between ΔESS-ECS and ΔFSS-ECS (r=-0.492, p<0.001) and between ΔESS-RS and ΔFSS-RS (r=-0.661, p<0.001). CONCLUSION: QLF technology can be used to confirm the presence of RI in teeth.

Assessing the use of Quantitative Light-induced Fluorescence-Digital as a clinical plaque assessment.

BACKGROUND: The aims of this study were to compare the relationship between red fluorescent plaque (RF plaque) area by Quantitative Light-induced Fluorescence-Digital (QLF-D) and disclosed plaque area by two-tone disclosure, and to assess the bacterial composition of the RF plaque by real time-PCR. METHODS: Fifty healthy subjects were included and 600 facial surfaces of their anterior teeth were examined. QLF-D was taken on two separate occasions (before and after disclosing), and the RF plaque area was calculated based on Plaque Percent Index (PPI). After disclosing, the stained plaque area was analyzed to investigate the relationship with the RF plaque area. The relationship was evaluated using Pearson correlation and paired t-test. Then, the RF and non-red fluorescent (non-RF) plaque samples were obtained from the same subject for real-time PCR test. Total 10 plaque samples were compared the ratio of the 6 of bacteria using Wilcoxon signed rank test. RESULTS: Regarding the paired t-test, the blue-staining plaque area (9.3±9.2) showed significantly similarity with the RF plaque area (9.1±14.9, p=0.80) at ΔR20, however, the red-staining plaque area (31.6±20.9) presented difference from the RF plaque area (p<0.0001). In addition, bacterial composition of Prevotella intermedia and Streptococcus anginosus was associated with substantially more the RF plaque than the non-RF plaque (p<0.05). CONCLUSIONS: The plaque assessment method using QLF-D has potential to detect mature plaque, and the plaque area was associated with the blue-staining area using two-tone disclosure.

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.

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.

An in vitro comparison of quantitative light-induced fluorescence-digital and spectrophotometer on monitoring artificial white spot lesions.

PURPOSE: The aim of this study was to evaluate the efficacy of quantitative light-induced fluorescence-digital (QLF-D) compared to a spectrophotometer in monitoring progression of enamel lesions. METHODS: To generate artificial caries with various severities of lesion depths, twenty bovine specimens were immersed in demineralizing solution for 40 days. During the production of the lesions, repeat measurements of fluorescence loss (ΔF) and color change (ΔE) were performed in six distinct stages after the demineralization of the specimens: after 3, 5, 10, 20, 30, and 40 days of exposure to the demineralizing solution. Changes in the ΔF values in the lesions were analyzed using the QLF-D, and changes in the ΔE values in lesions were analyzed using a spectrophotometer. The repeated measures ANOVA of ΔF and ΔE values were used to determine whether there are significant differences at different exposure times in the demineralizing solution. Spearman's rank correlation coefficient was analyzed between ΔF and ΔE. RESULTS AND CONCLUSION: The ΔF values significantly decreased based on the demineralizing period (p<0.001). Relatively large changes in ΔF values were observed during the first 10 days. There were significant changes in L(*), a(*), b(*), and ΔE values in lesions with increasing demineralizing duration (p<0.001). A strong correlation was observed between ΔF and ΔE with p=-0.853 (p<0.001). The results support the efficacy of QLF-D in monitoring color changes. Our findings demonstrate that QLF-D are a more efficient and stable tool for early caries detection.

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.

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.