In vitro quantitative light-induced fluorescence to measure changes in enamel mineralization

A Comparison of the Fluoride 'Paint- On' vs Tray Application Techniques for Enamel Remineralisation

BACKGROUND

Fluoride gel treatment is not recommended for children < 6 years old due to its potential toxicity. Hence the aim of this study was to compare the effect of 1.23% acidulated-phosphate fluoride (APF) gel paint-on and the conventional tray application techniques on artificial, deciduous enamel carious lesions embedded on wearable appliances.

METHODS

In a randomised crossover study, the volunteer children (n = 29) wore mandibular removable appliances containing embedded tooth specimens with artificial carious lesions. The volunteers had 3 different treatment protocols: (I) 0.4 mL non-fluoride (control) gel, (II) 0.4 mL paint-on 1.23% APF gel or (III) 5 mL 1.23% APF gel, 4 minutes tray application. After 1 hour, the appliances were removed and the specimens underwent an in vitro, 14 days of pH-cycling. The mean percentage reduction in fluorescence (ΔF, %) at baseline (ΔF0) and after the pH-cycling (ΔF1) were determined using quantitative light-induced fluorescence-digital analysis. The mean ΔΔF (ΔF1-ΔF0) was calculated to compare the differences between groups.

RESULTS

The mean ΔΔF of groups I to III were -1.42 ± 1.49, 1.06 ± 2.11, and 1.12 ± 3.57 and -1.25 ± 1.44, 1.13 ± 1.84 and 1.44 ± 3.62 for the smooth surface and proximal surface lesions, respectively. The mean ΔΔF in the 2 treatment groups were significantly greater compared with the control group (P < .001). There was no significant difference in ΔΔF between the APF gel tray and paint-on groups either in the smooth surfaces, or the proximal surfaces (P = .629 and P = .613, respectively).

CONCLUSION

Our study, for the first time, indicates that the paint-on application of APF gel or the tray application of APF had a similar enamel remineralisation effect. Clinically, this implies that, particularly in younger children, the paint-on application of fluoride is less cumbersome, and possibly more tolerable with a lesser likelihood of fluoride ingestion than the tray application technique.

TRIAL REGISTRATION

Thai Clinical Trial Registry (https://www.thaiclinicaltrials.org/show/TCTR20190724001).

Detection of pit and fissure sealant microleakage using quantitative light-induced fluorescence technology: an in vitro study

This in vitro study aimed to evaluate the feasibility of quantitative light-induced fluorescence (QLF) technology for detecting the presence and severity of microleakage of pit and fissure sealants. The areas of interest (AOIs) were 160 pits and fissures of 40 extracted permanent teeth. Fluorescent images were acquired using a QLF device, and the maximum fluorescence loss ΔFmax of each AOI was analyzed. After staining and cross-sectioning of the teeth, histological dye penetration was scored on a scale of 0 to 3. The relationship between ΔFmax and microleakage depth was analyzed, and the areas under the curve (AUCs) were calculated. The │ΔFmax│ increased as microleakage depth increased. The ΔFmax values of microleakage areas showed a strong significant correlation with the histological scores of dye penetration (r = - 0.72, P = 0.001). AUC analysis showed a high diagnostic accuracy for microleakage depth (AUC = 0.83-0.91). The highest AUC of 0.91 was found when differentiating the outer half microleakage of the sealant (histological score 0 vs. 1-3). QLF technology is effective in assessing the presence and severity of microleakage, suggesting its potential for noninvasive detection and monitoring of sealant microleakage in clinical settings.

Quantification of tongue coating using quantitative light-induced fluorescence-digital image analysis and its correlation with visual evaluation

BACKGROUND

The tongue coating is a grayish-white deposit that quickly reflects the state of health or disease of the human body. Quantitative light-induced fluorescence (QLF) is a novel digital imaging system that objectively quantifies tongue coating.

AIMS

The present study aims to evaluate the correlation between the visual assessment of tongue coating and tongue coating by analysis of QLF-digital (QLF-D) images.

SETTINGS AND DESIGN

This was an in vivo explorative study.

MATERIALS AND METHODS

Fifty children aged 11-13 years with clinically visible tongue coating were selected for the study. Tongue coating was assessed clinically by the Tongue Coating Index (Shimizu et al., 2007) and digitally by QLF-D Biluminator™ 2, C3 software.

STATISTICAL ANALYSIS

Data obtained were subjected to statistical analysis using SPSS 23.0 software. Spearman's rho correlation test was done, and P < 0.05 was considered statistically significant.

RESULTS

A statistically significant correlation was found between the visual assessment scoring and the QLF image analysis for the evaluation of tongue coating.

CONCLUSION

The Digital QLF tongue imaging system was found to be reliable due to its correlation with the clinical score and objective nature.

Instant identification of dental white spot using K-means algorithm via laser-induced fluorescence and associated hyperspectral imaging

Dental caries (DC) is a chronic illness that affects 2 billion individuals worldwide, with 520 million of those suffering from it in their primary teeth. It is apparent that early DC detection and subsequent minimally invasive therapy are crucial clinical requirements. The first reversible clinical indication of demineralization is dental white spot (DWS) lesions. However, diagnosing DWS poses extreme challenges for practitioners. In this investigation, a customized laser-induced fluorescence system with a hyperspectral imaging (HI) camera and a non-ionization laser light supply was created for DWS localization and early DC detection. A UV laser diode source with a wavelength of 395 nm was used for light stimulation for the 10 test samples of teeth. The emitted signature of the main tooth components, including dentin, DWS, enamel, and DC, was recorded. An attempt was made to increase the system's sensitivity to the fluorescent signal by applying a logarithmic scale to the spectral signature. Moreover, further discrimination may be achieved by signal strength. We identified that the fluorescent signal's peak intensity at 771 nm works best for discriminating DWS from normal areas, or DC. For characterizing dentin, the re-emitted frequency at 500 nm has the maximum intensity. Next, we presented our imaging grouping strategy that combines visual enhancement through a moving average, MA, filtering and segmenting an image using K-means clustering (K-mc) (K = 8) for instant and precise DWS grouping for the constructed HI images at (500 nm and 771 nm). Despite the tiny structure and its DWS white appearance, our approach could successfully demarcate the DWS on the tested teeth. Dental examiners might benefit from our simple, non-invasive, non-ionizing optical diagnosis approach to help them make their first assessments and experience accurate and exact delineation of the DWS to obtain immediate and higher rates of early-stage DC detection.

Evaluation of dental caries detection with quantitative light-induced fluorescence in comparison to different field of view devices

This study evaluated dental caries detection ability between the Qraycam and Qraypen on the same dental caries lesions. A total of 178teeth from 61patients were imaged using Qraypen C®(QC) and Qraycam Pro®(QP) devices and evaluated using analysis software (QA2). Occlusal, secondary, and proximal dental caries were evaluated and scored according to International Caries Detection and Assessment System(ICDAS II) and X-ray criteria. Bland–Altman plots were used to compare quantitative light-induced fluorescence(QLF) parameters obtained from the different QLF devices. Sensitivity, specificity, and area under the receiver operating characteristic curve(AUROC) were calculated. The ΔF_aver. of the QLF-parameters showed that the mean difference between the two different QLF devices was close to zero and that the ± 5 error value was included in the mean ± 1.96SD range for the detection of dental caries. The accuracies for diagnosing occlusal dental caries were 0.83–0.96 and 0.81–0.82 and the accuracies for diagnosing proximal dental caries were 0.52–0.62 and 0.52–0.71 for the QC and QP devices, respectively. In conclusion, the ΔF_aver. obtained from the QP showed diagnostic value mainly for screening of demineralized teeth. For teeth selected through screening, the depth of the lesion must be precisely evaluated using additional QP and radiographic imaging.

Multimodal hyperspectral fluorescence and spatial frequency domain imaging for tissue health diagnostics of the oral cavity

A multimodal, hyperspectral imaging system was built for diagnostics of oral tissues. The system, termed Hyperspectral-Fluorescence-Spatial Frequency Domain Imaging (Hy-F-SFDI), combines the principles of spatial frequency domain imaging, quantitative light fluorescence, and CIELAB color measurement. Hy-F-SFDI employs a compact LED projector, excitation LED, and a 16 channel hyperspectral camera mounted on a custom platform for tissue imaging. A two layer Monte Carlo approach was used to generate a reference table for quick tissue analysis. To demonstrate the clinical capabilities of Hy-F-SFDI, we used the system to quantify gingival tissue hemoglobin volume fraction, detect caries, bacterial activity, and measure tooth color of a volunteer at different time points. Hy-F-SFDI was able to measure quantitative changes in tissue parameters.

The diagnostic efficacy of quantitative light-induced fluorescence in detection of dental caries of primary teeth

OBJECTIVES

To evaluate a quantitative light-induced fluorescence (QLF) caries detection method using a portable device under clinical conditions and present a QLF scoring index (QS-index) for primary teeth.

METHODS

A total of 878 tooth surfaces (proximal and occlusal) of 44 children were studied. After visual inspection and radiographic examination, images of dental caries captured with the QLF device were classified according to caries progression stages and analyzed with a specialized software. Cut-off values, sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) were calculated for the QLF parameters: fluorescence loss (ΔF) and bacterial activity (ΔR). The reliability of logistic regression model to combine ΔF and ΔR was evaluated by the AUROC.

RESULTS

QLF parameters showed a good sensitivity (0.72-0.91), specificity (0.74-0.96), and AUROC (0.861-0.940). The AUROC of logistic regression model (0.90-0.957) was higher than ΔF or ΔR average alone in all types of carious lesions. Every level of the QS-index was properly defined to represent the progression of dental caries with corresponding statistical significance.

CONCLUSIONS

The reliability of QLF for dental caries detection in primary teeth was similar to or slightly higher than that of the traditional diagnostic methods of visual inspection or radiographic examination in clinical conditions.

CLINICAL SIGNIFICANCE

The results of QLF were reliable in detecting all types of dental caries in primary teeth. The QLF method can provide visual images as well as quantitatively analyze the carious lesion.

Light-based diagnostic methods for the in vivo assessment of initial caries lesions: Laser fluorescence, QLF and OCT

OBJECTIVES

To evaluate different light-based caries diagnostic methods for assessment of non-cavitated initial carious lesions on smooth surfaces.

METHODS

39 participants were included. For each participant, three regions of interest (ROI) with ICDAS codes 0, 1 or 2 were defined. All ROIs (n = 117) were investigated/imaged with laser fluorescence (LF, DIAGNOdent 2095; KaVo dental GmbH), quantitative light-induced fluorescence (QLF; Biluminator 2+, Inspektor Research Systems B.V.) and spectral-domain optical coherence tomography (SD-OCT; Telesto II, Thorlabs GmbH). The values of LF, ΔF of QLF, and the lesion extent assessed by OCT were categorized. Frequency distribution of LF-/QLF- and OCT-scores was determined for each ICDAS code included. Inter- and intra-examiner reproducibility of QLF and OCT measurements were assessed by unweighted kappa coefficient (ĸ) and Wilcoxon test (α = 0.05).

RESULTS

Compared with LF and QLF, OCT showed various manifestations of carious lesions for visually sound ROIs and a larger variation of caries extent in depth within the same ICDAS code groups. Intra-examiner reproducibility ranged between 0.49 and 1.00 for the QLF analysis and between 0.95 and 0.99 for the OCT analysis. Inter-examiner reproducibility ranged between 0.17 and 0.32 for the QLF analysis and between 0.65 and 0.79 for the OCT analysis.

CONCLUSION

LF and QLF were insensitive to less pronounced smooth-surface lesions while OCT allowed differentiation based on the penetration depth of the carious lesions. This makes OCT a suitable method to complement conventional visual inspection in order to detect and assess (very) early lesions.

Detection of Dental Caries and Cracks with Quantitative Light-Induced Fluorescence in Comparison to Radiographic and Visual Examination: A Retrospective Case Study

The aim of this study was to present an optimal diagnostic protocol by comparing and analyzing a conventional examination and the quantitative light-induced fluorescence (QLF) technique. Selected were 297 teeth of 153 patients to take QLF images and bitewing radiographs. Occlusal dental caries, proximal dental caries and cracks were evaluated and scored using QLF, X-ray and/or visual criteria. The sensitivity, specificity, and area under the curve (AUC) of a receiver operating characteristic analysis were calculated. Two fluorescence parameters (|ΔFmax| and ΔRmax) were utilized to evaluate the fluorescence pattern according to the severity of lesions based on QLF or X-ray criteria. QLF showed higher scores for detecting occlusal dental caries and cracks than the conventional method. ΔRmax increased more clearly than ΔFmax did with occlusal dental caries. The |ΔFmax| values of occlusal dental caries, proximal dental caries and cracks showed good AUC levels (0.84, 0.81 and 0.83, respectively). The ΔRmax of occlusal dental caries showed the highest AUC (0.91) and the ΔRmax of proximal dental caries showed a fail level (0.59) compared to bitewing radiographs. The QLF image could visualize and estimate the degree of occlusal dental caries or cracks. Consequently, the QLF technique may be an adjunct tool to conventional methods for the detection of occlusal caries and peripheral cracks.

Development of a Fluorescence-Based Caries Scoring System for an Intraoral Scanner: An in vitro Study

OBJECTIVES

To develop an automated fluorescence-based caries scoring system for an intraoral scanner and totest the performance of the system compared to state-of-the-art methods.

METHODS

Seventy-three permanent posterior teeth were scanned with a three-dimensional (3D) intraoral scanner prototype which emitted light at 415 nm. An overlay representing the fluorescence signal from the tissue was mapped onto 3D models of the teeth. Multiple examination sites (n = 139) on the occlusal surfaces were chosen, and their red and green fluorescence signal components were extracted. These components were used to calculate 4 mathematical functions upon which a caries scoring system for the scanner prototype could be based. Visual-tactile (International Caries Detection and Assessment System, ICDAS), radiographic (ICDAS), and histological assessments were conducted on the same examination sites.

RESULTS

Most index tests showed significant correlation with histology. The strongest correlation was observed for the visual-tactile examination (rs = 0.80) followed by the scanner supported by the caries classification function that quantifies the overall fluorescence compared to sound surfaces (rs = 0.78). Additionally, this function resulted in the highest intra-examiner reliability (κ = 0.964), and the highest sum of sensitivity (SE) and specificity (SP) (sum SE-SP: 1.60-1.84) at the 2 histological levels where the comparison with visual-tactile assessment was possible (κ = 0.886, sum SE-SP = 1.57-1.81) and at the 3 out of 4 histological levels where the comparison with radiographic assessment was possible (κ = 0.911, sum SE-SP = 1.37-1.78); the only exception was for the lesions in the outer third of dentin, where the radiographic assessment showed the highest sum SE-SP (1.78).

CONCLUSION

A fluorescence-based caries scoring system was developed for the intraoral scanner showing promising performance compared to state-of-the-art caries detection methods. The intraoral scanner accompanied by an automated caries scoring system may improve objective caries detection and increase the efficiency and effectiveness of oral examinations. Furthermore, this device has the potential to support reliable monitoring of early caries lesions.

Effects of Additional Use of Bioactive Glasses or a Hydroxyapatite Toothpaste on Remineralization of Artificial Lesions in vitro

OBJECTIVES

This in vitro study aimed to evaluate and compare the effect of two different bioactive glasses, a hydroxyapatite-containing, fluoride-free toothpaste (HTP) and a fluoride toothpaste (FTP) on the remineralization behavior of initial caries lesions.

MATERIALS AND METHODS

A total of 100 bovine enamel samples were randomly allocated to five groups of 20 samples each: NC = negative control group (artificial saliva); HTP = HTP group (Karex); FTP = FTP group (Elmex caries protection, 1,400 ppm); FTP + BGnano = FTP followed by Actimins bioactive glass; FTP + BGamorph = FTP followed by Schott bioactive glass. Radiographic documentation (advanced transversal microradiography; aTMR) was applied before and after all samples were exposed to a demineralizing gel for 10 days. Over a period of 28 days, samples were covered twice a day (every 12 h) with a toothpaste slurry of the respective test group or with artificial saliva in NC for 60 s and brushed with 15 brushing strokes. Samples in FTP + BGnano and FTP + BGamorph were additionally treated with the respective bioactive glass slurry for 30 s after brushing with the FTP. In the meantime, all samples were stored in artificial saliva. After 28 days, the structure of all samples was assessed again using aTMR and compared to the values measured after demineralization. The statistical evaluation of the integrated mineral loss was performed using Kruskal-Wallis test followed by a post hoc Conover test.

RESULTS

The FTP revealed the significantly highest increase of mineral content while the HTP showed the significantly lowest remineralization. Compared to artificial saliva, the use of the HTP or the combined application of FTP followed by bioactive glasses (FTP + BGnano and FTP + BGamorph) showed no significant remineralization.

CONCLUSION

Under remineralizing in vitro conditions, brushing with 1,400 ppm FTP induced significantly more remineralization compared to storage in artificial saliva. The additional administration of both bioactive glasses as well as the substitutional brushing with an HTP resulted in significantly less remineralization compared to brushing with 1,400 ppm FTP.

Effectiveness of S-PRG Filler-Containing Toothpaste in Inhibiting Demineralization of Human Tooth Surface

OBJECTIVES

Using an established pH-cycling caries model, the authors evaluated the effectiveness of toothpastes containing Surface Pre-reacted Glass-ionomer filler (S-PRG) in preventing tooth surface demineralization.

MATERIALS AND METHODS

210 tooth blocks were randomly assigned to seven experimental groups (30 blocks/group): no treatment (A), and toothpaste containing either NaF (B), 0 wt% S-PRG (C), 1 wt% S-PRG (D), 5 wt% S-PRG (E), 20 wt% S-PRG (F) or 30 wt% S-PRG (G). Groups were subjected to 14-day demineralization for development of early caries lesions using a pH-cycling caries model. Demineralization was assessed using Quantitative Light-induced Fluorescence (QLF) and Transverse Microradiography (TMR). All pairwise contrasts (between treatments) were tested using Analysis of Variance (ANOVA), and then Tukey's HSD for multiple comparisons. All p-values are considered significant if <0.05.

RESULTS

With QLF, there was a significant (ANOVA; p<0.001) difference in mean percent fluorescence loss (∆F) observed among the groups. Relative to control, all S-PRG-containing toothpastes significantly (Tukey's; p<0.0001) inhibited demineralization at varying percentages (48.6%, 61.3%, 67.4% and 69.8% reduction with S-PRG 1%, 5%, 20% and 30% respectively). Demineralization reduction was not significant with either NaF (15.6% reduction) or 0% S-PRG (-2.5% reduction i.e. 2.5% more demineralization than the Control) when compared to control group. Mineral loss assessed using TMR followed a similar trend as fluorescence loss.

CONCLUSION

Toothpaste containing S-PRG filler can serve as an effective caries control tool. S-PRG filler-containing dentifrice to be more effective in preventing tooth demineralization than 1100 ppm fluoride provided as sodium fluoride.

Spatial agreement of demineralized areas in quantitative light-induced fluorescence images and digital photographs

OBJECTIVES

Previous work has shown qualitatively that detection of demineralized tooth areas (white spot lesions, WSLs) is more reliable in digital photographs (DP) as in quantitative light-induced fluorescence (QLF) images. Based on non-rigid, multimodal image registration, we now quantitatively compare manual and automatic markings in both modalities.

METHODS

After braces removal, pairs of DP and QLF were acquired from 124 teeth of 31 patients. Three experienced raters marked the WSL on both DP and QLF images, each of which was presented twice in randomized order. For each tooth and each modality, a ground truth (GT) was established using the simultaneous truth and performance level estimation algorithm on the total of six manual markings per image. DP and QLF image pairs were spatially registered, by aligning the outline of the tooth area in DPs to that of the corresponding tooth area in QLF. Between all pairs of markings for all teeth, position and size were compared quantitatively by the Dice coefficient and the novel coefficient of inclusion.

RESULTS

Our hypotheses: (i) the clinical inspection supported by DP is more sensitive to WSL as that by QLF, disregarding whether the automatic analysis or the experts' manual assessment of QLF is applied, and (ii) detected lesions in QLF are included in those of DP, were confirmed and not confirmed, respectively.

CONCLUSION

DP and QLF are valuable methods to detect WSL in demineralized teeth. Combining both modalities can provide additional information on early lesion assessment.

Streptococcus oralis maintains homeostasis in oral biofilms by antagonizing the cariogenic pathogen Streptococcus mutans

Bacteria residing in oral biofilms live in a state of dynamic equilibrium with one another. The intricate synergistic or antagonistic interactions between them are crucial for determining this balance. Using the six-species Zürich "supragingival" biofilm model, this study aimed to investigate interactions regarding growth and localization of the constituent species. As control, an inoculum containing all six strains was used, whereas in each of the further five inocula one of the bacterial species was alternately absent, and in the last, both streptococci were absent. Biofilms were grown anaerobically on hydroxyapatite disks, and after 64 h they were harvested and quantified by culture analyses. For visualization, fluorescence in situ hybridization and confocal laser scanning microscopy were used. Compared with the control, no statistically significant difference of total colony-forming units was observed in the absence of any of the biofilm species, except for Fusobacterium nucleatum, whose absence caused a significant decrease in total bacterial numbers. Absence of Streptococcus oralis resulted in a significant decrease in Actinomyces oris, and increase in Streptococcus mutans (P < .001). Absence of A. oris, Veillonella dispar or S. mutans did not cause any changes. The structure of the biofilm with regards to the localization of the species did not result in observable changes. In summary, the most striking observation of the present study was that absence of S. oralis resulted in limited growth of commensal A. oris and overgrowth of S. mutans. These data establish highlight S. oralis as commensal keeper of homeostasis in the biofilm by antagonizing S. mutans, so preventing a caries-favoring dysbiotic state.

Effect of sodium fluoride on oral biofilm microbiota and enamel demineralization

OBJECTIVE

Fluoride is widely used as an anti-caries agent, e.g. in toothpastes and mouth rinses. However, the nature of the anti-caries action is not entirely clear. Mechanisms suspected to explain the cariostatic effect include inhibitory effects on acid formation by bacteria, inhibition of extracellular polysaccharide (EPS) production, inhibition of enamel demineralization and enhancement of remineralizaton or combination thereof. The aim of this study was to examine with the supragingival Zurich in vitro biofilm model the effect of fluoride in NaF formulation, on the microbiota and on demineralization.

METHODS

Biofilms consisting of Actinomyces oris, Candida albicans, Fusobacterium nucleatum, Streptococcus oralis, Veillonella dispar and Streptococcus sobrinus, were grown anaerobically on sintered hydroxyapatite or bovine enamel disks, exposed to 200, 400, and 1400 ppm of NaF, or 0.1% chlorhexidine (positive control). The biofilms were harvested after 64 h and CFUs were assessed for total bacteria. Demineralization of enamel disks was measured by quantitative light-induced fluorescence.

RESULTS

NaF did not affect the bacterial numbers. No enamel mineral loss was observed at 1400 and 400 ppm of fluoride, whereas the pH of the surrounding medium was increased to 5.5 and 5.0, respectively, compared to the untreated control (pH 4.5 and mineral loss ΔF of -32%). At 1400 ppm NaF the biofilm's EPS volume was also significantly reduced.

CONCLUSIONS

Administration of NaF completely prevented demineralization without affecting biofilm composition and growth. This protective effect may be attributed to the observed decrease in acid production or EPS volume, or to a shift in the de/remineralization balance.

The effects of three remineralizing agents on regression of white spot lesions in children: A two-week, single-blind, randomized clinical trial

BACKGROUND

This study investigated the effect of three remineralizing agents on improving white spot lesions (WSLs).

MATERIAL AND METHODS

This clinical trial included children who had at least one WSL on anterior teeth of upper or lower jaws. The participants were randomly assigned to 4 groups by treatment: 1) a cream containing casein phosphopeptide-amorphous calcium phosphate and fluoride (MI Paste Plus); 2) a cream containing hydroxyapatite and fluoride (Remin Pro); 3) a 2% sodium fluoride gel; and 4) usual home care (control). The treatment was performed for 3 times over 10 days using special trays for retaining remineralizing agents. The area and mineral content of WSLs were measured at baseline (T1) and 1 day after finishing treatment (T2). Blinding was applied for outcome assessment.

RESULTS

Eighty patients were assigned to MI Paste Plus, Remin Pro, NaF or control groups. The application of all remineralizing agents caused a significant decrease in area and a significant increase in mineral content of WSLs (p<0.05), whereas the control patients did not experience any significant alteration (p>0.05). At T2, the area of WSLs was significantly lower in three experimental groups compared to the control group (p=0.023), but between-group difference in mineral content of WSLs failed to achieve statistical significance (p=0.08).

CONCLUSIONS

The in-office application of either MI Paste Plus or Remin Pro was as effective as 2% NaF for reducing area and increasing mineral content of WSLs. MI Paste Plus and Remin Pro could be recommended as suitable alternatives to NaF for managing WSLs. Key words:White spot lesion, caries, casein phosphopeptide-amorphous calcium phosphate, hydroxyapatite, sodium fluoride, CPP-ACP, MPlus, Remin Pro, NaF.

Quantitative light-induced fluorescence images and digital photographs - Reproducibility of manually marked demineralisations

OBJECTIVE

Hard tooth tissue demineralisation is an undesirable side effect of orthodontic treatment with fixed appliances. Whereas both clinically and in digital photographs (DP), demineralisations appear as white spot lesions, WSLs appear as dark areas when quantitative light-induced fluorescence (QLF) imaging is used. This study aims at comparing the reproducibility of the detection of decalcified tooth areas in DP and QLF.

MATERIALS AND METHODS

DP and QLF pairs were acquired from 139 teeth of 32 patients after braces removal. Three raters manually marked the decalcified area on both DP and QLF images. The markings were repeated after 2 weeks. A ground truth was estimated for each tooth and modality using the simultaneous truth and performance level estimation (STAPLE) algorithm. The Dice coefficients (DC) of each rater marking to the ground truth were calculated for all teeth and modalities to quantify the spatial agreement. A three-way repeated measures analysis of variance (ANOVA) was used to compare the means of the DCs for both modalities ([Formula: see text]). Intra-observer and intercycle variabilities were assessed comparing the means across the raters and the cycles for both modalities.

RESULTS

ANOVA revealed a statistical significant difference between the modalities [[Formula: see text], [Formula: see text]]. The standard deviation of the DC for the photographs are lower than those for the QLF images. Intra-observer and intercycle differences are rather small as compared to the intermodality differences.

CONCLUSIONS

The results indicate a higher spatial reproducibility in identifying a decalcified area on a tooth surface using visual inspection of DP rather than QLF images.

Evaluation of dental enamel caries assessment using Quantitative Light Induced Fluorescence and Optical Coherence Tomography

An in vitro study of morphological alterations between sound dental structure and artificially induced white spot lesions in human teeth, was performed through the loss of fluorescence by Quantitative Light-Induced Fluorescence (QLF) and the alterations of the light attenuation coefficient by Optical Coherence Tomography (OCT). To analyze the OCT images using a commercially available system, a special algorithm was applied, whereas the QLF images were analyzed using the software available in the commercial system employed. When analyzing the sound region against white spot lesions region by QLF, a reduction in the fluorescence intensity was observed, whilst an increase of light attenuation by the OCT system occurred. Comparison of the percentage of alteration between optical properties of sound and artificial enamel caries regions showed that OCT processed images through the attenuation of light enhanced the tooth optical alterations more than fluorescence detected by QLF System. QLF versus OCT imaging of enamel caries: a photonics assessment.

[Increased susceptibility for white spot lesions by surplus orthodontic etching exceeding bracket base area]

INTRODUCTION

There is a paucity of information with regard to the susceptibility of iatrogenic white spot lesion formation after inattentive, surplus orthodontic etching with 30% phosphoric acid and the subsequent provision or absence of adequate oral hygiene.

METHODS

Ninety sound enamel specimens were randomly allocated to 6 trial groups (N = 15 each) for etching with 30% phosphoric acid for either 15 seconds and standardized daily enamel brushing or no brushing, etching for 30 seconds with daily brushing or no brushing, or nonetched controls with brushing or no brushing. Nutritive acidic assaults were simulated by demineralization cycles 3 times per day for 1 hour with interim storage in artificial saliva. Lesion depths in terms of percentage of fluorescence loss (delta F, delta Q) and lesion extension compared with the baseline were assessed by using quantitative light-induced fluorescence after 2, 7, 14, 21, and 42 days. Etching duration, trial time elapse, and oral hygiene, as well as the significance of factor interactions, were analyzed with 3-way analysis of variance (α=5%).

RESULTS

The impact of the factors of enamel brushing, trial time elapse, and etching each had a comparably significant effect on lesion progression. The effect of surplus etching on white spot lesion formation was significantly enhanced by the simultaneous absence of enamel brushing and also the progression of trial time. The combination of 30 seconds of surplus etching with inadequate oral hygiene was especially detrimental.

CONCLUSIONS

Excessive surplus orthodontic etching of the complete labial enamel surface, instead of the bracket bases only, must be avoided to prevent iatrogenic white spot lesions. Etching times not exceeding 15 seconds are favorable.

Demineralization adjacent to orthodontic brackets after application of conventional and self-etching primer systems

OBJECTIVES

The goal of this work was to compare the demineralization of enamel associated with two different self-etching primers and traditional acid etching.

MATERIALS AND METHODS

A total of 15 volunteers (23-32 years, 8 male and 7 female) were provided with a removable archwire/resin appliance to be worn 20 h/day for 28 days. The device was attached to the mandibular posterior teeth and included samples of human enamel (from extracted third molars) located in both posterior vestibules. Both sides featured the same distribution of samples, including one untreated control sample (group A) and three samples with brackets (Victory™ APC II) bonded to their surface after conditioning with a self-etching non-fluoride primer (iBond™ Gluma® Inside; group B), a self-etching fluoride-releasing primer (Transbond™ Plus; group C), or traditional acid-etching with 35% phosphoric acid and Transbond™ XT (group D). Mineral loss was assessed extraorally under standardized conditions using quantitative light-induced fluorescence (QLF) with a specialized camera system (Inspektor Pro). Results were expressed as relative fluorescence loss (ΔF in %). A baseline measurement (T0) was taken before the appliance was first inserted but with the brackets already bonded. Fluorescence loss was analyzed after 3 (T1), 7 (T2), 14 (T3), and 28 days (T4) and compared to the baseline loss (T0) for each of the four study groups (A to D). Kruskal-Wallis and Mann-Whitney U tests were used to compare the results for statistical significance.

RESULTS

The lowest percentages of fluorescence loss both at baseline and during the follow-up assessments was found in group C. While all three experimental groups (B, C, D) presented total decreases in fluorescence loss after 28 days, indicating remineralization, the decrease in group C was the largest. The Kruskal-Wallis test yielded no significant differences between the three groups other than a significantly lower percentage of fluorescence loss in group C than in group D during the last assessment (T4). The untreated samples of control enamel (group A) revealed increasing percentages of fluorescence loss over the entire study period.

CONCLUSION

Use of the self-etching primers (groups B and C) was not associated with patterns of enamel demineralization different from those noted after traditional etching with phosphoric acid (group D). The only significant difference we observed was between the self-etching fluoride-releasing primer (group C) and traditional etching (group D) at the final assessment (T4). Thus, the fluoride-releasing system Transbond™ Plus was advantageous.

Action of food preservatives on 14-days dental biofilm formation, biofilm vitality and biofilm-derived enamel demineralisation in situ

AIMS

The aims of this double-blind, controlled, crossover study were to assess the influence of food preservatives on in situ dental biofilm growth and vitality, and to evaluate their influence on the ability of dental biofilm to demineralize underlying enamel over a period of 14 days.

MATERIALS AND METHODS

Twenty volunteers wore appliances with six specimens each of bovine enamel to build up intra-oral biofilms. During four test cycles of 14 days, the subjects had to place the appliance in one of the assigned controls or active solutions twice a day for a minute: negative control 0.9 % saline, 0.1 % benzoate (BA), 0.1 % sorbate (SA) and 0.2 % chlorhexidine (CHX positive control). After 14 days, the biofilms on two of the slabs were stained to visualize vital and dead bacteria to assess biofilm thickness (BT) and bacterial vitality (BV). Further, slabs were taken to determine mineral loss (ML), by quantitative light-induced laser fluorescence (QLF) and transversal microradiography (TMR), moreover the lesion depths (LD).

RESULTS

Nineteen subjects completed all test cycles. Use of SA, BA and CHX resulted in a significantly reduced BV compared to NaCl (p < 0.001). Only CHX exerted a statistically significant retardation in BT as compared to saline. Differences between SA and BA were not significant (p > 0.05) for both parameters. TMR analysis revealed the highest LD values in the NaCl group (43.6 ± 44.2 μm) and the lowest with CHX (11.7 ± 39.4 μm), while SA (22.9 ± 45.2 μm) and BA (21.4 ± 38.5 μm) lay in between. Similarly for ML, the highest mean values of 128.1 ± 207.3 vol% μm were assessed for NaCl, the lowest for CHX (-16.8 ± 284.2 vol% μm), while SA and BA led to values of 83.2 ± 150.9 and 98.4 ± 191.2 vol% μm, respectively. With QLF for both controls, NaCl (-33.8 ± 101.3 mm(2) %) and CHX (-16.9 ± 69.9 mm(2) %), negative values were recorded reflecting a diminution of fluorescence, while positive values were found with SA (33.9 ± 158.2 mm(2) %) and BA (24.8 ± 118.0 mm(2) %) depicting a fluorescence gain. These differences were non-significant (p > 0.05).

CONCLUSION

The biofilm model permited the assessment of undisturbed oral biofilm formation influenced by antibacterial components under clinical conditions for a period of 14 days. An effect of BA and SA on the demineralization of enamel could be demonstrated by TMR and QLF, but these new findings have to be seen as a trend. As part of our daily diet, these preservatives exert an impact on the metabolism of the dental biofilm, and therefore may even influence demineralization processes of the underlying dental enamel in situ.

Cariotester, a new device for assessment of dentin lesion remineralization in vitro

This study aimed to evaluate the potential of a new device (Cariotester) for monitoring of incipient carious lesion remineralization in root dentin by topical fluoride in vitro. Demineralized bovine dentin specimens were treated by fluoride solutions (APF or neutral NaF) and remineralized for 4 weeks. Cariotester was used to measure penetration depth (CTR depth) of the indenter into the de- and remineralized specimen surface. The specimens were assessed by transverse microradiography (TMR) to determine lesion parameters (depth: LD, mineral loss: ΔZ). Pearson's correlation analysis showed an overall significant relationship between CTR depth and both TMR parameters. CTR depth appeared to distinguish the positive effect that topical fluoride application had on the remineralization of the outer zone of dentin lesions. Cariotester had the potential to serve as a quantitative tool for monitoring of incipient carious lesion remineralization in root dentin.

The effect of surface defects in early caries assessment using quantitative light-induced fluorescence (QLF) and micro-digital-photography (MDP)

OBJECTIVES

The purpose of this study was to consider the impact of surface defects on quantitative light-induced fluorescence (QLF) and micro-digital-photography (MDP) measures, in relationship to lesion depth.

METHODS

Simulated enamel carious lesions were developed on 45 extracted human teeth. Images of each tooth were captured with both QLF and MDP. The teeth were sectioned and lesion depth was measured with polarized light microscopy (PLM). Pearson correlations were computed using data from the 27 lesions which did not have surface loss, and then separately based upon the 18 lesions which did display surface loss. MDP variables ΔR and ΔX measure reflected light, whereas QLF variables ΔF and ΔQ measure fluorescence.

RESULTS

A strong correlation was identified between lesion depth and ΔF (r=-0.765, p<0.0001), and ΔQ (r=-0.827, p<0.0001) on intact lesions while a weak but suggestive, although non-significant, correlation was identified between average lesion depth and ΔR (r=0.369, p=0.059) and ΔX (r=0.595, p=0.0011). However, the corresponding correlation was not statistically significant, when lesions with surface loss were considered for QLF and MDP measures.

CONCLUSIONS

QLF measures ΔF and ΔQ were strongly correlated with lesion depth in lab-simulated lesions with no surface loss, but not among lesions with surface defects. The two MDP-associated measures, ΔR and ΔX, could not be said to differ significantly when lesions with and without surface defects were compared with lesion depth. Because intact lesions can be remineralized, accurate assessment of their status is imperative for caries treatment.

CLINICAL SIGNIFICANCE

Dental caries is still widely prevalent today. We now know that with early stage detection, remineralization can be accomplished. Being able to identify dental caries in its reversible stage (before physical surface loss) is paramount for the clinician to be able to treat the disease non-invasively.

Efficacy of different strategies in protecting enamel against demineralization during fixed orthodontic treatment

BACKGROUND AND OBJECTIVE

Sealant application is a common strategy for preventing enamel demineralization during multibracket treatment. The aim of this study was to assess the efficacy in enamel demineralization prevention of two fluoride-containing enamel varnishes compared to a non-fluoride varnish, weekly fluoride gel application, and a non-treated control group.

MATERIALS AND METHODS

Enamel specimens obtained from 75 human upper permanent incisors were randomly allocated to five trial groups (each n = 15): A), ProSeal (Reliance), B), Maximum Cure® (Reliance), C), CervitecPlus (Ivoclar Vivadent, Schaan, Liechtenstein), D) elmex® gelée (GABA, Lörrach, Germany), and E), a non-treated control group. Groups A-C received a baseline varnish application, whereas group D specimens received a once weekly gel application for 2 min. Six demineralization cycles per day were carried out for 5 min each using 0.05 M citric acid, with the specimens stored in remineralization solution between cycles. Lesion depth expressed in percentage fluorescence loss (Δ-F in %) compared to baseline (T0) was assessed quantitatively with light-induced fluorescence (QLF) after 3 (T1), 7 (T2), 14 (T3), and 30 (T4) days globally and for each time point, and analyzed for compounds using the Kruskal-Wallis test (α = 5%), and additional one-sample Wilcoxon tests for each time/compound combination (Bonferroni-corrected α-levels α* = 0.05/4 = 0.0125).

RESULTS

Significant fluorescence loss revealing greater lesion depth was detected in the untreated controls (E) at T3, and in groups A (ProSeal) and C (CervitecPlus) at T4. No significant Δ-F changes were seen in the specimens from groups B (Maximum Cure®) and D (elmex® gelée).

CONCLUSION

Maximum Cure® sealant seems to offer efficient protection against demineralization during fixed orthodontic treatment, as does weekly application of elmex® fluoride gel.

Quantitative evaluation of the kinetics of human enamel simulated caries using photothermal radiometry and modulated luminescence

Photothermal radiometry and modulated luminescence (PTR-LUM) is an emerging nondestructive methodology applied toward the characterization and quantification of dental caries. We evaluate the efficacy of PTR-LUM in vitro to detect, monitor, and quantify human enamel caries. Artificial caries are created in extracted human molars (n = 15) using an acidified gel system (pH 4.5) for 10 or 40 days. PTR-LUM frequency scans (1 Hz-1 kHz) are performed before and during demineralization. Transverse microradiography (TMR) analysis, the current gold standard, follows at treatment conclusion to determine the mineral loss and depth of the artificially demineralized lesions. A theoretical model is applied to PTR experimental data to evaluate the changes in optothermophysical properties of demineralized enamel as a function of time. Higher optical scattering coefficients and poorer thermophysical properties are characteristic of the growing demineralized lesions, as verified by TMR, where the generated microporosities of the subsurface lesion confine the thermal-wave centroid. Enhanced optical scattering coefficients of demineralized lesions result in poorer luminescence yield due to scattering of both incident and converted luminescent photons. PTR-LUM sensitivity to changes in tooth mineralization coupled with opto-thermophysical property extraction illustrates the technique's potential for nondestructive quantification of enamel caries.

Phylogenetic group- and species-specific oligonucleotide probes for single-cell detection of lactic acid bacteria in oral biofilms

BACKGROUND

The purpose of this study was to design and evaluate fluorescent in situ hybridization (FISH) probes for the single-cell detection and enumeration of lactic acid bacteria, in particular organisms belonging to the major phylogenetic groups and species of oral lactobacilli and to Abiotrophia/Granulicatella.

RESULTS

As lactobacilli are known for notorious resistance to probe penetration, probe-specific assay protocols were experimentally developed to provide maximum cell wall permeability, probe accessibility, hybridization stringency, and fluorescence intensity. The new assays were then applied in a pilot study to three biofilm samples harvested from variably demineralized bovine enamel discs that had been carried in situ for 10 days by different volunteers. Best probe penetration and fluorescent labeling of reference strains were obtained after combined lysozyme and achromopeptidase treatment followed by exposure to lipase. Hybridization stringency had to be established strictly for each probe. Thereafter all probes showed the expected specificity with reference strains and labeled the anticipated morphotypes in dental plaques. Applied to in situ grown biofilms the set of probes detected only Lactobacillus fermentum and bacteria of the Lactobacillus casei group. The most cariogenic biofilm contained two orders of magnitude higher L. fermentum cell numbers than the other biofilms. Abiotrophia/Granulicatella and streptococci from the mitis group were found in all samples at high levels, whereas Streptococcus mutans was detected in only one sample in very low numbers.

CONCLUSIONS

Application of these new group- and species-specific FISH probes to oral biofilm-forming lactic acid bacteria will allow a clearer understanding of the supragingival biome, its spatial architecture and of structure-function relationships implicated during plaque homeostasis and caries development. The probes should prove of value far beyond the field of oral microbiology, as many of them detect non-oral species and phylogenetic groups of importance in a variety of medical conditions and the food industry.

Optothermophysical properties of demineralized human dental enamel determined using photothermally generated diffuse photon density and thermal-wave fields

Noninvasive dental diagnostics is a growing discipline since it has been established that early detection and quantification of tooth mineral loss can reverse caries lesions in their incipient state. A theoretical coupled diffuse photon density and thermal-wave model was developed and applied to photothermal radiometric frequency responses, fitted to experimental data using a multiparameter simplex downhill minimization algorithm for the extraction of optothermophysical properties from artificially demineralized human enamel. The aim of this study was to evaluate the reliability and robustness of the advanced fitting algorithm. The results showed a select group of optical and thermal transport parameters and thicknesses were reliably extracted from the computational fitting algorithm. Theoretically derived thicknesses were accurately predicted, within about 20% error, while the estimated error in the optical and thermal property evaluation was within the values determined from early studies using destructive analyses. The high fidelity of the theoretical model illustrates its efficacy, reliability, and applicability toward the nondestructive characterization of depthwise inhomogeneous sound enamel and complex enamel caries lesions.

Caries Detection Methods Based on Changes in Optical Properties between Healthy and Carious Tissue

A conservative, noninvasive or minimally invasive approach to clinical management of dental caries requires diagnostic techniques capable of detecting and quantifying lesions at an early stage, when progression can be arrested or reversed. Objective evidence of initiation of the disease can be detected in the form of distinct changes in the optical properties of the affected tooth structure. Caries detection methods based on changes in a specific optical property are collectively referred to as optically based methods. This paper presents a simple overview of the feasibility of three such technologies for quantitative or semiquantitative assessment of caries lesions. Two of the techniques are well-established: quantitative light-induced fluorescence, which is used primarily in caries research, and laser-induced fluorescence, a commercially available method used in clinical dental practice. The third technique, based on near-infrared transillumination of dental enamel is in the developmental stages.

In vitro modeling of host-parasite interactions: the 'subgingival' biofilm challenge of primary human epithelial cells

Background

Microbial biofilms are known to cause an increasing number of chronic inflammatory and infectious conditions. A classical example is chronic periodontal disease, a condition initiated by the subgingival dental plaque biofilm on gingival epithelial tissues. We describe here a new model that permits the examination of interactions between the bacterial biofilm and host cells in general. We use primary human gingival epithelial cells (HGEC) and an in vitro grown biofilm, comprising nine frequently studied and representative subgingival plaque bacteria.

Results

We describe the growth of a mature 'subgingival' in vitro biofilm, its composition during development, its ability to adapt to aerobic conditions and how we expose in vitro a HGEC monolayer to this biofilm. Challenging the host derived HGEC with the biofilm invoked apoptosis in the epithelial cells, triggered release of pro-inflammatory cytokines and in parallel induced rapid degradation of the cytokines by biofilm-generated enzymes.

Conclusion

We developed an experimental in vitro model to study processes taking place in the gingival crevice during the initiation of inflammation. The new model takes into account that the microbial challenge derives from a biofilm community and not from planktonically cultured bacterial strains. It will facilitate easily the introduction of additional host cells such as neutrophils for future biofilm:host cell challenge studies. Our methodology may generate particular interest, as it should be widely applicable to other biofilm-related chronic inflammatory diseases.

Cariogenicity of soluble starch in oral in vitro biofilm and experimental rat caries studies: a comparison

AIMS

Common belief suggests that starch is less cariogenic than sugar; however, the related literature is quite controversial. We aimed to compare cariogenic and microbiological effects of soluble starch in both a standard animal model and an oral biofilm system, and to assess the possible substitution of the animal model.

METHODS AND RESULTS

Six-species biofilms were grown anaerobically on enamel discs in saliva and medium with glucose/sucrose, starch (average molecular weight of 5000, average polymerization grade of 31), or mixtures thereof. After 64.5 h of biofilm formation, the microbiota were quantitated by cultivation and demineralization was measured by quantitative light-induced fluorescence. To assess caries incidence in rats, the same microbiota as in the biofilm experiments were applied. The animals were fed diets containing either glucose, glucose/sucrose, glucose/sucrose/starch or starch alone. Results with both models show that demineralization was significantly smaller with starch than sucrose.

CONCLUSIONS

The data demonstrate that soluble starch is substantially less cariogenic than glucose/sucrose.

SIGNIFICANCE AND IMPACT OF THE STUDY

By leading to the same scientific evidence as its in vivo counterpart, the described in vitro biofilm system provides an interesting and valuable tool in the quest to reduce experimentation with animals.

Effect of supplementary amine fluoride gel in caries-active adolescents. A clinical QLF study

OBJECTIVE

To investigate whether supplementary daily use of amine fluoride toothpaste with weekly brushing with amine fluoride gel enhances the remineralization of white spot lesions on smooth surfaces and also to investigate the possible effect of this treatment on salivary bacterial counts and oral hygiene.

MATERIAL AND METHODS

The participants comprised 135 caries-active adolescents living in suburban Stockholm. They were given an amine fluoride dentifrice (1250 ppm F) to be used twice a day, and either a test gel (4000 ppm F) or a placebo gel for brushing for 2 min once a week. During the 12-month study period, the subjects were recalled every 3rd month (baseline, 3, 6, 9, and 12 months). At each visit, DF(average change in fluorescence, in%) and lesion area (in mm2) were measured using quantitative light-induced fluorescence(QLF), followed by dietary counseling, oral hygiene instruction, and professional tooth-cleaning. At baseline, 6, and 12 months, saliva was sampled for Streptococcus mutans and lactobacillus counts, and gingival bleeding index was registered.

RESULTS

QLF indicated no enhancement of remineralization of white spot lesions by additional weekly brushing with amine fluoride gel. No inter-group differences emerged with regard to salivary bacterial counts. However, the oral hygiene of both groups improved, with a strong significance over time.

CONCLUSION

Adjunctive weekly brushing of amine fluoride gel achieved no significant enhancement of remineralization of white spot lesions monitored with the QLF method.