Simulated Caries Research Articles

Preliminary Study of Dental Caries Detection by Deep Neural Network Applying Domain-Specific Transfer Learning

PurposeThe purpose of this study is to confirm whether it is possible to acquire a certain degree of diagnostic ability even with a small dataset using domain-specific transfer learning. In this study, we constructed a simulated caries detection model on panoramic tomography using transfer learning.MethodsA simulated caries model was trained and validated using 1094 trimmed intraoral images. A convolutional neural network (CNN) with three convolution and three max pooling layers was developed. We applied this caries detection model to 50 panoramic images and evaluated its diagnostic performance.ResultsThe diagnostic performance of the CNN model on the intraoral film was as follows: C0 84.6%; C1 90.6%; C2 88.6%. Finally, we tested 50 panoramic images with simulated caries insertion. The diagnostic performance of the CNN model on the panoramic image was as follows: C0 75.0%, C1 80.0%, C2 80.0%, and overall diagnostic accuracy was 78.0%. The diagnostic performance of the caries detection model constructed only with panoramic images was much lower than that of the intraoral film.ConclusionDomain-specific transfer learning methods may be useful for saving datasets and training time (179/250).

Application of 20% silver nanoclusters in polymethacrylic acid on simulated dentin caries; its penetration depth and effect on surface hardness

The aims of this study were: To evaluate the surface hardness of simulated dentin caries lesions treated with either silver nanoclusters (AgNCls) synthesized in polymethacrylic acid (PMAA) or 38% silver diammine fluoride (SDF), as well as observe the penetration of the treatment solutions into the simulated caries lesions. Dentin blocks 4 mm thick obtained from caries-free third molars were sectioned and then simulated caries lesions on the occlusal dentin surfaces were created. Each specimen (n = 8) was divided into four sections: (A) treated with 20% AgNCls/PMAA; (B) treated with SDF 38% (FAgamin, Tedequim, Cordoba, Argentina); (C) sound tooth protected by nail-varnish during artificial caries generation (positive control); and (D) artificial caries lesion without surface treatment (negative control). AgNCls/PMAA or SDF were applied on the simulated lesions with a microbrush for 10 s, then excess removed. The surface hardness was measured by means of Vickers indentation test. To trace the depth of penetration, up to 400 μm, of silver ions, elemental composition of the samples was observed using EDX, coupled with SEM, and measured every 50 μm from the surface towards the pulp chamber. Laser Induced Breakdown Spectroscopy (LIBS) was also employed to trace silver ion penetration; the atomic silver line 328.06 nm was used with a 60 μm laser spot size to a depth of 240 μm. Student’s-t test identified significant differences between treatment groups for each depth and the Bonferroni test was used for statistical analysis of all groups (p < 0.05). Mean surface hardness values obtained were 111.2 MPa, 72.3 MPa, 103.3 MPa and 50.5 MPa for groups A, B, C and D respectively. There was a significant difference between groups A and C compared with groups B and D, the group treated with AgNCls/PMAA achieved the highest surface hardness, similar or higher than the sound dentin control. A constant presence of silver was observed throughout the depth of the sample for group A, while group B showed a peak concentration of silver at the surface with a significant drop beyond 50 μm. The 20% AgNCls/PMAA solution applied to simulated dentin caries lesions achieved the recovery of surface hardness equivalent to sound dentin with the penetration of silver ions throughout the depth of the lesion.

Effect of silver nanoparticles associated with fluoride on the progression of root dentin caries in vitro.

To assess the anti-proteolytic effect and potential to inhibit dentin root caries progression of a silver nanoparticle and fluoride solution (CNanoF) in comparison to silver diamine fluoride (SDF). 48 specimens of root dentin artificial caries lesion were treated with 38% SDF, CNanoF, CNano or F (n = 6 per group). Ph cycling with demineralization and remineralization solutions simulated caries lesion progression. In addition, specimens were incubated with or without bacterial collagenase in the remineralization solution to induce dentin proteolytic degradation. Dentin degradation was assessed by weight loss rate and hydroxyproline (Hyp) release. Changes in cross-sectional microhardness, and lesion permeability and collagen integrity as determined by confocal laser scanning microscopy indicated potential for further demineralization inhibition. The effect of the solutions on the activity of metalloproteinases (MMP) -2 and -9 was also investigated. Statistical analysis consisted of ANOVA, Kruskal-Wallis, and linear mixed models with post-hoc pairwise Tukey, Dunn, and t-tests (α = 0.05). Treatment with SDF resulted in lower weight loss rate than did other solutions, but all groups showed similar Hyp release (p = 0.183). SDF resulted in greater microhardness at superficial layers of the caries lesions (p<0.05), while there were no differences among CNanoF, CNano, and F. Lesion permeability was similar among all groups after pH cycling (p>0.05), with or without the use of collagenase (p = 0.58). No statistically significant difference was noted among solutions regarding collagen integrity after pH cycling; however, SDF-treated dentin had a significant decrease in collagen integrity when collagenase was used (p = 0.003). Interestingly, only SDF was able to completely inactivate MMP-2 and -9. CNanoF and SDF both potentially prevent dentin degradation during caries lesion progression in vitro; however, SDF was more effective at inhibiting further tissue demineralization.

Color changes and shear bond strength to simulated caries lesions treated with a novel solution of 20% silver nanoclusters in polymethacrylic acid

The aims of the study were: (1) To compare the staining effect on demineralized dentin simulating caries between silver nanoclusters (AgNCls) synthesized using polymethacrylic acid (PMAA) and silver diammine fluoride (SDF), and (2) to measure the shear bond strength (SBS) of a glass ionomer cement (GIC) to simulated caries lesions with and without the application of AgNCls/PMAA or SDF. Dentine blocks 4 mm thick from twenty-four non-carious third molars were sectioned and coated with nail varnish (Revlon, New York, USA). Simulated caries lesions on occlusal dentin surfaces were created (66 h in 0.05 M acetate buffer 2.2 mM calcium/phosphate pH 5.0). Specimens were divided into groups and treated with (n = 8): (A) 20% AgNCls/PMAA; (B) SDF 38% (Fagamin, Tedequim, Córdoba, Argentina); or (C) without treatment. AgNCls/PMAA or SDF were applied on the exposed surfaces with a microbrush for 10 s. Samples were incubated for 24 h at 37 °C at 100% relative humidity. Surface color was measured according to the CIE-L*a*b* system before and after demineralization (R0 and R1), 24 h and one week after treatment (R2 and R3), using a spectrophotometer (CM-600D Konica Minolta Sesing Inc., Japan). Groups A and B received an extra application of AgNCls/PMAA or SDF before a conventional GIC (Fuji IX-Gold Label, GC Corp, Tokyo, Japan) was bonded using a mold, 4 mm diameter × 3 mm high. For SBS, a Universal Testing Machine (Digimess RS-8000-5, China)—crosshead speed of 1 mm/min—was used. Statistical analysis was performed using ANOVA, Student-t and Scheffe-test at a significance of p < 0.05. Group A presented a stable color p = 0.24 between R1-R2 and R1-R3 in contrast to significant color changes in Group B (p = 0.02). SBS was higher (p < 0.01) in Group A (10.4 ± 2.7 MPa) compared to Groups B (3.3 ± 1.3 MPa) and C (4.0 ± 0.4 MPa), where no differences between the latter groups were observed (p = 0.77). Results of this preliminary study demonstrated that 20% AgNCls/PMAA did not stain simulated carious dentin and improved SBS of the GIC. The relevance of this study relies on the development of a therapeutic system to potentially arrest caries lesions without staining.

Calcium Phosphate Nanoclusters for the Repair of Tooth Enamel Erosion.

The artificial repair of tooth enamel is still an urgent requirement because it has a complicated and well-arranged structure. Herein, calcium phosphate nanoclusters (CaP NCs) were synthesized, via a facile approach, for application in the repair of tooth enamel erosion. Structural and optical characterizations validated the successful preparation of spherical CaP NCs, with an average size of 2.1 ± 0.11 nm. By evaporating the ethanol and triethylamine (TEA) solvents, pure CaP was produced, which was further used to repair the tooth enamel. Simulated caries lesions were achieved via phosphoric acid etching to cause damage to enamel rods. After repair, the damaged enamel rods were directly covered with CaP. According to microhardness testing, after repair with CaP NCs, the hardness value of the tooth enamel with acid etching increased to a similar level to that of normal tooth enamel. The results of the microhardness test indicated that CaP NCs revealed great potential for repairing tooth enamel erosion. Our work demonstrates a promising potential for treating the early stage of tooth erosion with CaP NCs. Based on these findings, we believe that stable CaP NCs can be employed as a precursor for the tunable, effective repair of tooth enamel in the near future.

In vitro Effect of Occlusal Loading on Cervical Wall Lesion Development in a Class II Composite Restoration

The aim of this study was to determine the effect of simulated occlusal loading on wall lesion development in cervical gaps of class II composite restorations in vitro. Sixty-four extracted human molars received standardized (4.0 × 4.2 × 3.0 mm) box preparations. The teeth were randomly assigned to one of two restoration groups: restoration with a normal or a low E-modulus composite material (CLEARFIL AP-X: E-modulus 16.8 GPa or CLEARFIL MAJESTY ES Flow: E-modulus 6.6 GPa). A metal matrix was placed at the bottom of the box for each restoration, creating a cervical gap of about 100 μm wide. Samples were exposed to simulated caries lesion development in a lactic acid solution (pH 4.8) for 8 weeks in a Rub&Roll device. Half of the samples were subjected to 90 N cyclic loading. After demineralization, the teeth were sectioned. Wall lesion development was measured using microradiography (transversal wavelength-independent microradiography) in two different locations (location 1: 1,000 μm and location 2: 1,600 μm from the gap entrance) and recorded in lesion depth (LD) (μm) and mineral loss (μm × vol%). Linear regression modeling was used to estimate the effect of loading and material on wall lesion development. Mean wall LD in location 1 across all groups was 150.83 μm with a standard deviation (SD) of 61.83 μm. In location 2, mean overall wall LD was 102.98 μm with an SD of 64.92 μm. Linear regression showed no significant effect of either loading or material on wall lesion development. Occlusal loading had no significant effect on secondary caries lesion development in composite class II restoration in this in vitro study.

Accurate identification and detection of occlusal/smooth early caries using thermal-wave radar imaging (TWRI) technique under low temperature rising condition

Dental caries is a worldwide disease, which will cause adverse effects if it is not treated in time. To accurate detect the early caries, a dental caries recognized approach based on infrared thermal diffusion, titled thermal-wave radar imaging (TWRI) technique was utilized to detect dental caries at an early stage in this present study. One-dimensional (1D) thermal-wave model under linear frequency modulation (or -chirp) thermal flux was built and analyzed the chirp thermal-wave diffusion behavior. In addition, simulated caries environment in vitro was designed and proposed for the treatment of artificial dental caries. Four intact tooth tissues were demineralized with this etching agent for different time on the dental occlusal surface. For the safety of the laser application in clinical trials, the relationship between laser power intensity and dental surface temperature rise has been investigated. When the laser power intensity was controlled within 23.3 W under the irradiation area is 2 mm × 2 mm, the surface temperature rise of dental specimen can be dominated within 5 °C. The comparison experiment between TWRI and lock-in thermography was investigated, and TWRI phase represents a high signal-to noise ratio to the early caries. μCT was utilized to 3D tomography for the dental specimen to obtain the actual caries inside the specimen. The experimental results illustrated that TWRI approach can be used as an effective method for early caries diagnosis.

Remineralization of early enamel caries lesions induced by bioactive particles: An in vitro speckle analysis.

This study aimed at evaluating the remineralization effect promoted by different bioactive fillers on simulated early caries lesions in enamel (ECLE). Forty sound bovine incisors were used to prepare buccal enamel specimens (6 × 6 × 2 mm). The specimens were divided into two areas (3 × 3 mm²): control (CTR) and experimental (EXP). All the enamel specimens were then submitted to a specific protocol for a period of 48 h to induce simulated caries lesions. Subsequently, the specimens were treated for 7 days (2 min, twice a day) with a slurry pastes containing different bioactive particles (P/L ratio: 1 g/mL). All the specimens were analyzed by laser speckle before and after treatments. The results showed after the first analysis that the ECLE had very low average intensity (back-scattered light). Conversely, after application of the bioactive pastes, higher average intensity was always detected; this was comparable to CTR sound specimens. In conclusion, innovative pastes/gels developed for enamel remineralization should contain bioactive particles that when applied daily on early caries lesions may "boost" the remineralization process to reestablish a sound enamel.

Remineralization effects of conventional and experimental ion-releasing materials in chemically or bacterially-induced dentin caries lesions

ObjectivesThe aim of this study was to evaluate the remineralization effects of conventional and experimental ion-releasing materials on different artificial dentin carious lesions. MethodsForty human dentin discs were submitted to different demineralization protocols for simulated caries lesion: (D1) Shallow chemically-induced caries, (D2) deep chemically-induced caries, (D3) deep bacterially-induced caries. Each disc was divided in five parts; one of those served as baseline control. The remaining parts of each disc (n=12–16/group) were treated using the following materials: EXP, an experimental resin-based bioactive material consisting of a self-etch primer and an adhesive containing a fluoride-doped bioglass; GIC, a glass ionomer cement (Riva LC); MTA, Mineral Trioxide Aggregate (ProRoot MTA); BIO, a calcium silicate cement (Biodentine). Specimens were mounted in a dual-chamber device to simulate the exposure to pulpal pressure and oral fluids. After 3 months, mineral and mechanical gains were assessed using transverse microradiography (vol% × μm) and microhardness measurements (VHN). Characterization using confocal microscopy and transmission electron microscopy (TEM) was also performed. ResultsAll four restorative materials induced mineral gains regardless of the protocol for caries lesion, without significant differences between materials. Microhardness significantly increased in the groups BIO and MTA, but not GIC; EXP only provided hardness gains in D3-lesions. Fluorescence and confocal microscopy confirmed these results. There was a clear “top-down” remineralization in the groups BIO and MTA, and “bottom-up” intrafibrillar collagen remineralization in EXP. SignificanceMineral gains did not always translate into hardness gains. Biodentine and MTA induced evident mineral precipitation, but intra/inter-fibrillar collagen mineral infiltration was only provided by biomimetic remineralisation via the use of the experimental adhesive. Complete remineralization of caries lesions remains a challenge.

In situ monitoring and analysis of enamel demineralisation using synchrotron X-ray scattering

Dental caries is one of the most common chronic diseases that affect human teeth. It often initiates in enamel, undermining its mechanical function and structural integrity. Little is known about the enamel demineralisation process caused by dental caries in terms of the microstructural changes and crystallography of the inorganic mineral phase. To improve the understanding of the carious lesion formation process and to help identify efficient treatments, the evolution of the microstructure at the nano-scale in an artificially induced enamel erosion region was probed using advanced synchrotron small-angle and wide-angle X-ray scattering (SAXS and WAXS). This is the first in vitro and time-resolved investigation of enamel demineralisation using synchrotron X-ray techniques which allows in situ quantification of the microstructure evolution over time in a simulated carious lesion. The analysis revealed that alongside the reduction of mineral volume, a heterogeneous evolution of hydroxyapatite (HAp) crystallites (in terms of size, preferred orientation and degree of alignment) could be observed. It was also found that the rate and direction of dissolution depends on the crystallographic orientation. Based on these findings, a novel conceptual view of the process is put forward that describes the key structural parameters in establishing high fidelity ultrastructure-based numerical models for the simulation of the enamel demineralisation process. Statement of significanceHydroxyapatite (HAp) crystallites in the enamel dissolve during dental caries although little is known about the structural-chemical relationships that control the dynamic demineralisation process. For the first time this work investigated the in situ evolution of nano-scale morphology and the spatial distribution of ultrastructural HAp crystallites of human enamel during demineralisation in simulated caries. Advanced synchrotron SAXS and WAXS techniques showed that the heterogeneous evolution of crystallites (size, preferred orientation and degree of alignment) could be attributed to crystallographic-orientation-dependent anisotropic dissolution. Hence we propose a novel conceptual schematic diagram to describe the demineralisation process. These findings have important implications for understanding the detailed mechanisms of enamel demineralisation and provide insight into potential enamel remineralisation that could restore structural integrity and function.

A Feasibility Study of Photoacoustic Detection of Hidden Dental Caries Using a Fiber-Based Imaging System

In this paper, the feasibility of an optical fiber-based photoacoustic imaging system for detecting caries lesions inside a tooth is examined. Models of hidden caries were prepared using a pigment with an absorption spectrum similar to that of real caries lesions, and the occlusal surface of the model teeth containing the pigment was irradiated with laser pulses with a wavelength of 532 nm. An examination of the frequency spectra of the emitted photoacoustic waves revealed that the spectra from simulated caries lesions included frequency components in the range of 0.5–1.2 MHz that were not seen in the spectra from healthy parts of the teeth. This indicates that hidden caries can be detected via a photoacoustic imaging technique. Accordingly, an imaging system for clinical applications was fabricated. It consists of a bundle of hollow-optical fibers for laser radiation and an acoustic probe that is attached to the tooth surface. Results of ex vivo imaging experiments using model teeth and an extracted tooth with hidden caries lesions show that relatively large caries lesions inside teeth that are not seen in visual inspections can be detected by focusing on the above frequency components of the photoacoustic waves.

Near-IR image-guided laser ablation of demineralization on tooth occlusal surfaces.

Studies have shown that reflectance images at near-IR wavelengths coincident with higher water absorption are well-suited for image-guided laser ablation of carious lesions since the contrast between sound and demineralized enamel is extremely high and interference from stains is minimized. The objective of this study was to demonstrate that near-IR reflectance images taken at a wavelength range of 1,500-1,700 nm can be used to guide a 9.3 μm CO(2) laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in vitro study. Shallow simulated caries lesions with random patterns and varying depth and position were produced on tooth occlusal surfaces. Sequential near-IR reflectance images at 1,500-1,700 nm were used to guide the laser for the selective removal of the demineralized enamel. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess selectivity. Images taken before and after lesion removal suggest that the demineralized areas were removed with high selectivity. Although the estimated volume of tissue ablated was typically higher than the initial lesion volume measured with PS-OCT, the volume of enamel removed by the laser correlated well with the initial lesion volume. Sequential near-IR reflectance images at 1,500-1,700 nm can be used to guide a 9.3 μm CO(2) laser for the selective ablation of early demineralization on tooth occlusal surfaces.

Are All Dentiform Teeth with Simulated Caries the Same? A Six‐Year Retrospective Study in Preclinical Operative Dentistry

Dentiform teeth with simulated caries (DTSC), frequently used in preclinical courses, should show no variability in the amount of simulated caries from tooth to tooth. However, the level of caries variability among DTSC is currently unknown. The aim of this study was to assess the variation in simulated caries levels in one group of DTSC and determine whether variation among DTSC impacted the preclinical performance of dental students. In the study, 80 commercially available mandibular first molar DTSC with simulated mesio-occluso-distal caries were sectioned in coronal (n=40) and sagittal (n=40) planes where the caries depth/width was greatest. Section images were analyzed for variation in levels of simulated caries using image-processing software. Three years of practical performance data using DTSC were compared with three years of practical performance data using dentiform teeth without simulated caries, for a total of six years (students' performance on two exams, Practical 1 and Practical 2). The results showed that 70% of the coronally sectioned teeth had manufacturing defects that resulted in caries overextension at the dentino-enamel junctions (DEJs). Overextensions were found at the DEJ in 41.3% of the sagittally sectioned teeth. There was a statistically significant decrease in Practical 1 performance of the students who used DTSC as compared with students who used teeth without simulated caries (p=0.0001); there was no statistically significant difference on Practical 2 performance. Of the DTSC evaluated in this study, 56.6% contained manufacturing defects, and more than 80% were found to have excessive caries variation. Prediction of which DTSC will have caries overextension is not possible. Students preparing DTSC that contain caries overextension are therefore at increased risk of receiving undeserved negative summative assessment on practical examinations.

Assessment of remineralization via measurement of dehydration rates with thermal and near-IR reflectance imaging

ObjectivesPrevious studies have demonstrated that the optical changes due to the loss of water from porous lesions can be exploited to assess lesion severity with QLF, thermal and near-IR imaging. Since arrested lesions are less permeable to water due to the highly mineralized surface layer, changes in the rate of water loss can be related to changes in lesion structure. The purpose of this study was to investigate whether the rate of water loss correlates with the degree of remineralization and whether that rate can be measured using thermal and near-IR reflectance imaging. MethodsArtificial bovine enamel lesions (n=30) were prepared by immersion in a demineralization solution for either 8 and 24h and they were subsequently placed in an acidic remineralization solution for different periods. The samples were dehydrated using an air spray for 30s and surfaces were imaged using a thermal camera and an InGaAs camera at 1300–1700nm wavelengths. ResultsThe area enclosed by the time–temperature curve, ΔQ, from thermal imaging showed significant differences (P<0.05) between the lesion window and other windows. Near-IR reflectance intensity differences, ΔI, before and after dehydration decreased with longer periods of remineralization. Only near-IR reflectance imaging was capable of detecting significant differences (P<0.05) between the different periods of remineralization. ConclusionsThis study demonstrated that both thermal and near-IR reflectance imaging were suitable for the detection of remineralization in simulated caries lesions and near-IR wavelengths longer than 1400nm are well suited for the assessment of remineralization.

Selective removal of demineralized enamel using a CO2 laser coupled with near-IR reflectance imaging.

Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR light at 1500 - 1700 nm can be used to guide a 9.3-μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in-vitro study. Shallow simulated caries lesions of varying depth and position were produced on tooth occlusal surfaces using a demineralization solution. Sequential NIR reflectance images at 1500 - 1700 nm were used to guide the laser for selective ablation of the lesion areas. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess the selectivity of removal. This study demonstrates that high contrast NIR reflectance images can be used for the image-guided laser ablation of early demineralization from tooth occlusal surfaces.

Are All Dentiform Teeth with Simulated Caries the Same? A Six-Year Retrospective Study in Preclinical Operative Dentistry

Are All Dentiform Teeth with Simulated Caries the Same? A Six-Year Retrospective Study in Preclinical Operative Dentistry

Performance of Dental Students Versus Prosthodontics Residents on a 3D Immersive Haptic Simulator

This study evaluated the performance of dental students versus prosthodontics residents on a simulated caries removal exercise using a newly designed, 3D immersive haptic simulator. The intent of this study was to provide an initial assessment of the simulator's construct validity, which in the context of this experiment was defined as its ability to detect a statistically significant performance difference between novice dental students (n=12) and experienced prosthodontics residents (n=14). Both groups received equivalent calibration training on the simulator and repeated the same caries removal exercise three times. Novice and experienced subjects' average performance differed significantly on the caries removal exercise with respect to the percentage of carious lesion removed and volume of surrounding sound tooth structure removed (p<0.05). Experienced subjects removed a greater portion of the carious lesion, but also a greater volume of the surrounding tooth structure. Efficiency, defined as percentage of carious lesion removed over drilling time, improved significantly over the course of the experiment for both novice and experienced subjects (p<0.001). Within the limitations of this study, experienced subjects removed a greater portion of carious lesion on a 3D immersive haptic simulator. These results are a first step in establishing the validity of this device.

Automated detection of remineralization in simulated enamel lesions with PS-OCT.

Previous in vitro and in vivo studies have demonstrated that polarization-sensitive optical coherence tomography (PS-OCT) can be used to nondestructively image the subsurface structure and measure the thickness of the highly mineralized transparent surface zone of caries lesions. There are structural differences between active lesions and arrested lesions, and the surface layer thickness may correlate with activity of the lesion. The purpose of this study was to develop a method that can be used to automatically detect and measure the thickness of the transparent surface layer in PS-OCT images. Automated methods of analysis were used to measure the thickness of the transparent layer and the depth of the bovine enamel lesions produced using simulated caries models that emulate demineralization in the mouth. The transparent layer thickness measured with PS-OCT correlated well with polarization light microscopy (PLM) measurements of all regions (r2=0.9213). This study demonstrates that PS-OCT can automatically detect and measure thickness of the transparent layer formed due to remineralization in simulated caries lesions.

A novel biomimetic orthodontic bonding agent helps prevent white spot lesions adjacent to brackets

To compare changes in enamel microhardness adjacent to orthodontic brackets after using bonding agents containing various compositions of bioactive glass compared to a traditional resin adhesive following a simulated caries challenge. Extracted human third molars (n = 10 per group) had orthodontic brackets bonded using one of four novel bioactive glass (BAG)-containing orthodontic bonding agents (BAG-Bonds) or commercially available Transbond-XT. The four new adhesives contained BAG in varying percentages incorporated into a traditional resin monomer mixture. Teeth were cycled through low-pH demineralizing and physiologic-pH remineralizing solutions once each day over 14 days. Microhardness was measured on longitudinal sections of the teeth 100, 200, and 300 µm from the bracket edge and beneath the brackets, at depths of 25 to 200 µm from the enamel surface. Normalized hardness values were compared using three-way analysis of variance. Significantly less reduction in enamel microhardness was found with the experimental adhesives at depths of 25 and 50 µm at all distances from the bracket edge. In all groups, there were no significant changes in enamel microhardness past 125-µm depth. Results varied with the different BAG-Bonds, with 81BAG-Bond showing the smallest decrease in enamel microhardness. The BAG-Bonds tested in this study showed a reduction in the amount of superficial enamel softening surrounding orthodontic brackets compared to a traditional bonding agent. The results indicate that clinically, BAG-Bonds may aid in maintaining enamel surface hardness, therefore helping prevent white spot lesions adjacent to orthodontic brackets.

Erosive effects of beverages in the presence or absence of caries simulation by acidogenic challenge on human primary enamel: an in vitro study

To evaluate in vitro the erosive effects of beverages in the presence or absence of caries simulation (acidogenic challenge) on the microhardness of primary enamel. Forty human primary teeth were submitted to the erosive effects: 3 × 20-min-long daily immersion in fresh orange juice (orange group), strawberry yogurt drink (yog group), or cola soft drink (cola group) separately or in combination with acidogenic challenge (pH cycling for 10 days). Specimens were also submitted to acidogenic challenge alone, and in the negative control group specimens were not submitted to any treatment. Mineral loss was evaluated by cross-sectional microhardness determination. The data (Knoop hardness numbers, KHN) were subjected to 2-way analysis of variance and Tukey's post hoc test (α = 0.05%). All the test beverages significantly reduced the sample cross-sectional enamel hardness (KHN ± SD, 235.93 ± 18.15, 257.23 ± 21.79, and 253.23 ± 13.86 in the orange, yog, and cola groups, respectively) compared to samples in the negative control group (290.27 ± 3.92). In vitro acidogenic challenge exacerbated the mineral loss induced by all beverages (166.02 ± 4.28, 190.43 ± 17.55, and 198.39 ± 21.39 in the orange, yog, and cola groups combined to acidogenic challenge, respectively) compared to acidogenic challenge alone. All beverages exhibited erosive effects on primary enamel. Simulated caries challenge considerably exacerbated the enamel softening of primary teeth.