Demineralization Of Dental Enamel Research Articles

Energy-dispersive Laue diffraction analysis of the influence of statherin and histatin on the crystallographic texture during human dental enamel demineralization.

Energy-dispersive Laue diffraction (EDLD) is a powerful method to obtain position-resolved texture information in inhomogeneous biological samples without the need for sample rotation. This study employs EDLD texture scanning to investigate the impact of two salivary peptides, statherin (STN) and histatin-1 (HTN) 21 N-terminal peptides (STN21 and HTN21), on the crystallographic structure of dental enamel. These proteins are known to play crucial roles in dental caries progression. Three healthy incisors were randomly assigned to three groups: artificially demineralized, demineralized after HTN21 peptide pre-treatment and demineralized after STN21 peptide pre-treatment. To understand the micro-scale structure of the enamel, each specimen was scanned from the enamel surface to a depth of 250 µm using microbeam EDLD. Via the use of a white beam and a pixelated detector, where each pixel functions as a spectrometer, pole figures were obtained in a single exposure at each measurement point. The results revealed distinct orientations of hydroxyapatite crystallites and notable texture variation in the peptide-treated demineralized samples compared with the demineralized control. Specifically, the peptide-treated demineralized samples exhibited up to three orientation populations, in contrast to the demineralized control which displayed only a single orientation population. The texture index of the demineralized control (2.00 ± 0.21) was found to be lower than that of either the STN21 (2.32 ± 0.20) or the HTN21 (2.90 ± 0.46) treated samples. Hence, texture scanning with EDLD gives new insights into dental enamel crystallite orientation and links the present understanding of enamel demineralization to the underlying crystalline texture. For the first time, the feasibility of EDLD texture measurements for quantitative texture evaluation in demineralized dental enamel samples is demonstrated.

The use of mouthwash containing trimetaphosphate as an adjunct therapy to fluoridated toothpaste reduces enamel demineralization

IntroductionThe decline in dental caries has been attributed to the widespread use of fluoride (F). Two forms of presentation are fluoridated toothpaste (FT) and mouthwash (MW), widely used by the population. Materials and methodsThis study aimed to evaluate in vitro the effects of combining FT and MW, whether supplemented with sodium trimetaphosphate (TMP) or not, on dental enamel demineralization. Bovine enamel blocks (n = 60) were selected based on initial surface hardness (SHi) and divided into 5 experimental groups (n = 12 each): I) Placebo Toothpaste (without F/TMP); II) 1100 ppm F Toothpaste (FT); III) 1100F associated with a MW at 100 ppm F (FT + MW 100F); IV) 1100F associated with a MW at 225 ppm F (FT + MW 250F); and V) 1100F associated with a MW at 100 ppm F supplemented with 0.4 % TMP (FT + MW 100F-TMP). The blocks were treated twice a day, undergoing 5 pH cycles over 7 days. Thus, the percentage change in surface hardness (%SH), integrated subsurface hardness loss (ΔKHN), and the concentration of F, phosphorus (P), and calcium (Ca) in the enamel were determined. The data were submitted to ANOVA and Student-Newman-Keuls test (p < 0.001). ResultsThe 1100F group was statistically inferior to the groups associated with MW for %SH, ΔKHN, and the concentration of P and Ca in the enamel (p < 0.001). Blocks treated with FT + MW 225F and FT + MW 100F-TMP showed significantly lower %SH compared to the other groups (p < 0.001). The FT + MW 100F - TMP group exhibited the lowest depth mineral loss (ΔKHN), and higher concentration de P in enamel (p < 0.001). ConclusionThe adjunct use of MW with FT produces a greater protective effect in inhibiting enamel demineralization, and the supplementation of TMP to the MW with 100F provides a superior effect compared to MW with 225F. Clinical significanceThis combination of treatments could be regarded as one of several alternative fluoride supplements for subjects at elevated risk of caries.

Advanced Time-Stepping Interpretation of Fly-Scan Continuous Rotation Synchrotron Tomography of Dental Enamel Demineralization.

High-resolution spatial and temporal analysis and 3D visualization of time-dependent processes, such as human dental enamel acid demineralization, often present a challenging task. Overcoming this challenge often requires the development of special methods. Dental caries remains one of the most important oral diseases that involves the demineralization of hard dental tissues as a consequence of acid production by oral bacteria. Enamel has a hierarchically organized architecture that extends down to the nanostructural level and requires high resolution to study its evolution in detail. Enamel demineralization is a dynamic process that is best investigated with the help of in situ experiments. In previous studies, synchrotron tomography was applied to study the 3D enamel structure at certain time points (time-lapse tomography). Here, another distinct approach to time-evolving tomography studies is presented, whereby the sample image is reconstructed as it undergoes continuous rotation over a virtually unlimited angular range. The resulting (single) data set contains the data for multiple (potentially overlapping) intermediate tomograms that can be extracted and analyzed as desired using time-stepping selection of data subsets from the continuous fly-scan recording. One of the advantages of this approach is that it reduces the amount of time required to collect an equivalent number of single tomograms. Another advantage is that the nominal time step between successive reconstructions can be significantly reduced. We applied this approach to the study of acidic enamel demineralization and observed the progression of demineralization over time steps significantly smaller than the total acquisition time of a single tomogram, with a voxel size smaller than 0.5 μm. It is expected that the approach presented in this paper can be useful for high-resolution studies of other dynamic processes and for assessing small structural modifications in evolving hierarchical materials.

Anti-Cariogenic Effects of S. cerevisiae and S. boulardii in S. mutans-C. albicans Cross-Kingdom In Vitro Models.

Despite the well-documented health benefits of the probiotic Saccharomyces, its application in oral health has not been comprehensively assessed. Dental caries is a transmissible disease initiated by acid production of cariogenic bacteria and yeast, such as Streptococcus mutans and Candida albicans, on tooth enamel and followed by subsequent enamel demineralization. Here, we investigated the effect of two Saccharomyces strains (Saccharomyces boulardii and Saccharomyces cerevisiae) on S. mutans-C. albicans cross-kingdom interactions using a cariogenic planktonic model. Viable cells, pH changes, and gene expression were measured. S. cerevisiae and S. boulardii inhibited the growth of C. albicans in dual- and multi-species conditions at 4, 6, and 20 h. Saccharomyces also inhibited C. albicans hyphal formation. Furthermore, Saccharomyces reduced the acidity of the culture medium, which usually plummeted below pH 5 when S. mutans and C. albicans were present in the model. The presence of Saccharomyces maintained the culture medium above 6 even after overnight incubation, demonstrating a protective potential against dental enamel demineralization. S. boulardii significantly down-regulated S. mutans atpD and eno gene expression. Overall, our results shed light on a new promising candidate, Saccharomyces, for dental caries prevention due to its potential to create a less cariogenic environment marked by a neutral pH and reduced growth of C. albicans.

Multi-resolution Correlative Ultrastructural and Chemical Analysis of Carious Enamel by Scanning Microscopy and Tomographic Imaging.

Caries, a major global disease associated with dental enamel demineralization, remains insufficiently understood to devise effective prevention or minimally invasive treatment. Understanding the ultrastructural changes in enamel is hampered by a lack of nanoscale characterization of the chemical spatial distributions within the dental tissue. This leads to the requirement to develop techniques based on various characterization methods. The purpose of the present study is to demonstrate the strength of analytic methods using a correlative technique on a single sample of human dental enamel as a specific case study to test the accuracy of techniques to compare regions in enamel. The science of the different techniques is integrated to genuinely study the enamel. The hierarchical structures within carious tissue were mapped using the combination of focused ion beam scanning electron microscopy with synchrotron X-ray tomography. The chemical changes were studied using scanning X-ray fluorescence (XRF) and X-ray wide-angle and small-angle scattering using a beam size below 80 nm for ångström and nanometer length scales. The analysis of XRF intensity gradients revealed subtle variations of Ca intensity in carious samples in comparison with those of normal mature enamel. In addition, the pathways for enamel rod demineralization were studied using X-ray ptychography. The results show the chemical and structural modification in carious enamel with differing locations. These results reinforce the need for multi-modal approaches to nanoscale analysis in complex hierarchically structured materials to interpret the changes of materials. The approach establishes a meticulous correlative characterization platform for the analysis of biomineralized tissues at the nanoscale, which adds confidence in the interpretation of the results and time-saving imaging techniques. The protocol demonstrated here using the dental tissue sample can be applied to other samples for statistical study and the investigation of nanoscale structural changes. The information gathered from the combination of methods could not be obtained with traditional individual techniques.

In vitro effect of low-fluoride toothpaste supplemented with sodium trimetaphosphate, xylitol, and erythritol on enamel demineralization.

Regular use of toothpaste with fluoride (F) concentrations of ≥ 1000 ppm has been shown to contribute to reducing caries increment. However, when used by children during the period of dental development, it can lead to dental fluorosis. In this study, we aimed to evaluate the in vitro effect of a toothpaste formulation with reduced fluoride (F) concentration (200 ppm) supplemented with sodium trimetaphosphate (TMP: 0.2%), Xylitol (X:16%), and Erythritol (E: 4%) on dental enamel demineralization. Bovine enamel blocks were selected according to initial surface hardness (SHi) and then divided into seven experimental toothpaste groups (n=12). These groups included 1) no F-TMP-X-E (Placebo); 2) 16% Xylitol and 4% Erythritol (X-E); 3) 16% Xylitol, 4% Erythritol and 0.2%TMP (X-E-TMP); 4) 200 ppm F (no X-E-TMP: (200F)); 5) 200 ppm F and 0.2% TMP (200F-TMP); 200 ppm F, 16% Xylitol, 4% Erythritol, and 0.2% TMP (200F-X-E-TMP); and 7) 1,100 ppm F (1100F). Blocks were individually treated 2×/day with slurries of toothpastes and subjected to a pH cycling regimen for five days (DES: 6 hours and RE: 18 hours). Then, the percentage of surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), fluoride (F), calcium (Ca), and phosphorus (P) in enamel were determined. The data were analyzed by ANOVA (1-criterion) and the Student-Newman-Keuls test (p<0.001). We found that the 200F-X-E-TMP treatment reduced %SH by 43% compared to the 1100F treatments (p<0.001). The ΔKHN was ~ 65% higher with 200F-X-E-TMP compared to 1100F (p<0.001). The highest concentration of F in enamel was observed on the 1100F treatment (p<0.001). The 200F-X-E-TMP treatment promote higher increase of Ca and P concentration in the enamel (p<0.001). The association of 200F-X-E-TMP led to a significant increase of the protective effect on enamel demineralization compared to the 1100F toothpaste.

Principales repercusiones en la cavidad oral en pacientes con anorexia y bulimia

La profesión odontológica orientada hacia la población reconoce el papel de la nutrición en la práctica clínica y aplica los principios nutricionales a la salud bucal. El cirujano dentista tiene la oportunidad de observar las manifestaciones bucales debidas a una ingestión de alimentos inapropiada y orientar adecuadamente a sus pacientes. Los trastornos nutricionales, como la anorexia y la bulimia, tienen repercusiones importantes en la salud bucodental del paciente que las padece. Dentro de las manifestaciones más importantes y de mayor prevalencia destacan: desmineralización y erosión del esmalte, caries, alteraciones de la mucosa y del periodonto. Debido a la naturaleza de estos trastornos, comúnmente no se le da la importancia a los problemas bucodentales, sin embargo aunque éstos no ponen en riesgo la vida del paciente, debe tenerse en cuenta por su carácter irreversible y se debe actuar con prontitud en su diagnóstico y tratamiento. Es necesario advertir que el tratamiento dental no es sencillo y que el odontólogo debe considerar como un reto importante la recuperación y el mantenimiento del paciente, pero por tratarse de un padecimiento multisistémico deberá ser tratado por un equipo multidisciplinario especializado, quienes de manera conjunta ayudarán a salvarle la vida a la persona que la padece.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion

ObjectivesThe aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans. MethodsBovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100 ppm F, 225 ppm F, 100 ppm F + 0.2%TMP or 100 ppm F + 0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24 h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy. ResultsThe nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5–20 μm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log10cm2) and structurally affected the biofilms. ConclusionThe 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans. Clinical significanceThe focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

Enamel remineralisation and efficacy of remineralising agents: A Review

To review current information and technology for tooth remineralisation. Searches in the "Scopus" and "Web ofKnowledge" databases, which date back to 1970s. English was the only language allowed. The study incorporatedboth original research and previously published reviews. Tooth remineralisation agents, products, and treatmentshave progressively increased in recent years due to the growing awareness of the significance of good dentalhealth among patients and general community. Both in vitro and in vivo tooth remineralisation anddemineralization research have been published regularly. Theobromine has been proposed as an effectiveremineralising agent and a viable alternative to fluorides in recent years. According to research, fluoride treatmentscan prevent dental enamel demineralization and remineralisation. An increasing number of products containingcalcium salts or calcium-based compounds have been added to oral care products to boost the delivery andretentiveness of fluoride into teeth. Calcium salts or materials, which provide an additional source of calcium,may aid in accelerating enamel remineralisation or hinder demineralization processes. These effects are possiblebecause calcium is a mineral. A new area of research inspired by bioactive materials for bone repair andregeneration, bioglass, in particular calcium silicates, shows promise for improving enamel health and is one typeof bioglass that contains calcium silicate.

Dental Caries: A Review on Etiology, Therapeutic Approaches, Novel Formulations, and Marketed Preparations

Demineralization of dental enamel (dental caries) are widely prevalent throughout the world. According to the Global Oral Health Data Bank, this prevalence varies from 49% to 83% across different countries. Dental caries are a polyfactorial disease that still needs major pharmaceutical interventions to alleviate its prevalence. This paper delineates the latest understanding of pathological and protective factors associated with caries development. Based on the current knowledge of etiological factors, many therapeutic classes have been traversed since the past to decrease the severity of the disease. This includes drugs of herbal origin and synthetic molecules. On active ingredients, the latest pharmaceutical technologies have been applied to formulate novel drug delivery systems to accentuate the impact of drug delivery to combat the prevalence of the disease. A few of these novel formulations have been also been marketed. The present article explicates current etiological understanding on dental caries, therapeutic classes explored until now along with herbal classes and compounds, novel therapeutic systems, and marketed preparations used in dental formulations and future strategies to develop the efficient formulation.

Combined effect of casein phosphopeptide-amorphous calcium phosphate and sodium trimetaphosphate on the prevention of enamel demineralization and dental caries: an in vitro study.

To evaluate the effect of treatment with fluoridated toothpaste supplemented with a combination of sodium trimetaphosphate (TMP) and casein phosphopeptide-amorphous calcium phosphate (MI Paste Plus®) on the demineralization of dental enamel. Bovine enamel blocks selected by initial surface hardness (SHi) were randomly allocated into six groups (n = 12), according to the test toothpastes: (1) without F-TMP-MI Paste Plus® (Placebo); (2) 1100 ppm F (1100F); (3) MI Paste Plus®; (4) 1100F + MI Paste Plus® (1100F-MI Paste Plus), (5) 1100F + 3 % TMP (1100F-TMP); and (6) 1100F-TMP + MI Paste Plus® (1100F-TMP-MI Paste Plus). Blocks were treated two times per day with slurries of toothpaste (1 min), and groups 4 and 6 received an application of MI Paste Plus (3 min). Next, the samples were subjected to five pH cycles (demineralizing/remineralizing solutions) at 37 °C, to produce subsurface enamel lesions.Thereafter, the blocks were maintained for 2 days in fresh remineralizing solution. After pH cycling, the following were obtained: percentage of surface hardness loss (%SH); integrated loss of subsurface hardness (ΔKHN); profile analysis and lesion depth subsurface through polarized light microscopy (PLM); scanning electron microscopy (SEM); and fluoride (F), calcium (Ca), and phosphorus (P) in the enamel. The data were subjected to ANOVA (1-criterion), followed by the Student-Newman-Keuls test (p < 0.001). The 1100F-TMP-MI Paste Plus group showed better results for SHR, ΔKHN, and PLM (p < 0.001). The F concentration was similar among all groups (p > 0.001). The 1100F-TMP-MI Paste Plus group showed the highest concentration of Ca and P in the enamel (p < 0.001). The application of 1100F-TMP-MI Paste Plus promoted a higher inhibitory effect against enamel demineralization. The combination of treatments with F, TMP, and MI Paste Plus® can be an effective alternative to improve the oral health of individuals, especially those with high activity of dental caries and at high risk for its development.

Sub-ablative laser irradiation to prevent acid demineralisation of dental enamel. A systematic review of literature reporting in vitro studies.

Caries lesions begin with enamel acid demineralisation mediated by microorganisms. Lasers with sub-ablative energy might act as a prophylactic intervention to reinforce enamel against lesions caused by acid. A systematic review of the literature was performed evaluating only in vitro studies published from 2010 to 2018. The research was performed using the following databases: Medline, Embase and the Web Of Science. A further search was performed consulting the list of references of the included studies as well as book chapters which dealt with this topic. A total of 347 records were retrieved and, after their evaluation, 36 studies were included. CO2 lasers were the most described and effective device in preventing acid demineralisation. This type of laser was unique in improving the already positive results obtained with fluoride-based interventions. Er,Cr:YSGG (with fluencies > 8.5J/cm2), diode and argon lasers also improved enamel acid resistance (p-values ranging from 0.05 to 0.001) producing similar effects with fluoride-based interventions. Regarding the sealant retention outcome, the Er:YAG laser was able to perform an enamel etching which was as effective as the traditional acid etching with the advantage of being easier and usually well accepted by low-compliant patients (i.e. younger children). Nd:YAG presented the worst results. The most common structural changes after the laser irradiation were water and carbonate reduction in the enamel combined with a phosphate and calcium enamel content increase. Moreover, the calcium/phosphate ratio was found to reach the 1.67 ideal ratio. The in vitro studies that examined the prophylactic use of lasers for increasing enamel acid resistance presented interesting results that are enough to support a further in vivo experiment. This would entail the use of a clinical laser as an alternative or in combination with fluoride-based interventions.

Comparative Study of Acid Etching on Dental Enamel

This experimental study aims to analyse the effectiveness of various materials used in demineralisation of dental enamel. This work aims to create a mechanical bond by filling the pegs with sealing material. In order to achieve this goal, five teeth were compared using different concentrations of orthophosphoric acid and exposure times. In this regard, five different tests were performed and the results were analysed using the SEM technique (scanning electron microscopy). These comparative analyses revealed that etching using 35% orthophosphoric acid for one minute and etching using Icon Etch for two minutes were the most effective.

Acid resistance of dental enamel treated with remineralizing agents, Er:YAG laser and combined treatments.

It has been reported that lasers can increase resistance to enamel acids, and when it is associated with fluoride, both are reported to work in synergy, achieving a reduction of the solubility of enamel. Currently, other remineralizing agents have been shown to effectively inhibit enamel demineralization. The aim of the study was to evaluate acid resistance in the occlusal surface of permanent teeth, treated with remineralizing agents, erbium-doped yttrium aluminum garnet (Er:YAG) laser and combined treatments. Eighty samples of enamel were randomly assigned to 8 groups (n = 10): a control group, and groups treated with sodium fluoride (NaF), casein phosphopeptide-amorphous calcium phosphate with NaF (CPP-ACPF), hydroxyapatite-NaF-xylitol (HA-NaF-X), Er:YAG laser (L), L+NaF, L+CPP-ACPF, and L+HA-NaF-X. The samples were placed in an acid solution and the released calcium (Ca) was quantified by atomic absorption spectrometry. In the groups treated with NaF and L+NaF, a lower loss of Ca was observed - 15.27 ±5.17 mg/L and 15.20 ±3.85 mg/L, respectively - compared to the control group, which had the highest Ca loss: 21.93 ±13.24 mg/L. Although the combination of Er:YAG laser plus NaF and the single application of NaF showed values suggesting superior resistance to demineralization of dental enamel compared to all the other groups in the study, no statistically significant differences were found to support this assertion.

Efficacy of red propolis hydro-alcoholic extract in controlling Streptococcus mutans biofilm build-up and dental enamel demineralization

ObjectiveThe efficacy of a red propolis hydro-alcoholic extract (RP) in controlling Streptococcus mutans biofilm colonization was evaluated. The effect of RP on dental demineralization was also investigated. MethodsChemical composition was determined by High Performance Liquid Chromatography (HPLC). Minimum Inhibitory and Bactericidal Concentration (MIC and MBC, respectively) were investigated against Streptococcus mutans (ATCC 25175). The cytotoxic potential of 3% RP in oral fibroblasts was observed after 1 and 3 min. Bovine dental enamel blocks (N = 24) were used for S. mutans biofilm formation (48 h), simulating ‘feast or famine’ episodes. Blocks/biofilms were exposed 2×/day, for 3 days, to a cariogenic challenge with sucrose 10% (5 min) and treated (1 min) with: 0.85% saline solution (negative control), 0.12% Chlorhexidine (CHX, positive control for biofilm colonization), 0.05% Sodium Fluoride (NaF, positive control to avoid demineralization) and 3% RP. Biofilms were assessed for viability (CFU/mL), and to observe the concentration of soluble and insoluble extracellular polysaccharides (SEPS and IEPS). Dental demineralization was assessed by the percentage of surface hardness loss (%SHL) and through polarized light microscopy (PLM). ResultsThe RP presented 4.0 pH and ºBrix = 4.8. The p-coumaric acid (17.2 μg/mL) and luteolin (15.23 μg/mL) were the largest contents of phenolic acids and flavonoids, respectively. MIC and MBC of RP were 293 μg/mL and 1172 μg/mL, respectively. The 3% RP showed 43% of viably cells after 1 min. Lower number (p < 0.05) of viable bacteria (CFU/mL) was observed after CHX (1.8 × 105) followed by RP (1.8 × 107) treatments. The lowest concentration (μg/CFU) of SEPS (12.6) and IEPS (25.9) was observed in CHX (p < 0.05) followed by RP (17.1 and 54.3), and both differed from the negative control (34.4 and 63.9) (p < 0.05). Considering the %SHL, all groups differed statistically (p < 0.05) from the negative control (46.6%); but NaF (13.9%), CHX (20.1%) and RP (20.7%) did not differ among them (p > 0.05). After all treatments, suggestive areas of caries lesions were observed by PLM, which were lower for CHX and NaF. ConclusionThe 3% RP reduced S. mutans colonization, decreased concentration of extracellular polysaccharides and reduced dental enamel demineralization.

Zinc and Metallothionein in the Development and Progression of Dental Caries.

Chronic oxidative stress and reactive oxygen species (ROS) in oral cavity as well as acidic pH on dental enamel surface due to the metabolic activities of bacterial plaque are the major contributors in the development and progression of dental caries. Along with other factors, deposition or dissolution Ca and Mg mostly determines the re- or demineralization of dental enamel. Zn plays an important role for both Ca and Mg bioavailability in oral cavity. Metallothionein (MT), a group of small molecular weight, cysteine-rich proteins (~ 7kDa), is commonly induced by ROS, bacterial infection, and Zn. In the current review, we evaluated MT at the junction between the progression of dental caries and its etiologies that are common in MT biosynthesis.

Evaluation of crystalline changes and resistance to demineralization of the surface of human dental enamel treated with Er:YAG laser and fluoride using x-ray diffraction analysis and Vickers microhardness

This study aimed to investigate the changes in crystalline structure and resistance to demineralization of human dental surface enamel treated with erbium-doped yttrium aluminium garnet laser (Er:YAG) laser and fluoride.The enamel surfaces were divided into four groups according to the treatment process including, (L): irradiated with Er:YAG; (F): treated with acidulated phosphate fluoride gel (LF): Pre-irradiated surfaces with Er:YAG subjected to acidulated phosphate fluoride gel and (FL): laser irradiation was performed on the fluoridated enamel surface. Before and after the treatment procedure, the samples were evaluated using X-ray diffraction, scanning electron microscope (SEM) and the Vickers microhardness test. The surface microhardness values also were measured after a pH-cycling regime and acid challenge.The a-axis of all lased groups was contracted after treatment procedure. Measurement of the area under the peaks showed the highest crysallinity in the FL group. The hardness values of all laser treated samples significantly reduced after treatment procedure compared to the F group (p ⩽ 0.001). The morphological observations showed remarkable changes on the lased enamel surfaces including cracks, craters and exposed prisms.These findings suggest, irradiation of the Er:YAG laser accompanying with fluoride application can induce some beneficial crystalline changes regarding the acid-resistance properties of enamel, however, the craters and cracks produced by laser irradiation can promote enamel demineralization and consequently the positive effects of the Er:YAG laser will be eliminated.

Variation in Enamel Formation Genes Influences Enamel Demineralization In Vitro in a Streptococcus mutans Biofilm Model.

Genetic studies have shown that variations in enamel formation genes are associated with caries susceptibility. The aim of this study was to test in vitro whether variants in these genes are associated with dental enamel demineralization in a Streptococcus mutans biofilm model. DNA and enamel samples were obtained from 213 individuals. DNA was extracted from saliva, and 16 single nucleotide polymorphisms were analyzed. The physical and chemical properties of sound enamel samples and the mineral loss and the lesion depth of the demineralized enamel samples under cariogenic challenge were analyzed. Microhardness, enamel chemicals, mineral loss and demineralization depth were compared between different genotypes at each single nucleotide polymorphism. The GG genotype of TUFT1 (rs17640579) and the GT genotype of MMP20 (rs1612069) exhibited increased microhardness (p = 0.044 and 0.016, respectively). The GG genotype of AMBN (rs7694409) had a higher magnesium level, while the CT genotype of TFIP11 (rs2097470) had a lower magnesium level (p = 0.044 and 0.046, respectively). The GT genotype of MMP20 (rs1612069) had a higher calcium level (p = 0.034). The GG genotype of AMBN (rs13115627), the AG genotype of ENAM (rs12640848) and the AA genotype of MMP20 (rs2292730) had a lower phosphorus level (p = 0.012, 0.006, and 0.023, respectively). The GG genotype of AMBN (rs13115627) was also associated with a higher calcium-phosphorus ratio (p = 0.034). Individuals with the CC genotype of TFIP11 (rs134143) exhibited significantly more mineral loss (p = 0.011) and a deeper lesions (p = 0.042). Individuals with the TT genotype of TFIP11 (rs2097470) had more mineral loss (p = 0.018). Individuals with the GG genotype of TUFT1 (rs17640579) exhibited a shallower demineralization depth (p = 0.047). Individuals with the GT genotype of MMP20 (rs1612069) exhibited a shallower demineralization depth (p = 0.042). Individuals with the GG genotype of ENAM (rs12640848) exhibited less mineral loss (p = 0.01) and a shallower demineralization depth (p = 0.03). Genetic variations in TFIP11, TUFT1, MMP20, and ENAM influenced enamel demineralization in a Streptococcus mutans biofilm model.

Determination of demineralization depth in tooth enamel exposed to abusive use of whitening gel using micro-Energy Dispersive X ray Fluorescence

In this work, we present a methodology for the determination of the depth of demineralization in dental enamel caused by extended use of an Over-The-Counter (OTC) whitening product. Teeth whitening is a very common practice in Dentistry, but concerns have been raised regarding the invasiveness of the treatment, especially regarding OTC products, that can be used without medical supervision and sometimes with concentrations of active agent that exceed the allowed regulations. In this work, we studied tooth enamel samples, treated with a whitening product during an extended period of time, both directly on the enamel surface and in the cross-section. Specimens were analyzed using microbeam X-Ray Fluorescence (micro-XRF) using polycapillary optics to obtain a spot down to 25μm. Due to the relatively large spot size of our setup point analysis of the cross-sections would be inadequate. This way, line scans were performed instead, before and after whitening, and using appropriate data treatment the depth of demineralization was inferred. The used methodology indicated an average demineralization depth of 25μm, the same order of magnitude as the aprismatic enamel layer.

Biosynthesis of Silver Nanoparticles on Orthodontic Elastomeric Modules: Evaluation of Mechanical and Antibacterial Properties.

In the present study, silver nanoparticles (AgNPs) were synthesized in situ on orthodontic elastomeric modules (OEM) using silver nitrate salts as metal-ion precursors and extract of the plant Hetheroteca inuloides (H. inuloides) as bioreductant via a simple and eco-friendly method. The synthesized AgNPs were characterized by UV-visible spectroscopy; scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The surface plasmon resonance peak found at 472 nm confirmed the formation of AgNPs. SEM and TEM images reveal that the particles are quasi-spherical. The EDS analysis of the AgNPs confirmed the presence of elemental silver. The antibacterial properties of OEM with AgNPs were evaluated against the clinical isolates Streptococcus mutans, Lactobacillus casei, Staphylococcus aureus and Escherichia coli using agar diffusion tests. The physical properties were evaluated by a universal testing machine. OEM with AgNPs had shown inhibition halos for all microorganisms in comparison with OEM control. Physical properties increased with respect to the control group. The results suggest the potential of the material to combat dental biofilm and in turn decrease the incidence of demineralization in dental enamel, ensuring their performance in patients with orthodontic treatment.