Acid Challenge Research Articles

Comprehensive characterization of tobacco-induced changes in enamel surface topography.

Enamel translucency, essential for the aesthetic appeal of teeth, is primarily determined by its thickness, quality, and refractive index. Several factors, including age, genetics, diet, oral hygiene practices, fluoride exposure, and acidic challenges, can influence enamel translucency. Tobacco use, in particular, leads to significant alterations in enamel appearance by penetrating its micropores, causing yellowing and browning. Prolonged exposure to tobacco results in demineralization, increasing enamel porosity and reducing its translucency. Over time, this exposure leads to permanent discoloration and structural degradation, rendering teeth dull and opaque. To assess these changes, various methods such as visual examinations, digital photography, spectrophotometry, stylus profilometry, and atomic force microscopy (AFM) are utilized. This study analyzed human enamel samples, including one unstained sample (Grade 0) and three tobacco-stained samples (Grades 1-3) according to Modified Lobene Stain Index (MLSI), to investigate the impact of tobacco exposure on enamel structure. The samples were thoroughly cleaned and dried to ensure accurate results. High-resolution AFM imaging was employed to assess surface roughness, porosity, and microstructural changes induced by tobacco staining. A stylus profilometer was used to trace the surface topography, providing detailed measurements of surface irregularities. Additionally, a spectrophotometer was utilized to evaluate the optical properties of the enamel, focusing on changes in translucency and light absorption due to tobacco exposure. AFM analysis revealed a clear progression of enamel surface roughness from Grade 0 to Grade 3. The Sa and Sq values increased significantly with the severity of tobacco staining, indicating greater surface degradation. The stylus profilometer data corroborated these findings, with rising Ra values as the degree of staining intensified, highlighting the topographical alterations caused by tobacco exposure. Spectrophotometric analysis further demonstrated a decrease in enamel reflectance and an increase in light absorption from mild to severe staining, underscoring the detrimental optical effects of tobacco on enamel. The combined use of AFM, stylus profilometry, and spectrophotometry provided a comprehensive assessment of the impact of tobacco staining on enamel translucency and surface roughness. The findings show that as staining severity increases, enamel translucency diminishes, and surface roughness worsens. These alterations not only affect the aesthetic appearance of teeth but also have potential implications for enamel functionality and long-term oral health.

The influence of phosphoric acid and primer treatment on the evaluation of the adhesive resin cement/enamel interface.

This study evaluated the influence of phosphoric acid and primer on enamel bonding performance using Panavia V5. Ground bovine enamels were assigned: using K-etchant syringe and Tooth Primer (CT), using K-etchant syringe (PA), using Tooth Primer (TP), neither K-etchant syringe nor Tooth Primer was used (NC). The micro-tensile bond strength values of CT and PA were significantly higher than TP. After thermal cycling, the values were higher in CT and PA. In the leakage test, line-shaped signal pattern at the adhesive interface was detected in NC, and the signal was partially detected in PA and TP. Observation of the adhesive interface after acid and base challenge confirmed tooth-like structures in groups except NC. Large spaces were observed between the enamel and cement in NC. Limited in this study, the lack of application of phosphoric acid or Tooth Primer may affect the enamel bonding performance.

Alpha-1 Antitrypsin Inclusions Sequester GRP78 in a Bile Acid-Inducible Manner.

The homozygous PiZ mutation (PIZZ genotype) constitutes the predominant cause of severe alpha-1 antitrypsin (AAT) deficiency and leads to liver disease via hepatocellular AAT aggregation. We systematically analysed the composition of AAT aggregates and studied the impact of bile acids. AAT inclusions were isolated from livers of PiZ overexpressing mice and PIZZ humans via fluorescence-activated and immunomagnetic sorting (FACS/MACS), while insoluble proteins were obtained via Triton-X extraction. Inclusion composition was evaluated through mass-spectrometry (MS), immunoblotting and immunostaining. Hepatocytes with versus without AAT aggregates were obtained via microdissection. Serum bile acids were assessed in 57 PIZZ subjects and 19 controls. Mice were administered 2% cholic acid (CA)-supplemented chow for 7 days. MS identified the key endoplasmic reticulum chaperone 78 kDa glucose-regulated protein (GRP78) in FACS/MACS pulldowns. GRP78 was also enriched in insoluble fractions from PiZ mice versus wild types and detected in insoluble fractions/MACS isolates from PIZZ liver explants. In cultured cells/primary hepatocytes, PiZ overexpression was associated with increased GRP78 mRNA/protein levels. In human livers, hepatocytes with AAT aggregates had higher GRP78 levels than hepatocytes without. PIZZ subjects displayed higher serum bile acid levels than controls and the highest levels were seen in individuals with liver injury/fibrosis. In PiZ mice, CA-mediated bile acid challenge resulted in increased liver injury and translocation of GRP78 into the aggregates. Our results demonstrate that GRP78 is sequestered within AAT inclusions. Bile acid accumulation, as seen in PIZZ subjects with liver disease, may promote GRP78 segregation and thereby augment liver damage. NCT02929940.

Effect of Fluoride Varnishes on Demineralization and Acid Resistance in Subsurface Demineralized Lesion Models.

This study aimed to clarify the effects of high-concentration fluoride varnish application on the inhibition of the progression of initial enamel caries. Remineralization capacity and acid resistance following high-concentration fluoride varnish application were compared with untreated models and models treated with fluoride mouthwash. Bovine enamel was used to create a model of initial enamel caries. The high-concentration fluoride varnishes Enamelast and Clinpro White Varnish and the fluoride mouthwash Miranol were used. Specimens were evaluated using Contact Microradiography (CMR) and an Electron Probe Micro-Analyzer (EPMA). While a single application of high-concentration fluoride varnish and short-term fluoride mouthwash use did not appear to cause remineralization in the subsurface demineralized layer, improvements in acid resistance were observed, leading to reduced demineralization under subsequent acidic challenges.

Natural Amelioration of Chocolate-Induced Acidity: The Role of Pineapple in Maintaining Oral pH Balance

The consumption of chocolate, especially varieties high in sugar, can disrupt the delicate pH balance in the oral cavity, increasing the risk of dental caries. Pineapple, with its rich enzymatic and organic acid profile, presents a potential natural solution to counteract this acidic challenge. This study investigates the efficacy of pineapple consumption in mitigating the pH-lowering effects of chocolate and its impact on saliva volume, a crucial factor in maintaining oral health. A quasi-experimental design with a pre-test and post-test control group approach was employed. Participants included children aged 6-9 years (n=40), divided into two groups: a control group (chocolate consumption only) and an intervention group (chocolate consumption followed by pineapple consumption). Saliva volume and pH were measured before and after treatment, and the data were analyzed using paired t-tests. Pineapple consumption significantly increased saliva volume in the intervention group (from 2.01±1.29 mL to 5.3±0.88 mL, p<0.05), exceeding the volume observed in the control group. Furthermore, the decrease in saliva pH in the intervention group (from 7.45±0.13 to 6.25±0.37) was more controlled compared to the control group (from 7.30±0.09 to 5.28±0.25). In conclusion, the consumption of pineapple after chocolate effectively stimulates saliva production and helps maintain a balanced oral pH, mitigating the acidic effects of chocolate and potentially reducing the risk of dental caries. These findings suggest the potential of pineapple as a natural, dietary approach to support oral health.

Melatonin inhibits the activation of microglia and cough sensitivity of guinea pigs exposed to PM2.5.

The study aimed to examine the impact of melatonin on mitigating brain inflammation and cough sensitivity resulting from exposure to particulate matter 2.5 (PM2.5). Guinea pigs were randomly assigned to the blank control group, normal saline group, PM2.5 exposure group, and PM2.5 exposure + melatonin group. The PM2.5 exposure and PM2.5 exposure + melatonin groups were given intranasal instillations of PM2.5 suspension twice daily for 28 consecutive days. Starting on day 21, the PM2.5 exposure + melatonin group was treated with an intraperitoneal injection of melatonin at 10 pm. Cough sensitivity to citric acid, microglia activation, IL-1β and TNF-α levels in the airway and dorsal vagal complex (DVC), and ultrastructural changes in neurons within the DVC were assessed. The PM2.5 exposure group exhibited a significantly higher cough count to citric acid challenge (29.1±5.7 coughs) compared with the PM2.5 exposure + melatonin group (18.8±4.1 coughs), normal saline group (8.4±2.1 coughs), and blank control group (7.7±1.8 coughs). In addition, cough latency was shorter in the PM2.5 exposure group (26.9±6.5 seconds) than in the PM2.5 exposure + melatonin group (36.6±12.4 seconds), normal saline group (43.4±14.7 seconds), and blank control group (47.0±13.0 seconds). The PM2.5 exposure + melatonin group showed significantly reduced IL-1β (105.3±14.3 pg/ml) and TNF-α levels (113.0±23.5 pg/ml) in the DVC, as well as in the bronchoalveolar lavage fluid (IL-1β: 24.92±5.14 pg/ml, TNF-α: 12.72±3.99 pg/ml) compared with the PM2.5 exposure group (in the DVC: IL-1β: 132.7±17.6 pg/ml, TNF-α: 143.8±30.4 pg/ml; in the bronchoalveolar lavage fluid: IL-1β: 34.0±5.3 pg/ml; TNF-α: 15.8±0.8 pg/ml). Microglia in the DVC were less activated in the PM2.5 exposure + melatonin group (25.1±5.4) than in the PM2.5 exposure group (54.6±9.9). Furthermore, the PM2.5 exposure group exhibited an impaired blood-brain barrier in the DVC, which tended to alleviate the PM2.5 exposure + melatonin group. Exposure to PM2.5 induces airway inflammation, central facilitation, and heightened cough sensitivity in guinea pigs. Melatonin significantly inhibits microglia activation and reduces airway and DVC inflammation, which might contribute to attenuated cough hypersensitivity.

Effect of deproteinization with calcium hypochlorite on bond strength and hybrid layer formation of universal adhesives systems to eroded dentin

PurposeTo evaluate the microtensile bond strength and hybrid layer formation of universal adhesive systems applied to eroded dentin deproteinized with calcium hypochlorite. Material and methodsTwo hundred bovine teeth were sectioned, preconditioned with acid, and exposed to a 15-day acid and abrasive challenge. Specimens were divided into five groups (n = 40): deproteinization with calcium hypochlorite at 1 %, 2.5 %, and 5 % concentrations, and two controls (distilled water or 2.5 % sodium hypochlorite). Each group of 20 specimens was treated with either Solare Universal Bond or Scotchbond Universal adhesive systems and light-cured with LED. Bond strength was tested using microtensile tests. Adhesive interfaces were analyzed for failure modes and hybrid layer formation using scanning electron microscopy, and EDX analysis was used to determine elemental composition. ResultsCalcium hypochlorite (1 % and 2.5 %) significantly improved bond strength with both adhesives compared to controls (p < 0.05). Solare Universal Bond showed mainly adhesive fractures, while Scotchbond Universal had more mixed fractures. The 1 % and 2.5 % calcium hypochlorite treatments enhanced hybrid layer extension with Solare Universal Bond (p < 0.05), and matched distilled water with Scotchbond Universal (p < 0.05). Sodium hypochlorite resulted in a thinner hybrid layer (p < 0.05). EDX analysis showed a decrease in Silicon with higher deproteinization concentrations. ConclusionThe bonding effects of deproteinizing eroded dentin with calcium hypochlorite depend on the concentration and adhesive system used. Deproteinization with 5 % calcium hypochlorite improved both bond strength and hybrid layer formation for Solare Universal Bond, while 1 % and 2.5 % concentrations enhanced bond strength for Scotchbond Universal without impacting hybrid layer thickness, which did not adversely affect bond strength.

Functional characterization of peroxiredoxin 5 from yellowtail clownfish (Amphiprion clarkii): Immunological expression assessment, antioxidant activities, heavy metal detoxification, and nitrosative stress mitigation

Peroxiredoxin 5 (Prdx5) is the last recognized member of Prdx family. It is a unique, atypical, 2-Cys antioxidant enzyme, protecting cells from death caused by reactive oxygen species (ROS). In this study, the Prdx5 ortholog of Amphiprion clarkii (AcPrdx5) was identified and characterized to explore its specific structural features and functional properties. The open reading frame of AcPrdx5 is 573 bp long and encodes 190 amino acids containing a mitochondrial targeting sequence, thioredoxin domain, and two conserved cysteine residues responsible for antioxidant function. The predicted molecular weight and theoretical isoelectric point of AcPrdx5 are 20.3 kDa and 9.01, respectively. AcPrdx5 sequences were found to be highly conserved across the other orthologs from various organisms and it distinctively clustered within the fish Prdx5 subclade of the phylogenetic tree. The expression of AcPrdx5 was ubiquitously detected among twelve tested tissues, with the highest level in the brain. Furthermore, the mRNA levels of AcPrdx5 in the blood and head-kidney tissues were significantly (p < 0.05) upregulated following polyinosinic-polycytidylic acid (Poly I:C), lipopolysaccharide (LPS), and Vibrio harveyi immune challenge. A concentration-dependent antioxidant potential of recombinant AcPrdx5 was observed in insulin disulfide bond reduction, heavy metal detoxification, free radical and hydrogen peroxide (H2O2) scavenging assays. Additionally, AcPrdx5 overexpression in fathead minnow (FHM) cells upregulated the antioxidant-associated gene (Rrm1, MAPK, SOD2, and PRDX1) expression after H2O2 treatment, and promoted cell viability upon arsenic (As) exposure. In macrophages, AcPrdx5 overexpression effectively suppressed substantial nitric oxide production under lipopolysaccharide treatment. Collectively, our results suggest that AcPrdx5 may play roles in both antioxidant defense system and innate immune response against pathogenic invasions in A. clarkii.

In vitro study of the treatment of dentin hypersensitivity with gallic acid combined with sodium fluoride

BackgroundDentin hypersensitivity (DH) is a common oral condition that is associated with severe dental pain. Pain relief is a key focus of the treatment of DH. The purpose of this study was to evaluate the blocking and antacid effects of gallic acid (GA) combined with sodium fluoride (NaF) on dentinal tubules in vitro.MethodsNinety dentin discs from human third molars were treated with 6% citric acid for 2 min. Then, the surface morphologies of ten dentin discs were observed by scanning electron microscopy (SEM). The remaining samples were randomly divided into four groups: the NaF group, which was treated with 1000 ppm NaF; the GA group, which was treated with 4000 ppm GA; the GA + NaF group, which was treated with 1000 ppm NaF + 4000 ppm GA; and the blank group, which was treated with deionized water. The dentin permeability of each sample was measured with a water-filled system before processing and after 7 days of treatment. Dentin morphology and surface deposits were observed by SEM. Then, samples from the NaF, GA + NaF and blank groups were subjected to an acid challenge by incubation with 0.02% citric acid for 2 min. SEM and a water-filled system were used to evaluate the blocking and antacid effects of NaF and GA + NaF.Results1. NaF and GA + NaF significantly decreased dentin permeability. The effect of the GA + NaF treatment was more significant. After acid challenge, both groups still exhibited decreased dentin permeability compared with the initial assessment. 2. Compared with the NaF group, the GA + NaF group had more mineral deposits on the dentin surface and dentin tubules. After acid challenge, the deposits in the GA + NaF group were still clearly visible.ConclusionThe combined effect of GA and NaF on reducing dentin permeability by blocking open dentin tubules is better than that of NaF alone. After acid challenge, the GA + NaF treatment still had a better effect.

Acidic/abrasive challenges on simulated non-carious cervical lesions development and morphology

This in vitro investigation assessed how frequency of erosive challenges and duration of toothbrushing abrasion influenced non-carious cervical lesions (NCCLs) development and morphology. Experimental units were prepared using extracted human premolars assigned to four erosive-abrasive frequency protocols (n=16): F0. No acid exposure (negative control), F2.5 K. Acid exposure (1 % citric acid at natural pH) every 2500, F5K. 5000 and F15K. 15000 brushing-strokes. All groups were brushed for 55000 total brushing-strokes. Three-dimension images of the teeth were captured at baseline, after 15000, 35000 and 55000 brushing-strokes, using an intraoral scanner (TRIOS4, 3Shape). WearCompare software (Leeds Digital Dentistry) was used to analyze volumetric tooth loss (mm3) by superimposition followed by subtraction analysis. Lesion angle was measured (ImageJ, NIH) and morphology visually classified. Data were analyzed using ANOVA and Fisher's Exact tests adopting two-sided 5 % significance level. Tooth loss increased with brushing-strokes overall (p<0.001) and for each erosive-abrasive protocol (p<0.001). Acid exposure significantly increased tooth loss (p<0.001), regardless of brushing interval (p<0.001), however by 35000 strokes no tooth loss difference was observed among acid-exposed groups (p>0.05). Control had significantly sharper mean lesion angle (59°) than all acid-exposed groups (∼145°) (p<0.001), and significantly different lesion shape with 94 % wedge-shaped lesions versus 0 %, respectively (p<0.001). In contrast to the control, acid exposure was associated to more striated lesions. Simulated NCCLs developed and progressed differently and more rapidly in the presence of acidic challenges, regardless of their frequency. Exposure to acid impacted the morphology of lesions.

Oral biofilm composition and phenotype in caries-active and caries-free children.

During development of dental caries, oral biofilms undergo changes in microbial composition and phenotypical traits. The aim of this study was to compare the acid tolerance (AT) of plaque from two groups of children: one with severe caries (CA) and one with no caries experience (CF) and to correlate this to the microbial composition and metabolic profile of the biofilms. Dental plaque samples from 20 children (2-5 years) in each group were studied. The AT was analyzed by viability assessment after exposure to an acid challenge (pH 3.5), using LIVE/DEAD® BacLight™ stain and confocal microscopy. Levels of acid tolerance (AT) were evaluated using a scoring system ranging from 1 (no/low AT), to 5 (high/all AT). Metabolic profiles were investigated following a 20 mM glucose pulse for one hour through Nuclear Magnetic Resonance (NMR). Microbial composition was characterized by 16S rRNA Illumina sequencing. The mean AT score of the CA group (4.1) was significantly higher than that of the CF group (2.6, p < 0.05). When comparing the end-products of glucose metabolism detected after a glucose-pulse, the CA samples showed a significantly higher lactate to acetate, lactate to formate, lactate to succinate and lactate to ethanol ratio than the CF samples (p < 0.05). The bacterial characterization of the samples revealed 25 species significantly more abundant in the CA samples, including species of Streptococcus, Prevotella, Leptotrichia and Veillonella (p < 0.05). Our results show that AT in pooled plaque from the oral cavity of children with severe caries is increased compared to that in healthy subjects and that this can be related to differences in the metabolic activity and microbial composition of the biofilms. Thus, the overall phenotype of dental plaque appears to be a promising indicator of the caries status of individuals. However, longitudinal studies investigating how the AT changes over time in relation to caries development are needed before plaque AT could be considered as a prediction method for the development of dental caries.

Molecular mechanism of proteolytic cleavage-dependent activation of CadC-mediated response to acid in E. coli

Colonizing in the gastrointestinal tract, Escherichia coli confronts diverse acidic challenges and evolves intricate acid resistance strategies for its survival. The lysine-mediated decarboxylation (Cad) system, featuring lysine decarboxylase CadA, lysine/cadaverine antiporter CadB, and transcriptional activator CadC, plays a crucial role in E. coli’s adaptation to moderate acidic stress. While the activation of the one-component system CadC and subsequent upregulation of cadBA operon in response to acid and lysine presence have been proposed, the molecular mechanisms governing the transition of CadC from an inactive to an active state remain elusive. Under neutral conditions, CadC is inhibited by forming a complex with lysine-specific permease LysP, stabilized in this inactive state by a disulfide bond. Our study unveils that, in an acidic environment, the disulfide bond in CadC is reduced by the disulfide bond isomerase DsbC, exposing R184 to periplasmic proteases, namely DegQ and DegP. Cleavage at R184 by DegQ and DegP generates an active N-terminal DNA-binding domain of CadC, which binds to the cadBA promoter, resulting in the upregulated transcription of the cadA and cadB genes. Upon activation, CadA decarboxylates lysine, producing cadaverine, subsequently transported extracellularly by CadB. We propose that accumulating cadaverine gradually binds to the CadC pH-sensing domain, preventing cleavage and activation of CadC as a feedback mechanism. The identification of DegP, DegQ, and DsbC completes a comprehensive roadmap for the activation and regulation of the Cad system in response to moderate acidic stress in E. coli.

Cross-Over Application of Algerian Dairy Lactic Acid Bacteria for the Design of Plant-Based Products: Characterization of Weissella cibaria and Lactiplantibacillus plantarum for the Formulation of Quinoa-Based Beverage.

The food industry constantly seeks new starter cultures with superior characteristics to enhance the sensory and overall quality of final products. Starting from a collection of Algerian dairy (goat and camel) lactic acid bacteria, this work focused on the exploration of the technological and probiotic potential of Weissella cibaria (VR81 and LVT1) and Lactiplantibacillus plantarum R12 strains isolated from raw camel milk and fermented milk, respectively. These bioactive strains were selected for their high performance among ten other LAB strains and were used as starter cultures to develop a novel and nutritionally enhanced dairy-like plant-based yogurt using quinoa (Chenopodium quinoa Willd) as a raw matrix. The strains were evaluated for their antagonistic effects against Listeria innocua, Listeria ivanovii, Staphylococcus aureus, Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa, resilience to acidic and osmotic challenges, and tolerance to gastrointestinal mimicking conditions (i.e., pepsin and bile salt). Their aggregation and adhesion profiles were also analyzed. Furthermore, L. plantarum and W. cibaria were tested in single and co-culture for the fermentation and biocontrol of quinoa. The strains exhibited probiotic properties, including a high potential for biocontrol applications, specifically against L. innocua and P. aeruginosa (20 mm diameter zone with the neutralized cell-free supernatant), which disappeared after protease treatment, suggesting that bioactive peptides might be responsible for the observed antimicrobial effect. Additionally, they demonstrated resilience to acidic (pH 2) and osmotic challenges (1M sucrose), tolerance to gastro-intestinal conditions, as well as good aggregation and adhesion profile. Furthermore, the strains were able to produce metabolites of interest, such as exopolysaccharide (yielding up to 4.7 mg/mL) and riboflavin, reaching considerable production levels of 2.5 mg/L upon roseoflavin selection. The application of W. cibaria and L. plantarum as primary starters (both in single and co-culture) for fermenting quinoa resulted in effective acidification of the matrix (ΔpH of 2.03 units) and high-quality beverage production. in vivo challenge tests against L. innocua showed the complete inhibition of this pathogen when L. plantarum was included in the starter, either alone or in combination with W. cibaria. Both species also inhibited Staphylococcus and filamentous fungi. Moreover, the co-culture of mutant strains of L. plantarum R12d and W. cibaria VR81d produced riboflavin levels of 175.41 µg/100 g in fermented quinoa, underscoring their potential as starters for the fermentation, biopreservation, and biofortification of quinoa while also displaying promising probiotic characteristics.

Proteome of the 2-h in vivo Formed Acquired Enamel Pellicle of Adolescents with Erosive Tooth Wear, Caries, or Sound

Introduction: Acquired pellicle (AP) acts as a membrane preventing acids from coming into direct contact with the tooth. Possibly, individuals with different dental health status present changes in its composition that could disrupt this function. Thus, the aim of this study was to compare the protein composition of the AP in adolescents with erosive tooth wear (ETW), caries, or sound. Methods: Calibrated examiners in BEWE index and ICDAS-merged Epi criteria assessed ETW and caries in a sample of 454 systemically healthy adolescents aged 12–15 years old. Thirty subjects from that sample were selected for this study: ETW group (n = 10; total BEWE ≥9 and absence of dentinal caries lesions); caries group (n = 10; total BEWE <9 and with at least one dentinal caries lesion), and sound group (n = 10; total BEWE <9 and absence of dentinal caries lesions). Two-hour-formation AP samples were taken from buccal, occlusal/incisal, palatal/lingual tooth surfaces. Protein composition was analysed by liquid chromatography-tandem mass spectrometry. Using mean reporter ion values, relative abundances of proteins were compared among the three groups to calculate for fold changes. Twofold protein increases or decreases were reported (t test, p < 0.05). Gene Ontology (GO) of included proteins was assigned. Results: Mean age of participants was 13.1 ± 1.14 years and 56.6% were females. The prevalence of ETW was of 66.6% and of dentinal caries of 33.3%. The GO analyses showed that the majority of detected proteins were stress response related. The ETW group disclosed upregulated relative abundance of antileukoprotease (2.85-fold in ETW vs. sound and 2.34-fold in ETW group vs. caries group); histatin (2.42-fold in ETW group vs. sound group and 2.20-fold in ETW group vs. caries group), and prolactin-induced protein (2.30-fold in ETW group vs. sound group and 2.06-fold in ETW group vs. caries group) (p < 0.05). Hemoglobin subunits alpha (HBA) and beta (HBB) showed decreased relative abundances in the ETW and caries groups when compared to the sound group (HBA: 0.42-fold in ETW group and 0.40-fold in caries group; HBB: 0.45-fold in ETW group and 0.38-fold in caries group; p < 0.05). Conclusion: AP from individuals with ETW showed differences when compared to other dental conditions, with relative abundance increasing of some stress response-associated proteins in ETW and a decrease in proteins related to salivary protection against acid challenges.

Disruption of the signal recognition particle pathway leading to impaired growth, sugar metabolism and acid resistance of Lactococcus lactis

Lactococcus lactis is a well-known workhorse for dairy products, whose important industrial traits are tightly associated with numerous cytoplasmic membrane proteins. However, roles of the signal recognition particle (SRP) pathway responsible for membrane protein targeting have not been studied in L. lactis. In this work, the putative genes ffh and ftsY encoding SRP pathway components were identified in the genome of L. lactis NZ9000. Experimental evidence showed that sequence mutation in either the ffh or ftsY was not lethal, but prolonged the lag phase of the resultant mutants Δffh and ΔftsY by 2 h and lowered their biomass to 85.7 % of the wild type under static conditions, as well as deprived the mutants of improved growth capacity under aerobic respiration conditions. Besides, the speeds of glucose consumption and lactate production were significantly decreased in the mutants. Then, the impact of the SPR components on acid resistance was detected, showing that the ffh and ftsY were transcriptionally upregulated by 3.02 ± 1.21 and 8.66 ± 1.01-fold in the wild type during acid challenge at pH 3.0, and cell survival of the Δffh and ΔftsY decreased by10- and 100-fold compared with the wild type. To explore the possible mechanism about the SRP pathway involved in the above physiological traits, proteomics analysis was performed and revealed that disruption of the Ffh or FtsY led to decrease in ribosomal proteins, but increase in DnaK, GroEL and heat shock protein GrpE, indicating that the SRP pathway was closely linked to protein synthesis and folding in L. lactis. Decrease in the fructose-bisphosphate aldolase, respiratory complexes NADH dehydrogenase, as well as glutamate decarboxylase was also detected in the Δffh and ΔftsY, which is consistent with the phenomena of impaired sugar metabolism and acid resistance. Our results demonstrated the dispensable SRP pathway could contribute to the maintenance of metabolism homeostasis and acid resistance of L. lactis.

Effect of combining aminomethacrylate and fluoride against erosive and abrasive challenges on enamel and dentin.

This study evaluated the effect of solutions containing aminomethacrylate copolymer (AA) and sodium fluoride (F; 225ppm F-) or fluoride plus stannous chloride (FSn; 225ppm F-, 800ppm Sn2+) against enamel and dentin erosion/abrasion. Solutions F, FSn, AA, F+AA, FSn+AA, and deionized water as negative control were tested. Bovine enamel and dentin specimens (n=13/solution/substrate) underwent a set of erosion-abrasion cycles (0.3% citric acid [5min, 4×/day], human saliva [1h, 4×/day], brushing [15 s, 2×/day], and treatments [2min, 2×/day]) for each of five days. Initial enamel erosion was evaluated using Knoop microhardness after the first and second acid challenge on day 1, and surface loss with profilometry after day 5. KOH-soluble fluoride was assessed. Data were analyzed with ANOVA/Tukey tests. The combination of fluoride and AA resulted in higher protection against enamel erosion, whereas this was not the case for the combination of AA and FSn. All treatments protected against enamel and dentin loss. The lowest surface loss values were observed with F+AA and FSn+AA. The polymer did not significantly influence the KOH-soluble fluoride formation on enamel/dentin specimens. The aminomethacrylate copolymer effectively enhanced the efficacy of sodium fluoride against initial erosion and improved the control of enamel and dentin wear of F and FSn solutions.

A combination of carbonates and Opuntia ficus-indica extract protects esophageal cells against simulated acidic and non-acidic reflux in vitro

Buffering of stomach acid by antacids is a well-established symptomatic therapy for heartburn. In addition, preparations from prickly pear (Opuntia ficus-indica) have been shown to reduce tissue damage in experimental gastritis models and to attenuate gastrointestinal discomfort in patients. Both active principles have been included in a fixed-combination product for symptomatic treatment of heartburn containing carbonate antacids (CaCO3 and MgCO3) and an extract from Opuntia ficus-indica cladodes. The aim of the study was to characterize the acid neutralization and esophageal cell protective activities of the product and its individual active ingredients in a set of in vitro assays. Acid neutralization was assessed in a simulated stomach model. Protective activity of individual constituents and in combination was analyzed in an esophageal cell line (COLO-680 N) exposed to low pH and deoxycholic acid to simulate acidic and non-acidic reflux challenge. The combination product protected cells against low pH mediated cytotoxicity via acid neutralization by carbonates. Opuntia extract itself and the combination product attenuated bile acid-induced cell irritation as measured by reduced release of proinflammatory interleukin-6 and -8. In conclusion, addition of Opuntia extract to a mineral antacid provides dual protection against acidic and non-acidic simulated reflux challenge.

Effects of silver diammine fluoride with/without potassium iodide on enamel and dentin carious lesions in primary teeth.

To assess the effects of SDF and SDF+KI treatment on enamel and dentin carious lesions in primary teeth using x-ray Microtomography (XMT) and back scattered scanning electron microscopy (BSE-SEM). Artificial enamel caries of 3 caries free primary teeth were created by immersion of the samples in 50 ml demineralization solution for 72 h. Three other teeth with natural dentin caries were selected. Both groups were divided into 3 subgroups: EC-Enamel Control; ES-Enamel with SDF application; ESK-Enamel with SDF followed by KI application; DC-Dentin Control; DS-Dentin with SDF application; DSK-Dentin with SDF followed by KI application. Each tooth was imaged using XMT at 3 time points: (1) Pretreatment; (2) after immersion in remineralization solution for 120 h, with or without SDF or SDF+KI; (3) after subsequent immersion in demineralization solution for 72 h. The change of radiopacities of the lesions in these time points were assessed from the XMT images. After the XMT scans, all teeth were investigated microscopically using BSE-SEM. In EC, no change in linear attenuation coefficient (LAC) was observed after remineralization, but LAC reduction was observed after subsequent demineralization. For ES, thin layer of high LAC material was deposited on the enamel surface after remineralization, and further reduction of LAC was observed after demineralization. In ESK, the surface layer was lost after SDF+KI, and small reduction of LAC was observed after demineralization. In DC, no LAC change was observed after remineralization, but reduction of LAC was detected after demineralization. In DS, high LAC material was formed on the carious dentin surface and randomly inside the lesion. No further LAC change was found after demineralization. In DSK, thick layer of high LAC material was deposited on the carious surface and inside the dentinal tubules. No further LAC reduction was found after subsequent demineralization. SDF and SDF+KI did not protect artificial enamel under acid attack even though Ag products were deposited in the porous enamel. However, SDF and SDF+KI shows protective properties against acid challenges and Ag products are deposited in carious dentin lesion without tubular structure randomly; and within dentinal tubules when these structures are retained.

Validation of clinically related aging models based on enamel wear.

Physiological and erosive wear reported in clinical studies were reviewed, and in vitro aging models were developed to simulate and compare the effect of aging on human teeth with the review data obtained from clinical studies. A review of clinical studies and randomized clinical trials that quantify enamel wear was performed in the PubMed database. The first in vitro analysis evaluated the effect of mechanical chewing simulation only. Enamel specimens were aged in the chewing simulator (up to 1.2 million cycles) with two occlusal loads (30 and 50 N). In the second in vitro analysis, specimens were aged in two aging models. The first model (MT) simulated mechanical and thermal oral challenges: MT1- 240,000 chewing and 10,000 thermal cycles, MT2- 480,000 chewing and 20,000 thermal cycles, MT3- 1.2 million chewing and 50,000 thermal cycles. The second model (MTA) simulated mechanical, thermal, and acidic oral challenges as follows: MTA1- 240,000 chewing, 10,000 thermal and 3-h acidic cycles; MTA2: 480,000 chewing, 20,000 thermal and 6-h acidic cycles, MTA3- 1.2 million chewing, 50,000 thermal and 15-h acidic cycles. The review included 13 clinical studies evaluating tooth wear (eight physiological and five erosive). The results estimated the annual average physiological wear as 38.4µm (9.37-51). In comparison, the MT1 showed wear of 60 (24) µm. Also, the average annual erosive wear in the literature was 179.5µm (70-265) compared to MTA1-induced wear of 209 (14) µm. There was wide variation in tooth wear reported in clinical studies, suggesting a critical need for more accurate studies, possibly based on scanning technologies. Despite this, the data reported using the novel aging models are within a range to be considered consistent with and to simulate tooth wear measured in vivo.

Evaluation of the Efficacy of Ashwagandha and Ginger Paste in Comparison to Commercially Fluoride-Based Toothpaste on Dentinal Tubules Occlusion After Acid Challenge Using Scanning Electron Microscope: In Vitro Study

Evaluation of the Efficacy of Ashwagandha and Ginger Paste in Comparison to Commercially Fluoride-Based Toothpaste on Dentinal Tubules Occlusion After Acid Challenge Using Scanning Electron Microscope: In Vitro Study