Application of Silver Nanoparticles to Improve the Antibacterial Activity of Orthodontic Adhesives: An In Vitro Study.

There is a significant change in the bacterial plaque populations in the oral cavity during and after orthodontic treatment. Numerous studies have demonstrated that 2−96% of patients could increase the risk of white spot lesions. Streptococcus mutans and Lactobacilli ssp. are responsible for these white spot lesions. In this work, silver nanoparticles (AgNPs) with a diameter of 11 nm and dispersed in water were impregnated onto three different commercial orthodontic adhesives at 535 µg/mL. The shear bond strength (SBS) was assessed on 180 human premolars and metallic brackets. The premolars were divided into six groups (three groups for the commercial adhesives and three groups for the adhesives with AgNPs). All the groups were tested for their bactericidal properties, and their MIC, MBC, and agar template diffusion assays were measured. After adding AgNPs, the SBS was not significantly modified for any adhesive (p > 0.05), and the forces measured during the SBS did not exceed the threshold of 6 to 8 MPa for clinical acceptability in all groups. An increase in the bactericidal properties against both S. mutans and L. acidophilus was measured when the adhesives were supplemented with AgNPs. It was concluded that AgNPs can be supplement commercial orthodontic adhesives without modifying their mechanical properties with improved bactericidal activity.

Osteoregeneration of Critical-Size Defects Using Hydroxyapatite-Chitosan and Silver-Chitosan Nanocomposites.

Bone is a natural nanocomposite composed of proteins and minerals that can regenerate itself. However, there are conditions in which this process is impaired, such as extensive bone defects and infections of the bone or surrounding tissue. This study evaluates the osteoregenerative capacity of bone grafting materials in animals with induced bone defects. Colloidal chitosan dispersion nanocomposites, nanohydroxyapatite−chitosan (NHAP-Q) and nanosilver−chitosan (AgNP-Q), were synthesized and characterized. Non-critical-size defects in Wistar rats were used to evaluate the material's biocompatibility, and critical-size defects in the calvarias of guinea pigs were used to evaluate the regenerative capacity of the bones. Moreover, the toxicity of the nanocomposites was evaluated in the heart, liver, spleen, kidneys, and skin. Histological, radiographic, and electron microscopy tests were also performed. The results showed that neither material produced pathological changes. Radiographic examination showed a significant reduction in defects (75.1% for NHAP-Q and 79.3% for AgNP-Q), angiogenesis, and trabecular formation. A toxicological assessment of all the organs did not show changes in the ultrastructure of tissues, and the distribution of silver was different for different organs (spleen > skin > heart > kidney > liver). The results suggest that both materials are highly biocompatible, and AgNP-Q achieved similar bone regeneration to that reported with autologous bone. The main research outcome of the present study was the combination of two types of NPs to enhance antimicrobial and osteoregeneration activities. These colloidal chitosan dispersions show promise as future biomaterials in the medical field for applications in fast-healing fractures, including broken bones in the oral cavity and hip replacement infections.

Proteomic analysis of an Enterococcus faecalis mutant generated against the exposure to silver nanoparticles.

INTRODUCTION: Nanoparticles (NPs) have been widely studied as an alternative to antibiotic use due to their antimicrobial properties at lower concentrations. Enterococcus faecalis is a facultative Gram-positive microorganism inhabiting the gastrointestinal tract of humans and animals. It can also be present in other environments such as the oral cavity, water, sewage, soil and food. AIMS: We evaluated whether E. faecalis could develop resistance to silver NPs (AgNPs) after exposure to sublethal concentrations of the NPs. METHODS AND RESULTS: Proteomic analyses revealed that different pathways were activated during the acquired resistance under sublethal concentrations, and selected genes were validated by qPCR. CONCLUSIONS: The results of this study showed that E. faecalis is capable of generating resistance to AgNPs. SIGNIFICANCE AND IMPACT OF THE STUDY: To avoid the generation of resistance against AgNPs, future use of these NPs should be combined with other NPs prepared with different metals to prevent the dissemination of resistant strains.

Identification of Gingival Microcirculation Using Laser Doppler Flowmetry in Patients with Orthodontic Treatment-A Longitudinal Pilot Study.

Background and Objectives: Orthodontic tooth movement is associated with inflammatory responses. The aim of this study was to identify gingival microcirculation using laser Doppler flowmetry in patients with orthodontic treatment. Materials and Methods: A longitudinal pilot study was performed. The participants were selected using a non-probability consecutive sampling. Of the twenty-five subjects, a total of six (four women and two men) complied with the criteria. Before and during the treatment, the oral hygiene index, gingival index, probing depth, level of epithelial attachment, and gingival microcirculation were evaluated with laser Doppler flowmetry (integrated parameters: 1. integrated primary basal flow (IPBF), 2. integrated total secondary real flow (ITSRF), and 3. difference between integration (DBI)) in all of the participants). Results: (a) An increase in gingival blood flow was identified at all time intervals with different arches during orthodontic treatment. (b) The IPBF and ITSRF (with treatment) identified after 20 min (treatment initial stage) were compared with the different time intervals, and we observed an increase in gingival perfusion at the 24th, 48th, and 72nd hours in some arches. (c) In the DBI, we found statistically significant differences (p < 0.005) in the Nitinol group of 0.016 inches among all the time intervals (24 h, 48 h, and 72 h) within the 30-day interval, observing a flow increase three times greater than the basal flow after 30 days. Conclusions: Healthcare professionals must identify the inflammatory processes in treatment to observe and discontinue use of harmful methods in clinical practice.

Presence of SARS-CoV-2 and Its Entry Factors in Oral Tissues and Cells: A Systematic Review.

Background and Objectives: The aim of this systematic review is to summarize the current data about the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its entry factors in oral tissues and cells. Materials and Methods: This systematic review was carried out based on the Preferred Reporting Items for a Systematic Review and Meta-Analysis (PRISMA). Three databases were analyzed (Pubmed, Web of science and Scopus) by three independent researchers. From the 18 identified studies, 10 of them met the inclusion criteria. The presence of SARS-CoV-2 or its entry factors (angiotensin-converting enzyme II (ACE2), transmembrane serine proteases (TMPRSS), and furin) was analyzed in these 10 studies during the pandemic. Results: ACE2 expression was analyzed in 9 of the 10 studies. ACE2 is expressed mainly in the tongue, oral mucosa, salivary glands and epithelial cells. The expression of the TMPRSS2 gene or protein was analyzed in 6 studies. These studies reported that the expression of TMPRSS2 was mainly in the salivary glands, tongue, sulcular epithelium and oral mucosa; as well as in cells of the salivary glands (ductal, acinar and myoepithelial cells) and the tongue (the spinous-based cell layer, horny layer and the epithelial surface). Other TMPRSS were also reported. The expression of TMPRSS3, TMPRSS4, TMPRSS5, TMPRSS7 and TMPRSS11D was reported mainly in salivary glands and in epithelial-type cells. Furan expression was analyzed in three studies. The expression of furin was detected mainly in epithelial cells of the tongue. A variety of methods were used to carry out the detection of SARS-CoV-2 or its input molecules. Conclusions: These results show that SARS-CoV-2 can infect a wide variety of oral tissues and cells, and that together with the theories dedicated to explaining the oral symptoms present in SARS-CoV-2 positive patients, it provides us with a good scientific basis for understanding the virus infection in the oral cavity and its consequences.

Effective control of biofilms by photothermal therapy using a gold nanorod hydrogel.

Biofilms are matrices synthesized by bacteria containing polysaccharides, DNA, and proteins. The development of biofilms in infectious processes can induce a chronic inflammatory response that may progress to the destruction of tissues. The treatment of biofilms is difficult because they serve as a bacterial mechanism of defense and high doses of antibiotics are necessary to treat these infections with limited positive results. It has been demonstrated that photothermal therapy using gold nanorods (AuNRs) is an attractive treatment because of its anti-biofilm activity. The purpose of this work was to generate a novel chitosan-based hydrogel embedded with AuNRs to evaluate its anti-biofilm activity. AuNRs were synthesized by the seed-mediated growth method and mixed with the chitosan-based hydrogel. Hydrogels were characterized and tested against two bacterial strains by irradiating the produced biofilm in the presence of the nanoformulation with a laser adjusted at the near infrared spectrum. In addition, the safety of the nanoformulation was assessed with normal human gingival fibroblasts. Results showed that a significant bacterial killing was measured when biofilms were exposed to an increase of 10°C for a short time of 2 min. Moreover, no cytotoxicity was measured when normal gingival fibroblasts were exposed to the nanoformulation using the bactericidal conditions. The development of the reported formulation can be used as a direct application to treat periodontal diseases or biofilm-produced bacteria that colonize the oral cavity.

Expression of calcitonin gene-related peptide and pulp sensitivity tests in irreversible pulpitis.

The aim of the present study was to identify the relationship between the expression of calcitonin gene-related peptide (CGRP) and the responses of pulp sensitivity tests in healthy pulps and irreversible pulps by performing a cross-sectional study on patients. Two hundred subjects were evaluated. A total of 75 subjects complied with the criteria. The participants were divided into two groups: a) Healthy pulp (subjects [n = 35] having posterior teeth with clinically normal pulp tissue), and b) Irreversible pulpitis (subjects [n = 40] having posterior teeth with irreversible pulpitis). All participants were evaluated using the following variables: a) medical and dental history, b) pulp sensitivity tests, c) expression of CGRP by the enzyme-linked immunosorbent assay (ELISA), and d) expression levels of mRNA CGRP and mRNA CGRP receptor genes. We determined that the responses of the cold test between 4 and ≥12 s presented a higher average of the expression of CGRP in the group having irreversible pulpitis (p = 0.0001). When we compared the groups with the value of the electrical impulse, we found statistically significant differences (p = 0.0001), observing positive responses to the test with electrical impulses of 7 to 10, with an average of 72.15 ng/mL of CGRP in the irreversible pulpitis group. High values of CGRP expression were observed in that group in the responses of pulp sensitivity.

Diagnostic accuracy of three placement sites for the cold test in subjects amongst different age groups.

BACKGROUND: The cold test is a specific test of pulp sensitivity and is part of the endodontic diagnosis. The aim of this study was to identify the diagnostic accuracy including sensitivity, specificity, accuracy, positive predictive value and negative predictive value in three sites for the cold test in teeth with a need for endodontic treatment within different age groups from both genders. METHODS: A cross-sectional study was performed, evaluating 425 subjects. Two hundred and fifty-eight subjects from both genders from the ages of 17-27, 28-39, 40-50, and 51-65 years-old participated in the study. The cold test studied was 1, 1, 1, 2-tetrafluoroethane, and the gold standard was established through direct pulp inspection. The sites evaluated in the study were: The sites evaluated in the study were: a) the middle third of the buccal surface; b) the cervical third of the buccal surface, and c) the middle third of the lingual surface. RESULTS: The highest diagnosted accuracy was observed on the middle third buccal surface with an accuracy of = 0.97, a sensitivity of = 1.00, a specificity of 0.95, a predictive value of = 0.95 and a negative predictive value of = 1.00. This was in the female group aged from 40 to 50 years old. CONCLUSION: The tables of this study can be used as an auxiliary for pulp sensitivity tests.

Molecular Mechanisms of Bacterial Resistance to Metal and Metal Oxide Nanoparticles.

The increase in bacterial resistance to one or several antibiotics has become a global health problem. Recently, nanomaterials have become a tool against multidrug-resistant bacteria. The metal and metal oxide nanoparticles are one of the most studied nanomaterials against multidrug-resistant bacteria. Several in vitro studies report that metal nanoparticles have antimicrobial properties against a broad spectrum of bacterial species. However, until recently, the bacterial resistance mechanisms to the bactericidal action of the nanoparticles had not been investigated. Some of the recently reported resistance mechanisms include electrostatic repulsion, ion efflux pumps, expression of extracellular matrices, and the adaptation of biofilms and mutations. The objective of this review is to summarize the recent findings regarding the mechanisms used by bacteria to counteract the antimicrobial effects of nanoparticles.

Expression of calcitonin gene-related peptide and pulp sensitivity tests in irreversible pulpitis

Abstract The aim of the present study was to identify the relationship between the expression of calcitonin gene-related peptide (CGRP) and the responses of pulp sensitivity tests in healthy pulps and irreversible pulps by performing a cross-sectional study on patients. Two hundred subjects were evaluated. A total of 75 subjects complied with the criteria. The participants were divided into two groups: a) Healthy pulp (subjects [n = 35] having posterior teeth with clinically normal pulp tissue), and b) Irreversible pulpitis (subjects [n = 40] having posterior teeth with irreversible pulpitis). All participants were evaluated using the following variables: a) medical and dental history, b) pulp sensitivity tests, c) expression of CGRP by the enzyme-linked immunosorbent assay (ELISA), and d) expression levels of mRNA CGRP and mRNA CGRP receptor genes. We determined that the responses of the cold test between 4 and ≥12 s presented a higher average of the expression of CGRP in the group having irreversible pulpitis (p = 0.0001). When we compared the groups with the value of the electrical impulse, we found statistically significant differences (p = 0.0001), observing positive responses to the test with electrical impulses of 7 to 10, with an average of 72.15 ng/mL of CGRP in the irreversible pulpitis group. High values of CGRP expression were observed in that group in the responses of pulp sensitivity.

Cytotoxic and Bactericidal Effect of Silver Nanoparticles Obtained by Green Synthesis Method Using Annona muricata Aqueous Extract and Functionalized with 5-Fluorouracil.

Nanomaterials obtained by green synthesis technologies have been widely studied in recent years owing to constitute cost-effective and environmental-friendly methods. In addition, there are several works that report the simultaneous performance of the reducer agent as a functionalizing agent, modifying the properties of the nanomaterial. As a simple and economical synthesis methodology, this work presents a method to synthesize silver nanoparticles (AgNPs) using Annona muricata aqueous extract and functionalized with 5-fluorouracil (5-FU). The processes of reduction, nucleation, and functionalization of the nanoparticles were analyzed by UV-Vis absorption spectroscopy, and it was found that they are the function of the contact time of the metal ions with the extract. The structural characterization was carried out by transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD). The antibacterial properties of the synthetized nanomaterials were tested using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Enterococcus faecalis, Staphylococcus aureus, and Escherichia coli growth.

Effects of silver nanoparticles on the bonding of three adhesive systems to fluorotic enamel.

The objective was to evaluate the effect of adding silver nanoparticles into three commercial adhesive systems (Excite™, Adper Prompt L-Pop™ and AdheSE™). Nanoparticles were prepared by a chemical method then mixed with the commercial adhesive systems. This was later applied to the fluorotic enamel, and then micro-tensile bond strength, contact angle measurements and scanning electron microscopy observations were conducted. The commercial adhesive systems achieved the lowest micro-tensile bond strength (Excite™: 11.0±2.1, Adper Prompt L-Pop™: 14.0±5.4 and AdheSE™: 16.0±3.0 MPa) with the highest adhesive failure mode related with the highest contact angle (46.0±0.6º, 30.0±0.5º and 28.0±0.4º respectively). The bond strength achieved in all the experimental adhesive systems (19.0±5.4, 20.0±4.0 and 19.0±3.5 MPa respectively) was statistically higher (p<0.05) than the control and showed the highest cohesive failures related to the lowest contact angle. Adding silver nanoparticles in order to decrease the contact angle improve the adhesive system wetting and its bond strength.

Facile Synthesis, Characterization, and Cytotoxic Activity of Europium-Doped Nanohydroxyapatite.

The objective of this study was to synthetize europium-doped nanohydroxyapatite using a simple aqueous precipitation method and, thereafter, characterize and impregnate selected samples with 5-fluorouracil in order to explore the properties and the releasing capacity of this material. The nanohydroxyapatite was doped with 3, 5, 10, and 20 wt% of europium. The obtained samples were characterized after they were dried at 80°C and hydrothermal treated at 120°C by 2 hours. The samples were analyzed by transmission electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and photoluminescence. Also, impregnation and release of 5-fluorouracil were assessed in PBS. The toxicity effects of all samples were studied using viability assays on human fibroblasts cells (HGF-1) in vitro. The sizes of the crystallites were about 10-70 nm with irregular morphology and present the phase corresponding to the JCPDS card 9-0432 for hydroxyapatite. The results of the toxicity experiments indicated that doped and undoped powders are biocompatible with fibroblasts cells. Hydroxyapatite samples doped with 5% of europium and loaded with 5-fluorouracil release almost 7 mg/L of the drug after 60 minutes in PBS and decrease the viability of HeLa cells after 24 hours.

Synergistic bactericidal activity of Ag-TiO2 nanoparticles in both light and dark conditions.

High-throughput screening was employed to evaluate bactericidal activities of hybrid Ag-TiO2 nanoparticles comprising variations in TiO2 crystalline phase, Ag content, and synthesis method. Hybrid Ag-TiO2 nanoparticles were prepared by either wet-impregnation or UV photo deposition onto both Degussa P25 and DuPont R902 TiO2 nanoparticles. The presence of Ag was confirmed by ICP, TEM, and XRD analysis. The size of Ag nanoparticles formed on anatase/rutile P25 TiO2 nanoparticles was smaller than those formed on pure rutile R902. When activated by UV light, all hybrid Ag-TiO2 nanoparticles exhibited stronger bactericidal activity than UV alone, Ag/UV, or UV/TiO2. For experiments conducted in the dark, bactericidal activity of Ag-TiO2 nanoparticles was greater than either bare TiO2 (inert) or pure Ag nanoparticles, suggesting that the hybrid materials produced a synergistic antibacterial effect unrelated to photoactivity. Moreover, less Ag(+) dissolved from Ag-TiO2 nanoparticles than from Ag nanoparticles, indicating the antibacterial activities of Ag-TiO2 was not only caused by releasing of toxic metal ions. It is clear that nanotechnology can produce more effective bactericides; however, the challenge remains to identify practical ways to take advantage of these exciting new material properties.