Elastic Property Evaluation of Fiberglass and Epoxy Resin Composite Material Using Digital Image Correlation.

This study focused on evaluating the sensitivity and limitations of the simplified equipment used in the Digital Image Correlation (DIC) technique, comparing them with the analog extensometer, based on the mechanical property data of a composite made of fiberglass and epoxy resin. The objectives included establishing a methodology based on the literature, fabricating samples through manual lamination, conducting mechanical tests according to the ASTM D3039 and D3518 standards, comparing DIC with the analog extensometer of the testing machine, and contrasting the experimental results with classical laminate theory. Three composite plates with specific stacking sequences ([0]3, [90]4, and [±45]3) were fabricated, and samples were extracted for testing to determine tensile strength, modulus of elasticity, and other properties. DIC was used to capture deformation fields during testing. Comparisons between data obtained from the analog extensometer and DIC revealed differences of 11.1% for the longitudinal modulus of elasticity E1 and 5.6% for E2. Under low deformation conditions, DIC showed lower efficiency due to equipment limitations. Finally, a theoretical analysis based on classical laminate theory, conducted using a Python script, estimated the longitudinal modulus of elasticity Ex and the shear strength of the [±45]3 laminate, highlighting a relative difference of 31.2% between the theoretical value of 7136 MPa and the experimental value of 5208 MPa for Ex.

Does the Mixing Method of AH Plus Jet Affect its Physicochemical and Mechanical Properties?

INTRODUCTION: The purpose of this study was to evaluate whether the mixing method of AH Plus Jet sealer affects its physicochemical and mechanical properties. METHODS: The properties of AH Plus Jet sealer were analyzed when mixed using either the Auto Mix Tip or manual mixing. The evaluated properties included radiopacity (n = 5), initial and final setting times (n = 5), flow (n = 5), and solubility (n = 3), following specifications outlined in ISO 6876/2012 and ADA Nº 57/2000. pH levels were measured at intervals of 3, 24, 72, and 168 hours (n = 10). The push-out bond strength test was conducted using a universal testing machine and using bovine teeth (n = 30). Failure modes were analyzed with stereomicroscopy. Porosity was evaluated under micro-CT (n = 5), and scanning electron microscopy was also performed (n = 5). One-way analysis of variance and Tukey, unpaired t-tests, or Mann-Whitney tests were used with a significance level of 5%. RESULTS: The Auto Mix exhibited a radiopacity value of 12.11 mmAl, whereas manual mixing resulted in 12.55 mmAl (P > .05). For initial and final setting times, Auto Mix showed 901 minutes and 1779 minutes, respectively, while manual mixing recorded values of 631 minutes and 1504 minutes (P < .05). In terms of flow, Auto Mix demonstrated higher values (25.26 mm) than manual mixing (21.71 mm) (P < .05). No statistical differences were observed between the two methods for solubility and pH (P > .05). Manual mixing presented a higher bond strength value (14.52 MPa) than Auto Mix (9.81 MPa) (P < .05). The mixed failure mode was the most frequent outcome for both methods. The highest porosity was observed for Auto Mix (P < .05). Scanning electron microscopy analysis revealed that manual mixing resulted in a smoother surface with fewer pores and smaller, more evenly distributed agglomerates compared to automatic mixing. CONCLUSION: The mixing method employed for AH Plus Jet sealer influences some physicochemical and mechanical properties of the material.

A three-dimensional cell culture approach to investigate cytotoxic effects and production of inflammatory mediators by epoxy resin-based and calcium silicate-based endodontic sealer.

OBJECTIVES: The aim of the present study was to assess the cytocompatibility of epoxy resin-based AH Plus Jet (Dentsply De Trey, Konstanz, Germany), Sealer Plus (MK Life, Porto Alegre, Brazil), calcium silicate-based Bio-C Sealer (Angelus, Londrina, PR, Brazil), Sealer Plus BC (MK Life) and AH Plus BC (Dentsply) through a tridimensional (3D) culture model of human osteoblast-like cells. METHODS: Spheroids of MG-63 cells were produced and exposed to fresh root canal sealers extracts by 24 h, and the cytotoxicity was assessed by the Lactate Dehydrogenase assay (LDH). The distribution of dead cells within the microtissue was assessed by fluorescence microscopy, and morphological effects were investigated by histological analysis. The secreted inflammatory mediators were detected in cell supernatants through flow luminometry (XMap Luminex). RESULTS: Cells incubated with AH Plus Jet, AH Plus BC, Sealer Plus BC and Bio-C Sealer extracts showed high rates of cell viability, while the Sealer Plus induced a significant reduction of cell viability, causing reduction on the spheroid structure. Sealer Plus and Seaker Plus BC caused alterations on 3D microtissue morphology. The AH Plus BC extract was associated with the downregulation of secretion of pro-inflammatory cytokines IL-5, IL-7, IP-10 and RANTES. CONCLUSIONS: The new AH Plus BC calcium silicate-based endodontic sealer did not reduce cell viability in vitro, while led to the downregulation of pro-inflammatory cytokines. CLINICAL SIGNIFICANCE: Choosing the appropriate endodontic sealer is a crucial step. AH Plus BC demonstrated high cell viability and downregulation of pro-inflammatory cytokines, appearing reliable for clinical use, while Sealer Plus presented lower cytocompatibility.

Premixed calcium silicate-based root canal sealers have better biological properties than AH Plus: A systematic review and meta-analysis of in vivo animal studies and in vitro laboratory studies.

Objectives: The aim was to determine whether premixed calcium silicate-based root canal sealers have better biological properties than AH Plus. Materials and Methods: Searches of studies published up to January 2023 were performed in the PubMed/MEDLINE and EMBASE and via other methods (databases of the International Endodontic Journal, Journal of Endodontics, and gray literature). The inclusion criteria were in vivo animal and in vitro studies that analyzed the response in the dorsal subcutaneous tissue of rats, cell viability, and genotoxicity. Systematic Review Centre for Laboratory Animal Experimentation Risk of Bias (RoB) tool for in vivo studies and modified CONSORT checklist for in vitro were appraised. Meta-analysis was performed using the Stata. Results: Fifty-two studies were included. In the RoB, in vivo studies fulfilled 20%-50% of the items and in vitro 60%-100%. The studies included in the meta-analysis demonstrated better histocompatibility with the premixed calcium silicate-based sealers at 30 days and greater cell viability with these sealers when used in undiluted extracts in experimental period of 72 h and in extracts with 1:2 and 1:4 dilution in 24 and 72 h. In contrast, no difference between materials was found concerning genotoxicity. Conclusion: Premixed calcium silicate-based root canal sealers have better histocompatibility and are less cytotoxic than the epoxy resin-based sealer AH Plus, demonstrating favorable biological behavior.

Epoxy resin-based root canal sealers: An integrative literature review.

The correct obturation of the root canal system achieved by means of a core and a cement is essential for the success of endodontic treatment. There are several root canal cements (RCCs) on the market; however, because of their excellent characteristics, epoxy resin-based sealers (ERBSs) have been widely used. The main aim of this review was to analyze and integrate the available information on different ERBSs. An electronic search was performed in the PubMed and Scopus databases, using "epoxy resin" AND "root canal treatment", and "epoxy resin" AND "endodontics" as search terms. In general, ERBSs have good flow properties, film thickness, solubility, dimensional stability, sealing capacity, and radiopacity. They are also able to adhere to dentin while exhibiting low toxicity and some antibacterial effects. However, their main disadvantage is the lack of bioactivity and biomineralization capability. A large number of ERBSs are available on the market, and AH Plus keeps being the gold standard RCC. Yet, information on many of them is limited or non-existent, which could be due to the fact that some of them are relatively new. The latter emphasizes the need for relevant research on the physicochemical and biological properties of some ERBSs, with the aim of supporting their clinical use with sufficient evidence via prospective and long-term studies.

Characterization of Artificial Stone Produced with Blast Furnace Dust Waste Incorporated into a Mixture of Epoxy Resin and Cashew Nut Shell Oil.

The demand for materials with improved properties and less negative impact on the environment is growing. Artificial stones are examples of these materials produced with up to 90% of particulate material joined by a binder. This article evaluates the physical and mechanical properties of two artificial stones produced with processing steel residue (blast furnace dust waste) and quartz powder. Two binders were used: pure epoxy resin, denoted as ASPB100, or a mixture of 70 wt% epoxy resin with 30 wt% cashew nut shell oil, denoted as ASPB7030. The process took place under vibration, compression (3 MPa/20 min and 90 °C) and vacuum (80 Pa). ASPB100 showed water absorption of 0.07%, while for ASPB7030, it was 0.54%. They were classified as having high mechanical strength associated with bending stress values equal to 32 and 25 MPa, respectively. Stain resistance indicated that both artificial stones had their stains removed with the tested cleaning agents. In this way, the novel artificial stones produced are sustainable alternatives for the application of blast furnace waste and cashew nut shell oil, reducing their negative impacts on the environment.

ARE CALCIUM SILICATE SEALERS LESS CYTOTOXIC AND GENOTOXIC THAN EPOXY RESIN SEALERS? A SYSTEMATIC REVIEW OF IN VITRO STUDIES

Aims: This systematic review aimed to evaluate whether calcium silicate-based sealers are less cytotoxicity and genotoxicity than epoxy resin-based sealers. Materials and Methods: Systematic searches were conducted for studies published up to September 27th, 2022, without restriction for language or year of publication, in the following databases: MEDLINE/PubMed, Scopus, Web of Science and Grey Literature Report. Only in vitrostudies that evaluated the cytotoxicity or genotoxicity of calcium silicate and epoxy resin-based sealers were included. The quality assessment was performed. Results: After duplicate removal and eligibility criteria assessment, a total of thirty-four studies were included. Twenty-eight studies had a low risk of bias, and six studies had amoderate risk of bias. In general, calcium silicate-based sealers had a lower cytotoxic and genotoxic potential than epoxy-resin based sealers.Conclusions: Based on the findings from in vitrostudies, calcium silicate-based sealers are less cytotoxic andgenotoxic than epoxy resin-based sealers

POSTOPERATIVE PAIN INCIDENCE AND INTENSITY FOLLOWING ROOT CANAL OBTURATION WITH BIOCERAMIC AND OTHER SEALERS: A SYSTEMATIC REVIEW WITH META-ANALYSIS

Aims: To investigate whether bioceramicsealers induce a lower incidence and intensity of postoperative pain compared to other sealers. Materials and Methods: Six electronic databases were searched for studies published up to April 2022, following the PICOS strategy: (P) adult patients undergoing root canal treatment or retreatment; (I) root canal filling using bioceramic sealer; (C) root canal filling using other types of sealers; (O) Primary: postoperative pain incidence and/or intensity; Secondary: number of medication intake; (S) randomizedclinical trials. Risk of bias assessment was performed with the revised Cochrane risk of bias tools for randomized trials (RoB 2). Overall certainty of evidence was assessed through the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool. Results: Ten studies were included. Eight studies had a low risk of bias, and two had some concerns risk. Meta-analyses showed no differences regarding postoperative pain intensity and incidence between bioceramic sealers and AH Plus. Number of medication intake seemed to be associated to the preoperative diagnosis. Zinc oxide-eugenol sealer demonstrated an intense postoperative pain compared to bioceramic sealers and AH Plus. GRADE analysis showed a low certainty of evidence for all outcomes. Conclusions: There seem to be no differences between bioceramic sealers and AH Plus regarding postoperative pain intensity and incidence. Number of medication intake seem to be associated to the preoperative diagnosis. Zinc oxide-eugenol evoked a more pronounced postoperative pain.

The effects of heating on the physicochemical properties of tricalcium silicate root canal sealers

Abstract This study evaluated the effect of heating on the physicochemical properties and surface changes of tricalcium silicate sealers. Three tricalcium silicate root canal sealers (Bio-C Sealer, BioRoot-RCS, EndoSequence BC Sealer), and one epoxy resin-based sealer (AH Plus; control) were tested. The effect of heating on setting time (ST) and flowability were assessed according to ANSI/ADA 57 and ISO 6876 standards. Solubility and dimensional change (DC) of the set sealers were evaluated at 24 hours and after 30 days; the pH of the water used in the DC testing was also measured. Tests were repeated with heated sealers in an oven at 100 °C for 1 min. SEM and EDS analysis were performed. Data were analyzed using One-Way ANOVA and Tukey post-hoc tests (α=5%). Heating decreased the ST for AH Plus and EndoSequence (p<0.05). Heating reduced flowability (p<0.05) and increased pH for AH Plus (p<0.05). The solubility of Bio-C (dried specimens) was not in accordance with the ANSI/ADA standard. The solubility of EndoSequence was significantly higher (p<0.05) when it was heated and dried after 30 days. DC of Bio-C (24 h and 30 days), BioRoot-RCS (30 days) and AH Plus (24 h and 30 days) were not in accordance with the standards. SEM and EDS analysis showed significant changes in sealer microstructure after heating. In conclusion, heating decreased the ST and increased the solubility of EndoSequence BC sealer. No significant changes in flowability, DC, and pH were identified for all three tricalcium silicate sealers after heat application. However, all sealers had significant surface changes.

Resumo Este estudo avaliou o efeito do aquecimento nas propriedades físico-químicas e nas alterações superficiais de cimentos de silicato tricálcico. Três cimentos endodônticos de silicato tricálcico (Bio-C Sealer, BioRoot-RCS, EndoSequence BC Sealer) e um cimento à base de resina epóxi (AH Plus) foram testados para avaliar o efeito do aquecimento no tempo de presa (TP) e escoamento de acordo com as normas ANSI/ADA 57 e ISO 6876. A solubilidade e alteração dimensional (AD) dos cimentos foram avaliadas após 24 horas e 30 dias. O pH da água usada no teste de AD também foi medido. Os testes foram repetidos com cimentos aquecidos em um forno a 100 °C por 1 min. Análises em MEV e EDS foram realizadas. Os dados foram analisados pelos testes de ANOVA-1 via e post hoc de Tukey (α=5%). O aquecimento diminuiu o TP para AH Plus e EndoSequence (p<0,05). O aquecimento reduziu o escoamento (p<0,05) e aumentou o pH do AH Plus (p<0,05). A solubilidade do Bio-C (amostras desidratadas) não estava de acordo com o padrão ANSI/ADA. A solubilidade da EndoSequence foi significativamente maior (p<0,05) quando aquecida e desidratada após 30 dias. As AD de Bio-C (24 h e 30 dias), BioRoot-RCS (30 dias) e AH Plus (24 h e 30 dias) não estavam de acordo com as normas ADA e ISO. A análise em MEV e EDS mostrou alterações significativas na estrutura dos cimentos após aquecimento. Em conclusão, o aquecimento diminuiu o TP e aumentou a solubilidade do cimento EndoSequence BC. Não foram identificadas mudanças significativas no escoamento, AD e pH para os cimentos de silicato tricálcico após aquecimento. Porém, todos os cimentos tiveram alterações significativas na superfície.

Identification of Electrical Tree Aging State in Epoxy Resin Using Partial Discharge Waveforms Compared to Traditional Analysis.

Electrical treeing is one of the main degradation mechanisms in high-voltage polymeric insulation. Epoxy resin is used as insulating material in power equipment such as rotating machines, power transformers, gas-insulated switchgears, and insulators, among others. Electrical trees grow under the effect of partial discharges (PDs) that progressively degrade the polymer until the tree crosses the bulk insulation, then causing the failure of power equipment and the outage of the energy supply. This work studies electrical trees in epoxy resin through different PD analysis techniques, evaluating and comparing their ability to identify tree bulk-insulation crossing, the precursor of failure. Two PD measurement systems were used simultaneously-one to capture the sequence of PD pulses and another to acquire PD pulse waveforms-and four PD analysis techniques were deployed. Phase-resolved PD (PRPD) and pulse sequence analysis (PSA) identified tree crossing; however, they were more sensible to the AC excitation voltage amplitude and frequency. Nonlinear time series analysis (NLTSA) characteristics were evaluated through the correlation dimension, showing a reduction from pre- to post-crossing, and thus representing a change to a less complex dynamical system. The PD pulse waveform parameters had the best performance; they could identify tree crossing in epoxy resin material independently of the applied AC voltage amplitude and frequency, making them more robust for a broader range of situations, and thus, they can be exploited as a diagnostic tool for the asset management of high-voltage polymeric insulation.

Development of an Epoxy Matrix Hybrid Composite with Astrocaryum Aculeatum (Tucumã) Endocarp and Kaolin from the Amazonas State in Brazil.

Composites with natural lignocellulosic fillers are being cited as a viable and sustainable alternative to conventional materials, as they combine lower costs with lower weight. In many tropical countries, such as Brazil, there is a considerable amount of lignocellulosic waste that is improperly discarded, which causes pollution of the environment. The Amazon region has huge deposits of clay silicate materials in the Negro River basin, such as kaolin, which can be used as fillers in polymeric composite materials. This work investigates a new composite material (ETK) made of epoxy resin (ER), powdered tucumã endocarp (PTE), and kaolin (K), without coupling agents, with the aim of producing a composite with lower environmental impact. The ETK samples, totaling 25 different compositions, were prepared by cold molding. Characterizations of the samples were performed using a scanning electron microscope (SEM) and a Fourier-transform infrared spectrometer (FTIR). In addition, the mechanical properties were determined via tensile, compressive, three-point flexural and impact tests. The FTIR and SEM results showed an interaction between ER, PTE, and K, and the incorporation of PTE and K reduced the mechanical properties of the ETK samples. Nonetheless, these composites can be considered potential materials to be used for sustainable engineering applications in which high mechanical strength is not a main requirement of the material.

Postoperative pain after root canal filling with bioceramic sealers: a systematic review and meta-analysis of randomized clinical trials.

The aim of this systematic review and meta-analysis (SRM) was to assess postoperative pain (PP) after endodontic treatment with bioceramic root canal sealer compared to AH Plus® sealer. This SRM was carried out in accordance with the items on the PRISMA 2020 checklist and Cochrane guidelines and registered in PROSPERO (CRD42021259283). Only randomized clinical trials (RCTs) were included. Meta-analysis was conducted using R software, the standardized means difference (SMD) measure of effect was calculated for quantitative variables, and the odds ratio (OR) for binary variables. The Cochrane tool (RoB 2.0) was used to assess the risk of bias, and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to assess the quality of evidence. Qualitative and quantitative analysis included 18 and 17 studies, respectively. For quantitative variables, the bioceramic root canal sealer presented less occurrence of postoperative pain than the AH Plus® sealer in 24 h (SMD - 0.17 [- 0.34; - 0.01], p = 0.0340). For binary variables, there was no difference observed between the sealers evaluated, except for sealer extrusion where the bioceramic group had lower post-filling material extrusion (OR 0.52 [0.32; 0.84], p = 0.007). Regarding the risk of bias analysis, low risk was observed for most domains, except allocation that was considered unclear, while the certainty of evidence ranged from moderate to low. The results showed that bioceramics sealers reduced postoperative endodontic pain only after 24 h and showed less sealer extrusion compared to the AH Plus® sealer. However, more robust and standardized clinical trials are needed to confirm the results with less heterogeneity and higher quality of evidence.

Influence of Biochar and Bio-Oil Loading on the Properties of Epoxy Resin Composites.

In this study, we evaluated the use of bio-oil and biochar on epoxy resin. Bio-oil and biochar were obtained from the pyrolysis of wheat straw and hazelnut hull biomass. A range of bio-oil and biochar proportions on the epoxy resin properties and the effect of their substitution were investigated. TGA curves showed improved thermal stability for degradation temperature at the 5% (T5%), 10% (T10%), and 50% (T50%) weight losses on bioepoxy blends with the incorporation of bio-oil and biochar with respect to neat resin. However, decreases in the maximum mass loss rate temperature (Tmax) and the onset of thermal degradation (Tonset) were obtained. Raman characterization showed that the degree of reticulation with the addition of bio-oil and biochar does not significantly affect chemical curing. The mechanical properties were improved when bio-oil and biochar were incorporated into the epoxy resin. All bio-based epoxy blends showed a large increase in Young's modulus and tensile strength with respect to neat resin. Young's modulus was approximately 1955.90 to 3982.05 MPa, and the tensile strength was between 8.73 and 13.58 MPa for bio-based blends of wheat straw. Instead, in bio-based blends of hazelnut hulls, Young´s modulus was 3060.02 to 3957.84 MPa, and tensile strength was 4.11 to 18.11 Mpa.

Elaboración de modelos dentales didácticos en resina epóxica / Elaboration of didactic dental models in epoxy resin

Los modelos de estudio son un registro fundamental para el diagnóstico, el plan de tratamiento, la presentación de caso y la evaluación del progreso del tratamiento dental; son registros anatomofisiológicos de las arcadas dentarias que sirven para evaluar la dentición en los tres planos del espacio y la oclusión en la relación cúspide-fosa, en una dimensión estática y dinámica. Para obtener los modelos de estudio es imprescindible obtener impresiones totales con diversos materiales de impresión de los arcos dentarios, que reproduzcan fielmente todos los detalles anatómicos, para posteriormente obtener un modelo en yeso piedra. Los modelos obtenidos a partir de una impresión generalmente son a base de yeso odontológico, los cuales a pesar de sus mejoras aún conservan algunas características negativas como: baja resistencia a la fractura por impacto, baja resistencia al desgaste por abrasión, inestabilidad dimensional y radiopacidad que impide la simulación de procedimientos endodóncicos. Con la finalidad de mejorar la simulación en la práctica odontológica, se usa la resina epóxica que puede emplearse en la obtención de modelos, este material es más resistente y presenta una mayor resistencia a la abrasión; además es radiolúcido, por lo que es útil para la réplica de preparaciones y procedimientos de simulación endodóntica. Los detalles de la superficie obtenidos con resina epóxica son superiores a los obtenidos con yeso. El uso de simuladores es una herramienta educativa con la que se favorece la adquisición de ciertas habilidades, destrezas, técnicas y competencias necesarias para la formación de estudiantes o profesionales de odontología. En el presente trabajo se describe la técnica para la elaboración de modelos dentales didácticos en resina epóxica para utilizarlos en la enseñanza de la práctica odontológica (AU)

Study studies are a fundamental record for diagnosis, treatment plan, case presentation and evaluation of the progress of dental treatment. They are anatomo-physiological records of the dental arches to evaluate the dentition in the three planes of space and the occlusion in the cusp-fossa relationships, in a static and dynamic dimension. To obtain the study models, it is essential to obtain total impressions with various impression materials of the dental arches, which faithfully reproduce all the anatomical details, in order to later obtain a stone plaster model. Those obtained from an impression are generally based on dental plaster, which despite its improvements still retain some negative characteristics such as: low resistance to fracture by impact, low resistance to wear by abrasion, dimensional instability and radio opacity that prevents the simulation of endodontic procedures. In order to improve simulation in dental practice, the use of epoxy resin can be used to obtain models, this material is more resistant and has greater resistance to abrasion, it is radiolucent, which makes them Useful for replicating preparations and endodontic simulation procedures, the surface details obtained with epoxy resin are superior to those obtained with plaster. The use of simulators is an educational tool that favors the acquisition of certain abilities, skills, techniques and competencies necessary for the training of the student or professional in dentistry. In the present work, the technique for the elaboration of didactic dental models in epoxy resin to be used in the teaching of dental practice is described.(AU)

Water Immersion Aging of Epoxy Resin and Fique Fabric Composites: Dynamic-Mechanical and Morphological Analysis.

Fiber-reinforced composites are among the most investigated and industrially applied materials. Many studies on these composites using fibers, especially with natural fibers, were made in response to an urgent action for ambient preservation. A particularly relevant situation exists nowadays in the area of materials durability. In this respect, no studies on water-immersion-accelerated aging in fique fiber-epoxy composites are reported. This work aimed to fill this gap by investigating the epoxy matrix composites reinforced with 40 vol% fique fabric. The epoxy matrix and the composite, both unaged and aged, were characterized by weight variation, water absorption, morphology, colorimetry (CIELAB method), Fourier transform infrared spectroscopy (FTIR) and dynamic-mechanical analysis (DMA). The main results were that degradation by water presents appearance of complex microfibril structures, plasticization of epoxy resin, and debonding of the fique fiber/epoxy matrix. The most intense color change was obtained for the water-immersion-aged epoxy by 1440 h. Cole-Cole diagrams revealed the heterogeneity of the materials studied.

Cleaning and microstructural effects of amyl acetate on pulp chamber dentin impregnated with epoxy resin-based endodontic sealer.

OBJECTIVE: To evaluate the cleaning potential of 95% ethanol, acetone, and amyl acetate solutions used solely or in association, to remove epoxy resin-based sealer residues from pulp chamber dentin and their microstructural effects. MATERIALS AND METHODS: One hundred and eighty bovine incisor specimens were divided into nine groups according to the cleaning protocol: ET (ethanol); AC (acetone); AA (amyl acetate); E1: AA+AC; E2: AA+ET; E3: AC+ET; E4: AA+AC+ET; PC (positive control), and NC (negative control). All groups were impregnated with epoxy resin-sealer, except NC. Ninety specimens were divided into groups (n = 10) for evaluation of persistence of residues and amount of open dentinal tubules by SEM analysis and evaluation of chemical compounds on the dentin surface after cleaning with electron dispersive spectroscopy. The others 90 specimens were submitted to Knoop microhardness evaluation. Persistence of residues data were submitted to the Kruskal Wallis and Dunn tests (α = 0.05). Open dentinal tubules and microhardness data were submitted to one-way ANOVA and Mann Whitney tests (α = 0.05). RESULTS: AA and E4 protocols showed the lowest persistence of residues. E4 group had the highest incidence of open dentinal tubules. E3 and E4 groups showed no changes in the atomic ratio Ca/P, which was similar to NC group. E4 group did not present W, an element presents in all the other groups. ET and E4 protocols showed the smallest reduction in dentin microhardness. CONCLUSIONS: The combination of amyl acetate, acetone and ethanol is the most effective and safe protocol to remove epoxy sealer residues on pulp chamber dentin. Moreover, it has the lowest microhardness reduction. CLINICAL SIGNIFICANCE: The combined use of amyl acetate, acetone, and ethanol enhanced the cleaning of pulp chamber dentin with minimal microstructural damage.

Impact of cleansing protocols to remove endodontic sealer residues on the adhesive interface: Bonding with universal adhesive systems.

OBJECTIVE: The aim of this study was to evaluate the effectiveness of cleansing protocols to remove sealer residues using different cleaning strategies and the effect of bond strength of two universal adhesives to dentin impregnated with epoxy resin-based sealer. MATERIALS AND METHODS: Fifty bovine dentin specimens were impregnated with epoxy resin-based sealer containing calcium hydroxide (Sealer Plus) and submitted to cleansing protocols (n = 10): negative control (NC), positive control (PC), 95% ethanol (ET), xylol (XI), and amyl acetate (AA). Specimens were evaluated by scanning electron microscope (SEM). Other 100 specimens were submitted to the same protocols (n = 20). Each protocol was divided into subgroups (n = 10) according to the universal adhesive system used: Scotchbond Universal (SU); Ambar Universal (AU). Bond strength was evaluated by micro-shear bond test (µSBT). Persistence of residues data were assessed with Kruskal-Wallis and Dunn's tests. µSBT data were analyzed with two-way ANOVA (α = 5%). RESULTS: ET presented higher persistence of residues compared to AA and XI (p < 0.05). AA and XI were similar from each other (p > 0.05). AU and SU presented similar µSBT values, regardless of the cleansing solution (p > 0.05). SU-NC presented the highest µSBT among all conditions (p < 0.05). CONCLUSION: The bond strength of universal adhesives was not affected by different amounts of sealer residues after different cleaning protocols. CLINICAL SIGNIFICANCE: Non-polar substances such as amyl acetate and xylol are effective for removing residues from epoxy resin-based endodontic sealers.

Hybrid Materials Based on Nanoparticles Functionalized with Alkylsilanes Covalently Anchored to Epoxy Matrices.

In this work, the surface modification of zinc oxide nanoparticles (ZnO-NPs) with 3-glycidyloxy-propyl-trimethoxysilane (GPTMS) was investigated. The ZnO-NPs were synthesized using the physical method of continuous arc discharge in controlled atmosphere (DARC-AC). The surface modification was carried out using a chemical method with constant agitation for 24 h at room temperature. This surface functionalization of zinc oxide nanoparticles (ZnO-NPs-GPTMS) was experimentally confirmed by infrared spectroscopy (FT-IR), TGA, and XRD, and its morphological characterization was performed with SEM. The increase in mechanical bending properties in the two final hybrid materials compared to the base polymers was verified. An average increase of 67% was achieved with a moderate decrease in ductility. In the case of compressive strength, they showed mixed results, maintaining the properties. With respect to thermal properties, it was observed that inorganic reinforcement conferred resistance to degradation on the base material, giving a greater resistance to high temperatures.

Real-Time Monitoring Polymerization Reactions Using Dipolar Echoes in 1H Time Domain NMR at a Low Magnetic Field.

1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin, using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier-Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways, we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficiently used for monitoring and characterizing this type of reaction. Nonetheless, the DF-MSE method showed intrinsic advantages, such as easier data handling and processing, and seems to be the method of choice for monitoring this type of reaction. In general, the procedure is suitable for characterizing reactions involving the formation of solid products from liquid reagents, with some adaptations concerning the reaction model.

Influence of the use of chelating agents as final irrigant on the push-out bond strength of epoxy resin-based root canal sealers: A systematic review.

This systematic review (PROSPERO - CRD42020150722) was performed to answer the following question: Does the use of chelating agents affect the dislodgment resistance of epoxy resin-based root canal sealers? A search was conducted in PubMed, EMBASE, Scopus, LILACS and Web of Science, hand searching of two endodontic journals and grey literature until September 2020. Extracted data included: teeth used, sample size, root canal preparation, irrigant, chelating solution, neutralisation solution, type of resin-based sealer and obturation approach, storage method and duration, root third and slice thickness, plunger dimension and loading direction and the push-out testing parameters and values. The search retrieved a total of 2.389 studies. After analysis, 12 studies fulfilled the eligibility criteria and were included. Most of the final irrigation protocols with chelating agents had a positive impact and promoted an improvement in the dislodgment resistance of epoxy resin-based sealers to the root dentin.