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Introduction: Thrombogenesis, a major cause of implantable cardiovascular device failure, can be addressed through the use of biodegradable polymers modified with anticoagulating moieties. This study introduces a novel polyester urethane urea (PEUU) functionalized with various anti-platelet deposition molecules for enhanced antiplatelet performance in regenerative cardiovascular devices. Methods: PEUU, synthesized from poly-caprolactone, 1,4-diisocyanatobutane, and putrescine, was chemically oxidized to introduce carboxyl groups, creating PEUU-COOH. This polymer was functionalized in situ with polyethyleneimine, 4-arm polyethylene glycol, seleno-L-cystine, heparin sodium, and fondaparinux. Functionalization was confirmed using Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy. Bio-compatibility and hemocompatibility were validated through metabolic activity and hemolysis assays. The anti-thrombotic activity was assessed using platelet aggregation, lactate dehydrogenase activation assays, and scanning electron microscopy surface imaging. The whole-blood clotting time quantification assay was employed to evaluate anticoagulation properties. Results: Results demonstrated high biocompatibility and hemocompatibility, with the most potent anti-thrombotic activity observed on pegylated surfaces. However, seleno-L-cystine and fondaparinux exhibited no anti-platelet activity. Discussion: The findings highlight the importance of balancing various factors and addressing challenges associated with different approaches when developing innovative surface modifications for cardiovascular devices.
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Cancer is the main cause of death in the world, with lung cancer being responsible for most of the deaths, either because it is often diagnosed at a late stage or due to the lack of effective therapeutic methods. Crotoxin (CTX) is the main component of South American rattlesnake venom, corresponding to about 60% of its composition. In recent years, its immunomodulatory, anti-inflammatory, and antitumor properties have been described, making it a new possible candidate for therapeutic use. In order to study the regulatory role of CTX, lung carcinogenesis was induced by intraperitoneal injection of urethane (URT) in mice phenotypically selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory responses. From a genetic background, these animals have different sensitivity to urethane-induced lung tumorigenesis due to the fixation of alleles with opposite effects at the pas1 locus (Pulmonary adenoma susceptibility 1) during the selection process, with a susceptibility allele (pas1s ) in the AIRmin mice and a resistance allele (pas1r ) in the AIRmax mice. Considering these differences and the described effects of CTX, these animals were subjected to different treatments with CTX and evaluated regarding their tumorigenesis in terms of incidence and cellular dynamics in the lung. The results showed that the phenotypes of resistance and susceptibility in the mice were preserved, even after CTX administration. Additionally, possible modulatory effects of CTX were observed, mainly in histopathologic analysis on the groups where CTX was administered 10 days after tumor induction by urethane with a concentration of 8 μg/kg and 16 μg/kg, and also on the treatment where CTX was administered every 10 days with a concentration of 8 μg/kg.
O câncer é a principal causa de morte no mundo, sendo o câncer de pulmão o responsável pelo maior número de óbitos, seja por ser diagnosticado muitas vezes num estágio tardio ou pela falta de métodos terapêuticos eficazes. A crotoxina (CTX) é o principal componente do veneno da cascavel (Crotalus durissus terrificus), correspondendo a cerca de 60% da sua composição. Nos últimos anos, têm sido descritas as suas propriedades imunomoduladoras, anti-inflamatórias e antitumorais, sendo apresentada como uma possível candidata para utilização terapêutica. Com o intuito de estudar o papel regulador da CTX, foi induzida carcinogênese pulmonar por injeção intraperitoneal de uretana (URT), em animais fenotipicamente selecionados para resposta inflamatória aguda máxima (AIRmax) ou mínima (AIRmin). Do ponto de vista genético, estes animais apresentam uma sensibilidade diferenciada à tumorigênese pulmonar induzida por URT, relacionada à fixação de alelos de efeitos opostos no locus pas1 (Pulmonary adenoma susceptibillity 1) durante o processo de seleção, com um alelo de suscetibilidade (pas1s ) na linhagem AIRmin, e um alelo de resistência (pas1r ) na linhagem AIRmax. Considerando estas diferenças entre as linhagens e os efeitos descritos da CTX, esses animais foram submetidos a diferentes tratamentos com CTX e avaliados quanto à tumorigênese, no que concerne à incidência e dinâmica celular no pulmão. Os resultados demonstraram que os fenótipos de resistência e susceptibilidade estão preservados entre as linhagens, mesmo após a administração da CTX. Adicionalmente, foram observados possíveis efeitos moduladores da CTX, principalmente nas análises histopatológicas nos grupos de tratamento quando a CTX é aplicada 10 dias após a administração de URT na concentração de 8 μg/kg e 16 μg/kg, assim como quando aplicada continuamente de 10 em 10 dias numa concentração de 8 μg/kg.
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The title compound, C20H16N2O6 (systematic name: 4-hy-droxy-phenyl N-{4-[(4-hy-droxy-phen-oxy-carbon-yl)amino]-phen-yl}carbamate), contains two urethane groups substituting the central benzene ring in para positions. The mol-ecule is centrosymmetric, and displays a twisted conformation for the three aromatic rings [the dihedral angle between central benzene ring and the urethane group is 33.4â (6)°, and that between the latter and the terminal ring is 65.1â (1)°]. In the crystal, a three-dimensional framework is formed through O-Hâ¯O and N-Hâ¯O hydrogen bonds involving the hy-droxy and urethane functional groups, respectively.
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Dressings made with polyurethanes have been found to exhibit good and varied biological properties that make them good candidates for this application. However, as has been seen, the wound-healing process is complex, which includes four different stages. So far, the design and evaluation of polyurethane for wound dressing has focused on achieving good properties (mechanical, physicochemical, and biological), but each of them separates from the others or even directed at only one of the stages of skin wound-healing. Therefore, the aim of this systematic review is to explore the applications of polyurethanes in wound dressings and to determine whether could be designed to cover more than one stage of skin wound-healing. The PRISMA guidelines were followed. The current research in this field does not consider each stage separately, and the design of polyurethane dressings is focused on covering all the stages of wound healing with a single material but is necessary to replace polyurethanes in short periods of time. Additionally, little emphasis is placed on the hemostasis stage and further characterization of polyurethanes is still needed to correlate mechanical and physicochemical properties with biological properties at each stage of the wound-healing. Current research demonstrates an effort to characterize the materials physiochemically and mechanically, but in terms of their biological properties, most of the literature is based on the performance of histological tests of explants morphologically probing the compromised tissues, which give an indication of the potential use of polyurethanes in the generation of wound-healing dressings.
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This work reports the synthesis of a monomer 2-((2-(3-(prop-1-en-2-yl)phenyl)propan-2-yl)carbamoyl)oxy)ethyl methacrylate (MVTPM) and the evaluation of its performance as an additive in the formulation of Bis-GMA/TEGDMA based composite resins. Experimental composite resins formulated with the MVTPM monomer were compared with a control reference. Double bond conversion, polymerization kinetics, shrinkage and associated stress, sorption, and aqueous solubility, cell viability, as well as mechanical properties were evaluated according to international measurements standards. The experimental composite resins show comparable mechanical properties with the control reference and improvements in other properties, such as better hydrolytic and hygroscopic behavior and lower shrinkage stress, are reported. This makes MVTPM monomer potentially useful in the formulation of dental composite resins.
Assuntos
Resinas Compostas , Ácidos Polimetacrílicos , Bis-Fenol A-Glicidil Metacrilato/química , Resinas Compostas/química , Teste de Materiais , Metacrilatos , Polietilenoglicóis/química , Polimerização , Ácidos Polimetacrílicos/química , Poliuretanos/químicaRESUMO
Significant evidence shows that the acquisition of delay conditioning can occur in out-of-awareness states, such as under anesthesia. However, it is unclear to what extent and what type of conditioning animals may achieve during nonawake states. Trace conditioning is an appealing protocol to study under anesthesia, given the long empty gap separating the conditioned and unconditioned stimuli, which must be bridged for acquisition to happen. Here, we show evidence that rats develop physiological responses during the trace conditioning paradigm under anesthesia. We recorded the activity of the hippocampus (HPC) and lateral entorhinal cortex (LEC) in urethane-anesthetized rats, along with an electromyogram and an electrocardiogram. The protocol consisted of randomly presenting two distinct sound stimuli (CS- and CS+), where only one stimulus (CS+) was assigned to be trace-paired with a footshock. A trial-average analysis revealed that animals developed significant climbing heart rate activity initiating at the CS onset and persisting during the trace period. Such climbing arose for both CS- and CS+ with similar slopes but different intercepts, suggesting CS+ heart rates were typically above CS-. The power and coherence of HPC and LEC high-frequency bands (>100 Hz) significantly increased during CS presentation and trace, similarly to CS- and CS+ and insensitive to either activated or deactivated states. To the best of our knowledge, this is the first attempt to perform a trace conditioning protocol under anesthesia. Confirmation of this procedure acquisition can allow a new preparation for the exploration of brain mechanisms that bind time-discontinuous events.NEW & NOTEWORTHY Some forms of learning, such as some types of conditioning, can occur in anesthetized states. However, the extent to which memories can be formed in these states is still an open question. Here, we investigated the trace conditioning under urethane anesthesia and found heart rate, hippocampus, and lateral entorhinal cortex physiological changes to stimuli presentation. This new preparation may allow for exploration of memory acquisition of time-discontinuous events in the nonawake brain.
Assuntos
Anestesia , Condicionamento Clássico/fisiologia , Córtex Entorrinal/fisiologia , Hipocampo/fisiologia , Anestésicos Intravenosos/farmacologia , Animais , Eletrocardiografia , Eletromiografia , Masculino , Ratos , Ratos Sprague-Dawley , Fatores de Tempo , Uretana/farmacologiaRESUMO
Recent experimental results on spike avalanches measured in the urethane-anesthetized rat cortex have revealed scaling relations that indicate a phase transition at a specific level of cortical firing rate variability. The scaling relations point to critical exponents whose values differ from those of a branching process, which has been the canonical model employed to understand brain criticality. This suggested that a different model, with a different phase transition, might be required to explain the data. Here we show that this is not necessarily the case. By employing two different models belonging to the same universality class as the branching process (mean-field directed percolation) and treating the simulation data exactly like experimental data, we reproduce most of the experimental results. We find that subsampling the model and adjusting the time bin used to define avalanches (as done with experimental data) are sufficient ingredients to change the apparent exponents of the critical point. Moreover, experimental data is only reproduced within a very narrow range in parameter space around the phase transition.
Assuntos
Encéfalo/fisiologia , Simulação por Computador , Modelos Neurológicos , Rede Nervosa/fisiologia , Potenciais de Ação/fisiologia , Animais , Neurônios/fisiologia , RatosRESUMO
ABSTRACT: The objective of this study was to compare the polymerization shrinkage of Eclipse photopolymerization resin for prosthesis based on urethane dimethacrylate (UDMA) with that of three heat-cured acrylic resins based on polymethyl methacrylate (PMMA) after the polymerization process and immersion in water. A total of 40 prostheses were fabricated on a standard metallic upper edentulous model: group 1, Eclipse; group 2, Triplex hot; group 3, Veracril; and group 4, Lucitone 199. Subsequently, the polymerization contraction was tested using a microscope in which measurements were made in micrometres at 3 points located in the middle parts of the right and left sides and the middle part of the palate at three time points once the prosthesis was completed, after 30 days of immersion in water for 8 hours a day at a temperature of 37 °C, and after cutting the prosthesis at the level of the second premolar. ANOVA revealed that the contraction of the polymerization no statistically significant differences between the groups, (P> 0.05). The type of resin and its interaction with the processing method behaves similarly for all test resins. The Veracril heat-cured resin obtained the lowest contraction value in the three measurements (mm) and the highest value was obtained with the Eclipse photopolymerization resin. The Eclipse resin exhibited no lower polymerization shrinkage compared to conventional acrylic resins based on polymethyl methacrylate (PMMA), however it was not significantly affected by immersion in water.
RESUMEN: El objetivo de este estudio fue comparar la contracción de polimerización de la resina de fotopolimerización Eclipse para prótesis basadas en dimetacrilato de uretano (UDMA) con la de tres resinas acrílicas curadas con calor a base de polimetacrilato de metilo (PMMA) después del proceso de polimerización e inmersión en agua. Se fabricaron un total de 40 prótesis en un modelo edéntulo superior metálico estándar: grupo 1, Eclipse; grupo 2, triplex caliente; grupo 3, veracril; y grupo 4, Lucitone 199. Posteriormente, la contracción de la polimerización se probó utilizando un microscopio en el que se realizaron mediciones en micrometros en 3 puntos ubicados en las partes medias de los lados derecho e izquierdo y la parte media del paladar en tres puntos de tiempo una vez la prótesis se completó, después de 30 días de inmersión en agua durante 8 horas al día a una temperatura de 37 °C, y después de cortar la prótesis a nivel del segundo premolar. ANOVA reveló que la contracción de la polimerización no presenta diferencias estadísticamente significativas entre los grupos, (P> 0,05). El tipo de resina y su interacción con el método de procesamiento se comportan de manera similar para todas las resinas de prueba. La resina curada con calor Veracril obtuvo el valor de contracción más bajo en las tres mediciones (mm) y el valor más alto se obtuvo con la resina de fotopolimerización Eclipse. La resina Eclipse no mostró una contracción de polimerización menor en comparación con las resinas acrílicas convencionales basadas en polimetilmetacrilato (PMMA), sin embargo, no se vio afectada significativamente por la inmersión en agua.
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Resinas Compostas/química , Cimentos de Resina/química , Análise do Estresse Dentário/métodos , Bases de Dentadura , Polimerização , Resinas Acrílicas , Técnicas In Vitro , Hidrogel de Polietilenoglicol-Dimetacrilato , Análise do Estresse Dentário/instrumentaçãoAssuntos
Anel Fibroso/metabolismo , Materiais Revestidos Biocompatíveis/síntese química , Poliuretanos/síntese química , Adesivos Teciduais/síntese química , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Materiais Revestidos Biocompatíveis/administração & dosagem , Materiais Revestidos Biocompatíveis/metabolismo , Colágeno/química , Haplorrinos , Injeções , Cinética , Fenômenos Mecânicos , Camundongos , Cimento de Policarboxilato/química , Poliuretanos/administração & dosagem , Poliuretanos/metabolismo , Propriedades de Superfície , Temperatura , Termodinâmica , Aderências Teciduais/metabolismo , Adesivos Teciduais/administração & dosagem , Adesivos Teciduais/metabolismo , ViscosidadeRESUMO
Thio-urethane oligomers improve conversion and mechanical properties of resin cements. The objective of this study was to evaluate the effect of resin cements formulated with thio-urethane (TU) oligomers on microtensile bond strength (µTBS) of ceramics to composites subjected to thermal/mechanical cycling. Methods: BisGMA/UDMA/TEGDMA (50/30/20 wt%) containg 0 (control, EC) or 20 wt% aliphatic or aromatic thiourethane (HDDI and BDI, respectively) were mixed with CQ/amine (0.2/0.8 wt%) and 25 wt% 0.7um Ba glass. Rely X Ultimate (RU-3M ESPE) was used as the commercial control. The cements were sandwiched between ceramic (IPS e.max Press) and resin composite blocks (Filtek Supreme, 3 M-ESPE). Eight bonded blocks were produced per experimental group. Prior to bonding, ceramic surfaces were etched (20 s - 10% HF) and silanized. Composite surfaces were treated with Single Bond Universal (3 M ESPE). Specimens were stored for 24 h in distilled water at 37 °C, and then either tested immediately, or subjected to thermal (10,000, 5 °C and 55 °C) or mechanical cycling (300,000 cycles). Sticks (1 mm2, average of 25 sticks per block) were cut and tested for µTBS (1.0 mm/min). Data were analyzed with two-way ANOVA/Tukey's test (α = 5%). Fracture surfaces were analyzed to determine failure modes. Results: The µTBS for HDDI and RU was significantly higher than BDI and EC cements. BDI led to significantly higher µTBS than EC after 24 h, Tc and Mf. µTBS decreased significantly after thermal/mechanical cycling for all groups. Failure modes were predominantly adhesive or mixed. Significance: The use of selected thio-urethane oligomers was able to increase the µTBS of composite-cement-ceramic specimens. Tc and Mf reduced µTBS for all resins cements.
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OBJECTIVE: The aim of this study was to evaluate the color parameters and optical properties of resin cements (RCs) formulated with thio-urethanes (TUs). MATERIALS AND METHODS: Six TUs were synthesized by combining thiols (pentaerythritol tetra-3-mercaptopropionate [PETMP] or trimethylol-tris-3-mercaptopropionate [TMP]) with di-functional isocyanates (1,6-Hexanediol-diissocyante [HDDI] [aliphatic-AL] or 1,3-bis(1-isocyanato-1-methylethyl) benzene [BDI] [aromatic-AR] or Dicyclohexylmethane 4,4'-Diisocyanate [HMDI] [cyclic-CC]). TUs (20 wt%) were added to a BisGMA/UDMA/TEGDMA matrix. Filler was introduced at 60 wt%. Fluorescence was evaluated through an UV-light emitting equipment. Coordinates L*, a*, and b* were obtained in the black and white reflectance to evaluate the contrast ratio (CR) and translucency parameter (TP00 ). The coordinates obtained from transmittance were used to evaluate lightness (L*), chroma (C*), color difference (ΔE00 ) after 6 month, and whiteness index for Dentistry (WID ). RESULTS: RCs formulated with TUs presented significantly higher CR, and fluorescence (with T_AR). Significantly lower C*, L*, and TP00 (except for P_AR and T_AL) were also observed in RCs containing TUs. ΔE00 were not significant among the materials. WID was not influenced. CONCLUSION: RCs composed by TU oligomers present higher CR and lower translucency. The material also present higher fluorescence depending on the oligomer used. CLINICAL SIGNIFICANCE: The use of thio-urethanes to formulate resin cements can ensure a luting material with improved potential to mask colored substrates due to the higher contrast ratio and lower translucency obtained. A final higher fluorescence of restoration is also expected with the use of specific oligomer.
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Cimentos de Resina , Uretana , Cor , Colorimetria , Resinas Compostas , Módulo de Elasticidade , Teste de Materiais , Estresse MecânicoRESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Piper auritum Kunth is employed as an aphrodisiac in the traditional medicine, but corroborative evidence for such effect is scarce. AIM OF THE STUDY: The pro-sexual effect of an aqueous extract of P. auritum and its possible mechanisms were analyzed in two paradigms of male sexual function. MATERIAL AND METHODS: Effects of an aqueous extract of P. auritum (PA, single administration) were investigated in the fictive ejaculation, and copulatory behavior paradigms in sexually sluggish male rats. WAY 100635 (antagonist of 5-HT1A receptors), atosiban (antagonist of oxytocinergic receptors), L-NAME (inhibitor of the nitric oxide synthase) and baclofen (antagonist of GABAB receptors) were used as pre-treatments in order to investigate the role of different neurotransmitter systems in PA actions. Chemical profile of PA was determined by Gases Chromatography and Ultra Performance Chromatography-Electrospray Ionization-Masses Spectrometry (UPLC-ESI-MS). RESULTS: In males with retarded ejaculation, PA stimulated ejaculatory behavior and recovered electromyographic activity of pelvic musculature participating in seminal emission and ejaculation. All pre-treatments blocked stimulating effects of PA on the fictive ejaculation; additionally WAY 100635 interfered with PA actions on ejaculatory behavior. Safrol, apigenin dimethylether, myristicin, vaccihein A, sakuranin and sakuranetin flavonoids, were main constituents of PA, with possible participation in its pro-sexual effects. CONCLUSIONS: Pro-sexual effects of P. auritum elicited at level of ejaculation were mediated by several neurotransmitter systems, among which serotonin and its 5-HT1A receptors play an important role. Present findings support P. auritum reputation as an aphrodisiac, with potential use in delayed ejaculation disorder.
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Afrodisíacos/farmacologia , Piper , Extratos Vegetais/farmacologia , Comportamento Sexual/efeitos dos fármacos , Animais , Afrodisíacos/química , Comportamento Animal/efeitos dos fármacos , Ejaculação/efeitos dos fármacos , Feminino , Masculino , Compostos Fitoquímicos/análise , Compostos Fitoquímicos/farmacologia , Piper/química , Piperazinas/farmacologia , Extratos Vegetais/química , Folhas de Planta/química , Piridinas/farmacologia , Ratos Wistar , Receptor 5-HT1A de Serotonina/fisiologia , Antagonistas do Receptor 5-HT1 de Serotonina/farmacologiaRESUMO
OBJECTIVES: The use of thio-urethane oligomers has been shown to significantly improve the mechanical properties of resin cements (RCs). The aim of this study was to use thio-urethane-modified RC to potentially reinforce the porcelain-RC structure and to improve the bond strength to zirconia and lithium disilicate. METHODS: Six oligomers were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP, P) or trimethylol-tris-3-mercaptopropionate (TMP, T) - with di-functional isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic, AL) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic, AR) or Dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic, CC). Thio-urethanes (20â¯wt%) were added to a BisGMA/UDMA/TEGDMA organic matrix. Filler was introduced at 60â¯wt%. The microshear bond strength (µSBS), Weibull modulus (m), and failure pattern of RCs bonded to zirconia (ZR) and lithium disilicate (LD) ceramics was evaluated. Biaxial flexural test and fractographic analysis of porcelain discs bonded to RCs were also performed. The biaxial flexural strength (σbf) and m were calculated in the tensile surfaces of porcelain and RC structures (Zâ¯=â¯0 and Zâ¯=â¯-t2, respectively). RESULTS: The µSBS was improved with RCs formulated with oligomers P_AL or T_AL bonded to LD and P_AL, P_AR or T_CC bonded to zirconia in comparison to controls. Mixed failures predominated in all groups. σbf had superior values at Zâ¯=â¯0 with RCs formulated with oligomers P_AL, P_AR, T_AL, or T_CC in comparison to control; σbf increased with all RCs composed by thio-urethanes at Zâ¯=â¯-t2. Fractographic analysis revealed all fracture origins at Zâ¯=â¯0. CONCLUSION: The use of specific thio-urethane oligomers as components of RCs increased both the biaxial flexural strength of the porcelain-RC structure and the µSBS to LD and ZR. CLINICAL SIGNIFICANCE: The current investigation suggests that it is possible to reinforce the porcelain-RC pair and obtain higher bond strength to LD and ZR with RCs formulated with selected types of thio-urethane oligomers.
Assuntos
Cerâmica/química , Porcelana Dentária/química , Cimentos de Resina/química , Resistência à Tração , Uretana/química , Zircônio/química , Ácido 3-Mercaptopropiônico/análogos & derivados , Bis-Fenol A-Glicidil Metacrilato , Colagem Dentária , Materiais Dentários , Módulo de Elasticidade , Glicóis , Teste de Materiais , Fenômenos Mecânicos , Metacrilatos/química , Polietilenoglicóis , Polimerização , Ácidos Polimetacrílicos , Propilenoglicóis , Estresse Mecânico , Propriedades de SuperfícieRESUMO
Thio-urethane oligomers (TUs) have been shown to favorably modify methacrylate networks to reduce stress and significantly increase fracture toughness. Since those are very desirable features in dental applications, the objective of this work was to characterize restorative composites formulated with the addition of TUs. TUs were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP) or trimethylol-tris-3-mercaptopropionate (TMP) - with isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic) or dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic), at 1:2 isocyanate:thiol, leaving pendant thiols. 20wt% TU were added to BisGMA-TEGDMA (70-30%). To this organic matrix, 70wt% silanated inorganic fillers were added. Near-IR was used to follow methacrylate conversion and rate of polymerization (Rpmax). Mechanical properties were evaluated in three-point bending (ISO 4049) for flexural strength/modulus (FS/FM) and toughness (T), and notched specimens (ASTM Standard E399-90) for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Volumetric shrinkage (VS) was measured with the bonded disk technique. Glass transition temperature (Tg) and heterogeneity of network were obtained with dynamic mechanical analysis. The addition of TUs led to an increase in mechanical properties (except for Tg and FS). Fracture toughness ranged from 1.6-1.94MPam1/2 for TU-modified groups, an increase of 33-61% in relation to the control (1.21 ± 0.1MPam1/2). Toughness showed a two-fold increase in relation to the control: from 0.91MPa to values ranging from 1.70-1.95MPa. Flexural modulus was statistically higher for the TU-modified groups. The Tg, as expected, decreased for all TU groups due to the greater flexibility imparted to the network (which also explains the increase in toughness and fracture toughness). Narrower tan-delta peaks suggest more homogeneous networks for the TU-modified materials, though differences were marked only for TMP_AL. Degree of conversion was not affected by the addition of TUs. VS was similar for all groups, with one exception where VS dropped (PETMP-cyclic). Finally, PS showed a reduction of 23-57% for TU-modified groups (6.7 ± 1.3 to 11.9 ± 1.0MPa) in relation to the control (15.56 ± 1.4MPa). The addition of thio-urethane oligomers was able to reduce polymerization stress by up to 57% while increasing fracture toughness by up to 61%.
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Polímeros/química , Estresse Mecânico , Compostos de Sulfidrila/química , Uretana/química , Módulo de Elasticidade , Temperatura de TransiçãoRESUMO
The aim of this study was to synthesize and characterize new multifunctional-urethane-methacrylate monomers to be used as the organic matrix in restorative dental composites, and evaluate the main physical-chemical properties of the resulting material. Bis-GMA (bisphenol-A-diglycidylmethacrylate) and GDMA (glycerol dimethacrylate) were modified by reacting the hydroxyl groups with isocyanate groups of urethane-methacrylate precursors to result in the new monomeric systems U-(bis-GMA)-Mod and U-(GDMA)-Mod, U=Urethane and Mod=Modified. The modifications were characterized by FTIR and 1H NMR. The final monomeric synthesized system was used to prepare dental resins and composites. The physical-chemical properties were evaluated and compared with those of bis-GMA composites with varying filler contents or unfilled resins. U-(bis-GMA)-Mod and U-(GDMA)-Mod can be used to prepare dental restorative composites, with some foreseeable advantages compared with bis-GMA composites. One significant advantage is that these composites have the potential to be less toxic, once they presented a reduction of 50% in leaching of unreacted monomers extracted by solvent.
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Materiais Dentários/química , Polímeros/química , Uretana/química , Bis-Fenol A-Glicidil Metacrilato/química , Materiais Dentários/síntese química , Espectroscopia de Ressonância Magnética , Metacrilatos/química , Polímeros/síntese química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Água/químicaRESUMO
An interim partial removable dental prosthesis (RDP) is any dental prosthesis that replaces some teeth in a partially dentate arch designed to enhance esthetics, stabilization, and/or function for a limited period of time, after which it is to be replaced by a definitive dental prosthesis. This article describes a technique that uses a visible light-polymerized (VLP) resin as the base material for an interim partial RDP. This technique can be easily accomplished in a dental office or laboratory and results in a predictable dental prosthesis. This technique eliminates the need for laboratory processing.
Assuntos
Resinas Acrílicas/química , Planejamento de Dentadura/métodos , Prótese Parcial Removível , Prótese Parcial Temporária , Luz , Técnica de Moldagem Odontológica , Materiais Dentários/química , Humanos , PolimerizaçãoRESUMO
OBJECTIVES: Thio-urethane oligomers have been shown to reduce stress and increase toughness in highly filled composite materials. This study evaluated the influence of thio-urethane backbone structure on rheological and mechanical properties of resin cements modified with a fixed concentration of the oligomers. METHODS: Thio-urethane oligomers (TU) were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP) or trimethylol-tris-3-mercaptopropionate (TMP) - with isocyanates - 1,6-hexanediol-diissocyante (HDDI) (aliphatic) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic) or dicyclohexylmethane 4,4'-diisocyanate (HMDI) (cyclic), at 1:2 isocyanate:thiol, leaving pendant thiols. 20wt% TU were added to BisGMA-UDMA-TEGDMA (5:3:2). 60wt% silanated inorganic fillers were added. Near-IR was used to follow methacrylate conversion and rate of polymerization ( [Formula: see text] ). Mechanical properties were evaluated in three-point bending (ISO 4049) for flexural strength/modulus (FS/FM, and toughness), and notched specimens (ASTM Standard E399-90) for fracture toughness (KIC). PS was measured on the Bioman. Viscosity (V) and gel-points (defined as the crossover between storage and loss shear moduli (G'/Gâ³)) were obtained with rheometry. Glass transition temperature (Tg), cross-link density and homogeneity of the network were obtained with dynamic mechanical analysis. Film-thickness was evaluated according to ISO 4049. RESULTS: DC and mechanical properties increased and [Formula: see text] and PS decreased with the addition of TUs. Gelation (G'/Gâ³) was delayed and DC at G'/Gâ³ increased in TU groups. Tg and cross-link density dropped in TU groups, while oligomers let to more homogenous networks. An increase in V was observed, with no effect on film-thickness. Significant reductions in PS were achieved at the same time conversion and mechanical properties increased. SIGNIFICANCE: The addition of thio-urethane oligomers proved successful in improving several key properties of resin cements, without disrupting the procedures dentists use to polymerize the material. This approach has potential to be translated to commercial materials very readily.
Assuntos
Resinas Compostas , Uretana , Módulo de Elasticidade , Glicóis , Teste de Materiais , Metacrilatos , Maleabilidade , Estresse MecânicoRESUMO
Poly(urea-urethane) (PUU) nanoparticles with encapsulated superparamagnetic magnetite (Fe3O4) were obtained by interfacial miniemulsion polymerization and used as support for immobilization of lipase B from Candida antarctica (CALB). CALB enzyme was immobilized on magnetic PUU nanoparticles in two steps. The enzyme was immobilized in the lyophilized nanoparticles (magnetic PUU) after the support synthesis in phosphate buffer (pH 7.6) containing CALB, by the contact between nanoparticles and enzymatic solution. The mixture was incubated at 30 °C in an orbital shaker during 0.5 until 6 h to determine the time for maximum immobilization efficiency. The enzyme activity was determined by esterification reactions between lauric acid and propanol. Residual activities above 95 % in relation to free enzyme were obtained in 1 h of immobilization with enzyme concentration of 0.55 mg/mL. FTIR spectrum and SEM-FEG images were used to confirm the presence of CALB on magnetic support after immobilization and stability of support even after immobilization process, respectively. Thermal (40, 60, and 80 °C) and pH (pH 4, 7, and 10) stabilities, storage stability, and reuse were evaluated. CALB immobilized derivatives showed high stabilities with residual activities of 95, 100, and 100 % at 40, 60, and 80 °C, respectively, in 6 h of incubation. After incubation in different pH values, CALB immobilized derivative presented activities of 81, 76, and 69 % in relation to activities in the beginning of the stabilization process in pH 4, 7, and 10, respectively. Furthermore, CALB immobilized derivative reduces only 15 % of its activity after 30 days of storage at 4 °C. Reuse results showed that immobilized CALB on magnetic PUU nanoparticles led to 95 % of geranyl oleate conversion after 8 cycles of application demonstrating high stability of the CALB immobilized derivative under different conditions.
Assuntos
Candida/enzimologia , Enzimas Imobilizadas/metabolismo , Proteínas Fúngicas/metabolismo , Lipase/metabolismo , Nanopartículas de Magnetita/química , Poliuretanos/farmacologia , Ureia/farmacologia , Estabilidade Enzimática/efeitos dos fármacos , Ésteres/metabolismo , Concentração de Íons de Hidrogênio , Nanopartículas de Magnetita/ultraestrutura , Microscopia de Fluorescência , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
OBJECTIVE: To evaluate the ability of thio-urethane oligomers to improve the properties of restorative composite resins. METHODS: Oligomers were synthesized by combining 1,6-hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 0-20 wt% to BisGMA-TEGDMA (70-30 wt%). Silanated inorganic fillers were added (70 wt%). Materials were photoactivated at 800 mW/cm(2) filtered to 320-500 nm. Near-IR was used to follow degree of methacrylate conversion (DC). Mechanical properties were evaluated in three-point bending with 2 mm × 2 mm × 25 mm bars for flexural strength/modulus and toughness (FS/E, and T) according to ISO 4049, and 2 mm × 5 mm × 25 mm notched specimens for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Results were analyzed with ANOVA/Tukey's test (α=5%). RESULTS: Significant increase in DC was observed in thio-urethane-containing materials especially for the group with 20 wt% of aliphatic version. Materials composed by oligomers also promoted higher FS, E, and KIC in comparison to controls irrespective of thio-urethane type. A significant increase in toughness was detected by ANOVA, but not distinguished in the groups. The PS was significantly reduced by the presence of thio-urethane for almost all groups. CONCLUSIONS: The use of thio-urethane oligomer to compose methacrylate-based restorative composite promote increase in DC, FS, E and KIC while significant reduces PS. SIGNIFICANCE: A simple additive was shown to reduce stress while increasing convrersion and mechanical properties, mainly fracture toughness. This has he potential of increasing the service life of dental composites, without changing current operatory procedures.
Assuntos
Resinas Compostas/síntese química , Uretana/química , Ácido 3-Mercaptopropiônico/análogos & derivados , Ácido 3-Mercaptopropiônico/química , Compostos de Anilina/química , Bis-Fenol A-Glicidil Metacrilato/química , Hidroxitolueno Butilado/química , Módulo de Elasticidade , Isocianatos/química , Teste de Materiais , Metacrilatos/química , Polietilenoglicóis/química , Polimerização , Ácidos Polimetacrílicos/química , Propilenoglicóis/química , Silanos/química , Estresse MecânicoRESUMO
The antioxidant effects of Caryocar brasiliense Camb, commonly known as the pequi fruit, have not been evaluated to determine their protective effects against oxidative damage in lung carcinogenesis. In the present study, we evaluated the role of pequi fruit against urethane-induced DNA damage and oxidative stress in forty 8-12 week old male BALB/C mice. An in vivo comet assay was performed to assess DNA damage in lung tissues and changes in lipid peroxidation and redox cycle antioxidants were monitored for oxidative stress. Prior supplementation with pequi oil or its extract (15 µL, 60 days) significantly reduced urethane-induced oxidative stress. A protective effect against DNA damage was associated with the modulation of lipid peroxidation and low protein and gene expression of nitric oxide synthase. These findings suggest that the intake of pequi fruit might protect against in vivo genotoxicity and oxidative stress.