RESUMO
Materials capable of degradation upon exposure to light hold promise in a diverse range of applications including biomedical devices and smart coatings. Despite the rapid access to macromolecules with diverse compositions and architectures enabled by ring-opening metathesis polymerization (ROMP), a general strategy to introduce facile photodegradability into these polymers is lacking. Here, we report copolymers synthesized via ROMP that can be degraded by cleaving the backbone in both solution and solid states under irradiation with a 52 W, 390 nm Kessil LED to generate heterotelechelic low-molecular-weight fragments. To the best of our knowledge, this work represents the first instance of the incorporation of acylsilanes into a polymer backbone. Mechanistic investigation of the degradation process supports the intermediacy of an α-siloxy carbene, formed via a 1,2-photo Brook rearrangement, which undergoes insertion into water followed by cleavage of the resulting hemiacetal.
Assuntos
Polímeros/química , Silanos/química , Fotólise , Polimerização , Polímeros/síntese química , Polímeros/efeitos da radiação , Silanos/síntese química , Silanos/efeitos da radiação , Raios UltravioletaRESUMO
Herein, a chip imitating the desert beetle shell was presented for naked eye nucleic acid quantification. The hydrophobic photonic crystal substrate treated by ultraviolet local irradiation could effectively disperse the sample into hundreds of droplets for digital loop-mediated isothermal amplification (dLAMP). Pyrophosphate (PPI), a by-product of the LAMP reaction, combined with magnesium ions to form a poorly soluble precipitate. It could be fixed on a silica substrate due to complexation, resulting in the disappearance of the structural color of the photonic crystals. The number of points without structural color contains the information of the copy number of nucleic acids in the sample. This chip could achieve the naked eye quantitative detection of Salmonella DNA without fluorescence or other chromogenic reagents. Thus, the chip designed in this study can help the development of digital nucleic acid detection under limited resource settings (LRS) and can be suitable for POCT (point of care test) standards.
Assuntos
Materiais Biomiméticos/química , DNA Bacteriano/análise , Fluorocarbonos/química , Silanos/química , Colorimetria/métodos , Difosfatos/química , Fluorocarbonos/efeitos da radiação , Interações Hidrofóbicas e Hidrofílicas , Compostos de Magnésio/química , Nanopartículas/química , Técnicas de Amplificação de Ácido Nucleico/métodos , Estudo de Prova de Conceito , Salmonella/genética , Silanos/efeitos da radiação , Dióxido de Silício/química , Raios UltravioletaRESUMO
Gamma-ray radiation was used as a clean and easy method for turning the physicochemical properties of graphene oxide (GO) in this study. Silane functionalized-GO were synthesized by chemically grafting 3-aminopropyltriethoxysilane (APTES) and 3-glycidyloxypropyltrimethoxysilane (GPTES) onto GO surface using gamma-ray irradiation. This established non-contact process is used to create a reductive medium which is deemed simpler, purer and less harmful compared conventional chemical reduction. The resulting functionalized-GO were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), and Raman spectroscopy. The chemical interaction of silane with the GO surface was confirmed by FT-IR. X-ray diffraction reveals the change in the crystalline phases was due to surface functionalization. Surface defects of the GO due to the introduction of silane mioties was revealed by Raman spectroscopy. Thermogravimetric analysis of the functionalized-GO exhibits a multiple peaks in the temperature range of 200-650 °C which corresponds to the degradation of chemically grafted silane on the GO surface.
Assuntos
Grafite/química , Compostos de Organossilício/química , Propilaminas/química , Silanos/química , Compostos de Epóxi/síntese química , Compostos de Epóxi/química , Compostos de Epóxi/efeitos da radiação , Raios gama , Grafite/síntese química , Grafite/efeitos da radiação , Microscopia Eletrônica de Varredura , Compostos de Organossilício/efeitos da radiação , Propilaminas/síntese química , Propilaminas/efeitos da radiação , Silanos/síntese química , Silanos/efeitos da radiação , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Propriedades de Superfície/efeitos da radiação , Temperatura , Termogravimetria , Difração de Raios XRESUMO
OBJECTIVES: The purpose of this study was to evaluate the flexural strength and Vickers hardness of a microwave energy heat-cured acrylic resin by adding different concentrations of silane surface-treated nanoparticle silica. METHODS: Acrylic resin specimens with dimensions of 65 × 10 × 2.5 mm were formed and divided into five experimental groups (n = 10) according to the silica concentration added to the acrylic resin mass (weight %) prior to polymerisation : G1, without silica; G2, 0.1% silica; G3, 0.5% silica; G4, 1.0% silica; and G5, 5.0% silica. The specimens were submitted to a three-point flexural strength test and to the Vickers hardness test (HVN). The data obtained were statistically analysed by anova and the Tukey test (α = 0.05). RESULTS: Regarding flexural strength, G5 differed from the other experimental groups (G1, G2, G3 and G4) presenting the lowest mean, while G4 presented a significantly higher mean, with the exception of group G3. Regarding Vickers hardness, a decrease in values was observed, in which G1 presented the highest hardness compared with the other experimental groups. CONCLUSION: Incorporating surface-treated silica resulted in direct benefits in the flexural strength of the acrylic resin activated by microwave energy; however, similar results were not achieved for hardness.
Assuntos
Resinas Acrílicas/química , Materiais Dentários/química , Micro-Ondas , Silanos/química , Dióxido de Silício/química , Resinas Acrílicas/efeitos da radiação , Materiais Dentários/efeitos da radiação , Análise do Estresse Dentário/instrumentação , Vidro/química , Vidro/efeitos da radiação , Dureza , Temperatura Alta , Humanos , Teste de Materiais , Nanopartículas/química , Nanopartículas/efeitos da radiação , Maleabilidade , Polimerização , Silanos/efeitos da radiação , Dióxido de Silício/efeitos da radiação , Estresse Mecânico , Propriedades de SuperfícieRESUMO
The objective of this study was to investigate the effects of precuring of primer coated on bracket bases on the strength of bonds between metal brackets and gold alloy. Square type III gold alloy plates were sandblasted with 30 µm silicon dioxide. After silica coating, excessive particles were removed gently with air. Silane was then applied, and maxillary central incisor metal brackets were bonded to each conditioned alloy surface with Transbond XT. Half of the specimens were precured at the bracket base after primer coating and the other half was not precured before bonding to the alloy surface. After bracket positioning, samples were cured using a light emitting diode (LED) for 40 seconds. Shear bond strengths were tested and adhesive remnant index (ARI) was evaluated after 1 hour and 24 hours. The primer precuring and 24 hours group exhibited highest bond strength (12.53 MPa) and the no precuring and 1 hour group showed lowest bond strength (5.58 MPa). Precured groups showed lower ARI scores. Due to the shallow curing depth of LED light and inhibition of transillumination at the metal surface, primer precuring at the bracket base is required for secure bracket bonding on gold alloy surfaces using LED curing units.
Assuntos
Ligas Dentárias/química , Ligas de Ouro/química , Cura Luminosa de Adesivos Dentários/métodos , Braquetes Ortodônticos , Cimentos de Resina/efeitos da radiação , Lâmpadas de Polimerização Dentária/classificação , Corrosão Dentária/métodos , Análise do Estresse Dentário/instrumentação , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Cimentos de Resina/química , Resistência ao Cisalhamento , Silanos/química , Silanos/efeitos da radiação , Dióxido de Silício/química , Estresse Mecânico , Propriedades de Superfície , Temperatura , Fatores de Tempo , Água/químicaRESUMO
The use of decatungstate (W10O32(4-)) in combination with silanes to generate silyl radicals under green fluorescence bulb irradiation as well as sunlight exposure is described. The mechanisms are investigated by ESR and laser flash photolysis experiments. The high potential of this reaction is evidenced here when using a decatungstate/silane/diphenyl iodonium salt combination as an initiating system for the ring opening photopolymerization of epoxides.
Assuntos
Radicais Livres/síntese química , Luz , Silanos/química , Compostos de Tungstênio/química , Cátions/química , Oniocompostos/química , Oniocompostos/efeitos da radiação , Fotólise , Polimerização , Silanos/efeitos da radiação , Compostos de Tungstênio/efeitos da radiaçãoRESUMO
Smart response hydrogel has a broad application prospect in human health real-time monitoring due to its responses to a variety of stimuli. In this study, we developed a novel smart hydrogel dressing based on conductive MXene nanosheets and a temperature-sensitive PNIPAm polymer. γ-Methacryloxypropyltrimethoxysilane (KH570) was selected to functionalize the surface of MXene further to improve the interface compatibility between MXene and PNIPAm. Our prepared K-M/PNIPAm hydrogel was found to have a strain-sensitive property, as well as a respond to NIR phase change and volume change. When applied as a strain flexible sensor, this K-M/PNIPAm hydrogel exhibited a high strain sensitivity with a gauge factor (GF) of 4.491, a broad working strain range of ≈250%, a fast response of â¼160 ms, and good cycle stability (i.e., 3000 s at 20% strain). Besides, this K-M/PNIPAm hydrogel can be used as an efficient NIR light-controlled drug release carrier to achieve on-demand drug release. This work paved the way for the application of smart response hydrogel in human health real-time monitoring and NIR-controlled drug release functions.
Assuntos
Portadores de Fármacos/química , Hidrogéis/química , Materiais Inteligentes/química , Resinas Acrílicas/química , Resinas Acrílicas/farmacologia , Resinas Acrílicas/efeitos da radiação , Resinas Acrílicas/toxicidade , Animais , Linhagem Celular , Portadores de Fármacos/farmacologia , Portadores de Fármacos/efeitos da radiação , Portadores de Fármacos/toxicidade , Liberação Controlada de Fármacos/efeitos da radiação , Elasticidade , Hidrogéis/farmacologia , Hidrogéis/efeitos da radiação , Hidrogéis/toxicidade , Raios Infravermelhos , Masculino , Metacrilatos/química , Metacrilatos/farmacologia , Metacrilatos/efeitos da radiação , Metacrilatos/toxicidade , Camundongos , Ratos Sprague-Dawley , Silanos/química , Silanos/farmacologia , Silanos/efeitos da radiação , Silanos/toxicidade , Pele/efeitos dos fármacos , Materiais Inteligentes/farmacologia , Materiais Inteligentes/efeitos da radiação , Materiais Inteligentes/toxicidade , Estresse Mecânico , Tetraciclina/química , Titânio/química , Titânio/farmacologia , Titânio/efeitos da radiação , Titânio/toxicidade , Cicatrização/efeitos dos fármacosRESUMO
Surface modification through implanting functional groups has been demonstrated to be extremely important to biomedical applications. The usage of organic polymer phase is often required to achieve satisfactory results. However, organic surfaces usually have poor chemical reactivity toward other reactants and target biomolecules because these surfaces usually only consist of simple alkyl (C-H) and/or alkyl ether (ROR') structures. For the first time, we here report the potential to perform silanization techniques on alkyl polymer surface, which provide a simple, fast, inexpensive, and general method to decorate versatile functional groups at the molecular level. As an example, high-density primary amines could be obtained on a model polymer, polypropylene substrate, through the reaction between amine-capped silane, 3-aminopropyltriethoxysilane (APTES) and hydroxylated polypropylene surface. A model protein, immunoglobulin (IgG), could be effectively immobilized on the surface after transforming amines to aldehydes by the aldehyde-amine condensation reaction between glutaraldehyde (GA) and amines. The routes we report here could directly make use of the benefits from well-developed silane chemistry, and hereby are capable of grafting any functionalities on inert alkyl surfaces via changing the terminal groups in silanes, which should instantly stimulate the development of many realms such as microarrays, immunoassays, biosensors, filtrations, and microseparation.
Assuntos
Alcanos/química , Aminas/síntese química , Proteínas Imobilizadas/química , Imunoglobulinas/química , Polipropilenos/química , Silanos/química , Alcanos/efeitos da radiação , Aminas/química , Aminas/efeitos da radiação , Proteínas Imobilizadas/efeitos da radiação , Imunoglobulinas/efeitos da radiação , Tamanho da Partícula , Fotoquímica , Polipropilenos/efeitos da radiação , Silanos/efeitos da radiação , Propriedades de Superfície , Raios UltravioletaRESUMO
We have succeeded to immobilize fluorescent proteins selectively using a micro-structured organosilane self-assembled monolayer as a template. An organosilane layer with amino terminal group was formed on a thermally oxidized Si wafer by liquid-phase method and then was pattern-etched by vacuum ultraviolet light (VUV). The second organosilane layer with thiol terminal group was deposited on the etched area by chemical vapor surface modification method (CVSM). These micro-structured organosilane layer containing two reactive terminal groups were chemically modified using bi-functional linkers. Two kinds of fluorescent protein, Enhanced Cyan Fluorescent Protein (ECFP) and R-phycoerythrin were selectively immobilized on the chemically modified surface.
Assuntos
Nanoestruturas/química , Nanoestruturas/ultraestrutura , Compostos de Organossilício/química , Análise Serial de Proteínas/métodos , Proteínas/química , Proteínas/efeitos da radiação , Silanos/química , Cristalização/métodos , Substâncias Macromoleculares/química , Teste de Materiais , Miniaturização , Conformação Molecular , Nanotecnologia/métodos , Compostos de Organossilício/efeitos da radiação , Tamanho da Partícula , Proteínas/ultraestrutura , Silanos/efeitos da radiação , Propriedades de Superfície , Raios Ultravioleta , VácuoRESUMO
The objective of this study was to investigate the effect of UV irradiation on shear bond strength between a titanium (Ti) and a segmented polyurethane (SPU) composite through gamma-mercapto propyl trimethoxysilane (gamma-MPS). To this end, the shear bond strength of Ti/SPU interface of Ti-SPU composite under varying conditions of ultraviolet ray (UV) irradiation was evaluated by a shear bond test. The glass transition temperatures of SPU with and without UV irradiation were also determined using differential scanning calorimetry. It was found that the shear bond strength of Ti/SPU interface increased with UV irradiation. However, excessive UV irradiation decreased the shear bond strength of Ti/SPU interface. Glass transition temperature was found to increase during 40-60 seconds of UV irradiation. In terms of durability after immersion in water at 37 degrees C for 30 days, shear bond strength was found to improve with UV irradiation. In conclusion, UV irradiation to a Ti-SPU composite was clearly one of the means to improve the shear bond strength of Ti/SPU interface.
Assuntos
Colagem Dentária , Materiais Dentários/química , Poliuretanos/efeitos da radiação , Silanos/efeitos da radiação , Compostos de Sulfidrila/efeitos da radiação , Titânio/efeitos da radiação , Raios Ultravioleta , Varredura Diferencial de Calorimetria , Vidro/química , Vidro/efeitos da radiação , Humanos , Imersão , Compostos de Organossilício , Transição de Fase , Poliésteres/química , Poliésteres/efeitos da radiação , Poliuretanos/química , Resistência ao Cisalhamento , Silanos/química , Estresse Mecânico , Compostos de Sulfidrila/química , Temperatura , Fatores de Tempo , Titânio/química , Temperatura de Transição , Água/químicaRESUMO
Two-photon polymerization technique was applied to generate three-dimensional (3D) scaffold-like structures using the photosensitive organic-inorganic hybrid polymer ORMOCER. The structures were studied with respect to potential applications as scaffold for tissue engineering. Cell counting and comet assay, respectively, demonstrated that doubling time and DNA strand breaks of CHO cells, GFSHR-17 granulosa cells, GM-7373 endothelial cells, and SH-SY5Y neuroblastoma cells were not affected by ORMOCER. ORMOCER related alteration of formation of tissue specific cell-to-cell adhesions like gap junctions was ruled out by double whole-cell patch-clamp technique. Additionally, growth of cells on the vertical surfaces of 3D structures composed of ORMOCER is shown.
Assuntos
Proliferação de Células/efeitos dos fármacos , Cerâmica/farmacologia , Regeneração Tecidual Guiada/métodos , Fotoquímica/métodos , Silanos/farmacologia , Engenharia Tecidual/métodos , Alicerces Teciduais , Animais , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Materiais Biocompatíveis/efeitos da radiação , Células CHO , Adesão Celular/efeitos dos fármacos , Adesão Celular/fisiologia , Comunicação Celular/efeitos dos fármacos , Comunicação Celular/genética , Linhagem Celular Tumoral , Cerâmica/química , Cerâmica/efeitos da radiação , Desenho Assistido por Computador/tendências , Cricetinae , Cricetulus , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/fisiologia , Junções Comunicantes/efeitos dos fármacos , Junções Comunicantes/fisiologia , Regeneração Tecidual Guiada/instrumentação , Humanos , Lasers , Teste de Materiais/métodos , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Cerâmicas Modificadas Organicamente , Polímeros/química , Polímeros/farmacologia , Polímeros/efeitos da radiação , Silanos/química , Silanos/efeitos da radiação , Engenharia Tecidual/instrumentaçãoRESUMO
OBJECTIVES: The aim of this study was to develop a low shrinkage visible light curable nanocomposite dental restorative material without sacrificing the other properties of conventional materials. This nanocomposite was developed by using an epoxy resin 3,4-epoxycyclohexylmethyl-(3,4-epoxy)cyclohexane carboxylate (ERL4221) matrix with 55% wt of 70-100 nm nanosilica fillers through ring-opening polymerization. GPS (gamma-glycidoxypropyl trimethoxysilane) was used to modify the surfaces of silica nanoparticles. RESULTS: The nanocomposite was shown to exhibit low polymerization shrinkage strain, which is only a quarter of currently used methacrylate-based composites. It also exhibited a low thermal expansion coefficient of 49.8 microm/m degrees C which is comparable to that of the methacrylate based composites (51.2 microm/m degrees C). The strong interfacial interactions between the resin and fillers at nanoscales were demonstrated by an observed high strength and high thermal stability of the nanocomposite. A microhardness of 62 KHN and a tensile strength of 47 MPa were reached. A high degree of conversion ( approximately 70%) can be obtained after less than 60 s of irradiation upon the nanocomposite. A transmission electron microscope (TEM) study of the nanocomposite showed no aggregation of fillers. Comparable results to the methacrylate based composites were obtained from the one day MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) cytotoxicity test. SIGNIFICANCE: The developed epoxy resin based nanocomposite demonstrated low shrinkage and high strength and is suitable for dental restorative material applications.
Assuntos
Resinas Compostas/química , Resinas Epóxi/química , Nanoestruturas/química , Corantes , Resinas Compostas/efeitos da radiação , Resinas Compostas/toxicidade , Ácidos Cicloexanocarboxílicos/química , Ácidos Cicloexanocarboxílicos/efeitos da radiação , Ácidos Cicloexanocarboxílicos/toxicidade , Resinas Epóxi/efeitos da radiação , Resinas Epóxi/toxicidade , Dureza , Humanos , Luz , Teste de Materiais , Microscopia Eletrônica de Transmissão , Nanoestruturas/efeitos da radiação , Nanoestruturas/toxicidade , Polímeros , Silanos/química , Silanos/efeitos da radiação , Silanos/toxicidade , Dióxido de Silício/química , Dióxido de Silício/efeitos da radiação , Dióxido de Silício/toxicidade , Estresse Mecânico , Propriedades de Superfície , Temperatura , Resistência à Tração , Sais de Tetrazólio , Termodinâmica , TiazóisRESUMO
OBJECTIVES: The aim of this research was to better understand the relationships between interphase composition and the resultant mechanical properties of thermoset methacrylate nanocomposites, ultimately for the purpose of improving the properties of dental restorative materials through manipulation of the interphase. METHODS: Silica nanoparticles were silanized with three different silanes and blends of those silanes to generate six different interphase compositions. The silanes varied in their relative polarity, flexibility, and reactivity towards photo-polymerization. Composites containing 60% by mass of the silanized fillers were prepared and analyzed for uncured paste handling characteristics, vinyl conversion, biaxial flexure strength (BFS), modulus, and Knoop hardness. RESULTS: Dual silanization of the fillers improved the handling characteristics of the uncured composite pastes compared to those containing fillers silanized with 3-methacryloxypropyltrimethoxysilane. To obtain high BFS, functional groups reactive in free radical polymerization were needed in the composite interphase, but a high concentration of those groups was not necessary. Moduli were highest for composites with interphases that contained styrylethyltrimethoxysilane, a reactive aromatic silane. The hardness values of the composites with reactive interphases were all comparable. Methacrylate conversion was only modestly influenced by silane interphase composition. SIGNIFICANCE: This study suggests that dual silanization is a practical method for improving the handling characteristics of uncured dental restorative nanocomposites while maintaining or improving the mechanical properties of the cured composites.
Assuntos
Resinas Compostas/química , Materiais Dentários/química , Metacrilatos/química , Nanocompostos/química , Fenômenos Químicos , Físico-Química , Resinas Compostas/efeitos da radiação , Materiais Dentários/efeitos da radiação , Elasticidade , Eletroquímica , Dureza , Humanos , Luz , Teste de Materiais , Metacrilatos/efeitos da radiação , Nanocompostos/efeitos da radiação , Nanopartículas/química , Nanopartículas/efeitos da radiação , Maleabilidade , Polímeros/química , Polímeros/efeitos da radiação , Silanos/química , Silanos/efeitos da radiação , Dióxido de Silício/química , Dióxido de Silício/efeitos da radiação , Estresse Mecânico , Relação Estrutura-Atividade , Compostos de Vinila/química , Compostos de Vinila/efeitos da radiaçãoRESUMO
PURPOSE: A novel two-layer sample composed of a deoxyribonucleic acid (DNA) film and self-assembled monolayer (SAM) was prepared on an inorganic surface to mimic the processes in which DNA is damaged by soft X-ray irradiation. MATERIALS AND METHODS: A mercaptopropyltrimethoxysilane (MPTS) SAM was formed on a sapphire surface, then oligonucleotide (OGN) molecules were adsorbed on the MPTS-SAM. The thicknesses and chemical states of the layers were determined by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray fine structure (NEXAFS) around the phosphorus (P) and sulfur (S) K-edges. To induce the damage to the OGN molecules, the sample was irradiated with synchrotron soft X-rays. The chemical state of the OGN molecules before and after irradiation was examined by NEXAFS around the nitrogen (N) K-edge region. RESULTS: The thickness of the MPTS-OGN layer was approximately 7.7 nm. The S atom of the OGN molecules was located at the bottom of the OGN layer. The peak shape of the N K-edge NEXAFS spectra of the MPTS-OGN layers clearly changed following irradiation. CONCLUSIONS: The MPTS-OGN layer formed on the sapphire surface. The chemical states and the structure of the interface were elucidated using synchrotron soft X-rays. The OGN molecules adsorbed on the MPTS films decomposed upon exposure to soft X-ray irradiation.
Assuntos
Dano ao DNA , DNA/química , DNA/efeitos da radiação , Elétrons , Membranas Artificiais , Silanos/química , Adsorção , Materiais Biomiméticos/síntese química , Materiais Biomiméticos/efeitos da radiação , Materiais Revestidos Biocompatíveis/síntese química , Materiais Revestidos Biocompatíveis/efeitos da radiação , Relação Dose-Resposta à Radiação , Teste de Materiais , Compostos de Organossilício , Doses de Radiação , Silanos/efeitos da radiaçãoRESUMO
Possibility to shorten the total irradiation time in slow-curing with an intensity-changeable light source, Curetron 7 (CT-7), was investigated for four hybrid-type resin composites. Irradiation condition with CT-7 was assigned as 10 or 20 seconds at low light intensity (230 mW/cm2) and followed by 20 or 10 seconds at high intensity (600 mW/cm2) respectively (i.e., a total of 30 seconds). For a reference, irradiation was carried out for 30 seconds using a halogen lamp (900 mW/cm2). After irradiation, mechanical properties of the cured composites--in terms of microhardness and flexural strength--were evaluated. Also, cavity adaptation was examined in standardized, cylindrical dentin cavities treated with an adhesive system. Compared to the reference irradiation, slow-curing with CT-7 produced acceptable mechanical properties and better adaptation. These results suggested that total exposure time of slow-curing with CT-7 could be shortened to 30 seconds.
Assuntos
Resinas Compostas/efeitos da radiação , Equipamentos Odontológicos , Análise de Variância , Bis-Fenol A-Glicidil Metacrilato/efeitos da radiação , Adaptação Marginal Dentária , Dureza , Humanos , Luz , Teste de Materiais , Metacrilatos/efeitos da radiação , Transição de Fase , Maleabilidade , Silanos/efeitos da radiação , Dióxido de Silício/efeitos da radiação , Fatores de Tempo , Zircônio/efeitos da radiaçãoRESUMO
This study seeks to elucidate structure-property relationships in a series of unfilled dental copolymers and their composites. The copolymers/composites were derived from photo-activated binary monomer systems based on 2,2-bis[p-2'-hydroxy-3'-methacryloxypropoxy)phenyl] propane (Bis-GMA) and equimolar amounts of a bifunctional, surface-active comonomer, i.e., 2-hydroxyethyl methacrylate (HEMA), glycerol dimethacrylate (GDMA) or ethylene glycol methacrylate phosphate (PHEMA). Triethyleneglycol dimethacrylate, a widely used comonomer for Bis-GMA, was used as a control. Two types of fillers were investigated: (1) a hydrophilic, silica-modified amorphous calcium phosphate (Si-ACP) and (2) a more hydrophobic, silanized nanosized silica (n-SiO(2)). Both the unfilled copolymers and their composites were evaluated for biaxial flexure strength (BFS), both dry and wet after 30 days immersion in buffered saline, and for water sorption (WS) and their WS kinetic profiles. The Bis-GMA copolymers and composites derived from HEMA and GDMA had BFS and WS values, as well as WS kinetic profiles, similar to the controls. Copolymers and composites based on Bis-GMA/PHEMA had lower BFS and higher WS values. Si-ACP composites had significantly lower BFS values (that were further diminished on soaking) than their copolymers. WS increased as the level of this filler was increased except for Bis-GMA/PHEMA composites. With n-SiO(2) as the filler, a more moderate reduction in BFS occurred compared to the unfilled copolymers. By contrast to Si-ACP composites, the WS of all the n-SiO(2) composites decreased with increasing filler level. From this study it is evident that both the chemical structure of the polymer matrix and the type of filler system can have significant effects on the strength and water-related properties of dental composites.
Assuntos
Bis-Fenol A-Glicidil Metacrilato/química , Fosfatos de Cálcio/química , Força Compressiva , Materiais Dentários/química , Teste de Materiais , Silanos/química , Água/química , Absorção , Bis-Fenol A-Glicidil Metacrilato/síntese química , Bis-Fenol A-Glicidil Metacrilato/efeitos da radiação , Fosfatos de Cálcio/síntese química , Fosfatos de Cálcio/efeitos da radiação , Resinas Compostas/síntese química , Resinas Compostas/química , Resinas Compostas/efeitos da radiação , Materiais Dentários/síntese química , Análise do Estresse Dentário , Luz , Metacrilatos/síntese química , Metacrilatos/química , Metacrilatos/efeitos da radiação , Silanos/efeitos da radiação , Cloreto de Sódio/química , Relação Estrutura-Atividade , Resistência à TraçãoRESUMO
Because of its relatively high solubility in aqueous media and its rapid transformation to hydroxyapatite, amorphous calcium phosphate (ACP) has been utilized as the filler phase of resin-based bioactive composites that have remineralization potential. The objectives of this study were to determine how various methacrylate resins and various types of ACP fillers affect acrylic vinyl conversion and polymerization shrinkage (PS). Several types of photo-crosslinkable resin systems were prepared and admixed with a mass fraction of 40% of either unhybridized, silica- or zirconia-hybridized ACP. After visible light-activated photo-polymerization ACP composites were assessed by near infrared spectroscopy for degree of vinyl conversion and by mercury dilatometry for PS. It was found for these composites that vinyl conversion was independent of filler type but strongly dependent on the type and composition of the resin phase. PS, on the other hand, showed more complex dependence both on the resin type and composition and, in some cases, on the type of ACP. In order to obtain ACP/methacrylate-based composites with maximal vinyl conversion, resin type and composition are of primary importance. However, in order to minimize volume contraction on polymerization it appears necessary to consider both the resin and filler type of these bioactive composites.
Assuntos
Materiais Biocompatíveis/química , Materiais Biocompatíveis/efeitos da radiação , Fosfatos de Cálcio/química , Luz , Metacrilatos/química , Polímeros/química , Polímeros/efeitos da radiação , Fosfatos de Cálcio/efeitos da radiação , Resinas Compostas/síntese química , Resinas Compostas/química , Resinas Compostas/efeitos da radiação , Densitometria , Estabilidade de Medicamentos , Teste de Materiais , Metacrilatos/efeitos da radiação , Polímeros/síntese química , Silanos/síntese química , Silanos/química , Silanos/efeitos da radiação , Compostos de Vinila/síntese química , Compostos de Vinila/química , Compostos de Vinila/efeitos da radiaçãoRESUMO
The general collection efficiency in the dielectric liquids iso-octane (CaH18; 2-2-4 trimethylpentane) and tetramethylsilane (Si(CH3)4), used as sensitive media in a thimble liquid ionization chamber (LIC) with a liquid layer thickness of 1 mm, has been studied. Measurements were made for continuous radiation at varying dose rates using 140 keV photons from the decay of 99mTc for chamber polarizing voltages of 50, 100 and 500 V. The maximum dose rate in each measurement session was about 150 mGy min(-1). The experimental results were compared with theoretical general collection efficiencies calculated by the equation for the general collection efficiency in gases. The results show that the general collection efficiency in a thimble LIC for continuous radiation can be calculated with the equation for the general collection efficiency in gas ionization chambers, using the same chamber geometry correction factors and analogous characteristic ion recombination parameters for the dielectric liquids.
Assuntos
Octanos/efeitos da radiação , Radiometria/instrumentação , Silanos/efeitos da radiação , Desenho de Equipamento , Meia-Vida , Modelos Teóricos , Octanos/química , Imagens de Fantasmas , Sensibilidade e Especificidade , Silanos/química , Compostos de TrimetilsililRESUMO
First measurements with a prototype ionization chamber are described to be applied in online monitoring of modulated fields in radiation therapy. The liquids isooctane, isononane (TMP) and tetramethylsilane (TMS) are used in a high purity grade in order to realize high current signals for electronic read-out in parallel at frequencies exceeding 10 Hz. Signals of more than a factor 4 with respect to isooctane, analysis grade, are obtained. With an electrode structure of 400 pads, a uniformity in efficiency within 1.2% has been measured. The penumbra of a multileaf collimator could be resolved. Theoretical examination verifies that the free electrons in the liquids cause higher signals when the measured currents are compared with expectation for ion transport only.
Assuntos
Análise de Falha de Equipamento/métodos , Octanos/efeitos da radiação , Pentanos/efeitos da radiação , Proteção Radiológica/instrumentação , Radiometria/instrumentação , Radioterapia Conformacional/instrumentação , Silanos/efeitos da radiação , Transdutores , Simulação por Computador , Desenho de Equipamento , Estudos de Viabilidade , Modelos Teóricos , Sistemas On-Line/instrumentação , Projetos Piloto , Proteção Radiológica/métodos , Radiometria/métodos , Dosagem Radioterapêutica , Radioterapia Conformacional/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Soluções/efeitos da radiação , Compostos de TrimetilsililRESUMO
OBJECTIVES: The objective of this in vitro study was to evaluate surface roughness, hardness and wear resistance of an Ormocer (Admira), polymerized by a plasma arc system. A secondary objective was to investigate two placement technique bulk or incremental layers. METHODS: Blocks from Admira and Amelogen (a microhybrid composite) were prepared in cylinders, 3 mm in diameter, and 2 and 5 mm in thickness (bulk or incrementally placed) and polymerized by a plasma arc and a conventional light system. Surface roughness measurements were taken by a Surface Profilometer on the top of the specimens. Vickers hardness measurements, with a load of 600mN were taken on the top and bottom of 2 mm and top, intermediate and bottom of 5 mm thick specimens. For the wear test, specimes (8 mm in diameter and 2 mm in thickness) of Admira, Amelogen and amalgam were tested in a ball-on design, by circular movements of the antagonist (alumina ball; diameter 10 mm) under 10 N load. For the statistical evaluation of the results of surface roughness, microhardness and wear test; a paired samples t-test and Kruskal-Wallis analysis of variance test, were performed. RESULTS: Admira showed highest hardness values in all polymerization types at the top surface and this was statistically significant (p < 0.05). These highest hardness values were obtained with conventional polymerization (81.84 +/- 1.167 VHN). Meanwhile, the wear resistance of Admira was found to be higher than Amelogen (Wd(admira) = 0.024 +/- 0.00149 mm3; Wd(amelogen) = 0.032 +/- 0.00075 mm3). However, Admira demonstrated the highest surface roughness value compared to Amelogen, with plasma arc 5 s (0.65 +/- 0.023 microm). Amelogen was found to have the lowest surface roughness value with conventional 40 s (0.45 +/- 0.012 microm). SIGNIFICANCE: The results indicated that Ormocer, which was developed by Ormocer technology, demonstrated higher microhardness and wear resistance when compared to a hybrid composite; however, the polishability of Ormocer needs further investigation. Also the selection of visible light activated composite resins exhibited higher surface microhardness values when polymerized with conventional rather than with plasma arc.