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1.
J Biomed Mater Res B Appl Biomater ; 107(8): 2673-2683, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-30895695

RESUMO

Nearly 100 million of the 170 million composite and amalgam restorations placed annually in the United States are replacements for failed restorations. The primary reason both composite and amalgam restorations fail is recurrent decay, for which composite restorations experience a 2.0-3.5-fold increase compared to amalgam. Recurrent decay is a pernicious problem-the standard treatment is replacement of defective composites with larger restorations that will also fail, initiating a cycle of ever-larger restorations that can lead to root canals, and eventually, to tooth loss. Unlike amalgam, composite lacks the inherent capability to seal discrepancies at the restorative material/tooth interface. The low-viscosity adhesive that bonds the composite to the tooth is intended to seal the interface, but the adhesive degrades, which can breach the composite/tooth margin. Bacteria and bacterial by-products such as acids and enzymes infiltrate the marginal gaps and the composite's inability to increase the interfacial pH facilitates cariogenic and aciduric bacterial outgrowth. Together, these characteristics encourage recurrent decay, pulpal damage, and composite failure. This review article examines key biological and physicochemical interactions involved in the failure of composite restorations and discusses innovative strategies to mitigate the negative effects of pathogens at the adhesive/dentin interface. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2466-2475, 2019.


Assuntos
Adesivos , Materiais Dentários , Restauração Dentária Permanente , Dentina , Adesivos/química , Adesivos/uso terapêutico , Materiais Dentários/química , Materiais Dentários/uso terapêutico , Dentina/química , Dentina/metabolismo , Humanos
2.
Biointerphases ; 13(6): 061004, 2018 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-30558430

RESUMO

Dentin adhesive systems for composite tooth restorations are composed of hydrophilic/hydrophobic monomers, solvents, and photoinitiators. The adhesives undergo phase separation and concomitant compositional change during their application in the wet oral environment; phase separation compromises the quality of the hybrid layer in the adhesive/dentin interface. In this work, the adhesive composition in the hybrid layer can be represented using the phase boundaries of a ternary phase diagram for the hydrophobic monomer/hydrophilic monomer/water system. The polymer phases, previously unaccounted for, play an important role in determining the mechanical behavior of the bulk adhesive, and the chemomechanical properties of the phases are intimately related to the effects produced by differences in the hydrophobic-hydrophilic composition. As the composition of the polymer phases varies from hydrophobic-rich to hydrophilic-rich, the amount of the adsorbed water and the nature of polymer-water interaction vary nonlinearly and strongly correlate with the change in elastic moduli under wet conditions. The failure strain, loss modulus, and glass transition temperature vary nonmonotonically with composition and are explained based upon primary and secondary transitions observed in dynamic mechanical testing. Due to the variability in composition, the assignment of mechanical properties and the choice of suitable constitutive models for polymer phases in the hybrid layer are not straightforward. This work investigates the relationship between composition and chemomechanical properties of the polymer phases formed on the water-adhesive phase boundary using quasistatic and dynamic mechanical testing, mass transfer experiments, and vibrational spectroscopy.


Assuntos
Cimentos Dentários/química , Cimentos Dentários/farmacologia , Polímeros/química , Polímeros/farmacologia , Fenômenos Químicos , Fenômenos Mecânicos , Relação Quantitativa Estrutura-Atividade
3.
J Phys Condens Matter ; 30(26): 265901, 2018 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-29767631

RESUMO

Continuum modeling of finite temperature mechanical behavior of atomic systems requires refined description of atomic motions. In this paper, we identify additional kinematical quantities that are relevant for a more accurate continuum description as the system is subjected to step-wise loading. The presented formalism avoids the necessity for atomic trajectory mapping with deformation, provides the definitions of the kinematic variables and their conjugates in real space, and simplifies local work conjugacy. The total work done on an atom under deformation is decomposed into the work corresponding to changing its equilibrium position and work corresponding to changing its second moment about equilibrium position. Correspondingly, we define two kinematic variables: a deformation gradient tensor and a vibration tensor, and derive their stress conjugates, termed here as static and vibration stresses, respectively. The proposed approach is validated using MD simulation in NVT ensembles for fcc aluminum subjected to uniaxial extension. The observed evolution of second moments in the MD simulation with macroscopic deformation is not directly related to the transformation of atomic trajectories through the deformation gradient using generator functions. However, it is noteworthy that deformation leads to a change in the second moment of the trajectories. Correspondingly, the vibration part of the Piola stress becomes particularly significant at high temperature and high tensile strain as the crystal approaches the softening limit. In contrast to the eigenvectors of the deformation gradient, the eigenvectors of the vibration tensor show strong spatial heterogeneity in the vicinity of softening. More importantly, the elliptic distribution of local atomic density transitions to a dumbbell shape, before significant non-affinity in equilibrium positions has occurred.

4.
Cureus ; 8(3): e526, 2016 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-27081587

RESUMO

Inverted sinonasal papilloma (ISP) is a benign epithelial neoplasm arising from the Schneiderian membrane. We report a case of ISP in a 50-year-old male that clinically presented as a polypoid mass in the nasal cavity. Imaging studies revealed it to be an aggressive lesion showing intracranial extension. On histopathological examination of the excised specimen, a diagnosis of ISP was arrived at. However, an extensive sampling of the tissue revealed no evidence of any malignant transformation. Taking into account the suggested viral aetiology for such lesions and the aggressiveness observed in this case, human papillomavirus (HPV) profiling was done but it turned out to be negative. Only one other case of inverted sinonasal papilloma arising from the nasal cavity and involving the brain has been reported in the literature to date. Considering the alarming clinical course in spite of its benign nature, it is important for the pathologist and surgeon to be well informed about this lesion.

5.
Z Angew Math Mech ; 95(2): 215-234, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25755301

RESUMO

We have developed a micromechanics based model for chemically active saturated fibrous media that incorporates fiber network microstructure, chemical potential driven fluid flow, and micro-poromechanics. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's volume averaging. The advantage of this approach is that the resultant continuum model accounts for the discrete nature of the individual fibers while retaining a form suitable for porous materials. As a result, the model is able to predict the influence of micro-scale phenomena, such as the fiber pre-strain caused by osmotic effects and evolution of fiber network structure with loading, on the overall behavior and in particular, on the poromechanics parameters. Additionally, the model can describe fluid-flow related rate-dependent behavior under confined and unconfined conditions and varying chemical environments. The significance of the approach is demonstrated by simulating unconfined drained monotonic uniaxial compression under different surrounding fluid bath molarity, and fluid-flow related creep and relaxation at different loading-levels and different surrounding fluid bath molarity. The model predictions conform to the experimental observations for saturated soft fibrous materials. The method can potentially be extended to other porous materials such as bone, clays, foams and concrete.

6.
J Biomed Mater Res A ; 103(2): 646-57, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24753362

RESUMO

To investigate the time- and rate-dependent mechanical properties of collagen-adhesive composites, creep and monotonic experiments are performed under dry and wet conditions. The composites are prepared by infiltration of dentin adhesive into a demineralized bovine dentin. Experimental results show that for small stress level under dry conditions, both the composite and the neat adhesive have similar behavior. On the other hand, in wet conditions, the composites are significantly soft and weak compared to the neat adhesives. The behavior in the wet condition is found to be affected by the hydrophilicity of both the adhesive and the collagen. As the adhesive-collagen composites are a part of the complex construct that forms the adhesive-dentin interface, their presence will affect the overall performance of the restoration. We find that Kelvin-Voigt model with at least four elements is required to fit the creep compliance data, indicating that the adhesive-collagen composites are complex polymers with several characteristic time scales whose mechanical behavior will be significantly affected by loading rates and frequencies. Such mechanical properties have not been investigated widely for these types of materials. The derived model provides an additional advantage that it can be exploited to extract other viscoelastic properties which are, generally, time consuming to obtain experimentally. The calibrated model is utilized to obtain stress relaxation function, frequency-dependent storage and loss modulus, and rate-dependent elastic modulus.


Assuntos
Colágeno/química , Cimentos Dentários/química , Elasticidade , Água/química , Adesividade , Animais , Bovinos , Viscosidade
7.
Acta Biomater ; 10(7): 3038-47, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24631658

RESUMO

Current dental resin undergoes phase separation into hydrophobic-rich and hydrophilic-rich phases during infiltration of the over-wet demineralized collagen matrix. Such phase separation undermines the integrity and durability of the bond at the composite/tooth interface. This study marks the first time that the polymerization kinetics of model hydrophilic-rich phase of dental adhesive has been determined. Samples were prepared by adding varying water content to neat resins made from 95 and 99 wt.% hydroxyethylmethacrylate and 5 and 1 wt.% (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl1]-propane prior to light curing. Viscosity of the formulations decreased with increased water content. The photopolymerization kinetics study was carried out with a time-resolved Fourier transform infrared spectrometer. All of the samples exhibited two-stage polymerization behavior which has not been reported previously for dental resin formulation. The lowest secondary rate maxima were observed for water contents of 10-30 wt.%. Differential scanning calorimetry (DSC) showed two glass transition temperatures for the hydrophilic-rich phase of dental adhesive. The DSC results indicate that the heterogeneity within the final polymer structure decreased with increasing water content. The results suggest a reaction mechanism involving both polymerization-induced phase separation and solvent-induced phase separation for the model hydrophilic-rich phase of dental resin.


Assuntos
Cimentos Dentários , Dentina/química , Polímeros/química , Solventes/química , Varredura Diferencial de Calorimetria , Interações Hidrofóbicas e Hidrofílicas , Cinética
8.
Appl Spectrosc ; 67(12): 1473-8, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24359662

RESUMO

Water is ubiquitous in the mouths of healthy individuals and is a major interfering factor in the development of a durable seal between the tooth and composite restoration. Water leads to the formation of a variety of defects in dentin adhesives; these defects undermine the tooth-composite bond. Our group recently analyzed phase partitioning of dentin adhesives using high-performance liquid chromatography (HPLC). The concentration measurements provided by HPLC offered a more thorough representation of current adhesive performance and elucidated directions to be taken for further improvement. The sample preparation and instrument analysis using HPLC are, however, time-consuming and labor-intensive. The objective of this work was to develop a methodology for rapid, reliable, and accurate quantitative analysis of near-equilibrium phase partitioning in adhesives exposed to conditions simulating the wet oral environment. Analysis by Fourier transform infrared (FT-IR) spectroscopy in combination with multivariate statistical methods, including partial least squares (PLS) regression and principal component regression (PCR), were used for multivariate calibration to quantify the compositions in separated phases. Excellent predictions were achieved when either the hydrophobic-rich phase or the hydrophilic-rich phase mixtures were analyzed. These results indicate that FT-IR spectroscopy has excellent potential as a rapid method of detection and quantification of dentin adhesives that experience phase separation under conditions that simulate the wet oral environment.


Assuntos
Dentina/química , Metacrilatos/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Calibragem , Cromatografia Líquida de Alta Pressão/métodos , Retenção de Dentadura , Interações Hidrofóbicas e Hidrofílicas , Análise dos Mínimos Quadrados , Metacrilatos/análise , Análise Multivariada , Análise de Componente Principal , Reprodutibilidade dos Testes
9.
J Biomed Mater Res B Appl Biomater ; 101(8): 1437-43, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23744598

RESUMO

The aim of this study is to investigate the mechanical behavior of model methacrylate-based dentin adhesives under conditions that simulate the wet oral environment. A series of monotonic and creep experiments were performed on rectangular beam samples of dentin adhesive in three-point bending configuration under different moisture conditions. The monotonic test results show a significant effect of loading rate on the failure strength and the linear limit (yield point) of the stress-strain response. In addition, these tests show that the failure strength is low, and the failure occurs at a smaller deformation when the test is performed under continuously changing moisture conditions. The creep test results show that under constant moisture conditions, the model dentin adhesives can have a viscoelastic response under certain low loading levels. However, when the moisture conditions vary under the same low loading levels, the dentin adhesives have an anomalous creep response accompanied by large secondary creep and high strain accumulation.


Assuntos
Adesivos Dentinários/química , Metacrilatos/química , Osso e Ossos/metabolismo , Resinas Compostas , Colagem Dentária , Análise do Estresse Dentário , Dentina/química , Elasticidade , Dureza , Teste de Materiais , Cimentos de Resina , Estresse Mecânico , Propriedades de Superfície , Viscosidade
10.
Artigo em Inglês | MEDLINE | ID: mdl-25419475

RESUMO

The authors have derived macroscale poromechanics parameters for chemically active saturated fibrous media by combining microstructure-based homogenization with Hill's volume averaging. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill's Lemmas. The advantage of this approach is that the resultant continuum model assumes a form suited to study porous materials, while retaining the effect of discrete fiber deformation. As a result, the model is able to predict the influence of microscale phenomena such as fiber buckling on the overall behavior, and in particular, on the poromechanics constants. The significance of the approach is demonstrated using the effect of drainage and fiber nonlinearity on monotonic compressive stress-strain behavior. The model predictions conform to the experimental observations for articular cartilage. The method can potentially be extended to other porous materials such as bone, clays, foams, and concrete.

11.
J Mater Sci Mater Med ; 23(5): 1157-72, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22430592

RESUMO

The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10(-8) cm(2)/sec (co-monomer TMTMA) to 3.15 × 10(-8) cm(2)/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R(2) = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R(2) = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure.


Assuntos
Metacrilatos/química , Polímeros/farmacocinética , Água/metabolismo , Absorção , Reagentes para Ligações Cruzadas/farmacologia , Difusão , Teste de Materiais , Metacrilatos/farmacocinética , Modelos Biológicos , Modelos Teóricos , Concentração Osmolar , Polimerização , Polímeros/química , Cimentos de Resina/síntese química , Cimentos de Resina/química , Solubilidade , Água/química
12.
J Biomed Mater Res B Appl Biomater ; 100(4): 1086-92, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22331596

RESUMO

There have been reports of the sensitivity of our current dentin adhesives to excess moisture, for example, water-blisters in adhesives placed on over-wet surfaces, and phase separation with concomitant limited infiltration of the critical dimethacrylate component into the demineralized dentin matrix. To determine quantitatively the hydrophobic/hydrophilic components in the aqueous phase when exposed to over-wet environments, model adhesives were mixed with 16, 33, and 50 wt % water to yield well-separated phases. Based upon high-performance liquid chromatography coupled with photodiode array detection, it was found that the amounts of hydrophobic BisGMA and hydrophobic initiators are less than 0.1 wt % in the aqueous phase. The amount of these compounds decreased with an increase in the initial water content. The major components of the aqueous phase were hydroxyethyl methacrylate (HEMA) and water, and the HEMA content ranged from 18.3 to 14.7 wt %. Different BisGMA homologues and the relative content of these homologues in the aqueous phase have been identified; however, the amount of crosslinkable BisGMA was minimal and, thus, could not help in the formation of a crosslinked polymer network in the aqueous phase. Without the protection afforded by a strong crosslinked network, the poorly photoreactive compounds of this aqueous phase could be leached easily. These results suggest that adhesive formulations should be designed to include hydrophilic multimethacrylate monomers and water compatible initiators.


Assuntos
Dentina/química , Adesividade , Adesivos/análise , Materiais Biocompatíveis/química , Cromatografia Líquida de Alta Pressão/métodos , Adesivos Dentinários/análise , Desenho de Equipamento , Humanos , Interações Hidrofóbicas e Hidrofílicas , Metacrilatos/química , Metilmetacrilatos/química , Modelos Químicos , Espectrofotometria Ultravioleta/métodos , Água/química
13.
J Biomed Mater Res A ; 91(1): 251-62, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18980198

RESUMO

Fourier transform infrared (FTIR) chemical imaging can be used to investigate molecular chemical features of the adhesive/dentin interfaces. However, the information is not straightforward and is not easily extracted. The objective of this study was to use multivariate analysis methods, principal component analysis, and fuzzy c-means clustering and to analyze spectral data in comparison with univariate analysis. The spectral imaging data collected from both the adhesive/healthy dentin and adhesive/caries-affected dentin specimens were used and compared. The univariate statistical methods such as mapping of intensities of specific functional group do not always accurately identify functional group locations and concentrations because of more or less band overlapping in adhesive and dentin. Apart from the ease with which information can be extracted, multivariate methods highlight subtle and often important changes in the spectra that are difficult to observe using univariate methods. The results showed that the multivariate methods gave more satisfactory, interpretable results than univariate methods and were conclusive in showing that they can discriminate and classify differences between healthy dentin and caries-affected dentin within the interfacial regions. It is demonstrated that the multivariate FTIR imaging approaches can be used in the rapid characterization of heterogeneous, complex structure.


Assuntos
Adesivos/análise , Dentina/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Análise por Conglomerados , Humanos , Dente Molar/química , Análise Multivariada , Análise de Componente Principal
14.
J Biomed Opt ; 13(1): 014020, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18315378

RESUMO

This study presents the application of multivariate analyses to analyze micro-Raman spectral imaging data in reference to the adhesive/dentin interface as well as comparison with univariate analysis. The univariate statistical methods, such as mapping of specific functional group peak intensities, do not always detect functional group positions and quantities due to peak overlapping. A comprehensive chemical analysis of the adhesive/dentin interface, along with the multivariate statistical methods, principal component analysis, and fuzzy c-means clustering, is studied. Compared to univariate analysis, multivariate methods present the entire hyperspectral information from the specimen in a concise and uncorrelated way. Apart from the ease with which information can be extracted and presented, multivariate methods also highlight minute and often important variations in the spectra that are difficult to observe using univariate methods. The results show for the first time the clear chemical and structural classifications in the adhesive/dentin interface at successively greater resolutions.


Assuntos
Algoritmos , Adesivos Dentinários/química , Dentina/química , Dentina/citologia , Microscopia/métodos , Análise Espectral Raman/métodos , Adesividade , Humanos , Técnicas In Vitro , Dente Molar/química , Dente Molar/citologia , Análise Multivariada , Propriedades de Superfície
15.
Clin Imaging ; 30(5): 361-4, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16919562

RESUMO

Intravenous lipoleiomyomatosis (LPL) is a rare benign tumor composed of fat and smooth muscle. Intravenous LPL is a rare subtype of intravenous leiomyomatosis (IVL), of which only four cases have been reported. We report a case of intravenous LPL that extended into the inferior vena cava and right atrium. The imaging findings in this case were reported. A review of the world literature revealed no previous description of the imaging findings in a case of intravenous LPL. We discussed the reported imaging findings of typical IVL and briefly discussed relevant clinical features of intravenous LPL and IVL.


Assuntos
Doenças dos Anexos/diagnóstico , Leiomiomatose/diagnóstico , Neoplasias Vasculares/diagnóstico , Doenças dos Anexos/cirurgia , Feminino , Átrios do Coração/patologia , Átrios do Coração/cirurgia , Humanos , Leiomiomatose/cirurgia , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Invasividade Neoplásica , Artéria Pulmonar/patologia , Artéria Pulmonar/cirurgia , Tomografia Computadorizada por Raios X
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