| 1. |
- Lutgendorff, Femke, et al.
(author)
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Probiotics prevent intestinal barrier dysfunction in acute pancreatitis in rats via induction of ileal mucosal glutathione biosynthesis.
- 2009
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:2, s. e4512-
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Journal article (peer-reviewed)abstract
- BACKGROUND: During acute pancreatitis (AP), oxidative stress contributes to intestinal barrier failure. We studied actions of multispecies probiotics on barrier dysfunction and oxidative stress in experimental AP. METHODOLOGY/PRINCIPAL FINDINGS: Fifty-three male Spraque-Dawley rats were randomly allocated into five groups: 1) controls, non-operated, 2) sham-operated, 3) AP, 4) AP and probiotics and 5) AP and placebo. AP was induced by intraductal glycodeoxycholate infusion and intravenous cerulein (6 h). Daily probiotics or placebo were administered intragastrically, starting five days prior to AP. After cerulein infusion, ileal mucosa was collected for measurements of E. coli K12 and (51)Cr-EDTA passage in Ussing chambers. Tight junction proteins were investigated by confocal immunofluorescence imaging. Ileal mucosal apoptosis, lipid peroxidation, and glutathione levels were determined and glutamate-cysteine-ligase activity and expression were quantified. AP-induced barrier dysfunction was characterized by epithelial cell apoptosis and alterations of tight junction proteins (i.e. disruption of occludin and claudin-1 and up-regulation of claudin-2) and correlated with lipid peroxidation (r>0.8). Probiotic pre-treatment diminished the AP-induced increase in E. coli passage (probiotics 57.4+/-33.5 vs. placebo 223.7+/-93.7 a.u.; P<0.001), (51)Cr-EDTA flux (16.7+/-10.1 vs. 32.1+/-10.0 cm/s10(-6); P<0.005), apoptosis, lipid peroxidation (0.42+/-0.13 vs. 1.62+/-0.53 pmol MDA/mg protein; P<0.001), and prevented tight junction protein disruption. AP-induced decline in glutathione was not only prevented (14.33+/-1.47 vs. 8.82+/-1.30 nmol/mg protein, P<0.001), but probiotics even increased mucosal glutathione compared with sham rats (14.33+/-1.47 vs. 10.70+/-1.74 nmol/mg protein, P<0.001). Glutamate-cysteine-ligase activity, which is rate-limiting in glutathione biosynthesis, was enhanced in probiotic pre-treated animals (probiotics 2.88+/-1.21 vs. placebo 1.94+/-0.55 nmol/min/mg protein; P<0.05) coinciding with an increase in mRNA expression of glutamate-cysteine-ligase catalytic (GCLc) and modifier (GCLm) subunits. CONCLUSIONS: Probiotic pre-treatment diminished AP-induced intestinal barrier dysfunction and prevented oxidative stress via mechanisms mainly involving mucosal glutathione biosynthesis.
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| 2. |
- Emami, Nazanin, et al.
(author)
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Dynamic mechanical thermal analysis of two light-cured dental composites
- 2005
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In: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 21:10, s. 977-983
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Journal article (peer-reviewed)abstract
- ObjectivesClinical observations suggest that some composite resins are more often linked to post-operative sensitivity than others. These differences may relate to differences in modulus of elasticity and polymerization rates among materials. The aim of this study was to identify viscoelastic behavior of two light curable composites and determine whether significant differences in viscoelastic behavior exist between the two materials when light cured at each of three different irradiance values.MethodsTwo composites (Z100 and Z250 by 3M ESPE) were evaluated. Six specimens per composite and irradiance value (250, 500 and 850 mW/cm2) were made. The curing times were chosen to produce a fixed energy value of 30 J/cm2 independent of irradiation value. Dynamic mechanical thermal analysis (DMTA) was performed in single cantilever clamped mode.ResultsThere were significant differences in transition temperatures between the two materials and the three frequencies at their glass transition temperatures, while significant differences did not exist at the lower transitions. The glass transition of Z250 was lower and narrower than that of Z100. Z250 exhibited lower storage modulus values. The irradiance values did not affect any of the transition temperatures significantly.SignificanceThe lower and more distinct Tg of Z250 suggests that Z250 cures more efficiently than Z100. The lower storage modulus of Z250 suggests that Z250 develops less stress in the tooth than Z100 during curing if shrinkage is the same for the two materials. The findings suggest that the material chosen, rather than irradiance, determines the stress level developed during light curing.
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| 3. |
- Emami, Nazanin, et al.
(author)
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Effect of light power density variations on bulk curing properties of dental composites
- 2003
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In: Journal of Dentistry. - 0300-5712 .- 1879-176X. ; 31:3, s. 189-196
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Journal article (peer-reviewed)abstract
- Objective. The hypothesis that low light intensity and long but sufficient curing time can produce composites with volumetric shrinkage, degree of conversion (DC%) and Young's modulus (E-modulus) comparable to those of high light intensity cured composite was tested, when the contraction strain and heat generation were lower with low light intensity curing. Methods. Dental composites (Z100 and Z250, 3M ESPE) were investigated. Specimens were cured with light intensities of 200, 450 and 800 mW/cm2 for 140, 60 and 35 s from a distance of 7 mm. Strain-gages were used for contraction strain measurements. DC% was measured at the top and the bottom of 4 mm thick samples using FT-Raman spectroscopy. Volumetric polymerization shrinkage was determined using a water displacement method. E-modulus was determined in tension on composite specimens. Results. The results were analyzed using ANOVA and Duncan's multiple range tests and regular t-test. Polymerization stress level decreased significantly (p<0.05) when cured with 200 mW/cm2 rather than with 800 mW/cm2. Temperature rises were significantly different (p<0.05) for different composites and light intensity values. Reduction in light intensity did not decrease the DC% values significantly at the top surfaces. The most dramatic differences existed between top and bottom surfaces (p<0.05) rather than among curing groups. Measured E-modulus and volumetric shrinkage values were not significantly different (p>0.05) between different light intensity groups. Conclusion. DC%, E-modulus and the volumetric shrinkage values in cured composites were not affected by low light intensity, however, the contraction strain and polymerization's exotherm were decreased. Thus our results support the proposed hypothesis.
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| 4. |
- Emami, Nazanin, et al.
(author)
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How degree of conversion and E-modulus of light-cure dental-resins interact
- 2006
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In: 84th General Session and Exhibition of the IADR and 1st Meeting of the Pan-Asian-Pacific Federation. - : IADR.
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Conference paper (other academic/artistic)abstract
- Objectives: To investigate how E-modulus, degree of conversion (DC%) and rate of polymerization of the most used monomer resins in dental light-cure composites interact. Methods: Young's modulus and DC% were studied for 21 different resin combinations of three commonly used dental monomers, bis-GMA, TEGDMA and UEDMA (combinations of 0, 20, 40, 60 and 100 wt% as it is illustrated in the figure). For each resin combination 6 specimens were tested. Small Instron and differential scanning calorimetry (photo-calorimetry) were used as testing machines. The results were tested using ANOVA and Duncan's multiple range tests and regular t-test. Results: Rate of polymerization was significantly (p<0.05) higher when the wt% of the TEGDMA was high in the mixtures compare to highly concentrated bis-GMA. DC% was significantly high (p<0.05) for binary mixture of UEDMA and TEGDMA. The DC% was significantly lower for 100 wt% bis-GMA (p<0.05). The calculated values for DC% were between 53.1%± 0.9% and 85.6%±1%. Young's modulus values varied between 2.37± 0.15 GPa and 4.15± 0.2 GPa. It was noticeable that by adding TEGDMA to bisGMA or UEDMA, the Young's modulus decreased significantly (p<0.05). There were no significant (p>0.05) differences between Young's modulus values when the monomer mixtures contained bis-GMA, TEGDMA and UEDMA at different concentration levels. The higher the concentration of bisGMA in the monomer mixture, the lower was the degree of conversion. However, Young's modulus increased at higher concentration of bis-GMA. Conclusions: The differences in the values for degree of conversion were mostly justified by the differences in the molecular structures of the different monomers. It was also revealed that higher degree of conversion does not always result in a higher Young's modulus, because molecular and network structural parameters play major roles in the final mechanical/physical properties of the mixtures.
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| 5. |
- Emami, Nazanin, et al.
(author)
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How filler properties, filler fraction, sample thickness and light source affect light attenuation in particulate filled resin composites
- 2005
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In: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 21:8, s. 721-730
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Journal article (peer-reviewed)abstract
- The way by which variables such as filler type, filler surface treatment and light source affect light attenuation in particulate filled resin composites was presented. Mixture of 50 wt% bisGMA and 50wt% TEGDMA consisting of a photo-initiatior and a co-initiator was prepared. Three different filler types, HBB, SBB, and KU, which were either silane surface treated or not, were added to that mixture in eight different volume percentage. It was observed that of the two light sources, more light was absorbed by the composite when the laser light was used. It was also observed that the HBB filler absorbed most light and the KU filler the least.
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| 6. |
- Emami, Nazanin, et al.
(author)
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Influence of light-curing procedures and photo-initiator/co-initiator composition on the degree of conversion of light-curing resins
- 2005
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In: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 16:1, s. 47-52
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Journal article (peer-reviewed)abstract
- Objective: The hypothesis that the degree and rate of conversion can be modified favourably by using different light-curing procedures and different photo initiator/co-initiator combinations was tested.Method: A photo-initiator (0.02 mM/g resin); either camphorquinone (CQ) or 1-phenyl-1,2-propanedione (PPD), was mixed with bisGMA:TEGDMA (50:50 by weight). In addition, a co-initiator (0.04 mM/g resin); either N,N-dimethyl-p-aminobenzoic acid ethylester (DABE), N,N-cyanoethylmethylaniline (CEMA), or 2-dimethylaminoethyl methacrylate (DMAEMA), was added. These six combinations were subjected to three curing conditions (standard curing, soft-start curing or LED curing). The conversion levels (DC) were determined with differential scanning calorimetry (DSC). The DSC results were analysed using a general linear model (GLM) and Duncans multiple range test and regular t-test.Results: The fastest conversion initially was obtained by standard curing, followed by LED curing and soft-start curing. After 40 s of curing, conventional curing and soft-start curing produced a higher DC than LED curing. However, strong interactions occurred between the different variables (curing method, initiator and co-initiator). Initially, CQ was more efficient than PPD, but after 40 s, this difference was insignificant.Conclusion: By using soft-start curing and an appropriate photo initiator/co-initiator combination it is possible to achieve slow curing and a high DC at within a curing time of 40 s.
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| 7. |
- Söderholm, Karl-Johan M., 1942-
(author)
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Hydrolytic degradation of dental composites and effects of silane-treatment and filler fraction on compressive strength and thermal expansion of composites
- 1984
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Doctoral thesis (other academic/artistic)abstract
- Some researchers have suggested that the weakest link of dental composites is the filler-matrix bond. However, due to incompleteness of information dealing with this bond and its stability in a humid environment, it was considered desirable to investigate the effect of water on this region, as well as the influence of filler bonding and filler fraction on compressive strength and thermal expansionExperimental composites containing different filler fractions of either silane-treated or untreated fillers were made. Compressive strength and coefficient of thermal expansion were determined using routine methods, while the hydrolytic degradation was investigated by measuring changes in concentrations of elements in the storage water using atomic absorption spectrophotometry. Scanning electron microscopic investigations were made on fractured samples.The diffusion coefficient of a representative resin system was determined gravimetrically. Seven commercial composites were investigated regarding hydrolytic degradation. The filler compositions of these composite materials were determined by emission spectroscopy or energy-dispersive x-ray analysis before storage in distilled water. This water was replaced and analyzed monthly using plasma spectrophotometry or atomic absorption spectrophotometry.After completed water storage the samples were fractured and investigated by use of scanning electron microscopy. From the results of these studies the following conclusions were drawn:1. The compressive strength of composites changes linearly with increased filler fraction. Contrary to bonded fillers, composites containing unbonded fillers lost strength with increased filler fraction.2. Water diffuses through the polymer matrix and attacks the filler particles. This degradation is most pronounced for untreated fillers containing glass modifying elements such as sodium, barium and strontium.3. The resin, used as a matrix, influences the speed with which the hydrolytic degradation of the filler proceeds.4. The hydrolytic degradation of the filler seemed to be associated with micro-crack formation occurring in the matrix. Of the investigated composites, the micro-filled resin showed the lowest frequency of such crack formations.5. The coefficient of thermal expansion decreases linearly with increased filler fraction. Silane treatment did not influence this coefficient.6. Using a simplified model to predict stresses in a particle filled composite indicates that rather high stress levels are induced in the polymer matrix due to polymerization shrinkage. This shrinkage induces radial compressive and tangential tensile stresses with respect to the filler surface. Increased filler fraction increases the tangential tensile stresses but reduces the compressive radial stresses.
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