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At least 307 records · Page 17Linked to original sources

PubMed2004

Tensile and tear strength of carrageenan film from Philippine eucheuma species.

The tensile and tear strength of carrageenan film from Philippines Eucheuma species were investigated using NEC tensilon universal-testing machine according to American Society for Testing Materials methods. These properties are important for assessing carrageenan film as packaging material. The kappa and iota types were used in the study. The effect of glycerine on the tensile and tear strength including elongation was also evaluated. Addition of glycerine tended to lower the tensile strength of the film and increase its elongation properties including the tear strength. Carrageenan film without glycerine was much stronger. Glycerine made the film more flexible and easy to deform. The composite film of carrageenan and konjac gum did not exhibit elongation. It also showed higher tensile strength than did the composite film of carrageenan and xanthan gum. Compared with iota-type carrageenan film, kappa-type carrageenan film without glycerine was more comparable to low-density polyethylene (LDPE) film in terms of tensile strength as was the composite film of carrageenan-konjac gum. The kappa-type carrageenan film with glycerine was more comparable to LDPE film in terms of tear strength. The elongation reading for carrageenan film was lower than that for LDPE film. Morphologic studies showed that the carrageenan film had sets of pores distributed randomly at different places as compared to LDPE film. It also showed that the carrageenan film was more fibrous than LDPE film.

Amorphophallus↗

PubMed2006

Tissue and cell reactions to implanted root-end filling materials.

The use of root-end filling materials designed to stimulate hard and soft tissue repair in periradicular tissues is highly recommended. The materials should demonstrate good cell and tissue compatibility. The aim of the present study was to compare in vitro biocompatibility and in vivo tissue reaction with calcium hydroxide-based, eugenol-based and mineral trioxide aggregate root-end filling materials. The human osteosarcoma cell line was treated with immersed root end filling materials. The test materials were implanted in rats and the results observed at 6 and 8 weeks. In vitro, the highest survival rate was demonstrated for the mineral trioxide aggregate (p<0.05). In vivo, a radiopaque ring was evident in the calcium hydroxide implants on the eight-week radiograph. Histopathology revealed eugenol-based material with the inflammatory cells around the implant, with fibrous connective tissue forming around the calcium hydroxide-based analog. The mineral trioxide aggregate appears to be well tolerated by the tissue.

Aluminum Compounds↗

PubMed1996

Thickness measurement of soft tissue biomaterials: a comparison of five methods.

Thickness measurement in soft connective tissues is a continuing problem due to the apparent compression of the tissue by micrometer-type gauges. We have compared five methods for the measurement of thickness: (1) a Mitutoyo non-rotating thickness gauge; (2) a custom-built, instrumented thickness gauge which was strain-gauged to measure contact force; (3) a commercial Hall effect probe (Panametrics Magna-Mike); (4) a custom-built electrical resistance probe; and (5) measurement of fresh frozen histological sections under polarized light. Using bovine pericardium as a test material, all the methods examined were adequate to assess sample-to-sample and location-to-location differences in thickness. The resistance gauge gave significantly greater thicknesses than did the other methods, with little or no compression; indeed, extrapolation to zero load of thickness readings from the instrumented gauge yielded identical thickness. Thicknesses measured by frozen sections were indistinguishable from those measured with the non-rotating gauge, the instrumented gauge under 0.5-1.2 g compressive load, or the Hall effect probe. With the correct technique, the simple and inexpensive non-rotating gauge remains a pragmatic choice for thickness measurement in planar soft tissue.

Analysis of Variance↗

PubMed1994

Cytotoxicity of eluates from light-polymerized denture base resins.

This study examined the metabolic effects of eluates from four light-polymerized denture base resins and one heat-polymerized denture base resin on oral epithelial cells in vitro. The eluate was cell culture medium that contained either or both of apparently nonpolymerized components and reaction products that diffused out of the resin samples. Eluates were prepared by daily transfer of sample disks in a cell culture medium over 10 days. Toxicity of eluates was tested immediately after transfer (fresh) and after storage for 30 days (aged) by use of radioisotope incorporation and cell viability studies. The fresh eluates inhibited cell metabolism, whereas the aged eluates stimulated then inhibited the responses. Results suggest that the components that leach out of the tested materials do so at different rates and have prolonged toxic effects on cells. Thus soaking prosthesis in water before insertion may be beneficial.

Acrylic Resins↗

PubMed1991

Marginal adaptation of nine commercial intermediate resins.

The bonding efficacy of nine commercially available intermediate resins was examined by measuring the maximum contraction gap of a light-activated composite in a cylindrical cavity of human dentin. With only one exception, the marginal adaptation of the composite improved significantly when the intermediate resins were combined with an experimental dentin cleaning system of the neutralized 0.5 mol/L EDTA and a dentin primer composed of a 35% aqueous solution of either hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM). Complete marginal adaptation was obtained with four tested materials when dentin was pre-treated with EDTA and GM.

Analysis of Variance↗

PubMed1993

Temperature dependence of the dynamic viscoelastic behavior of chemical- and light-cured composites.

The relationship of temperature to the viscoelastic properties of six composites, three light-cured and three chemical-cured, was studied, using constant dynamic loading over the narrow range of temperatures (20-60 degrees C) which can be encountered in the mouth. The parameters measured were: storage modulus G(1), loss modulus G(2), tan delta, quality factor Q, coefficient of decay alpha, and dynamic viscosity. It was found that the dynamic viscoelastic properties of the tested materials are temperature-dependent, but probably not to a clinically significant degree. Chemical-and light-cured composites of the same filler loading do not exhibit significantly different viscoelastic dynamic properties.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1993

Early strength of glass ionomer cements.

The present study compared the compressive, tensile and flexural strengths of 26 commercial glass ionomer cements, which were evaluated 24 h after the beginning of the setting reaction. In order to give a global estimation of their overall strength, a coefficient was attributed to each glass ionomer cement. This strength coefficient provided a ranking of the tested materials. The highest scores were obtained by the restorative glass ionomers; however, these materials exhibited lower mechanical properties than the more classic restorative materials such as amalgams or composites. The results also showed a large scattering of the mechanical properties among the luting and lining glass ionomer cements. The creep behavior of the glass ionomer cements was also investigated.

Analysis of Variance↗

PubMed1996

The deleterious effect of tetanic contraction on rabbit's triceps surae muscle during cyclic loading.

To elucidate the effect of nerve stimulation on the mechanical property of muscle-tendon unit, the triceps surae muscle of New Zealand White rabbit was tested with material testing machine. After anaesthesia, the triceps surae muscle-tendon unit of rabbit was tested with cyclic loading during nerve stimulation. The differences between initial and residual force disappeared in the presence of low amplitude and low frequency nerve stimulation. Loading energy applied to the muscle-tendon unit did not change, but the unloading energy increased and energy loss decreased significantly. However, the residual force appeared again at the tetanic stimulation; the loading energy, unloading energy and energy loss all increased significantly.

Journal Article↗

PubMed2005

Effect of dual ion implantation of calcium and phosphorus on the properties of titanium.

This study is concerned with the effect of dual implantation of calcium and phosphorus upon the structure, corrosion resistance and biocompatibility of titanium. The ions were implanted in sequence, first Ca and then P, both at a dose of 10(17) ions/cm2 at a beam energy of 25 keV. Transmission electron microscopy was used to investigate the microstructure of the implanted layer. The chemical composition of the implanted layer was examined by XPS and SIMS. The corrosion resistance was determined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. The biocompatibility tests were performed in vitro in a culture of human-derived bone cells (HDBC) in contact with the tested materials. The viability of the cells was determined by an XTT assay and their activity by the measurements of the alkaline phosphatase activity in contact with implanted and non-implanted titanium samples. The in vitro examinations confirmed that, under the conditions prevailing during the experiments, the biocompatibility of Ca + P ion-implanted titanium was satisfactory. TEM results show that the surface layer formed by the Ca + P implantation is amorphous. The corrosion resistance of titanium, examined by the electrochemical methods, appeared to be increased after the Ca + P ion implantation.

Alkaline Phosphatase↗

PubMed2005

The effect of charged groups on protein interactions with poly(HEMA) hydrogels.

Proteins, lipids and other biomolecules interact strongly with the acrylic-based biomaterials used for contact lenses. Although hydrogels are nominally resistant to protein fouling, many studies have reported considerable amounts of protein bound to poly(2-hydroxyethylmethacrylate) (PHEMA) lenses. This study examined the binding of a series of biomolecules (tear protein analogues, mucin and cholesterol) to poly(methylmethacrylate) (PMMA) and three HEMA-based hydrogels (PHEMA, HEMA plus methacrylic acid (P(HEMA-MAA)), HEMA plus methacrylic acid plus N-vinylpyrrolidone (P(HEMA-MAA-NVP))) by use of a quartz crystal microbalance with dissipation (QCM-D) monitoring. The QCM-D estimates changes in the mass and viscous constant for the adsorbed layer through measurements of frequency and dissipation. Protein interaction with each of the test materials caused a net increase in mass of the material indicating protein binding except for lysozyme interacting with P(HEMA-MAA). A net decrease in mass was observed for lysozyme interacting with P(HEMA-MAA) which may be ascribed to lysozyme collapsing the hydrogel by expelling water. A net mass decrease was observed for cholesterol interacting with each of the hydrogel materials, while a mass increase was observed on PMMA.

Adsorption↗

PubMed2006

Anaphylactic and anaphylactoid causes of angioedema.

Anaphylactic and anaphylactoid (pseudoallergic) reactions can be expected to occur with greater frequency as the number of immunomodulators are employed. The immune system will become sensitized to these new therapeutic agents or there may be first-dose reactions depending on the pathogenetic mechanism involved. Physicians should review their office or procedure room emergency preparedness protocols and medications. The lack of penicillin major and minor determinants for penicillin testing has made management of penicillin and cephalosporin allergic patients more complicated. In the absence of skin-testing materials, test-challenges will be necessary and performed with less comfort because of not knowing the current level of immunologic sensitization to penicillin. The indication for readministration of any incriminated medication/therapeutic agent should be reviewed. Often, there are not suitable alternatives. Various approaches have been presented to permit safer readministration of essential medications or diagnostic agents to prevent episodes of anaphylaxis or upper airway angioedema.

Anaphylaxis↗

PubMed2002

Toxicity of methyl tert-butyl ether to marine organisms: ambient water quality criteria calculation.

In response to increasing concerns over the detection of methyl tert-butyl ether (MTBE) in groundwater and surface water and its potential effects in aquatic ecosystems, industry and the United States Environmental Protection Agency (USEPA) began to collaborate in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with USEPA requirements. Acute toxicity data for seven marine species, chronic toxicity data for an invertebrate, and plant toxicity data were developed to complete the saltwater database. The species tested were Cyprinodon variegatus, Gasterosteus aculeatus, Callinectes sapidus, Mytilus galloprovincialis, Palaemonetes pugio, Rhepoxynius abronius, Americamysis bahia, and Skeletonema costatum. The toxicity tests were conducted in accordance with USEPA and American Society for Testing and Materials testing procedures and Good Laboratory Practice guidelines. Data developed from this study were consistent with existing data and showed that MTBE has low acute and chronic toxicity to the marine species tested. Based upon measured MTBE concentrations, acute effects were found to range from 166 mg MTBE/l for the grass shrimp to 1950 mg MTBE/l for marine mussel. The no-observed effect concentration for the reproduction and growth of mysids was 26 mg MTBE/l during the life cycle test. The toxicity of MTBE to saltwater organisms is comparable to its toxicity to the freshwater species tested. Reported MTBE concentrations in coastal waters are several orders of magnitude lower than concentrations observed to cause effects in marine organisms.

Animals↗

PubMed2004

In vitro Ca-P precipitation on biodegradable thermoplastic composite of poly(epsilon-caprolactone-co-DL-lactide) and bioactive glass (S53P4).

Bioactive properties of composites containing poly(epsilon-caprolactone-co-DL-lactide) with molar ratio 96/4 and bioactive glass (BAG), S53P4, were tested in vitro. The glass content in the tested materials was 40, 60 or 70 wt%, and two granule size ranges (<45 and 90-315 microm) were used. The composites were analysed for their apatite-forming ability. This was determined as a function of time by the dissolution pattern of Si and Ca ions and structural changes on the specimen surfaces. Composite specimens were immersed in simulated body fluid at 37 degrees C for up to 6 months. The changes in Si and Ca concentrations of the immersion medium were determined with UV-Vis and atomic absorption spectrophotometry. The calcium phosphate precipitation and apatite formation were evaluated by scanning electron microscopy (SEM) and infra-red spectroscopy (IR) using the attenuated total reflectance (ATR) system. The SEM and SEM-EDX analysis of the depositions formed on the composite surfaces was in line with the changes in ion concentrations. The clearest results with IR were seen in the material containing 60 wt% small glass particles. The results indicate that composites containing over 40 wt% BAG granules are bioactive, and that a higher BAG surface area/volume ratio favors the apatite formation in vitro.

Absorbable Implants↗

PubMed1992

A new compound curved tapercut needle for oral surgery.

A new compound curved tapercut needle has been designed and developed for oral mucous membrane closure from a unique stainless steel alloy, American Society for Testing Materials (ASTM) 45500. This tapercut needle has a short, relatively straight point, followed by a curved distal section. Despite its geometry, it exhibited similar sharpness as well as resistance to bending and breakage, as did the standard tapercut needle with a single radius of curvature manufactured from the same alloy. The design of this new needle enabled the surgeon to pass it through the oral mucous membrane with a greater accuracy to a controlled depth and length of bite than the standard tapercut needle with a single radius of curvature. In addition, the new needle design aids in the suturing of mucous membranes in confined spaces.

Elasticity↗

PubMed1997

Crystal size and properties of superparamagnetic iron oxide (SPIO) particles.

The properties of a superparamagnetic iron oxide (SPIO) model contrast agent have been studied. The test material, HEP-SPIO, contained iron oxide multicrystal agglomerates coated with heparin, polyanionic, naturally occurring glycosaminoglycan. Fractionation of the HEP-SPIO suspension showed the existence of colloidally stable particles ranging from approx. 100 nm down to single crystal sizes. The small (< 20 nm) particles represented the major number fraction of particles present, but only approx. 2% of the total iron oxide mass. The volume weighted average diameter of the individual iron oxide crystals forming the multicrystal agglomerates was found to be 11-12 nm using transmission electron microscopy and vibrating sample magnetometry (VSM) techniques. Comparable results were obtained with X-ray diffraction and Mössbauer spectroscopy. A number of additional SPIO properties could also be determined on a routine VSM, such as the distribution standard deviation for the log-normal distribution of crystal sizes, the magnetic susceptibility, the magnetic remanence, and the intrinsic magnetization (magnetic moment) of the iron oxide. These parameters are useful tools for evaluation of the magnetic characteristics and contrast efficacy of SPIO contrast agents.

Chemical Fractionation↗

PubMed2002

Quantitation of platelet adhesion to Ti and DLC-coated Ti in vitro using (125)I-labeled platelets.

Measurement of platelet adhesion in vitro is a good indicator of its reactivity to implant devices in vivo. Platelets were labeled with I-125 without affecting its normal morphology and function and the labeled platelets were suspended in platelet poor plasma and exposed to Ti and diamond like carbon-coated (DLC) Ti discs, under dynamic conditions, using a parallel plate flow chamber. The test materials were washed, dried, exposed to a phosphor screen and scanned to get the images. The number of platelets that adhered to Ti was found to be higher than those that adhered to DLC coated Ti sample, irrespective of the shear stress which was varied between 2 and 16 dynes/cm(2).

Blood Platelets↗

PubMed1999

Comparison of shear bond strength of three bonding agents with metal and ceramic brackets.

Shear bond strengths of a light-cured composite resin, a light-cured glass ionomer cement, and a light-cured compomer used with metal and ceramic brackets were compared, and ARI scores were evaluated. Ceramic brackets showed statistically higher shear bond strengths than metal brackets when bonded with all test materials (p<0.001). When used with metal brackets, the light-cured glass ionomer cement (LCGIC) and compomer materials demonstrated statistically lower shear bond strengths than the light-cured composite (p<0.01 and p<0.001, respectively). When used with ceramic brackets, LCGIC was found to have significantly lower shear bond strength than the composite material (p<0.001). Despite its relatively low shear bond strength, LCGIC demonstrated optimal bonding values (8.39+/-3.24 MPa) with ceramic brackets. Bond failures within the LCGIC groups occurred at the adhesive-tooth interface, whereas in the compomer and composite groups, failures were detected at the adhesive-bracket interface. In the metal bracket group, clinically acceptable shear bond strength was obtained only with the composite resin (7.06+/-1.65 MPa). Compomer and LCGIC demonstrated values well below the accepted standard for metal brackets (4.32+/-1.75 MPa and 4.45+/-1.06, respectively), while in the ceramic bracket group, values for composite and compomer were above the desired level (14.40+/-5.88 MPa and 12.31+/-6.09, respectively). LCGIC showed reasonably good bond strength with ceramic brackets, suggesting that this material may be considered suitable for use with ceramic brackets in clinical situations where moisture cannot be controlled.

Acrylic Resins↗

PubMed2000

Morphological interface between hybrid ionomers and dentin with and without smear-layer removal.

To evaluate the micromorphological interface between dentin and several hybrid ionomer restoratives, a flat dentin surface was obtained on the occlusal surfaces of extracted human molar teeth after sectioning the enamel with an Isomet saw. Three poly-acid-modified composite resins, Compoglass, Dyract and F2000, and two resin-modified glass-ionomer cements, Fuji II LC and Photac-Fil were applied to the dentin surface. A second section, 2 mm apical from the first one, was made to produce a dentin segment containing the tested materials. Each disc was then split fractured along the dentin/material interface. For the poly-acid-modified composites, one half of the disc was stored in 6 mol/L HCl for 48 h to remove the dentin. The other was gently decalcified and deprotenized at the interface between the hybrid ionomer and the dentin. Both halves were then sputtered with gold and examined using SEM. For resin-modified glass-ionomer, samples were only evaluated at the interface. The three poly-acid-modified composite resins showed the formation of hybrid layers and resin tags at the interface to the dentin. Removal of the smear layer significantly improves hybridization of these materials. Also, Fuji II LC produced a hybrid layer while the Photac-Fil showed no evidence of hybridization.

Compomers↗