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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study investigated adhesion to dentin of a modified 4-META/MMA-TBB resin (4-methacryloxyethyl trimellitate anhydride in methyl methacrylate initiated by tri-n-butyl borane) which does not require PMMA powder to polymerize. Ground bovine dentin specimens were pre-treated with an aqueous solution of 10% citric acid and 3% ferric chloride (10-3). This solution removes the smear layer and demineralizes the dentin, exposing collagen. Improved bond strengths were obtained when a HEMA-primer was applied to 10-3 pre-treated dentin. SEM examination revealed the formation of a transitional zone of resin-reinforced-dentin (hybrid layer) in 10-3 pre-treated, HEMA-primed samples. The adhesive monomer impregnated exposed collagen fibrils and, upon polymerization, became entangled with them to create the hybrid layer, essential in achieving significantly high tensile bonding strengths. HEMA enhanced the penetration capability of dentinal substrates. After polymerization and formation of the hybrid layer, auto-cured acrylic resin, photo-cured composite and amalgam were all capable of adhering to the dentin. The modified 4-META/MMA-TBB resin created significant adhesive bonds to 10-3 pre-treated ground bovine dentin.
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PMID:Dentin adhesion of "modified" 4-META/MMA-TBB resin: function of HEMA. 129 94

This study examined the relationship between resin and dentin both in vitro and in vivo using phosphoric acid conditioning. Four groups of 10 teeth each had standardized Class V preparations made with the gingival cavosurface margin in the root. In Group 1, involving freshly extracted teeth, the enamel and dentin was conditioned with 37% phosphoric acid gel for 15 seconds. NTG-GMA/PMDM was applied to the enamel and dentin followed by an application of BIS-GMA/HEMA and restoration with P50. Group 2 served as a control omitting the conditioning step. Groups 3 and 4 were treated similarly to Groups 1 and 2 except in vivo and extracted 2 weeks after restoration placement. All teeth were sectioned longitudinally through the restoration. Impressions were taken of the tissue/restoration interface and examined by SEM for disclosure of gaps. The teeth were then demineralized and the fitting surface of the restoration was examined by SEM for evidence of resin penetration into the tissue. The results showed a total absence of gaps both in vitro and in vivo after acid conditioning compared to the controls commonly showing gaps. Penetration of resin into the dentin to form a zone of diffusion or hybrid layer was observed only in the conditioned specimens. The phenomenon was observed both in vivo and in vitro. It was concluded that a significant potential exists for phosphoric acid conditioning of dentin to promote bonding.
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PMID:Micromorphological relationship between resin and dentin in vivo and in vitro. 138 27

Samples of linear (additionally crosslinked) p(HEMA) with different amounts of fibrillar collagen were implanted into the popliteal region of rats. After 3 month, the implanted materials were harvested and examined by SEM. The implants underwent marked structural or morphological changes. While the fibrillar collagen was readily resorbed by invading cells, the synthetic constituent persisted to biodegradation. The p(HEMA) residues were shaped into spherical particles, approx. 1-15 microns in diameter. The possible fate of these microparticles in the host organism is discussed.
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PMID:Structural alterations of p(HEMA)--collagen implants. 189 80

The objective of this study was to determine the shear bond strength of dental amalgam bonded to dentin with adhesives. Four groups of 15 permanent posterior teeth were used in this study. The occlusal enamel of the teeth was removed to produce a flat dentin surface. The teeth were embedded in phenolic rings with acrylic resin. Vinyl polysiloxane ring molds 4 mm thick with 4.5 mm circular openings were attached to the exposed dentin surface. Adhesives applied to the dentin surfaces prior to amalgam placement and condensation included: Amalgambond, a 4-META/TBB-MMA, HEMA based system (A), Panavia EX, a modified phosphate ester of Bis-GMA luting system (P), and Ketac-Cem, a glass ionomer luting cement (K). A dentin bonding agent and composite resin restoration system (Scotchbond 2/Silux Plus) was included for comparison. The specimens were stored in 37 degrees C water for 7 days prior to testing. Shear bond tests were done in an Instron machine at a crosshead speed of 0.02 inches per minute. The data were analyzed by ANOVA at 5% level of significance. The differences in shear bond strengths of the four test groups were not statistically significant (P = 0.115). Fracture patterns of the bonded amalgams, examined by SEM, were adhesive in appearance for Groups A and K and cohesive for Group P.
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PMID:Shear bond strength of dental amalgam bonded to dentin. 190 Jun 93

A light-cured bonding agent consisted of 50 wt% BisGMA and 50 wt% 2 HEMA was prepared in order to investigate the effect of light curing system on the bonding to etched dentin treated with 37 wt% phosphoric acid (PA), 10 wt% citric acid (CA), 10 wt% maleic acid (MA), 10 wt% citric acid-3 wt% ferric chloride (10-3) and 0.5 M EDTA.2 Na (EDTA) solutions. The bond strength to dentin treated with 10-3 solution was statistically higher than to dentin treated with the other etchant. The acid-proof dentin layers with about 1-2 microns thickness at the interface between resin and dentin treated with CA, MA, and 10-3 solutions were visible with SEM. The presence of Ca, P, and Br elements in the layers was confirmed by EPMA analysis. The bond strength was greatly dependent upon the physical property of the layer because difference in Knoop hardness of the etched dentin surfaces and the dentin surface after bond testing was greatest when used 10-3 solution.
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PMID:[Studies on bonding of light-cured bonding agent to dentin]. 253 57

This paper reports in vivo protein adsorption onto polymers, including Biomer, PEO grafted Biomer (B-PEO-4K), heparin immobilized Biomer with PEO spacers (B-PEO-4K-HEP), and HEMA-Styrene block copolymer (H-S). Vascular grafts (6 mm ID, 7 cm in length) were fabricated with Biomer, coated on their luminal surfaces with test polymers, and implanted into the abdominal aorta of dogs. After 3 weeks-1 month, the grafts were retrieved and processed for TEM and SEM. TEM measured the thickness of adsorbed protein layers stained with a OsO4 solution, and the distribution pattern of adsorbed proteins (albumin, IgG and fibrinogen) using the immunoperoxidase technique. Retrieved grafts of Biomer and B-PEO-4K showed mural thrombi along the graft length, while thrombus formation on B-PEO-4K-HEP and H-S grafts was limited to the anastomotic sites. SEM pictures of B-PEO-4-HEP and H-S surfaces demonstrated clear morphology, with minimal platelet adhesion and activation, and microthrombi. Biomer and B-PEO-4K demonstrated a thick proteinaceous layer (1000-2000 A), whereas B-PEO-4K-HEP and H-S showed what can be described as a monolayer protein thickness (200-300 A). B-PEO-4K-HEP and H-S showed a monolayer-like adsorbed protein pattern, with high concentrations of albumin and IgG, and less fibrinogen, while Biomer and B-PEO-4K showed multilayered patterns with relatively high concentrations of fibrinogen, and less albumin. These results suggest that the surface properties of polymer may control protein adsorption pattern, and the composition of adsorbed protein is essential to in vivo long-term blood compatibility.
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PMID:In vivo protein adsorption onto polymers: a transmission electron microscopic study. 268 16

Glucose oxidase (GOD) was immobilized in a poly(2-hydroxyethyl methacrylate) (HEMA) membrane through matrix entrapment in order to investigate the effect of various parameters (e.g. concentration of ingredients, temperature, repeated interaction with glucose and shelf storage) on the activity of the enzyme. Permeability of the membrane to a model permeant was tested and SEMs were obtained. It was observed that upon immobilization the affinity of GOD towards glucose was substantially decreased, and increasing the GOD content of the membrane adversely affected the activity. Membranes with the highest enzyme activity were also found to be the most permeable. Changes were detected in the pH and temperature where GOD is most active. Membrane permeability was observed to increase when crosslinker, and/or HEMA concentrations were low. The same parameters were also found to alter the morphology of the membrane as observed under SEM.
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PMID:Immobilization of glucose oxidase in poly(2-hydroxyethyl methacrylate) membranes. 342 49

Three soft contact lenses of the HEMA type, discarded because of irritation of the cornea, were processed for and subsequently examined with the SEM, A large portion of the convex surface was covered with globular deposits of fungal spores. Cross-fractures of lenses showed penetration of the fungi into the matrix material of the lenses. The concave surface of the contact lenses showed at two points imprints of the epithelial cells of the cornea in the deposited material on that side of the lenses.
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PMID:Fungal growth on soft contact lenses: a SEM-study. 342 91

A restorative resin was bonded to EDTA-treated dentin by means of a mixture of glutaraldehyde and HEMA. The bond exhibited a tensile strength of 17.5 +/- 1.0 MPa (mean +/- SEM) and was unaffected by water storage at 37 degrees C for up to 6 months. The glutaraldehyde/HEMA mixture was found to be most effective when the pH was between 2 and 5; an application time of 10 s was found to be sufficient for the glutaraldehyde/HEMA mixture as well as for the EDTA-solution.
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PMID:Dentin-polymer bond mediated by glutaraldehyde/HEMA. 393 3

Two aspects of endothelial cell function were examined in two matched groups of male insulin-dependent diabetics, six with background retinopathy and seven without retinopathy. Leakage of fluorescein from the retinal capillaries was estimated by vitreous fluorophotometry. In addition, factors VIII/von Willebrand (vWF) and VIII-related antigen (VIII-RAG), which are synthesized by the endothelial cells, were measured, together with VIII-antihaemophilic factor (VIII-AHF). The patients without retinopathy had normal leakage of fluorescein in the macula (mean +/- SEM: 1.10 +/- 0.10 g X 10(-8)/ml) and the posterior vitreous (0.45 +/- 0.11 g X 10(-8)/ml), and normal circulating levels of vWF (123% of a normal reference plasma +/- 18%), VIII-RAG (137 +/- 14%) and VIII-AHF (112 +/- 18%). In contrast, the patients with background retinopathy showed higher leakage of fluorescein in the macula (6.34 +/- 1.74 g X 10(-8)/ml; p less than 0.01), and the posterior vitreous (3.09 +/- 0.94 g X 10(-8)/ml; p less than 0.02), as well as increased levels of vWF (177 +/- 16%; p less than 0.05). There was a trend towards increased VIII-RAG (195 +/- 24%; p less than 0.1), but not VIII-AHF (126 +/- 13%). Alterations of endothelial cell function thus accompany the development of retinopathy. It cannot be said from the present study whether these alterations also precede the appearance of retinopathy.
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PMID:Evidence for functional endothelial cell damage in early diabetic retinopathy. 679 Mar 26


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