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

An original method which uses in vitro anaerobic incubation at 37 degrees C followed by centrifugation, ultrafiltration, and ion exchange chromatography is described; it shows that faecal material suspended in physiological saline can destroy added creatinine. The rate of breakdown by suspensions from uraemic subjects (mean 780 mumol h-1kg-1 SEM 70) was slightly faster than in normal subjects (mean 550 mumol h-1kg-1 SEM 80). Methylamine concentration increased over eight hours as creatinine was metabolised and sarcosine appeared as an intermediate. The rates of these reactions varied within and between individuals and were inhibited by oxygen and centrifugation but not by oxytetracycline. Concentrations of free amino acids did not change significantly despite the formation of ammonia. This approach should be useful in studying the metabolic inter-relationships between intestinal contents and the host organism in health and disease.
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PMID:In vitro metabolism of creatinine, methylamine and amino acids by intestinal contents of normal and uraemic subjects. 48 52

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

A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect. A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga2O3 and SnO2, less than 1-2nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.
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PMID:ESCA study on dental alloy surfaces modified by Ga-Sn alloy. 161 84

Endothelium-derived relaxing factor (EDRF), believed to be nitric oxide or a compound that releases nitric oxide, has been previously identified in the pulmonary and systemic vasculature of the newborn guinea pig using isolated arterial rings. The aim of our study was to determine if EDRF regulates vasomotor tone at the level of resistance vessels in the neonatal pulmonary circulation. Isolated lungs from guinea pigs (1-3 d old, n = 4-8/protocol) were ventilated with room air and perfused with a Krebs-Henseleit solution containing albumin at a constant flow. Angiotensin II (AII, 6 nM) was added to the perfusate to give a stable elevation in mean pulmonary artery pressure (PAP) from 7.0 +/- 1.1 to 19.7 +/- 1.5 torr, a 182 +/- 32% (mean +/- SEM) increase above baseline. Addition of bradykinin (BK, 10 nM) or L-arginine (2 mM) markedly reduced the AII-induced elevation in PAP. At the steady state response to BK (33% above baseline), addition of Hb (10 microM, binds EDRF), NG-monomethyl-L-arginine (NMA, 100 microM, blocks EDRF production), NMA (200 microM), or NMA + Hb, reversed the effect of BK to the following levels of PAP above baseline: 77 +/- 5, 94 +/- 24, 163 +/- 20, or 246 +/- 25%, respectively (p less than 0.05). Indomethacin had no effect on BK-induced vasodilation. In separate studies, NMA (200 microM) increased baseline PAP by 46 +/- 13% and NMA pretreatment raised the AII-pressor response (AII 6 nM) from 133 +/- 49 to 306 +/- 65% above baseline PAP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Endothelium-derived relaxing factor: evidence that it regulates pulmonary vascular resistance in the isolated neonatal guinea pig lung. 186 8

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

Adhesion durability between dentin pretreated with 10-3 and 4-META/MMA-TBB resin was studied. Reduction of etching periods with 10-3 was not so effective as expected. The weakening of bond strength during immersion in water at 37 degrees C to the dentin pretreated for 1 sec occurred faster than those for either 5 sec or 10 sec. The strength decreased from 12 MPa at 1 day to 9 MPa at 3 months, 3 MPa at 6 months and finally 2 MPa at 1 year in the case of 1 sec pretreated dentin. On the other hand, the strength became half after the storage in water for 1 year in the cases of 5 and 10 sec pretreated dentins. Combination of 10-3 pretreatment and subsequent glutaraldehyde treatment could stabilize the decrease but not completely. SEM and TEM examinations suggested that dentinal collagen exposed by the etching but not entangled and impregnated by poly (4-META-co-MMA) easily deteriorated by water during the longer immersion. Collagen modified with 10-3 and then with glutaraldehyde was also changed by the longer immersion.
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PMID:[Durability of bonding between 4-META/MMA-TBB resin to dentin pretreated with 10-3. The effect of 10-3 pretreating period and subsequent glutaraldehyde treatment]. 213 46

Three types of succinoxy methacrylates [2-succinoxyethyl methacrylate (2SEM), 2-succinoxypropyl methacrylate (2PrM) and 2-succinoxy-3-phenoxypropyl methacrylate (SPPM)] were synthesized in order to develop a new direct-bonding adhesive which has sufficient bond strength to mild etched enamel and stainless steel brackets for occlusal and orthodontic force. Experimental direct-bonding adhesives consisted of a MMA solution containing synthesized monomers (5-10 mol%), PMMA powder and an oxidized tri-n-butyl borane as an initiator. A MMA solution without synthesized monomers was used as the control. Preparation of 10% and 40% phosphoric acid solutions and 1M maleic acid solution was carried out for use as etchants. The bond strength to unetched and etched enamel, polished stainless steel, simulated brackets and brackets was measured. The enamel surfaces etched with each etchant and the fractured resin and enamel surfaces after the bond test were observed with SEM and the ease of debonding of adhesive was investigated to totally evaluate the experimental direct-bonding adhesives. The results were as follows: 1) The amount of decalcification for 10% phosphoric acid and 1M meleic acid solutions was less than that for 40% phosphoric acid solution. The SEM micrograph showed most clearly the appearance of enamel prisms on the enamel surface treated with 40% phosphoric acid solution. 2) The experimental direct-bonding adhesives had higher bond strength to the polished enamel, the polished stainless steel and the simulated bracket than the control. 3) The bond strength to the etched enamel was comparable to that of the control. 4) The treatment of 1M maleic acid solution provided the same bond strength to enamel as that of 40% phosphoric acid solution and the higher bond strength than of 10% phosphoric acid solution. The bond strength to enamel treated with 1M maleic acid solution and 40% phosphoric acid solution decreased very slightly by immersion in water and thermal cycling. 5) The MMA solutions containing each 20 mol% synthesized monomer were adequate to direct-bonding adhesive monomers on the basis of the results of bond strength and manipulation. 6) The strongest bond strength between bracket and etched enamel was obtained with the direct-bonding adhesive containing 2SEM under all conditions. 7) The SEM micrographs showed that the tooth-resin interface failure for each adhesive occurred during bond testing. 8) There was little remaining of the resin on the tooth surface after debonding regardless of types of direct bonding adhesives.
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PMID:[Application of succinoxy methacrylates for direct bonding system]. 248 96

The purpose of this study was to investigate the state of the natural secondary caries and in vitro artificial secondary caries, associated with cast restorations cemented with zinc phosphate cement, histopathologically. For this study, the method of making and staining ground serial sections of teeth with cemented cast restorations was established. The material consisted of 50 extracted human permanent teeth with cemented cast restorations, and 12 human premolar teeth with in vitro secondary caries produced by the acid-gelatin system (pH 4.0). These specimens were embedded in MMA resin and then they were sliced to serial thin sections. Each section was etched by 0.1 N HCl, and stained with methylene blue fuchsin, and then observed with optical microscope, microradiography, and SEM. The result were as follows: 1. When the margin of restoration was set on dentine (cementum), the typical shape of natural secondary caries was found out. 2. The rate of natural secondary caries in case of margin set on dentine was about four times as many as the rate in case of margin set on enamel. 3. The shape of artificial secondary caries was very similar to the shape of natural secondary caries. 4. The resistance to secondary caries in case of the margin set on enamel was higher than the resistance in case of the margin set on dentine.
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PMID:[A study of secondary caries in cast restored teeth]. 248 74

EDTA 3-2 (Fe.NH4), EDTA 3-2 (Co.NH4) and EDTA 3-2 (Cu.NH4) at pH 7.4 were investigated to determine effective pretreatment to promote strong adhesion of 4-META/MMA-TBB resin to enamel with minimum demineralization. EDTA 5-0 (NH4) solution which does not contain a metal salt was also investigated as a control. The amount of Ca2+ demineralized during the pretreatment and the tensile bond strength to enamel were measured. The pretreated enamel surface and the resin surface of the adhesion junction were observed with SEM. When the enamel surface was pretreated with EDTA 3-2 (Fe.NH4) for 60 seconds, the tensile bond strength of the resin to enamel was 7.1 MPa after the thermal cycling test. No direct correlation was observed between the amount of Ca2+ demineralized and the tensile bond strength. The stable and strong bonding to enamel was taken place without strong mechanical retention.
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PMID:[Adhesion of 4-META/MMA-TBB resin to enamel treated with EDTA metal ammonium solutions. Effect of Fe.NH4, Co.NH4 and Cu.NH4 salts]. 251 67

EDTA metal ammonium salt solution containing Fe3+, Co3+ or Cu2+ was studied to determine the pretreatment reagent that causes no denaturation of dentin collagen and promotes good adhesion to dentin. After application of EDTA 3-2 (Fe.NH4), EDTA 3-2 (Co.NH4) or EDTA 3-2 (Cu.NH4) at pH 7.4 on the dentin surface, the amount of Ca2+ demineralized and the tensile bond strength were measured. The pretreated dentin surfaces were also observed with SEM. No correlation was obtained between the amount of Ca2+ demineralized and the tensile bond strength. On the EDTA 3-2 (Fe.NH4) treated dentin a small amount of smear remained partially, but the tensile bond strength of 4-META/MMA-TBB resin to the dentin was higher than 13 MPa. This indicates that complete removal of the smear on dentin is not always necessary for better bonding.
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PMID:[Adhesion of 4-META/MMA-TBB resin to dentin treated with EDTA metal ammonium solutions. Effect of Fe.NH4, Co.NH4 or Cu.NH4 salts]. 251 58


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