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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

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

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

Nitrosodimethylamine (NDMA) is a potent carcinogen in a wide variety of animal species. In experimental animals, dimethylamine and nitrite, precursors of NDMA, are found in gastric fluid where the acidic conditions are suitable for formation of nitrosamines. In this study we measured the concentrations of mono-, di- and trimethylamine (MMA, DMA and TMA) in gastric fluid from humans, rats, dogs and ferrets, as well as in saliva, blood and urine from humans. Human gastric fluid contained 3.7 +/- 0.4 (SEM) nmol/ml MMA, 12.6 +/- 1.4 nmol/ml DMA and 2.0 +/- 0.4 nmol/ml TMA. MMA, DMA and TMA concentrations in human gastric fluid were similar to those present in human saliva and blood, but were much lower than those present in human urine. The concentrations of these amines in human gastric fluid were lower than those measured in gastric fluid from experimental animals. When we added sodium nitrite to human gastric fluid, NDMA was formed. We have shown that DMA is normally present in human gastric fluid, and that it can be nitrosated to form NDMA.
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PMID:Mono-, di- and trimethylamine in human gastric fluid: potential substrates for nitrosodimethylamine formation. 333 43

This study determined the effect of polymerization shrinkage of polymethyl methacrylate (PMMA) coating of fiber roving on the transverse strength of an acrylic resin-glass fiber composite. The test specimens were heat-cured acrylic resin reinforced with glass fibers. The glass fiber rovings were treated with four PMMA-MMA mixtures (30 specimens per group) of various ratios assumed to have different amounts of polymerization shrinkage. A transverse strength test was used to determine the fracture resistance of the test specimens and the polymerization shrinkage of the PMMA-MMA mixtures was measured. After the specimens were fractured, single glass fibers used to reinforce the test specimens were studied by SEM. The fracture resistance of the specimens was statistically different (p < 0.001) among treatments, and the polymerization shrinkage of the PMMA-MMA mixture also varied as the calculations predicted. The SEM micrographs showed differences in thickness of the acrylic resin layer on the surface of the fibers with PMMA-MMA mixtures of various ratios. According to the results, the ratio that caused only minor polymerization shrinkage of PMMA in the glass fiber roving improved the fracture resistance of the test specimens and seemed to increase the amount of PMMA inside the fiber roving.
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PMID:Acrylic resin-fiber composite--Part II: The effect of polymerization shrinkage of polymethyl methacrylate applied to fiber roving on transverse strength. 804 Aug 26


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