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

The influences of nine dentin surface treatments were evaluated on the shear bond strength of a new light-cured glass-ionomer cement (GIC) and on the SEM morphology of the treated dentin surfaces. The following treatments were performed: saline solution (control), NaOCl, acidic glycine, EDTA, malic acid, malic acid plus glycine, polyacrylic acid, tannic acid, and neutral+acidic oxalate solutions. Buccal dentin surfaces were polished with #320-grit abrasive paper, treated with one of the chemicals, washed, and air-dried. Cylindrical GIC samples were then applied to the dentin surface, stored in 100% humidity, and tested after 24 h. SEM observations demonstrated no effect of saline or NaOCl treatment on the smear layer but its complete removal with exposure of collagen fibrils after malic or malic acid plus glycine treatment. Partial removal of the smear layer occurred following glycine treatment and with tannic or polyacrylic acids. Complete removal of the smear layer was seen after EDTA or pyruvic acid treatment. Oxalate treatment produced a layer of crystals, which completely covered the dentin surface. Shear bond strength of GIC was significantly increased only by treatment with the oxalate solutions.
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PMID:Effects of dentin surface treatments on the shear bond strength of Vitrabond. 152 80

Although nitric acid is a component in some new bonding systems, the action of nitric acid as an etchant for the improvement of adhesion of bonding systems for resin composites to dentin and enamel has not been reported. A determination of the extent of etching on both dentin and enamel using 2.5% HNO3 solution at various application time periods was the purpose of this study. Extracted human molars were cleaned and sectioned so that flat samples of dentin and enamel would be produced. Surfaces were abraded with 320-grit aluminum-oxide paper, washed with distilled water for 10 s, and blown with air for 10 s. Duplicate samples of dentin and enamel were treated with a drop of 2.5% HNO3. Application periods varied by 10-second intervals, from 10 s up to 60 s. After being rinsed with distilled water and dried, the sections were routinely processed for observation by SEM. The micrographs of the treated surfaces showed various degrees of etching and erosion proportional to the length of application time. The 30-second application revealed a well-etched surface with minimal erosion.
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PMID:Time dependence of 2.5% nitric acid solution as an etchant on human dentin and enamel. 196 36

The surface characteristics of eight posterior and two anterior composite resins were studied by SEM and profilometric tracings. The materials included both chemically cured and light-cured resin systems. Two posterior materials were microfilled composites; the others were conventional or hybrid types. The anterior composites were of conventional and hybrid types. At various steps in the procedures the following polishing/brushing treatments were evaluated: 1) dry polishing with Sof-lex discs followed by brushing with toothpaste; and 2) wet polishing with diamond pastes of increasing fineness, followed by brushing with toothpaste. The base line before the polishing/brushing procedures was obtained by wet polishing on silicon-carbide paper (4000 grit). All materials could be polished to a comparable smoothness by the Sof-lex discs, but this polishing procedure was associated with the development of an amorphous surface layer. Polishing with diamond pastes gave various results, with a 20-fold difference in surface roughness values from the smoothest to the roughest material. Toothbrushing after polishing with the Sof-lex system increased the surface roughness for all materials, but to various degrees. The two microfilled and four of the conventional posterior composites showed comparable surface roughness values, whereas two remaining posterior and the two anterior materials showed two to three times higher surface roughness values after toothbrushing.
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PMID:Surface characteristics of posterior composites after polishing and toothbrushing. 347 39

Grit blasting is a common procedure of roughening surfaces to promote physical attachment of porous coatings, but it has been shown to reduce fatigue strength. Shot peening is known to increase fatigue strength by inducing compressive surface stresses; however, it is not known how subsequent grit blasting affects these benefits. This study examines the endurance limits, Se, of ELI grade Ti-6A1-4V specimens under rotating cyclic bending, including polished (control); belted and beaded; belted, beaded, and grit blasted; and belted, beaded, shot peened, and grit blasted. Belting and beading resulted in a slight increase in Se, grit blasting caused a 15% reduction in Se from polished. Fifty percent of this reduction was recovered when shot peening preceded grit blasting, suggesting that residual compressive surface stresses, induced by peening, were not eliminated by the blast process. Roughness averages and RMS values did not correlate with Se trends. SEM results showed classical fatigue fractures, consistent with surface crack initiation.
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PMID:Effects of precoating surface treatments on fatigue of Ti-6A1-4V. 749 7

The tensile median fatigue limits and fracture mode of 4-META cement were evaluated after bonding Ni-Cr, Ni-Cr-Be, and Co-Cr alloys to enamel. Alloy surfaces, 6 mm in diameter, were grit blasted with 50 microns Al2O3 and cemented to etched bovine enamel under a 2 kg load. Samples were cycled in tension to failure or 10(6) cycles at 5 Hz in Ringer's solution at 37 degrees C. Two-point strategy was used to determine median fatigue limits (S50). Fracture modes were evaluated by SEM on samples failing before 10(6) cycles. Results indicated differences between all sample groups where S50 (Ni-Cr-Be) > S50 (Co-Cr) > S50 (Ni-Cr). Failure analysis revealed mixed cohesive fractures near both interfaces with small areas of delamination within the cement. Comparison to reported median fatigue limits of two commercially available cements were discussed.
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PMID:Tensile fatigue of 4-META cement bonding three base metal alloys to enamel and comparison to other resin cements. 778 18

Research into polymer systems capable of bonding to dentin and enamel have resulted in improved bond strengths that allow more conservative restoration and strengthening of teeth. However, pretreatment of the dentin and enamel of various sorts, including exposure to laser energy, have been espoused to enhance this bonding. This study investigated the effects of two pretreatments, acid and CO2 laser exposure, both alone and in combination, on the surface topography of prepared dentin specimens as observed by scanning electron microscopy. Eighteen dentin specimens were flat-sanded with 600 grit sandpaper and exposed to 10% maleic acid and CO2 laser both alone and in combination. SEM observation suggested that laser treatment prior to acid etching could increase the resistance of the smear layer to acid removal, that laser exposure after acid treatment could expose a porous topography suggestive of the underlying dentin inorganic structure by way of vaporization of the collagen surface left after acid demineralization, and that these effects varied in degree with the laser exposure energy.
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PMID:SEM comparison of acid-etched, CO2 laser-irradiated, and combined treatment on dentin surfaces. 783 Apr 72

Tensile bond strength data for resin-bonded bridge cements would predict failure loads in excess of 1000 N when based on available bonded surface area. Such loads are unlikely to be encountered clinically, yet these bridges frequently fail. Loading conditions resulting in a peeling action at the adhesive interface may provide a more probable explanation for failure rather than being attributable to poor clinical or laboratory technique. This hypothesis was investigated by bonding grit-blasted Ni/Cr alloy beams of different thicknesses to a block of the same alloy using a resin-bonded bridge cement, leaving half the length of the beam free. Beams were pulled off the block with a peeling action by applying a tensile load to the free end of the beam and load at failure recorded. Fractured surfaces were examined under SEM. A two-dimensional finite element model of a section through the peel test arrangement was used to produce data of the stress distribution in the adhesive layer. Load at failure was closely correlated to beam thickness. Using this data and known tensile bond strength values it was possible to predict the loads necessary to cause adhesive failure of the beam, which were found to correlate closely with the experimental measurements. It was concluded that design and the stiffness of the retainers can have a potentially profound effect on the adhesive quality of resin-bonded bridges.
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PMID:Tensile peel failure of resin-bonded Ni/Cr beams: an experimental and finite element study. 787 19

The aim of this in vitro study was to compare the adhesive properties of a manufacturer's third and fourth generation dentin adhesive. Vestibular sections of recently extracted third molars were embedded in chemical-cured acrylic resin and ground with 600-grit silicon carbide sandpaper. Fifteen samples were prepared with the adhesive products and the dentin surfaces were analysed by SEM. Twenty-four samples were divided into two groups and prepared with third and fourth generation systems, respectively. Composite filled tubes were then positioned on the prepared dentin surfaces and photopolymerized. The treated samples were kept in distilled water at 37 degrees C for 24 h. Four samples were used to analyze the resin-dentin surface. A tension test was performed on the remaining twenty samples at a crosshead speed of 0.5 mm/min. The results were analyzed using the Fisher and Student t-tests. The fractured surfaces were examined by SEM. The resistance to tensile forces of specimens prepared with the fourth generation system was significantly higher than that obtained after using the third generation system. Thus, as expected from the in vitro tests, the fourth generation system provided better adhesion to dentin than the third generation material.
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PMID:An in vitro study of two adhesive systems: third and fourth generations. 798 69

This study investigated the interfacial shear bond strength of a contaminated, aged, heat- and pressure-processed, indirect composite resin (Concept) repaired with a direct, visible-light-cured composite resin (Heliomolar). Concept samples were aged by thermocycling and contaminated in tobacco juice. The bonding surfaces were prepared by sanding with 500-grit sandpaper or air abrading with 50-micron aluminum oxide. Prepared Concept surfaces received one or more of the following intermediary resin treatments before the addition of Heliomolar: Heliobond, Special Bond 2, All-Bond system, All-Bond bonding agent, or no bonding agent, and they were immediately thermocycled. Air abrasion produced significantly higher bond strengths than sanding for all intermediary resin surface treatments. The All-Bond-treated Concept surfaces showed the highest interfacial bond strengths within the air abraded and sanded groups. Visual and SEM examination of fractured repair surfaces indicated adhesive failure within all treatment groups.
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PMID:Repair of an aged, contaminated indirect composite resin with a direct, visible-light-cured composite resin. 815 88

The purpose of this in vitro study was to determine the shear bond strength [SBS] of Syntac to dentin; to determine the quantitative microleakage (ML) of Class V preparations in dentin restored with the Syntac system; and to study resin penetration into the dentin tubules by SEM. The occlusal surfaces of 30 extracted human mandibular permanent first and second molars were ground wet on 600-grit SiC to expose the superficial dentin. The teeth were embedded in brass tooth cups with cold cure acrylic resin. The Syntac Primer and the Syntac Adhesive were applied to the demarcated bonding sites as recommended by the manufacturer. Radiopaque Heliomolar was transferred to the opening in a split teflon mold in three increments, each compressed firmly and cured for 40 seconds. Fifteen of the test specimens were disassembled 60 seconds after cure [A], and the remainder 15 min after cure and the latter specimens stored in saline at 37 degrees C for 24 hours [B]. A shear load was applied at a crosshead speed of 0.5 mm/min, the SBS calculated and expressed in MPa. The data were analyzed by a two-sample t-test. Class V cavities were prepared on the facial surfaces of 15 human premolars and restored. The ML was determined quantitatively by a spectrophotometric dye recovery method and expressed as microgram dye/restoration. The mean +/- SD of the SBS in MPa were: A: 10.14 +/- 2.80; B: 15.90 +/- 2.13 and the ML 2.57 +/- 0.97 microgram dye/restoration. The SBS recorded after 24 hours storage was significantly greater than after 1 minute (P < 0.0001). The bonding resin penetrated deeply into the dentin tubules.
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PMID:Evaluation of the Syntac bonding system. 832 56


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