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

The purpose of this study was to investigate the influence of the light-irradiation times to the bonding agent and the composite resin on resin adhesion to the primary enamel. One hundred bovine mandibular ground primary incisors were used. Materials used in this study were 40% phosphoric acid gel, Photo Bond and Photo Clearfil A (Kuraray Co., Kurashiki, Japan). The etching time was 30 seconds. The light-irradiation times for the bonding agent were 10, 20 and 30 seconds and the light-irradiation times for the composite resin were 20, 40 and 60 seconds. Specimens were divided into the non-thermal cycled groups and the thermal cycled groups. Shear bond strengths were tested. After the shear bond strength test. the test surfaces of the enamel and the resin specimens were observed using the SEM. The optimum light-irradiation time on the bonding agent was 10 seconds. Both in the non-thermal cycled group and the thermal cycled group, the light irradiation time on the composite resin which showed the significantly higher bond strength was 40 seconds. Higher bond strength was not always obtained with the longer light-irradiation time on the bonding agent and the composite resin.
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PMID:Resin adhesion to the primary enamel: influence of light-irradiation times. 861 87

Estrone sulfatase is an important enzyme which catalyzes the production of estrone from estrone sulfate in a variety of human and animal tissues. We report, for the first time, on the presence of estrone sulfatase activity in thrombocytes from human blood. Incubation of [3H]estrone sulfate in the presence of human thrombocyte lysates resulted in the formation of [3H]estrone as assessed by two-dimensional TLC. Estrone sulfatase activity was localized in the mitochondrial-microsomal fraction in thrombocytes from human blood. The enzyme was thermostable and had an optimum pH of 5.60 in acetate buffer. The highest activity was obtained in the presence of 0.1% of either Nonidet P-40 or Triton X-100. Phosphate ions (1 mM) inhibited the enzyme activity by 64% and similar effects were observed in the presence of platelet-free plasma. Endogenous inhibitors had no effect on the observed enzyme activity under assay conditions as evidenced in this study. The apparent Km value was 3.16 +/- 0.08 microM for [3H]estrone sulfate and V was 188.5 +/- 2.6 (mean +/- SEM, n = 22) pmol.mg protein-1.h-1. Comparison between two thrombocyte preparative procedures provided evidence that thrombocyte estrone sulfatase activity should be measured in thrombocyte samples representing the whole thrombocyte population. This parameter appeared critical for accurate measurements of enzyme activity. The presence of estrone sulfatase activity in human thrombocytes provides a new non-invasive tool for the study of this activity both in physiological and pathological conditions which could be of potential clinical relevance.
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PMID:Characterization of estrone sulfatase activity in human thrombocytes. 866 70

It has been reported that the presence of a smear layer on dentinal substrates can compromise bonding. Typically, smear layers are removed by acidic agents that selectively extract calcium salts from dentin surfaces to leave a collagen-rich substrate. Acid-conditioned dentin (i.e., demineralized) is then primed and an adhesive agent applied. In the present study, we removed smear layers by "polishing" dentin specimens with a hydroxyapatite paste and ultrasonication. Bonding procedures were carried out by means of an aqueous solution of 20% 2-methacryloyloxyethyl phenyl phosphoric acid (phenyl-P) and 30% 2-hydroxyethyl methacrylate, referred to as 2OP-30H, a "self-etching primer". The 20P-30H solution was applied to "intact" dentin (i.e., non-demineralized) for either 30 or 60 s. Control samples received no application (O s) of the self-etching primer. Mean tensile bond strengths (10 MPa) were similar in both the 30-second- and 60-second-primed groups. The widths of formed hybrid layers varied from 0.3 +/- 0.2 micron at O s application (control) to 2.1 +/- 0.3 micron for the 30-second group and 4.1 +/- 0.2 micron for the 60-second group. SEM and TEM observations revealed that the 20P-30H self-etching primer created diffusion channels into "intact" calcium-rich dentin which permitted monomer to infiltrate dentin substrates. Hybrid layers identified under microscopic examination demonstrated resistance to both HCI and NaOCI treatments, suggesting that the hybrid layer was not defective, and that bonding was stable.
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PMID:Bonding to intact dentin. 895 25

This article evaluated possible differences between dentin conditioned in vivo and in vitro with 10 percent maleic acid or with 36 percent phosphoric acid. Semispherical Class V cavities were prepared in vivo and in vitro at the cementum-enamel junction and were divided into four groups. After etching procedures, the in vivo samples were extracted and fixated in 10 percent buffered formaldehyde. Both the in vivo and in vitro samples were then fractured in two parts along their long axis, critical-point dried, and subsequently examined with SEM. Both the acids removed completely the smear layer and demineralized the dentin, leaving a layer of collagenous network. No morphological differences were found between in vivo and in vitro dentin samples.
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PMID:Comparison of in vivo and in vitro demineralized dentin with phosphoric and maleic acid. 909 13

The literature suggest differences between primary and permanent teeth regarding the composition and morphology of the dentin. The purpose of this study was to compare the effect of two dentin conditioners on the micromorphology of the dentin surface of primary and permanent teeth. Human extracted and noncarious molars were divided into four groups and conditioned with either 10% phosphoric acid (All-Bond 2) or 10% maleic acid (Scotchbond Multi-Purpose) for different time periods. SEM photomicrographs (1500x) were taken from the conditioned dentin and evaluated blindly by three calibrated examiners. The results indicate that the smear layer was removed more easily from primary teeth than from permanent teeth (P = 0.0001), which suggests greater reactivity to acidic dentin conditioners. We also found that the longer the time of application of dentin conditioner the more smear layer is removed (P = 0.0094). In comparing primary and permanent dentin, the results of this study indicate that less time is required for appropriate acid conditioning of primary dentin surfaces. Such a differentiated protocol for bonding to primary tooth dentin results in surface morphological characteristics similar to those found in conditioned permanent teeth.
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PMID:Dentin bonding: SEM comparison of the dentin surface in primary and permanent teeth. 920 Jan 95

This study determined the shear bond strength of resin composites to primary dentin using three dentin adhesives and the presence or absence of a hybrid zone. The buccal and lingual surfaces of 40 recently extracted noncarious primary teeth were ground flat with SiC paper ending with the 600 grit. The teeth were divided at randomly into eight groups of five teeth (10 surfaces) each: 1) Unetched dentin, dry dentin, All-Bond 2/Bis-Fil P; 2) Unetched dentin, moist dentin, All-Bond 2/Bis-Fil P; 3) Dentin etched for 15 sec with 10% phosphoric acid, dry dentin, All-Bond 2/Bis-Fil P; 4) Dentin etched for 15 sec with 10% phosphoric acid, moist dentin, All-Bond 2/Bis-Fil P; 5) Dentin etched with 10% maleic acid for 15 sec, dry dentin, Scotchbond Multi-Purpose/Z100; 6) Dentin etched with 10% maleic acid for 15 sec, moist dentin, Scotchbond Multi-Purpose/Z100; 7) Dentin etched with 10 citric acid/3% ferric chloride, dry dentin, Amalgambond Plus/Z100; 8) Dentin etched with 10 citric acid/3% ferric chloride, moist dentin, Amalgambond Plus/Z100. All teeth were thermocycled 1000x (5 and 55 degrees C, 30-sec dwell time), and shear bond strength testing was conducted using an Instron (crosshead speed 0.5 mm/min). Failure sites after debonding were examined with the SEM. For each group, one additional tooth was used to prepare two class V cavities (one facial and one lingual) restored according to the specification in each group, sectioned buccolingually and examined with the SEM. The results, in MPa, were: 1) 12.55 +/- 5.97; 2) 10.41 +/- 6.16; 3) 9.94 +/- 7.26; 4) 12.25 +/- 4.70; 5) 13.02 +/- 8.01; 6) 16.51 +/- 8.62; 7) 12.51 +/- 8.95; 8) 17.93 +/- 6.44. ANOVA and Student-Newman-Keuls tests showed no statistically significant differences. SEM evaluation showed that the smear layer was removed in all groups exposing primary dentin tubules infiltrated by resin. A resin-reinforced hybrid layer was readily seen in all specimens.
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PMID:A comparison of three resin bonding agents to primary tooth dentin. 920 Jan 96

Bonding systems make use of different types and concentrations of enamel etchants. The purpose of this in vitro investigation was to determine the shear bond strength of composite resin to etched enamel using different enamel etchants. The following etchants were used: 35 per cent phosphoric acid for 30 seconds, (Group 1, control), 10 per cent phosphoric acid for 20 seconds (Group 2), 10 per cent maleic acid for 15 seconds (Group 3), 65 per cent phosphoric acid for 30 seconds (Group 4) and 10 per cent citric acid/3 per cent ferric chloride for 30 seconds (Group 5). Composite (Z100) stubs were bonded to the adhesively treated etched enamel surfaces using a rubber split mould. The bonded specimens were stored in distilled water for 24 hours before they were stressed to failure using a shear load in an instron testing machine. Data were analysed statistically (Student-t-test). The micromorphology of the enamel etched with the different etchants was also evaluated in a SEM. Shear bond strength (MPa) for the different groups were as follows: group 1 (23.9), group 2 (18.9), group 3 (18.0), group 4 (20.4) and group 5 (15.6). Ten per cent maleic acid, 10 per cent phosphoric acid and 10 per cent citric acid/3 per cent ferric chloride demonstrated lower enamel bond strengths than conventional 35 per cent phosphoric acid.
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PMID:Bonding of composite resin using different enamel etchants. 946 9

The purpose of this study was (1) to evaluate the effect of a 2-minute exposure of 5% NaOCl following acid conditioning of the dentin on the shear bond strength for two adhesive systems and (2) to examine the ultrastructure of the resindentin interface under SEM. The mesial and distal surfaces of 28 extracted human third molars were ground to expose dentin, then polished with 600-grit SiC. Teeth were randomly assigned to four test groups (n = 14) and received the following treatments: Scotchbond Multi-Purpose (SBMP)--Samples were conditioned with 37% phosphoric acid, rinsed and left moist, SBMP primer and adhesive were applied according to the manufacturer's directions, and Restorative Z-100 composite resin was bonded to the dentin surface. SBMP/NaOCl--The same procedures were followed as for SBMP except the surfaces were treated with 5% NaOCl for 2 minutes, after acid conditioning. All-Bond 2 (AB2)--The same technique was followed as for SBMP, using AB2 according to the manufacturer's recommendations. AB2/NaOCl--The same procedure was followed as for SBMP/NaOCl, using AB2. Specimens were thermocycled in a water bath 300 times between 5 degrees-55 degrees C, then sheared in a Zwick Universal Testing Machine. A one-way ANOVA and Duncan's Multiple Range Test were used for statistical analysis of the data. A 2-minute exposure of dentin to 5% NaOCl following acid conditioning of the dentin had no significant effect on the dentin shear bond strength for Scotchbond Multi-Purpose, but significantly increased the bond strength of All-Bond 2 specimens. The interfacial structure of the dentin to resin bond for two dentin treatments and two adhesive systems was studied morphologically under the scanning electron microscope. Argon ion beam etching and acid demineralization clearly revealed the hybrid layer for the conventional treatment with phosphoric acid and indicated an absence of this resin-impregnated collagen network in those specimens treated with both phosphoric acid and NaOCl.
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PMID:Resin-dentin shear bond strength and interfacial ultrastructure with and without a hybrid layer. 948 56

This study evaluated the bonding mechanism of Compoglass compomer to dentin in primary teeth. Buccal or labial dentinal surfaces of 20 human extracted, non carious primary teeth stored in 4 degrees C physiological saline solution were obtained by grinding on silicon carbide paper (final grit 600). The specimens were divided into two groups of 10 teeth each: (1) unetched dentin, Compoglass SCA, Compoglass; and (2) dentin etched with 10% phosphoric acid (Etch-AII), Compoglass SCA, Compoglass. The Compoglass SCA and Compoglass compomer were placed according to the instructions of the manufacturer, except Group 2 were the dentin was first etched with 10% phosphoric acid for 30 seconds. Twenty-four hours after placing the compomer over the treated dentinal surface, the specimens were dehydrated with a series of alcohol and freon. Then critically point dried. The specimens were split with a chisel and the compomer/dentin interface evaluation was performed with the SEM. The results showed that when the instructions of the manufacturer were followed (Group 1) the compomer showed a very close relation to the dentin with some tag structures penetrating the dentin. When phosphoric acid etching preceded the compomer placement a hybrid layer with tags penetrating the dentin was noted in most specimens.
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PMID:Bonding mechanism of Compoglass to dentin in primary teeth. 964 Oct 96

Acid etching with phosphoric acid on the prismless layer of human dental enamel may produce different patterns of dissolution. Consequently, the presence of several patterns of enamel acid conditioning may indicate better or worse formation of resin tags. In this study, the heterogeneous patterns of 35% phosphoric acid conditioning of human non-erupted deciduous teeth were reported. SEM images demonstrated type I, type II and type III aspects reported by Silverstone et al. (Caries Research 1975; 9:373-387), in spite of the etching time used and the surface area (buccal incisal, middle or cervical thirds). These characteristic features on the enamel surface may indicate the convenient use of this technique in deciduous teeth.
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PMID:Three-dimensional aspects of etched enamel in non-erupted deciduous teeth. 1021 22


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