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

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

243 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars with the conventional acid-etch restorative procedure and eight modifications of this technique. The teeth were extracted after 4 months and, following demineralization, the filings were examined in SEM concerning their enamel and dentin replica patterns on the inner cavity faced surface. Results showed a significant correlation between the enamel replica patterns and the marginal adaptation of the restorations while the dentin replica patterns did not influence the in vivo adaptation. Furthermore it was found that the improved adaptation obtained by low viscous resin applied as an intermediary layer in etched cavities is due to fewer porosities in the restorative material interface with enamel and dentin. Beveling of preparations prevents stress-induced fractures of unsupported enamel prisms along the cavity periphery. Treatment of etched cavities with the surface active comonomer NPG-GMA increases the general interfacial contact between resin restoratives and cavity walls, and surface coating of finished and re-etched restorations fills up spaces created along cavity margins during the filling and finishing procedure.
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PMID:Replica patterns on composite restorations performed in vivo with different acid-etch restorative procedures. 389 44

29 experimental Class V restorations using a chemically cured composite resin were inserted in human third molars in cavities which after acid-etching had been treated with absolute ethanol. After extraction and demineralization of the teeth, the fillings were examined in SEM concerning their enamel and dentin replica patterns on the inner cavity-faced surface. The SEM findings were compared with previous findings concerning the replica patterns on fillings from acid-etched cavities and from cavities which after acid-etching had been treated with an ethanol solution of the surface active comonomer N-phenylglycine-glycidyl methacrylate (NPG-GMA). It was found that cavity treatment with absolute ethanol further improved the increased enamel replica patterns obtained with the NPG-GMA/ethanol comonomer solution while only the NPG-GMA/ethanol treatment improved the dentin replica patterns. Based on these results the effect of each of the two main components in the comonomer solution on replica patterns on resin restorations could be disclosed.
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PMID:Effect of ethanol and NPG-GMA on replica patterns on composite restorations performed in vivo in acid-etched cavities. 389 45

The purpose of this experiment was to investigate histo-pathologically and clinico-pathologically the pulpal reaction to a composite resin restoration system with a NPG primer and an adhesive bonding agent containing a carboxylate adhesive monomer, PMDM, using beagle dog and human teeth. The contact area between the composite resin with the primer and the monomer and the dentin cavity wall was observed through the SEM imaging. In the histo-pathological study, the average evaluation score of pathological results in group M (the composite resin restoration using the NPG primer and the bonding agent containing PMDM monomer "Mirage-Bond") was superior and almost the same as in group P as a contrast group (the composite resin restoration using a bonding agent "Clearfil Photo Bond" after enamel and dentin wall etching with 40% phosphoric acid). The dispersion of pathological results by score in group M was much narrower than in group P. Microorganism growth in group M was less than that of group P. Gap spaces caused by coming off in the region of contact area between the filled resin and the dentin cavity wall were observed through the SEM imaging. The number of cases coming off in group M were fewer than in group P. Gap spaces in group M were narrower in width than in group P. In the SEM imaging, microorganisms were observed in most cases with gap areas. In the clinico-pathological study on restoration with "Mirage-Bond", unpleasant sings symptoms had not occurred except in a few cases. The pathological result by score was comparatively superior. The pathological results of human teeth were similar to the pathological results of dog teeth. The pulpal irritation due to this composite resin restoration system with the NPG primer and the PMDM monomer containing adhesive bonding agents was generally minor, and the system was considered to be safe and useful even though the contraction gap spaces were found in some cases.
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PMID:Study of pulpal response to an adhesive composite resin restoration using A NPG primer and a PMDM monomer (Mirage-Bond). 818 Nov 9

Results from in vitro experiments suggest that development of nitrate tolerance is due to a depletion of vascular thiol compounds (ie, cysteine and glutathione [GSH]) necessary for the bioconversion of organic nitrates. However, it is unknown whether in vivo tolerance development is associated with changes in thiol levels. This study measures plasma and vessel tissue GSH and cysteine levels in nontolerant rats, nitrate-tolerant rats, and rats treated with the two characteristically different thiol donors N-acetyl-L-cysteine and L-2-oxothiazolidine-4-carboxylic acid (OXO). Chronically catheterized conscious rats received an intravenous infusion of either nitroglycerin (NTG, 0.2 mg/h) or matching placebo for 3 days. At day 3, the hypotensive effect of 2.5 mg NTG/kg was decreased by 74 +/- 6% (mean +/- SEM, P < .05) in the NTG-treated group (n = 7), indicating the development of tolerance. No change in the hypotensive effect of NTG was seen in the placebo group (n = 6, P > .05). Hemodynamic tolerance is not associated with changes in aorta cysteine or GSH levels as compared with the placebo group (cysteine, 77 +/- 14 versus 57 +/- 11 [mean + SEM] nmol/g; GSH, 414 +/- 62 versus 399 +/- 89 nmol/g; P > .05). However, the increase in vascular thiol levels seen after OXO treatment in nontolerant rats is completely absent in nitrate-tolerant animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nitrate tolerance in vivo is not associated with depletion of arterial or venous thiol levels. 826 84

Earlier generations of excimer lasers, designed for industrial or non-cardiovascular medical applications, have been previously shown consistently to induce vasorelaxation of vascular smooth muscle in vitro. Such lasers were typically characterized by pulse durations of < or = 15 nanoseconds (ns). Excimer lasers currently employed for cardiovascular applications were designed with longer pulse durations (up to 220 ns) to facilitate fibreoptic transmission. Because arterial spasm has been observed in patients undergoing percutaneous revascularization with such lasers, we investigated the effect of so-called 'stretched pulse' excimer laser irradiation on vasomotor reactivity. A total of 69 rings of aorta harvested from New Zealand white rabbits were mounted isometrically in Krebs buffer solution and exposed to 308 nm from an excimer laser with a pulse duration of 120 ns. Fifty rings were exposed without pharmacological pre-treatment. The remaining 19 rings were exposed after pharmacological pre-treatment: 11 were precontracted with norepinephrine (NE, 10(-9)-10(-5) M), while eight were irradiated in Ca(2+)-free buffer after pre-relaxation with nitroglycerin (NTG, 7 x 10(-5) M). Without pharmacological pre-treatment, the vasomotor response to the excimer laser was variable: vasoconstriction was observed in 27 rings (16.1 +/- 0.8% (mean +/- SEM) of response to 5-HT), vasorelaxation in 21 rings (43.2 +/- 17.0% of response to 5-HT), and a heterogeneous response (vasoconstriction 4.9 +/- 1.0%, vasorelaxation 12.9 +/- 0.3%) in two rings. The vector of vasomotor response in non-precontracted rings was not predicted by fluence, frequency or temperature rise. A consistent vasomotor response was recorded only when pharmacological pre-treatment was employed. Among 11 rings pre-contracted with NE, the excimer laser produced vasorelaxation in 34/34 (100%) exposures; in contrast, among eight rings pre-relaxed with NTG in Ca(2+)-free buffer, the excimer laser produced vasoconstriction in 40/40 (100%) exposures. For all rings, including pre-contracted, pre-relaxed and those which were not pharmacologically pre-treated, the vector of vasomotor response was endothelium-independent. The magnitude of all vasomotor responses, including vasoconstriction in non-precontracted rings, could be diminished by limiting the duration of exposure. Thus, in contrast to the earlier generation, short-pulse excimer lasers, long pulse-duration excimer lasers in current clinical trials produce an unpredictable, heterogeneous vasomotor response. This in-vitro finding is consistent with the unpredictable development of vascular spasm in patients undergoing excimer laser angioplasty. Furthermore, these findings support the concept of employing abridged pulse trains to diminish the likelihood of laser-induced vasoconstriction during excimer laser angioplasty.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Excimer laser-induced vasoreactivity. 826 87

Hypertriglyceridemia is commonly associated with triglyceride (TG) enrichment of high density lipoprotein (HDL) and reduction in HDL cholesterol and apolipoprotein A-I levels. We have recently reported that lipolytic modification of TG-rich HDL, which reduces particle size, enhances its clearance from the circulation. In the present study, we examined the role of particle size and lipid composition in determining the metabolic clearance of human HDL, in the absence of substantial in vivo modification of the particle by hepatic lipase. The rabbit, which has a very low hepatic lipase activity, was used for this purpose. Plasma fractions d < 1.21 g/ml were first isolated by ultracentrifugation from fasting humans with normal (NTG, n=6, mean plasma TG concentration=1.26+/-0.21 (SEM) mmol/l) or elevated plasma TG levels (HTG, n=5, TG=4.49+/-0.65 mmol/l). Small and large HDL particles were separated by gel filtration chromatography and were labeled with either 125I or (131)I. Large HDL were cleared more rapidly than small HDL in 10 out of 11 studies (P=0.006). There was, however, no difference in the fractional catabolic rate (FCR) of large HDL isolated from NTG versus from HTG subjects or in the FCR of small HDL from NTG versus HTG individuals. There was also no correlation between the TG content of HDL and its FCR. In summary, large, lipid-rich human high density lipoproteins (HDL) are cleared more rapidly than small human HDL in rabbits. These results, combined with our previous observation, also support the hypothesis that triglyceride enrichment of HDL, in the absence of substantial lipolytic modification, is not sufficient to enhance its clearance from the circulation.
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PMID:Analysis of particle size and lipid composition as determinants of the metabolic clearance of human high density lipoproteins in a rabbit model. 964 47