Direct composite resin restorations in posterior teeth.
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Bicuspid↗
Biomedical subjects
R W Bryant
Publications and source records attributed to R W Bryant.
Phorbol esters increase synthesis of decay-accelerating factor, a phosphatidylinositol-anchored surface protein, in human endothelial cells.
A number of cell-surface proteins are anchored by a phosphatidylinositol (PI)-glycan moiety. These proteins can be released by PI-specific phospholipases C (PI-PLC). Decay-accelerating factor (DAF) is such a cell-surface protein that protects cells from inadvertent complement attack by binding to and inactivating C3 and C5 convertases. We have studied the regulation of DAF synthesis in human umbilical vein endothelial cells (HUVEC), a cell that has the highest level of surface DAF among those human cells that have been studied. HUVEC DAF was measured by immunoradiometric assay of detergent extracts and of cell supernatants after treatment of cells with a bacterial (Bacillus thuringiensis) PI-PLC. Eighty percent of the HUVEC DAF (4 to 8 x 10(5) molecules/cell) was released by exogenously added PI-PLC, indicating that it is predominantly PI-anchored. The level of PI-PLC-sensitive HUVEC DAF was increased three- to fourfold by overnight treatment of cultures with the protein kinase C activators, PMA (1 to 10 nM), phorbol-12,13-dibutyrate (10 to 100 nM), and teleocidin A (1 to 10 nM) under conditions where cell number, protein, and lactate dehydrogenase remain unchanged. This DAF synthesis was blocked by the protein kinase C inhibitor K-252a in a dose-dependent manner (ED50 = 0.06 microM). The biologically inactive phorbols, 4-alpha-phorbol-12 myristate-13-acetate (1 microM) and 4-alpha-phorbol-12, 13-didecanoate (1 microM) did not increase DAF levels. The newly expressed DAF in PMA-stimulated cells was still largely PI-anchored. In contrast, another PI-anchored protein, alkaline phosphatase, was not altered by PMA treatment, demonstrating that the PMA effect is not uniform among all surface proteins. The increased expression of DAF only was evident 8 h after PMA addition and was blocked by the RNA and protein synthesis inhibitors, actinomycin D and cycloheximide, indicating that both transcription and translation are required for DAF synthesis induced by phorbol esters. It is concluded that protein kinase C activators cause selective induction of endothelial cell DAF and that DAF synthesis involves protein kinase C activation.
Alkaline Phosphatase↗
Comparison of three standards for quantifying occlusal loss of composite restorations.
Occlusal loss of resin composite in posterior restorations may be measured by assessing the exposure of cavity walls. The purpose of this study was to compare three standard scales used to quantify occlusal loss on stone replicas of posterior composites. Measurements of occlusal loss, on 60 stone replicas selected from two clinical studies, were obtained by comparison with three standard scales: L-calibrated die stone standards derived from clinical restorations (Leinfelder), M-dies with cylindrical incremental defects (M-L scale), and V-tooth-sized dies with restoration-like incremental defects (Vivadent). Evaluators with different dental and evaluating experience carried out the assessment using each standard on two different occasions. Differences among results obtained using the three standard scales were comparatively small when assessments were carried out by experienced evaluators. Use of the V standard consistently achieved a higher level of agreement by pairs of evaluators.
Composite Resins↗
Substituted 1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-ones as potential antiinflammatory agents.
A series of analogues based on the 1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one ring system have been synthesized and shown to possess oral antiinflammatory activity in both the reverse passive Arthus reaction (RPAR) pleural cavity assay in rats and in the adjuvant-induced arthritic rat model (AAR). Several members of this series additionally exhibit an inhibitory effect on the in vivo production of prostaglandin- and leukotriene-derived products or arachidonic acid metabolism although these compounds exhibit no significant inhibitory activity against the cyclooxygenase and 5-lipoxygenase enzymes in vitro. Structure-activity relationships in this series are discussed.
Animals↗
Some factors influencing the depth of cure of visible light-activated composite resins.
Some of the factors influencing the depth of cure of four composite resins of different composition were examined. Knoop hardness measurements were carried out at the surface and 1, 2, 3, 4 and 6 mm below the surface to which the light was applied. The hardness of the composites decreased with increasing depth and shorter exposure times. The composites continued to polymerize after removal of the light source. Composition of the composite resin has a major effect on the surface hardness and depth of polymerization.
Acrylic Resins↗
The finishing and early marginal fracture of clinical amalgam restorations.
One operator placed 249 Tytin amalgam restorations in Class I and II preparations in the permanent teeth of 60 patients each of whom received a minimum of three restorations. At least one of these restorations was carved-only, at least one was immediately finished (at 8 or 10 min after trituration), and at least one restoration was polished (more than 24 h after placement). Restorations were principally assessed for marginal fracture at baseline and 1 year using the 11-unit scale for the evaluation of photographs developed by Mahler. Five factors were also assessed clinically at 1 year. Amalgam restorations, polished using finishing burs and rubber points at least 24 h after placement, exhibited more initial marginal fracture than carved-only or immediately finished restorations. At 1 year, the three techniques were comparable except for the superior surface texture of the polished restorations. The technique of immediate finishing of amalgam restorations has nothing to commend it in preference to existing techniques.
Chemical Phenomena↗
Long-term implications for composite resin restorations.
This paper examines factors that might influence the future use of composite resin to restore anterior and posterior teeth. Factors considered include recent developments in composite resins and bonding systems, current trends and concerns in the use of composites to restore anterior and posterior teeth, the longevity of composite resin restorations, perceptions about the patient's view of composite restorations, and the implications of two community factors, namely, the fluoride-controlled dentition and the influence of the media.
Composite Resins↗
Antiallergy agents. 1. Substituted 1,8-naphthyridin-2(1H)-ones as inhibitors of SRS-A release.
A novel class of antiallergy agents, the substituted 1,8-naphthyridin-2(1H)-ones, is described. The present compounds are orally active, potent inhibitors of allergic and nonallergic bronchospasm in animal models. Structure-activity studies of the lead compound in this series, 1-phenyl-3-n-butyl-4-hydroxynaphthyridin-2(1H)-one (11), identified three compounds of interest, 1-phenyl-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1H)-one (12), 1-(3'-chlorophenyl)-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1H )-one (87), and 1-(3'-methoxyphenyl)-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1 H)-one (89). The mechanism of antiallergy activity may involve inhibition of the release of the sulfidopeptide leukotrienes. 1-Phenyl-3-(2-propenyl)-4-acetoxy-1,8-naphthyridin-2(1H)-one, Sch 33303 (12), was selected for preclinical development as an antiallergy agent.
Animals↗
The effect of head position on electromyographic evaluations of representative mandibular positioning muscle groups.
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Adult↗
Posterior composite resin restorations--a review of clinical problems.
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Bicuspid↗
Stereospecific induction of starfish oocyte maturation by (8R)-hydroxyeicosatetraenoic acid.
Oocyte maturation (meiosis reinitiation) in starfish is induced by the natural hormone 1-methyladenine. This induction of meiotic divisions can be triggered also by four fatty acids: 5,8,11-20:3; 5,8,11,14-20:4 (arachidonic acid); 6,9,12,15-20:4; 5,8,11,14,17-20:5, all other fatty acids being completely inactive. This maturation triggered by eicosanoids occurs in the micromolar range and is facilitated by the presence of calcium. A variety of arachidonic acid derivatives (esters, epoxides, etc.) and metabolites (cyclooxygenase and lipoxygenase products) has been tested; the biological activity is restricted to 8-hydroxyeicosatetraenoic acid (8-HETE), other mono- and poly-HETEs being completely inactive. Maturation triggered by 8-HETE occurs around 10 nM and is insensitive to the presence of calcium. 8-HETE methyl ester and 8-hydroperoxyeicosatetraenoic acid are able to induce maturation at higher concentrations. Both (8S) and (8R) stereoisomers have been tested; the biological activity is strictly restricted to the (8R) isomer. 8-HETE triggers a complete maturation, i.e. maturation-promoting factor appearance, germinal vesicle breakdown, emission of the polar bodies, and formation of a female pronucleus. (8R)-HETE, but not (8S)-HETE, triggers the typical decrease in cyclic AMP concentration induced by 1-methyladenine and the burst of protein phosphorylation associated with maturation. Starfish oocytes oxidize exogenous arachidonic acid into 8-HETE and other HETEs. 8-HETE was identified, after high pressure liquid chromatography purification, by gas chromatography mass spectrometry. Furthermore, it was found that the starfish oocytes only produce the (8R)-HETE isomer. This highly stereospecific induction of oocyte maturation by (8R)-HETE suggests that this fatty acid, or a very closely related fatty acid, may play a role in the transduction of the 1-methyladenine message at the plasma membrane level.
Animals↗
Augmentation of leukotriene C4 and D4 release due to severe stenosis in the canine coronary artery stimulated by the calcium ionophore A23187.
In dogs undergoing 24- or 72-hr severe narrowing of the left anterior descending coronary artery (LAD), the in vitro formation of immunoreactive leukotriene C4 (LTC4) by the stenosed LAD was greatly augmented by 1 microM A23187 in a 10-min incubation at 37 degrees. This stimulated LTC4 formation was abolished by 30 microM nordihydroguaiaretic acid (NDGA). The incubation products were identified by high performance liquid chromatography and radioimmunoassay to be largely composed of LTC4 and LTD4 in similar proportion. In contrast to the stenosed LAD, the non-stenotic left circumflex coronary artery, apex of the heart, and renal artery of the same experimental animals failed to respond to the calcium ionophore up to 10 microM. The vascular and cardiac tissues from sham-operated animals also remained quiescent in the presence of A23187. The normal coronary artery showed low levels of leukotriene formation and was resistant to the ionophore. It is proposed that a latent portion of leukotriene synthesis, which can be triggered by the calcium ionophore, may play a significant role in the pathogenesis of coronary artery spasm associated with acute myocardial infarction and angina pectoris in patients with obstructive coronary artery disease.
Animals↗
Amalgam-related chronic ulceration of oral mucosa.
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Aged↗
Calcium ionophore and chemotactic peptide stimulation of peptidoleukotriene synthesis in DMSO-differentiated HL60 cells.
The human promyelocytic leukemia cell line HL60 can be differentiated to mature granulocytes upon exposure to DMSO (1.3%, 6 days). The ability of these cells to metabolize arachidonic acid via the 5-lipoxygenase pathway to form 5-HETE, LTB4, and 5,12-diHETEs, has been previously documented. However, the production of peptidoleukotrienes by DMSO-differentiated HL60 cells has not been previously reported. Arachidonic acid metabolites produced via 5-lipoxygenase were identified by reverse-phase, high-performance liquid chromatography, immunoreactivity specific for peptidoleukotriene, glutamyl transpeptidase transformation, characteristic UV spectra, and GC mass spectra. Leukotriene synthesis in the DMSO-differentiated HL60 cell is maximal at 5 min when stimulated with the calcium ioniphore, A23187 (1 microM), in the presence of calcium. These cells produce 12.94 +/- 1.8 ng/10(6) cells of LTC4 and 3.8 +/- 0.4 ng/10(6) cells of LTB4. LTC4 and LTB4 are also synthesized in the undifferentiated cell when stimulated with 1 microM A23187 and 1 mM Ca2+, but in much smaller quantities, i.e., 1.91 +/- 0.42 ng/10(6) cells of LTC4 and 0.41 ng +/- 0.06/10(6) cells of LTB4. The synthetic chemotactic peptide, f-Met-Leu-Phe, also elicits formation of LTC4 and LTB4 in a dose-dependent manner in the presence of exogenously added calcium. Maximal stimulation of DMSO-differentiated cells with f-Met-Leu-Phe produces 2.5 +/- 0.2 ng of LTC4 and 1.45 +/- 0.2 ng of LTB4 per 10(6) cells. The observation that DMSO-differentiated HL60 cells produce LTC4, as well as other 5-lipoxygenase products, increases the utility of this cell line for unraveling the regulation of leukotriene biosynthesis by granulocytes.
Arachidonic Acids↗
Modulus of elasticity in bending of composites and amalgams.
In this study, the modulus of elasticity in bending (a measure of rigidity) and transverse strength (a measure of edge strength) were determined for composites and amalgams. the results were as follows. The modulus of elasticity of microfilled composites is approximately one-third that of the macrofiller-containing composites. Composites containing a relatively coarse-sized macrofiller have a higher elastic modulus than those containing a finer macrofiller. The transverse strength of microfilled composites is approximately one half that of the macrofiller-containing composite, which, in turn, is close in value to the transverse strength of amalgam. High-copper amalgams are substantially more rigid than the traditional low-copper amalgams, but do not show large differences among themselves. The transverse strength among various amalgams does not appear to be related to amalgam type but does correlate to final Hg content. The modulus of elasticity of composites most likely to be used in posterior teeth is approximately one third of the modulus of elasticity of amalgam; that is, amalgams are three times more rigid.
Composite Resins↗
Modulation of the 5-lipoxygenase activity of MC-9 mast cells: activation by hydroperoxides.
In order to identify regulatory steps in leukotriene synthesis, the biochemical characteristics of a 5-lipoxygenase activity in the 100,000 xg supernatant from sonicates of cells of an IL-3 dependent murine mast cell clone, MC-9 were determined. Principal products from exogenous 14C-arachidonic acid were identified as leukotriene B4, diastereomeric 5,12-dihydroxy-eicosatetraenoic acids (5,12 diHETEs) 5-hydroperoxy and hydroxyeicosatetraenoic acids (5-HPETE and 5-HETE) as well as a novel metabolite 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE). The crude lipoxygenase activity had a pH optimum of 6.9 and was highly dependent upon added Ca++. The effective Ca++ concentration for 50 per cent activation (EC50) was 3 microM. Activity was also stimulated by ATP (EC50 = 160 microM). The cytosolic 5-lipoxygenase activity exhibited a biphasic concentration dependence for arachidonic acid with maximum product formation occurring at 35 microM (ca. 20 nmole/mg/4 min). The lipoxygenase activity exhibited apparent lag phase kinetics which were more pronounced at low protein concentrations (0.3 mg/ml). In addition, the lag phase was greatly accentuated by the addition of a hydroperoxide scavenging system consisting of glutathione (1 mM) plus glutathione peroxidase (0.4 unit/ml). In contrast, addition of any of several hydroperoxides, i.e. 5-,8-,9- or 15-HPETE (EC50 ca. 1 microM), but not the corresponding alcohols (5-HETE and 15-HETE), shortened the lag phase. These results show that the 5-lipoxygenase requires hydroperoxide for activation and that cellular level of hydroperoxides may be an important factor regulating leukotriene synthesis.
Adenosine Triphosphate↗
Contrasting effects of fatty acids on oocyte maturation in several starfish species.
Oocyte maturation (meiosis reinitiation) in starfish is induced by the natural hormone 1-methyladenine. In some species (group 2) oocyte maturation can be induced by micromolar concentrations of a few fatty acids such as arachidonic and eicosapentaenoic acids or by nanomolar concentrations of hydroxyeicosatetraenoic acid. Complete maturation is triggered: increased protein phosphorylation, appearance of the cytoplasmic "maturation-promoting factor", germinal vesicle breakdown, emission of the two polar bodies and formation of the female pronucleus. In other species (group 1), however, no maturation can be induced by the fatty acids active in the species of group 2, despite a large variety of experimental conditions.
Adenine↗