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Biomedical subjects

R E Jordan

Publications and source records attributed to R E Jordan.

At least 37 records · Page 2Linked to original sources
PubMed1993

Clinical evaluation of a new generation universal bonding system for conservative aesthetic restoration.

This study evaluated the clinical effectiveness of a new generation bonding material, used for conservative restoration of cervical erosion lesions. One hundred lesions were selected. At two-year recall, 79 have been reviewed to date. In those, 97.5% of the restorations were still present; 95% of restorations present had retained color, 96% had retained marginal integrity, and 100% had retained abrasion resistance, surface texture, and staining resistance.

Dental Restoration, Permanent↗
PubMed1990

Glass ionomer-composite sandwich technique.

Glass ionomer cement characteristics of biological acceptability, fluoride release, dentin bondability, and marginal integrity are excellent; at the same time, they have always been regarded as secondary choices for anterior and posterior restorations. Slow set, brittleness, poor finishability, lack of translucency, and the technique-sensitive nature of the glass ionomers hardly compare with the composite resins which are easier to handle, polishable, and esthetically acceptable. The combined ionomer-composite restoration provides a reliable chemical bond to dentin, micromechanical bonding of the composite to ionomer surface, and an acceptable esthetic result.

Composite Resins↗
PubMed1989

Antithrombin inactivation by neutrophil elastase requires heparin.

In certain thrombotic states, large declines in the levels of functional circulating antithrombin occur, which may reflect the highly active nature of the endothelial surface in suppressing excessive amounts of activated coagulation enzymes. Alternatively, we have recently observed an unexpected and paradoxical in vitro functioning of heparin that could result in the inactivation of antithrombin in pathologic conditions. Specifically, antithrombin was rendered nonfunctional as an inhibitor of clotting enzymes as a result of a limited, heparin-dependent cleavage by neutrophil elastase. This inactivation occurred only in the presence of the active anticoagulant heparin fraction, which suggested that the heparin-antithrombin complex was the substrate for elastase attack. Interestingly, neutrophil elastase was found to bind tightly to heparin and heparin-like materials. Neutrophil elastase has been previously linked to nonspecific proteinolysis occurring in inflammatory thrombotic reactions. This affinity of both antithrombin and elastase for heparin suggests a novel mechanism of potential specificity. An important component of this hypothesis is the localization of the elastase/antithrombin reaction away from the high circulating levels of elastase inhibitors. The proposed inactivation of antithrombin on the vascular surface would likely occur only in pathologic states associated with neutrophil sequestration and activation. Nevertheless, this mechanism could lead to a localized reversal of the nonthrombogenic nature of the endothelium and potentially lead to significant reductions of functional antithrombin in certain disease states.

Antithrombins↗
PubMed1989

Inactivation of human antithrombin by neutrophil elastase. Kinetics of the heparin-dependent reaction.

Human neutrophil elastase catalyzes the inactivation of antithrombin by a specific and limited proteinolytic cleavage. This inactivation reaction is greatly accelerated by an active anticoagulant heparin subfraction with high binding affinity for antithrombin. A potentially complex reaction mechanism is suggested by the binding of both neutrophil elastase and antithrombin to heparin. The in vitro kinetic behavior of this system was examined under two different conditions: 1) at a constant antithrombin concentration in which the active anticoagulant heparin was varied from catalytic to saturating levels; and 2) at a fixed, saturating heparin concentration and variable antithrombin levels. Under conditions of excess heparin, the inactivation could be continuously monitored by a decrease in the ultraviolet fluorescence emission of the inhibitor. A Km of approximately 1 microM for the heparin-antithrombin complex and a turnover number of approximately 200/min was estimated from these analyses. Maximum acceleratory effects of heparin on the inactivation of antithrombin occur at heparin concentrations significantly lower than those required to saturate antithrombin. The divergence in acceleratory effect and antithrombin binding contrasts with the anticoagulant functioning of heparin in promoting the formation of covalent antithrombin-enzyme complexes and is likely to derive from the fact that neutrophil elastase is not consumed in the inactivation reaction. A size dependence was observed for the heparin effect since an anticoagulantly active octasaccharide fragment of heparin, with avid antithrombin binding activity, was without effect on the inactivation of antithrombin by neutrophil elastase. Despite the completely nonfunctional nature of elastase-cleaved antithrombin and the altered physical properties of the inhibitor as indicated by fluorescence and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the inactivated inhibitor exhibited a circulating half-life in rabbits that was indistinguishable from native antithrombin. These results point to an unexpected and apparently contradictory function for heparin which may relate to the properties of the vascular endothelium in pathological situations.

Antithrombins↗
PubMed1989

Relationship between composite resins and dentin treated with bonding agents.

This study determined if and where gaps exist at the dentin-composite resin interface when bonding materials are used. Dentin bonding agents tested did not create an uninterrupted connection strong enough to withstand polymerization contraction forces of the resin materials often found in three-dimensional caries restoration preparations.

Composite Resins↗