Cationic liposomes target angiogenic endothelial cells in tumors and chronic inflammation in mice.

This study sought to determine whether angiogenic blood vessels in disease models preferentially bind and internalize cationic liposomes injected intravenously. Angiogenesis was examined in pancreatic islet cell tumors of RIP-Tag2 transgenic mice and chronic airway inflammation in Mycoplasma pulmonis-infected C3H/HeNCr mice. For comparison, physiological angiogenesis was examined in normal mouse ovaries. We found that endothelial cells in all models avidly bound and internalized fluorescently labeled cationic liposomes (1,2-dioleoyl-3-trimethylammonium-propane [DOTAP]/cholesterol or dimethyldioctadecyl ammonium bromide [DDAB]/cholesterol) or liposome-DNA complexes. Confocal microscopic measurements showed that angiogenic endothelial cells averaged 15-33-fold more uptake than corresponding normal endothelial cells. Cationic liposome-DNA complexes were also avidly taken up, but anionic, neutral, or sterically stabilized neutral liposomes were not. Electron microscopic analysis showed that 32% of gold-labeled liposomes associated with tumor endothelial cells were adherent to the luminal surface, 53% were internalized into endosomes and multivesicular bodies, and 15% were extravascular 20 min after injection. Our findings indicate that angiogenic endothelial cells in these models avidly bind and internalize cationic liposomes and liposome-DNA complexes but not other types of liposomes. This preferential uptake raises the possibility of using cationic liposomes to target diagnostic or therapeutic agents selectively to angiogenic blood vessels in tumors and sites of chronic inflammation.

The strengthening of aluminous porcelain with bonded platinum foils.

Results are presented to demonstrate the effect of bonding thin platinum foils to aluminous dental porcelain. The increased strength is explained in terms of a reduction in surface and subsurface pores in the porcelain brought about by improved wetting.

RGD-containing peptides inhibit adhesion of 293 cells transfected with GpIIb/IIIa to fibrinogen: comparison to inhibition of platelet aggregation.

Cyclic RGD-containing peptides caused a dose-dependent inhibition of binding of human embryonic kidney cells transfected with recombinant GpIIb/IIIa (r293 clone B) to human fibrinogen coated on to non-tissue culture plates. The inhibitory activity, IC50, of a panel of seventeen RGD-containing peptides ranged from 0.12 to 89.2 microM. These IC50 values correlated with those determined by the inhibition of platelet aggregation (r = 0.99). Even though there was a correlation, there were differences between the platelet aggregation and the bioadhesion assay. The binding of r293 clone B to fibrinogen was not increased by ADP suggesting that GpIIb/IIIa expressed on the surface of r293 clone B cells may be in the 'activated' form. Moreover, preincubation of r293 clone B cells with a monoclonal antibody (mAb) specific for GpIIIa (4B12) resulted in a dose-dependent decrease of binding to fibrinogen while a mAb specific for GPIIb (2D2) had no effect. Neither of these mAbs inhibited platelet aggregation. The binding of r293 clone B cells to fibrinogen required Ca2+ or Mg2+. This cell-based bioadhesion method can provide a tool for screening potential GpIIb/IIIa antagonists and investigating the interaction of GpIIb/IIIa and fibrinogen not possible with platelet aggregation.

Cermet cements.

Cermet ionomer cements are sintered metal/glass powders, which can be made to react with poly(acids). These new cements are significantly more resistant to abrasion than regular glass ionomer cements and are widely accepted as core build-up materials and lining cements. They can strengthen teeth and provide the clinician with an opportunity to treat early dental caries.

Clinical applications of glass-ionomer cements.

The use of glass-ionomer cements in clinical dentistry is now well established. They have a number of unique properties, including adhesion to moist tooth structure, biological compatibility, and anticariogenic properties due to their fluoride release. Their use in treating early carious or erosion lesions has been widely investigated. Established techniques include fissure filling and sealing, restoration of class 5 erosion lesions without cavity preparation, and the internal occlusal fossa or tunnel restoration. The "sandwich" technique using glass-ionomer cements as "dentin substitutes" has enabled composite restorations to be used with greater safety where pulpal damage may occur. The future probably lies in using a laminate technique where materials that attach to dentin and form a biological seal can be covered by tougher and harder enamel veneers, thus mimicking the structure of the tooth. The deficiencies of glass-ionomer cements are well known, including lack of toughness, early water sensitivity, low abrasion resistance, and porosity leading to poor surface polish. Solving these problems is formidable, since inherently the strength of these cements is related to their water content. The clinician should be aware of these deficiencies and stay within the parameters of the techniques outlined in this paper. In particular, clinical success depends upon early protection of the cement from hydration or dehydration, and the current use of light-cured bonding agents has largely solved this problem.

The clinical use of glass-ionomer cements.

The use of glass-ionomer cements in clinical dentistry has expanded greatly over the last decade. Their use in treating early carious or erosion lesions has been investigated widely and established techniques include fissure filling, restoration of erosion lesions without cavity preparation, and the internal or tunnel restoration. Because of their adhesion to moist tooth structure, biologic compatibility, and fluoride release, increasing use also has been made of their anticariogenic properties in treating geriatric patients. Glass-ionomers have proved very successful as dentin substitutes for attaching composites to enamel without involving risk of pulpal damage in the deeper cavity. The deficiencies of glass-ionomer cements are well known, including lack of toughness, early water sensitivity, low abrasion resistance, and porosity, leading to poor surface polish. Solving these problems is formidable because inherently the strength of these cements is related to their water content. The clinician should be aware of these deficiencies and stay within the parameters of the techniques outlined in this article. In particular, clinical success depends on early protection of the cement from hydration or dehydration and the current use of light-cured bonding agents largely has solved this problem. The future probably lies in using laminate techniques in which materials that attach to dentin and form a biologic seal can be covered by tougher and harder enamel veneers, thus mimicking the structure of the tooth. It is possible that future materials will be developed on the lines of these polyelectrolyte cements in which higher molecular weight polymers are used in conjunction with polymers that contain photoinitiators to effect light curing and toughen the matrix. In addition, the possibility of developing laboratory-cured glass-ionomer inlays in which porosity can be reduced and tougher polymers used should be considered.

The failed restoration: causes of failure and how to prevent them.

Ceramic restorations lack tensile strength and suffer from static fatigue. The margins of safety required to prevent fracture are much greater than for metal. Composite restorations, even laboratory cured, have yet to be fully tested over long periods. The hydrolytic stability of these materials still requires improvement. Glass-ionomer cements lack fracture toughness and will not accept a high polish due to their porous surfaces. Failure in restorations can only be avoided by recognizing the deficiencies in physical properties of all our restorative materials and using them in areas where the hostile oral environment causes minimal damage. The cast-gold restoration will probably remain supreme for crown and inlay work. The unique properties of the metallic bond are ideally suited to withstand maximum occlusal stress under most clinical conditions.

A preliminary report on the effect of storage in water on the properties of commercial light-cured glass-ionomer cements.

Two commercially available light-curable glass-ionomer cements, Vitrebond and XR-Ionomer, have been studied and their compressive strengths measured following storage under wet and dry conditions for varying lengths of time up to 3 months. The strongest cements were those stored in air and allowed to age. On the other hand, cements that were stored in water were found to become progressively weaker with time. Their failure mode was different from that of cements stored in air in that specimens became barrel-shaped as they were loaded and exhibited considerable plastic deformation prior to fracturing. By contrast, air-stored specimens behaved as predominantly brittle materials, the specimens essentially maintaining their integrity up to the point of catastrophic failure. Both of these findings indicate that the properties of these particular light-cured cements change markedly on exposure to moisture, a fact which is of clinical significance.

The bonded alumina crown. 1. The bonding of platinum to aluminous dental porcelain using tin oxide coatings.

A method has been evolved for bonding aluminous porcelain to pure platinum foil used for making porcelain crowns by the conventional 'tinner's joint' technique. It was found that good bonding was achieved when the platinum was coated with 0.2-2.0 mum of tin before firing on the porcelain. This paper describes experimental work for determining the optimum composition and thickness of the coating and the applicability of the technique to substrates other than platinum.

The clinical development of the glass-ionomer cement. III. The erosion lesion.

A clinical trial of the glass-ionomer cement, ASPA IV, as a restorative material for erosion lesions is reported. The failure rate, in a three-year trial, was nine per cent; most failures occurring within the first few months after placement.

The clinical development of the glass-ionomer cement. II. Some clinical applications.

A description is given of the varied clinical applications of this cement; these applications include its use as a filling material, as a sealant and as a luting agent.

The bonded alumina crown. 2. Construction using the twin foil technique.

A technique has been developed for making aluminous procelain crowns bonded to thin tin oxide coatings on platinum foil. These crowns require only very thin metal linings of less than 0.05 mm, thus reducing metal costs and considerably improving aesthetics. In addition, by using the "twin foil" technique, porcelain butt fits may be obtained without loss of fit.

Dentinal bonding agents versus glass-ionomer cements.

The long-term bonding of dental material to dentin remains an area of great controversy and the results of in vitro testing do not always reflect those found in vivo. The clinician is faced with a large number of dentinal bonding agents that have had limited testing in vivo and are frequently replaced before any long-term clinical testing has been completed. Glass-ionomer cements, although having a longer history of good adhesion to dentin, are not suitable for use in high-stress-bearing areas. The selection of materials for specific clinical situations has become more and more difficult. This paper gave a personal view of the history and evolution of both resin bonding agents and glass-ionomer cements and their potential in clinical use.