Adam Baszkin

Complete denture retention. Part II: Wettability studies on various acrylic resin denture base materials

The objective of this study was to characterize in vitro selected acrylic resin denture base materials by water-contact angle measurements. The sessile drop method and the underwater-bubble method were used. The results obtained from these measurements are discussed in terms of contact angle and polymer-water work of adhesion hysteresis. On polished heat-polymerized samples this hysteresis results from the reorientation of superficial polymer chains. The combined effect of increased sample roughness and of the entrapment of water droplets in the pores of material gives rise to the highest contact-angle hysteresis observed on sand-abraded samples. On the basis of physical analysis of the mechanism involved in complete denture retention, developed in Part I of this work, it is believed that the sand-abraded material is the most convenient for the retention of the complete denture.

Adsorption of bovine submaxillary mucin on surface-oxidized polyethylene films

Bovine submaxillary mucin (BSM) was isolated from fresh salivary glands obtained at a slaughterhouse. Radioactive labeling of this mucin by acetylation with [1-14C]acetic anhydride yielded [14C]BSM having the same surface properties as the unlabeled mucin. In situ adsorption of this mucin at the air/BSM solution interface and onto untreated and surface-oxidized polyethylene films was studied as a function of time and BSM bulk concentration under static conditions. The amount adsorbed increased with the degree of polymer oxidation and thick adsorbed mucin layers were obtained on strongly oxidized samples. The presence of a loosely adsorbed protein layer was also noted under the experimental conditions used in this study. The specific character of surface-oxidized polyethylene and its influence on adsorption patterns is discussed.

Penetration of poly(oxyethylene)-poly(oxypropylene) block copolymer surfactant into soya phospholipid monolayers

Abstract The surface tension of aqueous solutions of ABA poly (oxyethylene)-poly (oxypropylene) block copolymer nonionic surfactant, has been measured as a function of time. The kinetics and final equilibrium values were surfactant concentration dependent. From these values, using the simple form of the Gibbs equation, the area per molecule has been calculated. The small molecular area (40.7 A2) suggests that surfactant molecules form close-packed coil monolayers with hydrophilic poly (oxyethylene) groups immersed in the aqueous phase. The penetration of the surfactant into monolayers of soya phosphatidylcholine spread at the air-water interface was followed by the variation of the surface pressure (△π) at constant area. As revealed by the results at low surfactant concentrations, the adsorption of surfactant is enhanced by the presence of the phospholipid film. Analysis of equilibrium penetration values, obtained by the use of different thermodynamic approaches, shows that the equations of Pethica and Alexander-Barnes are better adapted for calculation of surfactant penetration into the monolayers only in their condensed state (102–122 A2/molecule). Conversely, the equation of Motomura et al. enabled the calculation of the adsorbed surfactant quantities, for the expanded state of phospholipid monolayers (140–230 A2/molecule).

Adsorption of bovine submaxillary mucin on silicons contact lenses grafted with poly(vinyl pyrrolidone)

Bovine submaxillary mucin is considered to be an analogue of the high molecular protein present in the conjunctival mucus. This mucin was isolated from fresh salivary glands and acetylated with [1-14C]acetic anhydride. In situ adsorption of the bovine submaxillary mucin on silicone contact lenses ungrafted and grafted with poly(vinyl pyrrolidone) was performed for the first time using an original radiotracer technique. The results show that the adsorbed amounts of mucin are higher on grafted samples and that thick layers are adsorbed when mucin concentration in the bulk solution is increased. Desorption experiments reveal that in addition to the tightly adsorbed protein layer, a loosely bound mucin layer of the same thickness exists on grafted and ungrafted silicones.

In situ adsorption of bovine submaxillary mucin at the mica/aqueous solution interface

An in situ adsorption measurement method at the mica/protein solution interface is described. n nAn apparatus especially constructed for this purpose permits direct and continuous measurement of total adsorption (reversible and Irreversible) of 14 C-labelled proteins. n nBovine submaxillary mucin (BSM), extracted from salivary glands, was acetylated with (CH3, 14CO)2 O. The results show the increase of BSM adsorbed on mica surfaces with its concentration in solution and adsorption time. Pseudo plateaux are obtained for all concentrations studied, Indicating the formation of thick layers. The loosely bound fraction of adsorbed mucin is proportional to the bulk concentration in solution. The amount of BSM adsorbed increases in the neighbourhood of the isoelectric point of BSM (pH 3).

The effect of the surface free energy of pharmaceutical tablets on liquid penetration.

The surface free energies (γsv) of the integral and partial tablet formulations of an antiarrhythmic drug—cibenzoline succinate, have been assessed by contact angle measurements using high‐viscosity polyols and Neumanns equation of state. Independent measurements of penetration for these liquids into the tablets yielded pore size values through the use of the Washburn equation. The role of different constituents of the formulations are analysed in terms of their influence upon the free surface energy of the tablets and penetration rates. The relation between (γsv) and penetration rates yields for a series of liquids two threshold values: (γsv)s ‘start’ and (γsv)r ‘rapid’, which define respectively the beginning of the measurable penetration and the rapid penetration.

Direct evidence for symmetry control in cyclodextrin-water interactions

Abstract The cyclodextrins, cyclic oligosaccharides possessing generally 6, 7, or 8 α, 1 –4 linked glucopyranose units, are widely used for the solubilisation and transport of organic molecules in aqueous media.3 Their solubilities 145 gL−1, α-Cd; 20 gL−1, β-CD; 220 gL−1, γ-CD, are considerably lower than those of simple saccharides and in particular that of β-CD, the most widely available compound, is anomalously low. We have previously shown that the solubilities arise from symmetry determined interactions of the CDs with the dynamic hexagonal structure of water. In the case of the unmodified cyclodextrins all three compounds exist in solution as large aggregates, thus the solubility of these systems is controlled by the interactions between these hydrogen bonded aggregates and the hydrogen bonding networks present in water. In the case of α- or γ-CD there are favorable overlaps with the hexagonal water structure, however for the seven-fold symmetry of β-CD no such favorable interactions can occur betwe...

Chemical structures and wettability of polyethylene grafted with maleic acid: I. Wettability, effect of sodium and calcium ions

Abstract Maleic anhydride was grafted on the surfaces of the low density polyethylene films by free radical polymerization. The reaction was allowed to run for a short period of time, such that only a very low degree of grafting was obtained. After hydrolysis, the grafted samples were equilibrated with solutions of different alkali and organic cations at constant pH. Their wettability towards the equilibrating solutions was determined by contact-angle measurements. It varies with the nature of the neutralizing cation and the pH of the wetting solution. The works of adhesion and the field strengths of Ca Na substituted surfaces were determined as a function of the ionic percentage of calcium.

Characterization and Albumin Adsorption on Surface Oxidized Polyethylene Films

One of the initial events occuring as blood comes in contact with a polymer is the adsorption of a protein layer at the blood-material interface This layer modifies the original surface and has an important influence on subsequent phenomena such as platelet adhesion and blood coagulation 1–7.

Chemical structures and wettability of polyethylene grafted with maleic acid: II. Calcium-sodium ion exchange. Effect of ionic strength

Abstract Polyethylene films grafted with maleic acid at their surfaces were equilibrated with buffer solutions containing 45CaCl2 of different concentrations. The isotherms of calcium adsorption were established for different ionic strengths of the underlying solutions. The effect of different alkali ions on the adsorption equilibrium of Ca2+ ions was found be to nonspecific. Organic ions such as (CH3)4N+ and (C2H5)4N+ were less effective in desorbing Ca++ ions than the alkali ions. The equilibrium constants and the free energies of Na Ca exchange reaction were calculated. They vary with the ionic strength of the equilibrating solution.