Aqueous embedding media

Beat-Cured Restm. For optimum comfort and to impede further loss of chewing efficiency, close adaptation of the denture base to contiguous oral tissues is required, which necessitates custom-made appHances. Nearly all dentures are made of acryHc resins. A wax pattern is used to form a custom denture base in which the denture teeth are embedded. A plaster or dental-stone investment spHt mold of this wax denture base and teeth is prepared. The wax portion is removed and the surface of the resulting mold cavity is painted with a separating medium, usually an aqueous solution of alginate, to aid in the removal of the cured acryHc from the plaster mold. 

The ion selective behavior of a carrier molecule embedded in a given medium, say, a membrane, may be described in terms of the changes in free energy associated with the transfer of a cation from an aqueous solution into the cavity enclosed by the multidentate ligand ... 

The cell membrane, also called the plasma membrane, surrounds the cytoplasm and physically separates the intracellular components from the extracellular environment. It has a thickness around 7.5-10 nm and controls the flux of molecules between the cytosol and the extracellular environment. The plasma membrane is composed of a lipid bilayer, in which the polar groups are exposed to the internal and external cell aqueous medium, protecting the embedded hydrophobic tails. Various proteins with distinct functions can be found partially or totally immersed in this bilayer. 

If we compare this with the abnormal vacuolation of the gum arabic — toluidine blue coacervate discussed above (p. 454, 4 a) one can in a certain sense speak of an analogous case laying down of a large centred vacuole, after a certain time followed by withdrawal of the vacuole. A point of difference is, that there the vacuole bursts out into the surrounding aqueous medium, here however into the enveloping coacetv-ate in which for a certain time it remains embedded. 

To achieve needed comfort, dentures must be custom-made. To form the customized denture, in which the artificial teeth are embedded, a wax pattern is used. The wax pattern is inserted in a plaster or dental stone in a split mold flask. After removal of the wax, the surface of the resulting mold cavity is painted with a separating medium, usually an aqueous alginate solution, followed by the addition of the acrylic resin. The separating medium aids in removal of the cured acrylic from the mold. 

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