Plasters, applications/preparation

The use of monomer-polymer doughs has been largely confined to the production of dentures. A plaster of Paris mould is first prepared from a supplied impression of the mouth. Polymer powder containing a suitable polymerisation initiator is then mixed with some monomer to form a dough. A portion of the dough is then placed in the mould, which is closed, clamped and heated in boiling water. After polymerisation, which usually takes less than half an hour, the mould is cooled and opened. This technique could also be usefully employed for other applications where only a few numbers-off are required but does not seem to have been exploited. 

Calcium hydroxide has wide industrial applications. It is used to make cement, mortar, plaster, and other building materials. It also is used in water soluble paints, and for fireproofing coatings and lubricants. Other applications are in the manufacture of paper pulp as a preservative for egg in vulcanization of rubber as a depilatory for hides and in preparation of many calcium salts. 

Coping with the large exotherm is less of a problem when lime is slaked with a liberal amount of water because of the high heat capacity of the excess water present. In the preparation of cement mixes, mortars, and plasters the low solubility of slaked lime in water (1.84 g/L at 0°C 0.77 g/L at 100°C) does not pose any problems. However, this factor does have to be considered in applications of calcium hydroxide as an industrial base. 

Cover verrucas with a plaster to encourage maceration and improve penetration of the medicament. (Some gel-based preparations do not require application of... 

Plaster 040 An external application of a consistency harder than ointment, prepared for use by spreading it on linen, etc., to heal or soothe. 

Plasters. External applications that possess sufficient consistenco not to adhere to tho fingers when cold, but which become soft and adhesive at tho temperaturo of the human body. Plasters are chiefly composed of unctuous substances united to metallic oxides, or to powders, wax, or resin. They arc usually formed whilst warm, into 4 pound rolls about 3 or 9 inches long, and wrapped in paper. TThen required for use, a little iw melted off the roll by means of a heated iron spatula, and spread upon leather, linen, or silk. The less adhesivo piasters, when spread, arc usually surrounded with a margin of resin plaster, to cause them to adhere. lu the preparation of plasters, tho heat of a watcr-uatn, or steam, should bo alone employed,... 

Calcium sulphate pellets impregnated with tobramycin are now available in a ready prepared pack and can be used with deep, severely infected ulcers in combination with systemic antibiotic treatment. The Osteoset T (Wright Medical) is a prefabricated plaster of parts pellet impregnated with tobramycin and the Bone Void Filler is available as a mixing kit allowing fabrication of pellets of various sizes and strengths. Following application the pellets remain in place and are reabsorbed over a 2-3-month period. 

Dilute silica sols were prepared and studied over 70 years ago. Their uses as binders in catalyst preparation, as glazes on ceramics, as coatings on concrete and plaster of Paris, as agents for treating paper and textiles, and several other applications were investigated [1]. These early sihca sols contained less than 10% by weight of silica, were fairly unstable and did not have reproducible properties. Her [2] predicted that colloidal sihca would not be accepted for wide commercial use before these shortcomings were remedied. 

SemisoUd preparations for cutaneous application are subdivided in ointments, creams, gels, pastes, poultices (wet dressings), medicated plasters or patches and cutaneous patches. 

Relatively new developments of enhanced skin penetration are cutaneous and transdermal patches. The European Pharmacopoeia distinguishes medical plasters and cutaneous patches which are classified as Semisolid Preparations for Cutaneous Application [4] and transdermal patches which are described in a separate monograph [4]. 

The European Pharmacopoeia also defines medicated plasters as semisolid preparations for cutaneous application. According to the European Pharmacopoeia medicated plasters are flexible preparations containing 1 or more active substances. They are intended to be applied to the skin. They are designed to maintain the active substance(s) in close contact with the skin such that these may be absorbed slowly, or act as protective or keratolytic agents . 5-Aminolevulinic acid medicated plasters represent this dosage form. They are used in photodynamic/radiatiOTi therapy. The plasters are applied to mild to moderate actinic keratosis lesions. Four hours after application the plasters are removed and the lesions are exposed to red light. 

The preparation of medicinal soaps appears to have been first taken up in a scientific manner by TJnna of Hamburg in 1886, who advocated the use of soap in preference to plasters as a vehicle for the application of certain remedies. 

The mixture of dodecylammonium lactate and dodecylammonium salicylate possesses a wide spectrum of microbicidal efficacy which covers Gram-positive and Gram-negative bacteria, fungi and algae. It may be used for the preparation of microbicidal wash solutions for the antimicrobial treatment for surface coatings, masonry, brick, wood and plaster. The wash solution should contain 0.5-3% of the mixture (concentrate) a 5% solution may be necessary in cases of particularly severe surface infestation. Other applications Treatment of industrial water circuits, eradication of dry-rot of timber. 

The application of the colloidal method is certainly not new to ceramic powder preparation, for example, ancient applications include the cigeing of clays for hand moulding. In addition, colloidal methodology has been applied for more than one hundred years to prepare clay slurries for casting into porous moulds, usually plaster-of-paris, to form thin walled, complex shaped bodies. Colloidal methods are also commonly used to fractionate ceramic abrasive media to obtain a desired narrow particle size distribution, however their use prior to consolidation of a ceramic body to eliminate or reduce in size the common heterogeneities associated with ceramic powders, such as agglomerates and inclusions, is relatively rare. 

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