Plastics, dental applications

Acrylic resins are the materials of choice for almost all dental applications wherever synthetic plastics are favored for the restoration of missing teeth or tooth structures. This is not surprising because polymers derived from methacrylate esters fulfill most requisites of a restorative adequate strength, resilience and abrasion resistance dimensional stability during processing and subsequent use translucency or transparency simulating the visual appearance of the oral tissue that it replaces satisfactory color stability after fabrication resistance to oral fluids, food or other substances with which it may come Into contact satisfactory tissue tolerance low toxicity, and ease of fabrication into a dental appliance. 

The largest volume of plastics for dental applications is consumed in the construction and repair of dentures. Other uses include artificial teeth, restoratives—especially for anterior... 

Dental fields of application of methacrylates are, among others, dental prostheses, composite resins and primers. Methacrylic plastics are formed by polymerization of chemically highly reactive methacrylic monomers. For dental applications, it is most common to use a powder of pre-polymerized (meth)acrylates, which has to be mixed with the right amount of liquid methacrylic monomers. Depending on the polymer-... 

In most medical and paramedical applications of plastics, the materials used are those already produced by the manufacturers in a polymerized or formulated form. Certain surgical and dental applications, however, require that the material be polymerized or formulated just prior to use. Surgical cements and adhesives, a host of dental filling materials, materials for dentures, cavity liners, and protective coatings for tooth surfaces are in this category. 

Acrylic resins, because of their desirable esthetics, ease of processing, optical clarity that can duplicate in appearance the oral tissues it replaces, satisfactory mechanical properties and excellent biocompatibility, are the materials of choice wherever plastics have found applications in dental practice. The ready acceptability of these materials is the result of the ease with which they can be converted into their final state even under clinical conditions. In practically all dental applications a liquid monomer-solid mixture is cured by a free radical initiated polymerization that is generated by heat, light, an initiator, or a redox initiator-accelerator system adapted to the constraints imposed by the oral environment. 

Applications. The applications sought for these polymers include composites, stmctural plastics, electronics/circuit boards, aircraft/spacecraft coatings, seals, dental and medical prosthetics, and laser window adhesives. However, other than the early commercialization by Du Pont of the NR-150 B material, Httie development has occurred. These polymers are quite expensive ( 110 to 2200 per kg for monomers alone). 

Tribasic calcium phosphate occurs in nature as minerals, oxydapatite, whitlockite, voelicherite, apatite, phosphorite. It has many industrial applications. Some are similar to the monobasic and dibasic salts. It is used in fertilizers, dental products, ceramics and pohshing powder. Some other important applications are in plastics as a stabdizer as an anticaking agent as a nutrient supplement in cattle food for clarifying sugar syrup as a mordant in dyeing textiles and as a buffer to control pH. 

Zinc oxide occurs in nature as mineral zincite. It is the most important zinc compound and has numerous industrial applications. Zinc oxide is the pigment in white paints. It is used to make enamels, white printing inks, white glue, opaque glasses, rubber products and floor tiles. It is used in cosmetics, soaps, pharmaceuticals, dental cements, storage batteries, electrical equipment, and piezoelectric devices. Other applications are as a flame retardant, as a UV absorber in plastics, and a reagent in analytical chemistry. A major application of zinc oxide is in the preparation of most zinc salts. In medicine, the compound is used as an antiseptic, an astringent and a topical protectant. 

Ester polymers of methacrylic and acrylic acid are important in a wide range of applications. They are used in dental materials, glazing, adhesives, plastic bottles, elastomers, floor polishes, paint bases, plastic films, and leather finishes, to mention only a few. 

MAJOR PRODUCT APPLICATIONS exterior paints, coatings, synthetic plastering compounds, thermoplastic road marking compounds, adhesives, sealants, plastics, abrasives, cables, stucco, kitchen sinks and laminates, dental, mihtary, electronics... 

MAJOR PRODUCT APPLICATIONS paints, coatings, rubber, abrasive polishes, cleaning waxes, seed coatings, anticaking agent, antiblock applications, pesticide formulations, asphalt extender, automotive windshields, catalyst support, concrete additive, dental molds, drilling mud, filter papers and pads, specialty p ers, paperboard, foundry, waste disposal aids, stucco, battery boxes, plastic film... 

Most material studies reported in medical journals are of interest to those involved in mainstream plastic applications. Some medical plastics must perform under constant water immersion. It was reported that absorption of 1 % water reduces the fatigue life of PMMA by a factor of four, since bone cement can only be replaced by a surgical operation such a performance is clearly unacceptable. The use of silane to treat the hydroxyapatite filler in this material reduced water uptake. The water uptake increased with increased concentration of hydroxyapatite. In applications, such as dental fillings, increased water uptake is considered helpful since it compensates for the loss of volume due to shrinkage of the filling during curing. 

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