Dental applications, acrylic resins

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 low polymerization shrinkage of cycloolefins which is typically <5% (e.g. ca. 4% for DCPD polymerization), compared with >10% for acrylate and methacrylate polymerization, makes PROMP systems attractive for stereolithography or dental applications. Indeed we could formulate stereolithographic resins, which were laser cured by PROMP. However, the lack of an appropriate quenching mechanism (once initiated, the polymerization continues even in the absence of light and leads finally to... 

There are many types of acrylated urethanes on the market. While some are based on aromatic isocyanates, others are of the aliphatic type. Acrylated urethanes are used not only in prepolymers in UV-curable inks or coatings, for example vinyl floorings, but also as resins with dental applications. The acrylated urethanes used in dentistry are of the methacrylated type. 

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-... 

GC alone can be a valuable monomer for the synthesis of hyperbranched poly(hydroxyether)s (Scheme 25). In case of polymerization, GC, containing a l,3-dioxolan-2-one ring and hydroxyl group in a single molecule, is considered a latent cyclic AB2-type monomer. The anionic ROP of the GC, which proceeds with CO2 liberation, leads to a branched polyether. l,l,l-Tris(hydroxymethyl)propane or other multihydroxyl molecules are usually used as a initiator-starter and central core of the polyether. The hyperbranched polyglycerol structure is obtained by slow addition of the cyclic carbonate monomer at above 150 °C. Such polymers are characterized by a flexible polyether core and a multihydroxyl outer sphere. They are suitable for preparation of acrylic resins for dental applications or additives for polyurethane foams. Hyperbranched poly (hydroxyether)s from biscyclic carbonate with phenol group (2, Scheme 24) were also reported. 

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. 

In the 1960s, the photopolymerization of polyol acrylates found a variety of applications in dentistry, including dental composite resins, adhesives, dentures, and... 

The formation of networks by addition polymerization of multifunctional monomers as minor components included with the monofunctional vinyl or acrylic monomer is industrially important in applications as diverse as dental composites and UV-cured metal coatings. The chemorheology of these systems is therefore of industrial importance and the differences between these and the step-growth networks such as amine-cured epoxy resins (Section 1.2.2) need to be understood. One of the major differences recognized has been that addition polymerization results in the formation of microgel at very low extents of conversion (<10%) compared with stepwise polymerization of epoxy resins, for which the gel point occurs at a high extent of conversion (e.g. 60%) that is consistent with the... 

Dental composite resins (DCRs) based on bisphenol A and (meth)acrylates, e.g. BIS-GMA, have been used since 1962 (Bowen 1962). In addition to acrylics, DCRs contain additives that trigger polymerisation at an appropriate time. These additives include initiators, e.g. benzoyl peroxide, activators, e.g. tertiary aromatic amine, and inhibitors, e.g. hydroquinone they are aU sensitizers (Kanerva et al. 1989). Sensitisation from epoxy acrylates has been reported in dental personnel (Kanerva et al. 1989) and in the ultraviolet (UV) or light-printing industry (Nethercott et al. 1983 Bjorkner 1984). Acrylated urethanes are allergens. They are used in dental composite and sealant applications and have the same role as BIS-GMA (Nethercott et al. 1983 Bjorkner 1984). 

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