Composite resins sealants

Since this time, there have been numerous studies to compare the clinical effectiveness of glass-ionomer cements with that of composite resin sealants. These have typically determined the relative retention rates, and they have usually found that glass-ionomer sealants show inferior performance [149]. However, when caries rate in teeth are compared it turns out that glass-ionomers are at least as effective as composite resins [150,151]. It has been suggested that this is due to retention of glass-ionomer cement deep within the fissure and also because of the fluoride release into the enamel prior to the loss of the bulk cement [1]. 

Bisphenols is a broad term that includes many chemicals with the common chemical structure of two phenolic rings joined together by a bridging carbon. Bisphenol A is a monomer widely used in the manufacture of epoxy and phenolic resins, polycarbonates, polyacrylates and corrosion-resistant unsaturated polyester-styrene resins. It can be found in a diverse range of products, including the interior coatings of food cans and filters, water containers, dental composites and sealants. [4]. BPA and BP-5 were selected for testing by the whole... 

The main application of composite resins in contemporary dentistry is as direct repair materials in a variety of cavities teeth [117] and it is estimated that 95% of all anterior restorations and 50% of all posterior restorations are now made with composite resin [118], In addition, they are also being increasingly used as indirect repair materials for a number of uses, including as onlays and inlays [119], and as fissure sealants. 

Polyacid-modified composite resins are aimed to be used in similar applications to conventional composites, such as Class II [44] and Class V cavities [45,46], and fissure sealants [47], They have also been used as bonding agents in orthodontics [48]. 

Polyacid-modified composite resins have been evaluated for other clinical applications. For example, they have been found to perform well as sealants for pits and... 

PMMA and other methacrylate and acrylate polymers are widely used in dentistry. PMMA is used for dentures and root canal sealants. Polymers of 2,2-bis[4-(2-hydroxy-3-methacry-loyolxypropoxy)phenyl]propane (BisGMA), triethyleneglycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) are used in dental composite resins, most commonly with a silica filler. Such composite resins are used for filling cavities, reshaping, and restoring teeth and for full and partial crowns. 

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). 

Uses monofunctional methacrylic monomer in dental composites and sealants UV-curable resins for inks etc. A... 

The largest voliune of polsrmeric materials used in dentistry is in prosthetic applications. Polymeric materials are also important in operative dentistry, being used to produce composite resins, dental cements, adhesives, cavity liners, and as a protective sealant for pits and fissures. Elastomers are employed as impression materials. Resilient prosthetic devices are oft en fabricated to restore external soft-tissue defects. Mouth protectors are fabricated to prevent injury to teeth, as well as prevent head and neck injinaes. Other polymer applications include fabricating patterns for metal castings and partial denture frameworks, impression trays, orthodontic and periodontal devices, space maintainers, bite plates, cleft palate obdurators, and oral implants. Polymeric materials may also be used to fabricate an artificial tongue, when disease results in its loss. 

Composite Restoration Seaiants. Systems nsed in this case consist essentially of dimethacrylate mononers, such as BisGMA, homologues of BisGMA, urethane dimethacrylate, and silanated inorganic fillers, as discnssed in the section on Composite Resins. The sealants used for restorations (called bonding agents) are applied onto the cavity walls prior to the placement of composites and bond the two substances tightly. 

Sung Gun Chu, chemist, received a Ph.D. degree in physical polymer chemistry from the University of Texas at Austin in 1978. His main interests are in the property-structure processing relations of polymeric materials, and the rheology of polymers. Since Dr. Chu began work at Hercules in April 1981, he has been involved in the study of adhesives and sealants. He is also involved in the development of new, tough matrix resins for graphite composite applications, has published over 20 papers, and has several patents on adhesives and composite resins. He is presently a Project Leader in Adhesives at the Hercules Research Center. 

Modern resin-based restorative materials used in stomatology originated with the invention of the so-called Bowen s monomer and the introduction of composites [142]. This monomer is known as BisGMA, a label easier to use than chemical name of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane.Today, both unfilled and composite resins are widely employed in dentistry—as binding agents, pit and fissure sealants, direct filling materials, orthodontic adhesives, and resin cements [143]. 

For some time, the material of choice was considered to be an unfilled resin, essentially a low viscosity blend of the type of monomers used in conventional composite resins. Such fissure sealants have good retention, which is obviously highly desirable. 

There is a need to further enhance the durability of dental composite restorative and sealant materials. Dimethacrylates such as BIS-GMA (the diadduct of bisphenol A and glycidyl methacrylate) are now widely used to formulate the resin component of these materials. Some of the deficiencies of dental composites and sealants are traceable to impurities and inherent structural imperfections in the monomer systems. Structure-property studies are needed to explore ways of achieving minimal shrinkage on polymerization, reducing water sorption, promoting adhesion, generally optimizing the chemical,... 

Harmful Effects of Near-Ultraviolet Radiation Used for Polymerization of a Sealant and a Composite Resin", D. C. Birdsell, P. J. Gannon, and R. B. Webb, J. Am. Dent. Assn., 94, 311 (1977)... 

Hydrocarbon resins are used extensively as modifiers in adhesives, sealants, printing inks, paints and varnishes, plastics, road marking, flooring, and oil field appHcations. In most cases, they ate compounded with elastomers, plastics, waxes, or oils. Selection of a resin for a particular appHcation is dependent on composition, molecular weight, color, and oxidative and thermal stabiHty, as weU as cost. A listing of all hydrocarbon resin suppHers and the types of resins that they produce is impractical. A representative listing of commercially available hydrocarbon resins and their suppHers is included in Table 6. 

Thermosetting resins have been used extensively in industry for applications such as structural adhesives, composites, RIM, coatings and sealants which need to resist severe service conditions. Thermosetting resins are generally composed of low molecular weight oligomers which allow fabrication convenience. 

Construction. Polymeric materials such as adhesives, sealants, and composites have been used considerably in the last several decades for the construction, repair, and rehabilitation of our transportation infrastructures. Even though most processes were experimental until recently, they have evolved to the point where many are now standardized and well accepted. Table 1.6 hsts several common applications for advanced polymeric materials (as well as the polymeric resins that are most commonly employed). In the construction or repair of roads and bridges, epoxy adhesives have primarily been used for bonding concrete and for bonding stiffening members or repair structures to degrading concrete facilities. 

In the aerospace industry, resinous polymers encompass a wide variety of hardware applications for aircraft, missiles, and space structures. In aircraft, resins are used as a matrix material for primary (flight-dependent) and secondary fiber-reinforced composite (FRC) structures, adhesives for the bonding of metal and composite hardware components, electronic circuit board materials, sealants, and radomes. Missile applications include equipment sections, motor cases, nose cones, cartjon-carbon composites for engine nozzles, adhesive bonding, and electronics. As the exploration of outer space intensifies, applications will become even more exotic. FRC will be used to construct telescopes, antennas, satellites, and eventually housing and other platform structures where special properties such as weight, stiffness, and dimensional stability are important. 

Drying sealants are represented by solutions of rubber blends in organic solvents. As soon as the solution is impregnated into the clearance and the solvent evaporates, the sealant becomes rubbery and gains elasticity. The original compositions contain adhesive additives (coumarone, terpenic and phenolic resins, rosin or its esters), PI and solvents (toluene, xylol, benzine, etc.), fillers (chalk, titanium dioxide, talc, etc.) and stabilizers. These compositions can be easily impregnated with Cl [15]. 

Polybutenes have heen used for almost a century and while they are still used, most of this type sealant contains butyl rubber, which is a copolymer of butene and isoprene. Most building specifications, including Federal Specification, TT-S-001637, require solutions of butyl rubber instead of oil-based caulking compositions. Self curing butyl rubber sealants may contain phenolic resins,IS. resorcinol and hexamethylenetetramine. ... 

Polysulfides are used in synthetic rubber compositions [1], epoxy resin modifiers [2], coatings [3], adhesives [4], sealants [5], and many other products as described in recent Chemical Abstract issues. 

It was not until the commercialization of synthetic plastics resins in the 1930s that an almost unlimited variety of base materials became available for compounding into adhesives and sealants. Most of the thermoplastic resins were soluble in organic solvents and were used as solvent adhesives for molded plastic articles of the same base composition and sometimes for other materials. Poly(vinyl chloride) (PVC), a thermoplastic developed in 1927, is used today in solvent formulations to bond PVC articles such as coated fabrics, films, foams, and pipe. In the early 1930s, phenolics came into importance as adhesive resins. Before that time they were used as coating varnishes [9, p. 239). About 1931 development of the use of a new phenolic resin for plywoods and veneers began [9, p. 239]. 

Thermoplastic rubber block copolymers, with completely new adhesive performance, were developed in 1965 [21]. The first commercial product was Shell Chemical s Kraton 101, of styrene polybutadiene-styrene composition. This development led to the carboxy-terminated nitrile (CTBN) rubber modifiers used to flexibilize epoxy and other brittle resin adhesives in the late 1960s. Today, the thermoplastic rubber block copolymer adhesives are used in hot melt-, solvent- and water-based adhesives, and as hot melt- and solvent-based sealants. Major applications are as pressure-sensitive adhesives, construction adhesives and sealants, and general assembly adhesives. 

Sealant adhesion is improved by the incorporation of additives. Typical phenolic resin additives are Methylon AP-108, Durez 16674, Bakelite BRL 2741, and Resinox 468. Epoxies are also good adhesion promoters. Silanes (e.g., A-187 and A-189) are known to increase adhesion. Table 1 lists five types of sealant formulations suggested by Panek that are useful in several end applications [10]. Generally, the integral fuel tank polysulfide sealant consists of two parts 9 parts by weight of sealant base components mixed with 1 part by weight of accelerator. A typical composition is shown in Table 2. 

H.C. Gungor, N. Althay, R. Alpar, Clinical evaluation of a polyacid-modified resin composite-based fissure sealant two-year results, Oper. Dent. 29 (2004) 254—260. 

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