Denture base resins

Table 12. Physical Properties of Denture-Base Resins...

Requirements for heat- and cold-curing denture-base resins prepared from powder—liquids, gels, preopolymerized blanks, and fluid resins composed of acryflc, vinyl, and polystyrene polymers are given in ANSI/ADA specification no. 12 for denture-base polymers. 

Fissure sealants are clear, low-viscosity, photocurable liquids, based on a mixture of fefrafunctional and difuncfional mefhacrylafes. Other dental photocurable materials are cements, adhesives, and denture base resins. " ... 

Thermal analyses of other dental polymers have also been reported. The compositions of waxes have been studied by differential thermal analysis (DTA) [64-66] and DMA [67], Conventional DSC and DMA recently showed the superiority of microwave-processed denture base resins to those processed by the slower traditional dental laboratory heating regimen [68], In contrast, comparisons of Tg and other relevant properties for a soft denture liner that was processed by the dental laboratory procedure and a more convenient chairside procedure indicated that both procedures yielded equivalent results [69],... 

Lassila, L. V. Mutluay, M. M. Tezvergil-Mutluay, A. Vallittu, P. K. Bond strength of soft liners to fiber-reinforced denture-base resin. J. Prosthodont., 2010,19(8), 620-624. 

In conclusion, the porosity, hardness, and strength of microwave cured acrylic resins that are processed for less than 5 min exhibited no significant differences in properties when compared with conventionally polymerized resins [60-63]. However, the investigation of color stability of several commercially available heat-cured, quick heat-cured denture and microwave cured denture base resins (tested exclusively under microwave conditions) revealed that the materials demonstrated differences in color stability, but the standard heat-cured materials treated under microwave irradiation exhibited color changes that were negligible [64]. 

For a long time, denture base systems relied completely on the use of metallic materials. The first non-metalUc denture base material. Vulcanite, was introduced in the 1850s, and served as a denture base system for almost 100 years, when it was then replaced by poly(methyl methaaylate) (PMMA). Although PMMA was first developed in 1931 [93], the first commercially available product was not manufactured until 1935. PMMA for denture base resins is usually maiketed as pre-polymerized beads of 35-200 p,m in diameter, and cured via emulsion polymerization, whereby the methyl methacrylate (MMA) monomer, supplied as a liquid, is mixed with powder forming a dough upon initiation of curing, which will proceed via addition polymerization as reinforcements, small proportions of other alkyl methacrylates (ethyl or butyl) may be added to copolymerize with MMA. Other modifications to... 

Vaidyanathan, J., and Vaidyanathan, T. K., 1995, Dynamic mechanical analysis of heat, microwave and visible ligh cure denture base resins. J. Mater. Sci. Mat. Med. 6 670-674. 

A new denture base resin system which has an unusually high hydrophilic character has been marketed. This material consists, evidently, of a conventional poly(methyl methacrylate) and a monomer composition containing both methyl methacrylate and 2-hydroxyethyl methacrylate. 

Prosthetic composites (crown and bridge veneers and denture base resins) (5) are discussed elsewhere in this volume (6,7). It... 

Medicine. The polymethacrylates have been used for many years in the manufacture of dentures, teeth, denture bases, and filling materials (116,117) (see Dental materials). In the orthodontics market, methacrylates have found acceptance as sealants, or pit and fissure resin sealants which are painted over teeth and act as a barrier to tooth decay. The dimensional behavior of curing bone-cement masses has been reported (118), as has the characterization of the microstmcture of a cold-cured acryUc resin (119). Polymethacrylates are used to prepare both soft and hard contact lenses (120,121). Hydrogels based on 2-hydroxyethyl methacrylate are used in soft contact lenses and other biomedical appHcations (122,123) (see Contactlenses). 

Sticky waxes are used as thermoplastic cements. The broken pieces of a plaster impression are reassembled and held in position with sticky wax. Broken denture bases may be held in proper alignment for repair. Orthodontic apphances may be assembled with a sticky wax prior to investing and soldering. Plaster splints may be sealed to stone models in the production of porcelain or resin facings. Thus, sticky wax is useflil in almost any operation where it is desired to position and hold several small pieces in a temporary relationship. 

Dentures require accurate fit, reasonable chewing efficiency, and lifelike appearance (189). The chewing efficiency of artificial dentures is one-sixth that of natural dentition (190). AcryHc resins are generally used as powder/Hquid formulations for denture base, bone cement, and related appHcations. Polymerization is achieved thermally using initiators photochemicaHy using photoactive chemicals and either uv or visible light irradiation and at ambient temperatures using initiator/activator systems. 

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. 

Radiopaque materials are used to determine the location of aspirated dentures and fragments (205,206). Opacifying additives include barium sulfate, barium fluoride, barium or bismuth glasses, and brominated organic monomers and polymers. The incorporation of these additives into the resin base or tooth can adversely affect physical properties. Radiopaque materials meeting the requirement for ANSI/ADA specifications for denture-base polymer have been described (207). 

Silicone reliners are supplied as either a one-component system that cures in the presence of moisture or heat, or a two-component system containing base and catalyst. Both types adhere poody to denture base and carmot be polished satisfactorily. Some silicones support propagation of bacteria such as Candida albicans. Acrylic-based sifloxane monomers and resins have been proposed for overcoming these deficiencies (211). 

Soft reliners can weaken the strength of the heat-cured resin, because they reduce the thickness of the denture base and allow the diffusion of the monomer or solvent from the reliner into the base. Reflned dentures stain readily and are difficult to clean. A polyphosphazine fluoroelastomer has also been developed in an attempt to overcome the deficiencies of available liners (218). 

Almost all denture bases are made of methacrylic (acrylic) resins, which give a good fit and a natural appearance. A compression molding process is used where the monomer-polymer dough or slurry contain PMMA or poly(methyl acrylate). Often, there is a change in the contour of the soft tissue and a liner is fitted onto the denture base. Silicon reliners are often used for this purpose. 

Caprolactone is claimed as a component in one-paste-type resin compositions for denture bases <2002JPP2002104912> and e-caprolactone copolymers are suggested as components in polyurethane-based multilayered artificial leather sheets <2004JPP2004250808, 2004JPP2004250809>. 

Sano, M., Negishi, M., Yamamoto, S., Baba, K., Kobayashi, S., 2005. Comparison of the water absorption characteristics of denture bases produced with sulfone and resin. J. Nippon Acad. Dental Tech. 26 10-15. 

Most of the dental composite resin materials and denture-base polymers are diluted with the less viscous difunctional acrylates. These are the met-hacrylic monomers of which EGDMA, DEGDMA, triethylene glycol dimethacrylate (TREGDMA) (Fig. 3) and 1,4-butanediol dimethacrylate (BUDMA) (Fig. 4) are the most widely used (Table 2). The use of acrylates in dentistry is an expanding field. Some are... 

More recently, Al Doori et al. studied microwave and conventional polymerization of denture base acrylic materials in respect of their molecular weights, conversion of monomer and porosity [54]. For this purpose, four commercially available resins that contained benzoyl peroxide as an initiator were compared while a household microwave oven was applied as a microwave source. It was found that molecular weight values of polymerized materials cured under microwave irradiation and in a water bath were essentially the same. Moreover, the conversion of monomer under microwave conditions was substantial, but minimum residue... 

Technique, J. Dental Res. 53(3), 1074 (1974). IPNs as denture-base materials. Celanese Coatings Company, Resin Compositions, Br. Pat. 1,205,682 (1970). Unsaturated polyester-styrene/epoxy SIN. 

Medicine. For years, dentures, dental fillings, and denture bases have been made using methacrylic ester polymers (129,130) (see DENTAL Materials). These polymers can also be used to prevent tooth decay in natural teeth by serving as a barrier which can be coated over the surface of the tooth. The dimensional behavior of these bone-cement composites has been reported (131) as has the structure of the cold-cured acrylic resin (132). Both hard and soft contact lenses have been made using polymethacrylates (133,134). hHYDROGELS (qv) comprising poly(2-hydroxyethyl methacrylate) are used in soft contact lenses (135,136). 

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