Resins dental composites

The new specification for dental composite resin systems will establish criteria for both water sorption and solubility. According to the new ISO standard, these measurement are to be made on a 15x1 mm disc immersed in water for... 

Observations Typical dental composite resins contain low-viscosity dimethacrylate... 

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

MPa, compressive strength 245-303 MPa, water sorption 0.5-0.7/cm ) considerably exceeded the minimum requirement of the specification for dental composite resins (37). If low concentrations are employed in the formulations especially with DEAPAA as accelerator, the cured composites are nearly colorless. No perceptible change occurs in the color of the specimens containing a UV absorber after 24 hours exposure to a UV light source. Because of the excellent overall physical properties, nearly colorless appearance and the potentially better biocompatibility, compositions using these accelerators should yield improved restoratives. 

Dental composite resins have been worldwide utilized for the restorations in adult and young patients a careful evaluation of the interactions between the components of these materials and the host is therefore important. In this study, experiments on proliferation and differentiation have been performed to select the monomers concentrations capable of inducing cell differentiation albeit concurrently with an increased mortality, probably through a non-specific receptor-less way in an unspecific way. The experiments have been carried out using as controls both untreated and ATRA differentiated cells, the latter in order to checkout... 

Teeth with decayed regions have traditionally been restored with metals such as silver amalgam. Metallic restorations are not considered desirable for anterior teeth for cosmetic reasons. Acrylic resins and sihcate cements had been used for anterior teeth, but their poor material properties led to short service life and clinical failures. Dental composite resins have virtually replaced these materials and are very commonly used to restore posterior teeth as well as anterior teeth [Cannon, 1988]. 

Dental composite resins have become established as restorative materials for both anterior and posterior teeth. The use of these materials is likely to increase as improved compositions are developed and in response to concern over long term toxicity of silver-mercury amalgam fillings. 

In addition, some dental composite resins are based on BPA and methacrylates (e.g., BPA-GMA), and there are also initiators (mainly benzoyl peroxide), activators (tertiary aromatic amines) and inhibitors (hydroquinone), as well as certain UV-sensitisers added. 

J.L. Ferracane, Current trends in dental composite resins, Crit. Rev. Oral Biol. Med. 6 (1995)302-318. 

The majority of the polymerization of a dental composite resin occurs very quickly, typically during the 20-40 s or so of light irradiation from the dental cure lamp. However, free radicals within the material do not terminate immediately the lamp switches off. Hence they are able to continue their propagation steps for some time after this initial cure, as growing polymer molecules containing free radical centres continue to incorporate extra monomer molecules [24]. Shrinkage, which is associated with polymerization, has been shown to continue for up to 24h after initial setting [25] in a process known as post-polymerization [26]. 

K. Arakawa, Shrinkage forces dne to polymerization of light-cured dental composite resin in cavities, Polym. Test. 29 (2010) 1052-1056. 

W.D. Cook, M.P. Chong, Colour stabUity and visual perception of dimethacrylate based dental composite resins. Biomaterials 6 (1985) 257—264. 

Polyacid-modified composites were introduced into clinical use in about 1992, and aimed to combine the benefits of traditional dental composite resins with those of glass-ionomer cements [2]. Details of the latter materials are found in Chapter 6. The trivial name compomer was applied to these modified composite materials, the term being derived from the words composite ( comp- ) and glass-ionomer ( -omer ). 

One of the key features of polyacid-modified composite resins is their lack of adhesion to tooth tissnes [5]. This is a feature that they share with conventional dental composite resins, and the contrasts with the behaviour of the glass-ionomer cement. It is further evidence that these materials are essentially composite resins, and have very little of the anticipated hybrid character of composites and glass-ionomers. Bonding therefore reqnires the type of bespoke bonding agents used for conventional composite resins, together with the appropriate preparation of the freshly cut tooth surface [6]. 

To formulate a successful composite material, and in particnlar to ensnre that there is adequate stress transfer from matrix to filler phase, a conpling agent is deployed at the matrix-filler interface. The type of silane nsed for conventional dental composite resins effectively forms a mono-molecnlar hydrophobic layer on the snrface of the inorganic filler particles. In silanating the reactive ionomer glass in this way, the chemical reactivity of the glass is affected. It is no longer quite so hydrophilic, and hence is less susceptible to acid attack in the presence of moisture. 

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. 

In this investigation two classes of monomers were synthesized, nonvinyl cyclic acetals and vinyl cyclic acetals (NVCA and VGA, respectively (Figure 2)). All monomers w evaluated for their ability to homo- and copolymerize under free radical conditions. The monomers that displayed sufficient reactivity to warrant further study were then incorporated into dental composite resin systems. The diametral tensile strength (DTS) of several experimental composites were determined and compared with various controls. 

M. Uo et al. reported on a dental composite resin cured under near-infrared irradiation. They showed the following composite resin (CR). The mixture of Bis-GMA and TEGDMA was used as the base resin matrix. Bis-GMA and TEGDMA are mixed to be 2 1 in weight ratio. 

Furthermore, PMMA-Ca0-Si02 nanohybrid materials were shown to be suitable for bone cement and dental composite resin applications, due to their good bioactivity and improved mechanical properties [363]. PDMS-zirconia nanohybrids were proposed as suitable materials for tissue-implant integration purposes because they have beneficial effects on the proliferation and viability of human primary osteoblast and fibroblast cells and thus can be used as promising coatings for orthopedic trauma implants [364]. 

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... 

Jolanki R, Kanerva L, Estlander T (1995) Occupational allergic contact dermatitis caused by epoxy diacrylate in ultraviolet-light-cured paint, and bispheol A in dental composite resin. Contact Dermatitis 33 94-99... 

Jolanki R, Kanerva L, Estlander T, Tarvainen K (1997b) Skin allergy caused by organic acid anhydrides. In Amin S, Lahti A, Maibach HI (eds) Contact urticaria syndrome. CRC Press LLC, Boca Raton, FL, pp 217-224 Kanerva L, Alanko K (1998) Stomatitis and perioral dermatitis caused by epoxy diacrylete in dental composite resins. J Am Acad Dermatol 38 116-120... 

Kanerva L, Estlander T (1998) Simultaneous active sensitization to multiple chemicals. Contact Dermatitis 38 174-175 Kanerva L, Estlander T, Jolanki R (1989) Allergic contact dermatitis from dental composite resins due to aromatic epoxy acrylates and aliphatic acrylates. Contact Dermatitis 20 201-211... 

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). 

Jolanki R (1991) Occupational skin diseases from epoxy compounds. Epoxy resin compounds, epoxy acrylates and 2,3-epoxypropyl trimethyl ammonium chloride. Acta Derm Venereol Suppl (Stockh) 159 1-80 Jolanki R, Estlander T, Kanerva L (1987) Occupational contact dermatitis and contact urticaria caused by epoxy resins. Acta Derm Venereol Suppl (Stockh) 134 90-94 Jolanki R, Estlander R, Kanerva L, Tarvainen K (1992) Occupational allergic contact dermatitis caused by a finished reinforced polyester plastic product. In Proceedings of the 18th World Congress of Dermatology. New York City, June 12-18 Jolanki R, Kanerva L, Estlander T (1995) Occupational allergic contact dermatitis caused by epoxy diacrylate in ultraviolet-light-cured paint, and bisphenol A in dental composite resin. Contact Dermatitis 33 94-99... 

Kanerva L, Jolanki R, Estlander T (1986) Occupational dermatitis due to an epoxy acrylate. Contact Dermatitis 14 80-84 Kanerva L, Estlander T, Jolanki R (1989) Allergic contact dermatitis from dental composite resins due to aromatic epoxy acrylates and aliphatic acrylates. Contact Dermatitis 20 201-211 Kanerva L, Jolanki R, Tupasela O, Halmepuro L, Keskinen H, Estlander T, Sysilampi M-L (1991) Immediate and delayed allergy from epoxy resins based on digjycidyl ether of bisphenol A. Scand J Work Environ Health 17 208-215 Kanerva L, Estlander T, Jolanki R (1996) Occupational allergic contact dermatitis caused by 2,4,6-tris-(dimethylaminome5i-... 

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