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Current Status and Role of Dental Polymeric Restorative Materials
Published in Mary Anne S. Melo, Designing Bioactive Polymeric Materials for Restorative Dentistry, 2020
Haohao Wang, Suping Wang, Xuedong Zhou, Jiyao Li, Libang He, Lei Cheng
Amalgam, a traditional material of dental restorations, has been successfully used for over 150 years and is still the choice in some places of the world because of its effectiveness and low cost (Spencer 2000). Amalgam mainly consists of liquid mercury with an alloy made of silver, tin, copper, and zinc solid particles (Anusavice et al. 2013). When mixing, the mercury and the alloy toundergo an amalgamation reaction and gradually condense and harden, forming a silver-grey mass (Anusavice et al. 2013). Because the material’s color differs from a natural tooth’s color, as illustrated in Figure 2.1, amalgam is mostly used for permanent posterior restorations. In long-term clinical application, amalgam showed higher longevity compared to composites (Moraschini et al. 2015). This may be because amalgam has a potential antimicrobial effect by releasing toxic mercury and results in low viability of oral biofilms on its surfaces (Busscher et al. 2010). However, the release of mercury is also the primary concern preventing the use of amalgam. An increasing attention has been paid to the risk of mercury exposure from amalgam and the potential adverse effects (Reinhardt 1988).
Mercury in Dentistry
Published in Dag K. Brune, Christer Edling, Occupational Hazards in the Health Professions, 2020
Metallic mercury appears in three forms: solid, liquid, and vapor. Mercury is the only common metal liquid at room temperature. It easily forms alloys with many metals, such as gold, silver, and tin, which are called amalgams. Dental amalgam is made by mixing alloy powder and mercury. Conventional amalgam is formed by mixing metallic mercury (ratio of approximately 1:1) with an alloy powder containing about 70% silver, 25% tin, and a small amount of copper and zinc. Later a nongamma-2 amalgam with a higher copper concentration was developed. Copper amalgam alloy containing approximately 65% mercury, 30% copper, and a few percent cadmium and zinc is also available. This alloy is in limited use due to its susceptibility to corrosion.
Free Radical Polymerization of Expandable Oxaspiro Monomers
Published in Rajender K. Sadhir, Russell M. Luck, Expanding Monomers, 2020
There are many specific polymer applications where zero shrinkage or slight volume expansion would be warranted. Precision castings, potting resins, and high strength adhesives are just a few examples of the areas where expanding monomers could have a significant impact. One application which can well utilize the potential advantages offered through ring-opening polymerization is that of dental composite filling materials. The use of aesthetic composites in tooth restoration is a technique that offers a widely accepted alternative to amalgam fillings. While effective attachment of the current polymeric systems can be achieved to etched enamel through micromechanical retention, polymerization shrinkage associated with the composite matrix is usually sufficient to compromise the tenuous bond with the underlying dentin.54,55 The result is the introduction of a marginal gap which can provide an avenue for staining as well as secondary caries formation.56
The management of mercury from dental amalgam in wastewater effluent
Published in Environmental Technology Reviews, 2021
Simon D. Fairbanks, Sumit Kumar Pramanik, Jim A. Thomas, Amitiva Das, Nicolas Martin
Although dental amalgam is being gradually phased down and replaced by mercury-free alternatives in agreement with the Minamata Convention [11], it remains one of the main restorative filling materials applied in the reconstruction of teeth affected by caries, especially in developing economies. Dental amalgam is composed of approximately 50% mercury, estimated by Danish data to be equivalent to 0.4–1.2 g of mercury per filling [12]; the remaining proportion being an alloy of mainly silver, tin, copper and other trace elements. The rationale for the use of mercury as the main constituent of dental amalgam is that it remains in a liquid state within a very wide temperature range (−38°C to 356°C), making it ideal for use at normal ambient temperatures; it is stable in air and water and can easily mix with other metals to form amalgams. Once mixed with other metals it gives a malleable paste-like substance, which the dental practitioner packs into the dental cavity and carves into its final shape. The setting reaction is an amalgamation reaction to form a hard-restorative material. Dental amalgam has been successfully employed in this application for centuries and due to its mechanical, inert, durable and cost-effective properties, it is still the predominant filling material in dental practices [13–15].
An overview of development and status of fiber-reinforced composites as dental and medical biomaterials
Published in Acta Biomaterialia Odontologica Scandinavica, 2018
Although amalgam has shown its many benefits as dental restorative material its use is ending due to environmental reasons. Treatment of damaged tooth structure involves direct resin composite restorations on the population level allowing high cost-effect ratio for the treatment outcome. Particulate filler resin composites have fulfilled direct application requirements in terms of material cost but often failed in terms of longevity of restorations made by general practitioners. One reason for the limited longevity of restorations is low mechanical strength of the particulate filler resin composite as material and inadequately adjusted occlusion, which can cause high local stress concentrations and damage the restoration. Resin composite restorations, like ceramic restorations, do not become adjusted to the occlusion like amalgam restorations did during long lasting setting reaction. Adjustment of occlusion of the resin composite and ceramic restorations must be made by the dentist with high precision.
Living Then and Now with Gold and Mercury
Published in Ambix, 2023
At 250 Water Street and 33 Liberty Street, gold and mercury live side by side. These elements are found side by side in chemistry, too. They occupy the same row in the periodic table, assigned the atomic numbers 79 and 80, respectively.7 Here, however, is where the similarity ends. Gold and mercury may have very similar atomic sizes, yet as elements they exhibit very different chemical properties.8 Gold is relatively unreactive, often occurring in nature in a metallic state.9 Due to gold’s atomic size and structure, it can change and augment the arrangement of atoms (i.e. how the atoms connect to each other) in a surprising number of ways. This ability is manifested at the macro scale as the properties of gold’s softness and exceptional malleability and ductility.10 Mercury is also exceptional in that its filled outer electron shell is more closely packed than other comparable elements. This arrangement reduces its capacity to form a metallic crystalline structure, which means it is more prone to turn into a liquid – mercury is the only metal that is a liquid at ambient room temperature.11 Mercury, moreover, will readily combine with certain other metals (e.g. gold, silver, tin) to form amalgams, and with non-metallic elements (e.g. chlorine, sulphur, oxygen) to form inorganic compounds or “salts.” Mercury will also form organic compounds, including the extremely toxic compound, methylmercury.12 But unlike most mixtures of metals, which form solid alloys, when mercury combines with certain other metallic elements, such as gold, it forms an amalgam. A mercury-gold amalgam consists of multiple small crystals made of the two metals floating in the excess mercury. The consistency of the amalgam depends on the mercury-gold ratio: the more crystals that form, the more pasty the amalgam becomes.13 When the amalgam is heated, the chemical bonds in the crystals break down and the mercury volatilises. The gold is left behind as a pure spongy mass that can be melted down and shaped and reshaped into any number of products that assume a cultural life as they circulate and recirculate around the world. The mercury, however, immediately begins to transform into different, pervasive forms that go on to penetrate human bodies, biota, and the biosphere. Mercury is everywhere, in everything.