History and Background of Dental Amalgam - Dental amalgam was used in the Tang dynasty in China and in Germany by Strockerus in the 16th century. - The use of amalgams may date even earlier in the Tang dynasty. - Amalgam was introduced to the Western world in the 19th century and faced controversies due to its mercury content. - Polish-Jewish dentists brought amalgam to the United States in 1833, but faced backlash and had to flee. - The use of amalgam caught on and by 1844, half of all dental restorations in upstate New York consisted of amalgam.

Composition and Properties of Dental Amalgam - Dental amalgam is made by mixing liquid mercury with an alloy of silver, tin, and copper particles. - The composition of the alloy particles is controlled by ISO standards. - Amalgam is used for direct, permanent, posterior restorations and large foundation restorations. - The reaction between mercury and alloy is called an amalgamation reaction. - Alloy powder is mixed with liquid mercury to produce dental amalgam. - Amalgam expands slightly on setting. - Amalgam is a mixture of metals with mercury, with major components being silver, tin, and copper. - The composition of the alloy powder is controlled by ISO standards. - Amalgam is subject to plastic deformation or creep under intra-oral stresses. - The γ2 phase of amalgam is responsible for high values of creep. - Corrosion can occur in dental amalgam due to the presence of electrolytes.

Corrosion and Mechanical Properties - Amalgam can contribute as an anode or cathode with saliva as electrolytes. - Corrosion significantly affects the structure and mechanical properties of dental amalgam. - The γ2 phase in conventional amalgam is the most reactive and forms an anode, leading to corrosion and release of mercury. - Copper-enriched amalgams have lower corrosion rates compared to conventional amalgam. - Corrosion products gather at the tooth-amalgam interface, reducing microleakage. - Amalgam restorations develop strength slowly and may take up to 24 hours to reach a high value. - Patients should avoid applying undue stress to freshly placed amalgam fillings. - Amalgam restorations are brittle and susceptible to corrosion. - Strength of set amalgam depends on alloy composition, particle size, shape, and distribution. - Heat treatment controls the characteristic properties of the amalgam.

Liners and Bases - A protective layer or liner should be placed prior to amalgam placement to reduce post-operative sensitivity. - Different lining materials containing zinc, such as zinc oxide eugenol, zinc phosphate, glass ionomer cement, zinc poly-carboxylate, and resin, can be used. - Liners act as a buffer and provide a good marginal seal for the amalgam restoration. - Liners help to seal dentinal tubules and improve the longevity of the restoration. - The use of liners is recommended to enhance the success of amalgam restorations. - Varnish can be applied to the cavity wall to provide a good marginal seal. - The varnish should be insoluble in water and composed of a resin in a volatile solvent. - The solvent evaporates, leaving the resin behind to seal the dentinal tubules. - Sealing the cavity with varnish helps to prevent microleakage and improve the longevity of the amalgam restoration. - Proper sealing techniques contribute to the success of amalgam restorations.

Dental Amalgam Toxicity and Environmental Impact - Concerns have been raised about potential mercury poisoning from dental amalgam. - Major health and professional organizations consider amalgam safe, but questions have been raised. - Acute allergic reactions to amalgam have been reported, although they are rare. - Studies on mercury vapor and dental amalgam have provided insufficient information for definitive conclusions. - Research gaps exist regarding potential neurotoxic and neuropsychological effects, co-exposure to mercury and methylmercury, and other occupational health effects. - Dental amalgam is considered relatively safe in low doses. - Amalgam vapor release through chewing is minimal and not considered a health risk. - Patients may develop allergic reactions to amalgam, and alternatives like resin composite, glass ionomer cements, and ceramic or gold inlays can be used. - Electromagnetic fields generated by MRI machines can increase mercury release, but the amount is not believed to pose a health risk. - Amalgam waste should be properly separated and disposed of to prevent environmental contamination. - In the United States, dental offices are prohibited from disposing of amalgam waste down the drain. - Dental offices are required to use amalgam separators to capture and recycle the waste material. - The U.S. Environmental Protection Agency (EPA) promulgated effluent guidelines in 2017 to regulate dental amalgam waste disposal. - The European Commission has classified amalgam waste as hazardous and requires the use of amalgam separators in dental practices. - Proper disposal of amalgam waste is necessary to prevent mercury contamination in the environment.