Teeth amalgam filling

The lower limit of quantitation is 0.5 ng/L (parts per trillion). To measure such small quantities requires extraordinary care at every stage of analysis to prevent contamination. Mercury amalgam fillings in a worker s teeth can contaminate samples exposed to exhaled breath. 

Fig. 3. H SPI images of human teeth a. shows a three-dimensional maximum intensity image of a 64 data set, TR, 100 ms b. is a slice from the same tooth, taken just below the cusp c. shows another tooth with an amalgam-filled caries. The bright areas are caries under the amalgam filling, the grey areas are healthy tooth material, and the black area the filling. Note that there is no apparent image distortion caused by the metal amalgam filling." ...

PIXE, being an ion-beam based trace-element technique, is capable of analyzing at a lateral resolution of micrometres (Malmqvist, 1986). This has been used, for example, in a study of mercury migration in teeth with amalgam fillings (Lindh and Tveit, 1980). In a more recent investigation, trace element profiles in human blood cells were determined by microPIXE (Johansson and Lindh, 1987). 

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. 

A student who has mercury amalgam fillings in some of her teeth is eating a piece of candy. She accidentally bites down on a piece of the aluminum foil wrapper and experiences a sharp sensation in her mouth. Explain what has happened in terms of electrochemistry. 

Dentistry. Mercury is used in dental amalgams for fillings in teeth (see Dental materials). Dental uses have accounted for 2—4% of total U.S. mercury consumption since 1980 and generally 3—6% before that time (3). Dental amalgams used to fill cavities in teeth are approximately 50% mercury by weight. Dental use of mercury can be expected to continue to decrease, in part because of more effective cavity prevention as well as development and increasing use of alternative dental materials such as plastics and ceramics, and increasing awareness of the environmental and health effects of mercury. 

Insolubility in water and other common solvents. No metals dissolve in water electrons cannot go into solution, and cations cannot dissolve by themselves. The only liquid metal, mercury, dissolves many metals, forming solutions called amalgams. An Ag-Sn-Hg amalgam is used in filling teeth. 

Alloys are metallic materials prepared by mixing two or more molten metals. They are used for many purposes, such as construction, and are central to the transportation and electronics industries. Some common alloys are listed in Table 5.5. In homogeneous alloys, atoms of the different elements are distributed uniformly. Examples include brass, bronze, and the coinage alloys. Heterogeneous alloys, such as tin-lead solder and the mercury amalgam sometimes used to fill teeth, consist of a mixture of crystalline phases with different compositions. 

The properties of alloys are affected by their composition and structure. Not only is the crystalline structure important, but the size and texture of the individual grains also contribute to the properties of an alloy. Some metal alloys are one-phase homogeneous solutions. Examples are brass, bronze, and the gold coinage alloys. Other alloys are heterogeneous mixtures of different crystalline phases, such as tin-lead solder and the mercury-silver amalgams used to fill teeth. 

While it feels as though all the mouth fills with this pain, in fact the pain only manifests itself through those teeth filled with metal, the metal being silver dissolved in mercury to form a solid - we call it a silver amalgam. Corrosion of the filling s surface causes it to bear a layer of oxidized silver, so the tooth filling also represents a redox couple, with silver and silver oxide coexisting. 

In the mid-1800s, Thomas Wilberger Evans (1823—1897) introduced the practice of using an amalgam of silver, which is a solution-type alloy (mixture) of mercury and silver. (Sometimes tin is also added.) In essence, the mercury is used to cement or bind the silver so that it can be used as a filling for decayed teeth. Due to the toxic nature of mercury, fillings are now made with mercury-free, nontoxic compounds. 

One silver alloy containing about 70% silver. 26% tin. 3% copper, and 1% zinc is unique in that it is used extensively by dentists in combination with mercury to fill cavities in teeth. The amalgam manufacturers supply dentists with the alloy in the form of powder (filed, or more recently, atomized). This is mixed with mercury, using from 8 to 5 parts of mercury to 5 of alloy, and the cavity is packed. In the cavity, a metallurgical reaction takes place in which the silver-tin compound in the alloy becomes a durable silver-tm-mercury compound. 

An alloy that is made of a metal dissolved in mercury is called an amalgam. A traditional dental amalgam, used to fill cavities in teeth, contains 50% mercury. Due to concern over the use of mercury, which is toxic, dentists now use other materials, such as ceramic materials, to fill dental cavities. 

Palladium amalgam is sometimes used as a filling for teeth. 

But even as recendy as the mid-20th cenmry, there was relatively litde concern about mercury metal and many mercury compounds. High school chemistry students often played with tiny droplets of mercury in the laboratory. They used mercury to coat pennies and other pieces of metal. Mercury was also widely used in dentistry. It was used to make amalgams, alloys of mercury with other metals, used to fill teeth. Most people even today are likely to have dental fillings that contain a small amount of mercury metal. The question of whether mercury is still safe to use in... 

Small amounts of silver are used in a variety of other products. For example, it is used in dental amalgams. An amalgam is an alloy in which mercury is one of the metals used. Silver amalgams work well for filling decayed teeth. They are non-toxic and do not break down or react with other materials very readily. Silver is also used in specialized batteries, cell phone covers, circuit boards, and Radio Frequency Identification Devices (RFIDs). 

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