Dental-filling alloys

Dental-filling alloy Solid Solution of a liquid (Hg) in a sohd (Ag plus other metals)... 

Solid solutions are also possible. In the chapter opening, we mentioned gold-silver alloys. Dental-filling alloy is a solution of mercury (a liquid) in silver (a solid), with small amounts of other metals. 

Hakansson, B., Yontchev, E., Vannberg, N.-G. and Hedegard, B. An Examination of the Surface Corrosion State of Dental Fillings and Constructions. 1. A Laboratory Investigation of the Corrosion Behaviour of Dental Alloys in Natural Saliva and Saline Solutions , Journal of Oral Rehabilitation, 13, 235-246 (1986)... 

Daniel Gray perfected a stable bath from which indium can be plated simultaneously with other elements (90). Alloyed with precious metals, indium has been made into jewelry, alloyed with silver, it is sometimes used to plate silverware with a suiface resistant to tarnish in the form of an amalgam, it can be used for dental fillings (88, 89, 93) The portraits of Reich and Richter and much of the information about indium have been obtained through the kind assistance of Professor L. W. McCay of Princeton University and Professor O. Brunck, Rectoi of the Freiberg Academy. 

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... 

Heterogeneous alloys include tin-lead solder and mercury amalgams for dental fillings. 

In another type of mixture, the boundaries between the substances cannot be seen. This is called a homogeneous mixture. Its composition is uniform throughout. Homogeneous mixtures are also called solutions. Solutions are crucial to life and to many processes. We often encounter them in daily life. The air we breathe, our soft drinks, the amalgam used in dental fillings, the alloys used in the production of cars, the fog that causes traffic jams, coins, seas, lakes, and even our own body fluids are solutions. 

Solutions include different combinations in which a solid, liquid, or gas acts as either solvent or solute. Usually the solvent is a liquid. For instance, sea water is an aqueous solution of many salts and some gases such as carbon dioxide and oxygen. Carbonated water is a saturated solution of carbon dioxide in water. Solutions are common in nature and are extremely important in all life processes, in all scientific areas, and in many industrial processes. The body fluids of all forms of life are solutions. Variations in concentrations of our bodily fluids, especially those of blood and urine, give physicians valuable clues about a person s health. Solutions in which the solvent is not a liquid are also common. Air is a solution of gases with variable composition. Dental fillings are solid amalgams, or solutions of liquid mercury dissolved in solid metals. Alloys are solid solutions of solids dissolved in a metal. 

Progressive dental reconstructions within the life-time of a patient, and in particular the use of different alloys for total or partial dentures, for dental fillings, for porcelain-fused restorations, and transcutaneous implants, generate unavoidable oral polymetallism. Indeed, two alloys of different composition have different electric potentials and inevitably induce corrosion and subsequently the release of metal ions into the human organism (Bundy 1994 Homez et al. 2000). 

Products and Uses A mixture of mercury with silver tin alloy in dental fillings, and for silvering mirrors. It is also a binder for precious metals such as gold and silver. 

Amalgams are alloys of mercury with other metals used extensively as chemical reagents and catalysts. The proportion of mercury dictates whether the amalgam is solid or liquid. They include sodium amalgam (Na Rgy), used to manufacture sodium hydroxide, and dental amalgams (alloys of mercury with some combination of silver, copper, tin, gold, or silver) used to fill dental cavities. 

An amalgam is a mixture or alloy of mercury with another metal. For many years silver amalgams were used in dental fillings. 

Biomaterials are synthetic or natural materials that are in contact with biological tissues or fluids and may enhance or replace tissues, bones, organs, or body functions (4). They include metals, alloys, glasses, ceramics, natural or syndetic polymers, biomimetics, and composites. Typical biomaterials may be used in artificial skin, tissues, and bones, dental fillings, wire plates and pins for bone repair, artificial hips and joints, implantable drug delivery systems, and other dental, surgical, and medical devices. New and improved biomaterials continue to be sought... 

The tendency of mercury to form amalgams has been utilized in dentistry. An amalgam for dental fillings may be composed of 52% mercury, 35% silver and 13% tin. It is prepared by stirring a silver-tin alloy into mercury. The mixture is vibrated to a plastic mass, which is placed in the bored tooth and compressed. 

Amalgams are alloys that contain mercury. They are soft and pliable when first produced, but later become solid and hard. Dental fillings were once made of an amalgam of mercury and silver. Concerns about the possible toxicity of mercury led to the development of other filling materials. 

Heterogeneous alloys include tin-lead solder mercury amalgams (once used for dental fillings) and Bi/Cd, which melts over a range of temperatures, except for one composition (eutectic), which melts at a fixed temperature like a pure compound. 

Dental amalgams, mainly silver—tin—mercury alloys, have been used as fillings for many years (see Dental MATERIALS). The most common alloy contains 12 wt % tin. 

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