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Glossary of Terms

Alphabetical list of some of the more common terms in the dental alloy industry.

Annealing – Heating to and holding at a suitable temperature and then cooling at a suitable, usually rapid rate, for such purposes as reducing hardness or obtaining other desired properties.

Ductility – The ability of a metal to deform plastically without fracturing, usually measured by elongation in a tensile test.

Elongation – The increase in the gage length of a tensile specimen after fracturing.

Fusion Temperature – The temperature at which an alloy begins to melt upon heating (also known as solidus or lower end of melting range).

Grain Refiner – An element added to a metal alloy to attain finer grains and thereby reduce the probability of a brittle fracture due to concentration of grain boundary precipitates. This process is used almost universally for all commercial dental alloys.

Grain Size – A measure of the volume of the average size grain in a polycrystalline metal.

Hardness – A measure of resistance to abrasion or wear usually expressed in terms of Brinell, Rockwell, diamond pyramid, or Vickers scales.

Heat Capacity – Amount of energy required to increase the temperature of a given mass of metal by a given amount, usually expressed as calories per gram or BTU per pound.

Heat Treating – Heating and cooling an alloy in such a way as to obtain desired properties.

Liquidus – The temperature at which an alloy finishes melting upon heating.

Melting Range – The temperature span over which an alloy transforms completely from the solid state to the liquid state, the lower end of which is the solidus and upper end of which is the liquidus.

Modulus of Elasticity – A measure of the rigidity or stiffness of a metal within the elastic range, expressed as a ratio of stress to corresponding strain.

Nanotechnology – 1 The art of manipulating materials on an atomic or molecular lever to build microscopically sized components. 2. The use of nano-sized particles, 0.000000001 of a meter, in the use of materials.. See White Paper “How Is Nanotechnology Used in Radiance Porcelain?”

Quenching – Rapid cooling of a metal from a high temperature, usually by immersion in a liquid.

Rheology – A branch of science dealing with the flow of materials. See White Paper: “What is Rheology?”

Solidus – The temperature at which an alloy begins to melt upon heating.

Specific Gravity – The weight of a given volume of metal expressed in terms of a multiple of the weight of an identical volume of water.

Strain – A measure of the change in gage length of a tensile specimen when a stress is applied.

Stress – A force per unit area, usually measured in either pounds per square inch (psi) or kilopascals (kp).

Tarnish – Surface discoloration of a metal caused by a thin film of a corrosion product.

Thermal Conductivity – A measure of the rate at which heat travels through a metal.

Thermal Expansion Coefficient – A measure of the relative increase in length of a metal for a unit increase in temperature.

Ultimate Tensile Strength – The maximum strength In tension that a metal can withstand without fracturing.

Yield Strength – The stress at which a metal exhibits a specified deviation from elastic behavior.