expansion (redirected from Thermal expansion)

expansion /ex·pan·sion/ (ek-span´shun)

1. the process or state of being increased in extent, surface, or bulk.

2. a region or area of increased bulk or surface.

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clonal expansion  an immunological response in which lymphocytes stimulated by antigen proliferate and amplify the population of relevant cells.

dorsal digital expansion , extensor expansion extensor aponeurosis; a triangular aponeurotic extension of the digital extensor tendon on the dorsum of the proximal phalanx of each digit, to which the tendons of the lumbrical and interosseous muscles are also attached, forming a movable hood around the metacarpophalangeal joint.

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ex·pan·sion (k-spnshn)

n.

1. An increase in size.

2. The spreading out of a structure, such as a tendon.

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expansion,

n an increase in extent, size, volume, or scope.

expansion, delayed (secondary expansion),

n 1. an expansion occurring in amalgam restorations as a result of moisture contamination.
n 2. an expansion exhibited by amalgam that has been contaminated by moisture during trituration or insertion.

expansion, dental arch,

n the therapeutic increase in circumference of the dental arch by buccal or labial movement of the teeth.

expansion, hygroscopic,

n an expansion, caused by absorption of water during setting of an investment, used to compensate for the shrinkage of metal from the molten to the solid state.

expansion, secondary,

n See expansion, delayed.

expansion, setting,

n an expansion that occurs during the setting or hardening of materials such as amalgam and gypsum products.

expansion, thermal,

n an expansion caused by heat. Thermal expansion of the mold is one of the important factors in achieving adequate compensation for the contraction of cast metal when it solidifies.

expansion, thermal coefficient,

n a number indicating the amount of expansion caused by each degree of temperature change. The rate of change in restorative materials and tooth substance should be relatively the same.