Quantcast Physical Properties of Amalgam. - Dental Materials

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PROPERTY
INGREDIENT
Silver
Tin
Copper
Zinc
Strength
Increases
Durability
Increases
Hardness
Increases
Expansion
Increases
Decreases
Increases
Flow
Decreases
Increases
Decreases
Color
Imparts
Setting time
Decreases
Increases
Decreases
Workability
Increases
Increases
Cleanliness
Increases
Table 1-1. Effects on properties of an amalgam restoration imparted by ingredients.
d. Physical Properties of Amalgam. The most important physical properties of
amalgam are flow and creep, dimensional change, and strength.
(1)  Flow and creep. Flow and creep are characteristics that deal with an
amalgam undergoing deformation when stressed. The lower the creep value of an
amalgam, the better the marginal integrity of the restoration. Alloys with high copper
content usually have lower creep values than the conventional silver-tin alloys.
(2)  Dimensional change. An amalgam can expand or contract depending
upon its usage. Dimensional change can be minimized by proper usage of alloy and
mercury.
(3)  Compression strength. Sufficient strength to resist fracture is an
important requirement for any restorative material. At 50 percent mercury content, the
compression strength is approximately 52,000 pounds per square inch (psi). In
comparison, the compressive strength of dentin and enamel is 30,000 psi and 100,000
psi, respectively. The strength of an amalgam is determined primarily by the
composition of the alloy, the amount of residual mercury remaining after condensation,
and the degree of porosity in the amalgam restoration.
MD0502
1-6



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