2/1: Amalgam Flashcards
What are the benefits to amalgam?
Easy to manipulate
Can be placed in its plastic state and carved before it hardens
Excellent physical properties
Cost effective
What are the excellent physical properties of amalgam?
Strong and predictable
Self-sealing
- due to corrosion over time
What is an effective barrier against recurrent caries with amalgam?
Its self-sealing properties
What is the composition of amalgam?
From most to least
Ag, 70%, strength
Sn, 16%, expansion
Cu, 13%, strength
Zn, 1%, deoxidizer
What is amalgam an alloy of?
Silver, copper, tin, and zinc
What is amalgam mixed with?
Mercury to form an alloy that can be packed into a dental prep
What is conventional amalgam known as?
“low copper”
What does high copper amalgam contain?
9-30% copper
The presence of copper in high copper amalgam eleminates:
Gamma-2 phase, resulting in stronger restoration
What kind of amalgam do we use at the school?
High copper amalgam
What are the three phases of amalgam setting?
Gamma
Gamma-1
Gamma-2
What is gamma amalgam setting?
Tin and silver react with mercury, forms silver mercury (gamma-1) and tin mercury (gamma-2)
What kind of amalgam is strong, corrosion resistant?
Gamma
What is gamma-1 amalgam?
Silver-mercury
What amalgam is weaker, susceptible to corrosion?
Gamma-1
What is gamma-2 amalgam made of?
Tin-mercury
What amalgam is weakest, most susceptible to corrosion?
Gamma-2
What happens when you add copper to amalgam?
Creates a copper-tin phase (eta), eliminates tin-mercury gamma-2 phase
What is the equation for low copper amalgam?
gamma + mercury -> gamma + gamma-1 + gamma-2
What is the equation for high copper amalgam?
gamma + copper + mercury -> gamma + gamma-1 + CuSn
What is lathe shape?
Outdated - particles were formed by cutting a block of alloy with a lathe
What does lathe shape for amalgam result in?
Large, irregular particles
What are admixed particles?
Lathe type particles mixed with small spheres
What force do admixed particles require?
More condensation force
What type of particle is most commonly used type of amalgam?
Admixed
What kind of strength do admixed particles have?
Low early strength (1-hour)
What are examples of admixed particles?
Kerr Contour and Ivoclar valiant
What are the strength of spherical particles?
Higher early strength (1-hour) and higher 24-hour strength than admixed