Chapter 9 Flashcards
Definition of alloy
mixture or two or more metals
Definition of amalgamation
reaction that occurs when silver-based alloy is mixed with mercury
Definition of dental amalgam
restorative material composed of silver-based alloy mixed with mercury
Definition of lathe-cut alloy
irregularly shaped particles formed by shaving fine particles from an alloy ingot
Definition of spherical alloy
alloy particles produced as small spheres
Definition of admixed alloy
mixture of lathe-cut and spherical alloys
Definition gamma-2 phase
chemical reaction between tin in the silver-based alloy and mercury that causes corrosion in the amalgam
Definition of tarnish
oxidation affecting a thin layer of a metal at its surface
Definition of corrosion
oxidation from interaction of two dissimilar metals in the presence of a solution containing electrolytes
Definition of creep
gradual change in the shape of a restoration caused by compression from occlusion or adjacent teeth
Definition of triturator (amalgamator)
mechanical device used to mix the silver-based alloy particles with mercury to produce amalgam
True or False
Less than 0.01% of people have adverse reactions to amalgum
True
True or False
An alloy is a mixture of two or more metals
True
True or False
Modern dental alloy’s have a higher copper content compared to their predecessors
True (now 13-30%, previously 4-6%)
What is the function of silver?
increases strength, decreases setting time, tarnishes easily
What is the high-cu/low-cu alloy, % of silver?
40-70, 68-72
What is the function of tin?
improves physical properties when comounded with Ag
reduces setting expansion
reduces strength
What is the high-cu/low-cu alloy % of tin?
12-30 high
28-36 low
What is the function of copper?
increases strength
hardness
increases setting expansion
decreases creep
What is the high-cu/low-cu alloy % of copper?
10-30 high
4-6 low
What is the function of zinc?
reduces oxidation of other metals
delayed expansion with moisture contamination
What is the high-cu/low-cu alloy % of copper?
0-1 high
0-2 low
True or False
High-copper amalgams do not have a gamma-2 phase and are superior in their clinical performance
True
True or False
When the alloy in powder form is mixed with the liquid mercury, a chemical reaction occurs, the mixture has a pulp like consistency
True
True or False
The first phase, called the gamma phase, is the silver alloy phase. It is the strongest phase and has the least corrosion
True
What is the compression MPA of amalgams?
400-450
True or False
Under triturated alloy has a dry, crumbly appearance and sets too quickly
True
True or False
Over triturated alloy is too wet
True
How much mercury vapor is released daily from amalgam?
1-2 mcg / day
The acceptable level of exposure to mercury is?
0.05 mg for a 40 hour work week
True or False
Heating of amalgam to 800 degree Celsius causes a release of free mercury vapor
True
