Chapter 9

Question 1

Definition of alloy

Answer 1

mixture or two or more metals

Question 2

Definition of amalgamation

Answer 2

reaction that occurs when silver-based alloy is mixed with mercury

Question 3

Definition of dental amalgam

Answer 3

restorative material composed of silver-based alloy mixed with mercury

Question 4

Definition of lathe-cut alloy

Answer 4

irregularly shaped particles formed by shaving fine particles from an alloy ingot

Question 5

Definition of spherical alloy

Answer 5

alloy particles produced as small spheres

Question 6

Definition of admixed alloy

Answer 6

mixture of lathe-cut and spherical alloys

Question 7

Definition gamma-2 phase

Answer 7

chemical reaction between tin in the silver-based alloy and mercury that causes corrosion in the amalgam

Question 8

Definition of tarnish

Answer 8

oxidation affecting a thin layer of a metal at its surface

Question 9

Definition of corrosion

Answer 9

oxidation from interaction of two dissimilar metals in the presence of a solution containing electrolytes

Question 10

Definition of creep

Answer 10

gradual change in the shape of a restoration caused by compression from occlusion or adjacent teeth

Question 11

Definition of triturator (amalgamator)

Answer 11

mechanical device used to mix the silver-based alloy particles with mercury to produce amalgam

Question 12

True or False

Less than 0.01% of people have adverse reactions to amalgum

Answer 12

True

Question 13

True or False

An alloy is a mixture of two or more metals

Answer 13

True

Question 14

True or False

Modern dental alloy’s have a higher copper content compared to their predecessors

Answer 14

True (now 13-30%, previously 4-6%)

Question 15

What is the function of silver?

Answer 15

increases strength, decreases setting time, tarnishes easily

Question 16

What is the high-cu/low-cu alloy, % of silver?

Answer 16

40-70, 68-72

Question 17

What is the function of tin?

Answer 17

improves physical properties when comounded with Ag
reduces setting expansion
reduces strength

Question 18

What is the high-cu/low-cu alloy % of tin?

Answer 18

12-30 high

28-36 low

Question 19

What is the function of copper?

Answer 19

increases strength
hardness
increases setting expansion
decreases creep

Question 20

What is the high-cu/low-cu alloy % of copper?

Answer 20

10-30 high

4-6 low

Question 21

What is the function of zinc?

Answer 21

reduces oxidation of other metals

delayed expansion with moisture contamination

Question 22

What is the high-cu/low-cu alloy % of copper?

Answer 22

0-1 high

0-2 low

Question 23

True or False

High-copper amalgams do not have a gamma-2 phase and are superior in their clinical performance

Answer 23

True

Question 24

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

Answer 24

True

Question 25

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

Answer 25

True

Question 26

What is the compression MPA of amalgams?

Answer 26

400-450

Question 27

True or False

Under triturated alloy has a dry, crumbly appearance and sets too quickly

Answer 27

True

Question 28

True or False

Over triturated alloy is too wet

Answer 28

True

Question 29

How much mercury vapor is released daily from amalgam?

Answer 29

1-2 mcg / day

Question 30

The acceptable level of exposure to mercury is?

Answer 30

0.05 mg for a 40 hour work week

Question 31

True or False

Heating of amalgam to 800 degree Celsius causes a release of free mercury vapor

Answer 31

True