Dental Alloys

Question 1

pure gold is – for use in the mouth

Answer 1

too soft

Question 2

– form natural barrier to the movement of dislocations

Answer 2

grain boundaries

Question 3

solute atom – directly for the solvent atom at the normal lattice site of the crystal

Answer 3

substitutes

Question 4

alloys are liquid – liquidous line

Answer 4

above

Question 5

– can crystalize at a constant temp (have a melting point) but not over a range of temp

Answer 5

partial solid solution

Question 6

defect known as – weakens the crystalline structure

Answer 6

dislocation

Question 7

dislocations are frequent in – such as gold

Answer 7

face centered cubic (FCC)

Question 8

FCCs:

Answer 8

Ag, Au, Cu, Pt, Pd,

Question 9

why is a fine grain desirable in a dental metal

Answer 9

high strength
but
high corrosion
low ductility

Question 10

rate of cooling controls –

Answer 10

grain size

Question 11

few nuclei, larger grains –

Answer 11

slow cooling

Question 12

more nuclei, smaller grains from –

Answer 12

rapid cooling and add grain refiners

Question 13

restricting dislocation motion makes material –

Answer 13

stronger

Question 14

3 ways to restrict dislocation

Answer 14

control grain size, alloying, strain hardening

Question 15

gold crown alloy: parent atom = gold (95%), common substitute atom

Answer 15

Cu

Question 16

substitute atoms have same –

Answer 16

crystal structure

Question 17

atomic size of parent and substitute atoms are within – of each other

Answer 17

15%

Question 18

parent and substitute atoms must have same –

Answer 18

valency

Question 19

alloys are solid – the solidus line

Answer 19

below

Question 20

alloys are – between the liquids and solidus lines

Answer 20

mixture of solid and liquid

Question 21

wide melting ranges make – difficult to cast

Answer 21

alloys

Question 22

examples of wide melting ranges

Answer 22

Au-Ag-Pt

Ag-Pd

Question 23

partial solid solution: liquids and solidus lines meet at –

Answer 23

eutectic composition

Question 24

partial solid solution behaviors like a – at eutectic composition

Answer 24

pure metal

Question 25

alloy at eutectic composition

Answer 25

eutectic alloy

Question 26

eutectic alloy has a melting temp –

Answer 26

lower than either pure components

Question 27

eutectic alloy’s – can be utilized to form low melting temp materials such as solders to join other metals

Answer 27

low melting pt