Lecture 7

Question 1

what are the mechanical properties of FPDs

Answer 1

chewing, bruxism

Question 2

what are the physical properties of FPDs

Answer 2

color, thermal expansion

Question 3

what are the chemical properties of FPDs

Answer 3

wear, solubility

Question 4

what are the biologic properties of FPDs

Answer 4

living tissues

Question 5

noble metals resist what?

Answer 5

• oxidation
• tarnish
• corrosion

Question 6

what are the two mechanisms to improve alloy mechanical properties?

Answer 6

• solid solution hardening

- grain refining

Question 7

what does is mean to strengthen noble metals

Answer 7

• must be made to resist deformation

- modified to impede dislocations

Question 8

these resist deformation in alloys so having more of them would make the alloy stronger

Answer 8

grain boundaries (grain formation)
grain refining

Question 9

concerning grain refining, small amounts of what elements produce metals with very fine grains?

Answer 9

Ir, Ru

Question 10

grain boundaries act to block what?

Answer 10

dislocation movements

Question 11

classification of casting alloys is based on what?

Answer 11

noble metal content (Au, Pd, Pt)

hardness

Question 12

what are the types of alloy casting classifications based on Vickers Hardness?

Answer 12

• type I: soft (59-90)
• type II: medium (90-120)
• type III: hard (120-150)
• type IV: extra hard (>150)

*type IV is still less than enamel

Question 13

a very high noble metal has ___% noble metal content

Answer 13

> 80% (Au)

Question 14

a high noble metal has ____% noble metal content

Answer 14

60% (>40% Au)

Question 15

a noble metal has ____% noble metal content

Answer 15

25% (no Au requirement)

Question 16

predominantly base metal has ___% noble metal content

Question 17

for the Midas material used at OSU, what are the two elements use for solid solution hardeners?

Answer 17

Au, Pd

Question 18

for the Midas material used at OSU, what element is the grain refiner?

Answer 18

Ir

Question 19

Argenco Y+ is a type ____ noble yellow alloy

Answer 19

three

Question 20

what two reasons are there for using alloys and not metals for metal-ceramic restorations?

Answer 20

• improve mechanical and physical properties

- improve metal-ceramic bonding

Question 21

for the Super-Star material used at OSU, what elements are the solid solution hardeners?

Answer 21

Au, Pd, Ag

Question 22

for the Super-Star material used at OSU, what element is the grain refiner?

Answer 22

Ru

Question 23

for the Super-Star material used at OSU, what element is used for metal-ceramic bonding

Answer 23

Sn

Question 24

describe the dental porcelain composition

Answer 24

70-80% potash feldspar
10-30% quartz
0-3% Kaolin (clay)(added for workability)

Question 25

what types of bonds are associated with ceramics?

Answer 25

ionic and covalent - both are stronger than metallic bonds - colvalent stronger than ionic

Question 26

bond that has an electron donor and acceptor

Answer 26

ionic

Question 27

bond that shares electrons equally

Answer 27

covalent

Question 28

what is the building block of dental porcelain?

Answer 28

SiO4 | primarily a glass with some crystalline residuals

Question 29

why do ceramics fail?

Answer 29

- brittle fracture (griffith's law) - initiated form internal surface - cyclic fracture (low loads, many cycles) - stress corrosion

Question 30

properties of ceramics

Answer 30

- electrical and thermal insulators - high compressive strength - atoms have no ability to deform brittle fracture

Question 31

you can strengthen porcelain with a metal substructure known as a what and how do they work?

Answer 31

thermal barrier coating (offers heat management) (keeps part operating longer at higher temps) (increases life by reducing oxidation to metal and thermal fatigue)

Question 32

what are the requirements for porcelain to bond?

Answer 32

- lower melt temperature of porcelain than that of the metal - must have similar expansion coefficient - must wet the surface of the metal

Question 33

what is the result if metal shrinks more than porcelain? | remember that these should have similar expansion coefficients

Answer 33

compression still okay to use though

Question 34

what is the result if ceramic shrinks more than metal? | remember that these should have similar expansion coefficients

Answer 34

tension NOT okay to use

Question 35

type of porcelain that masks the color of metal. it is the one that is actually bonded to the metal

Answer 35

opaque porcelain

Question 36

type of porcelain that provides a majority of the color by mimicking the dentin color and translucency

Answer 36

body porcelain

Question 37

type of porcelain that is typically more translucent and mimics enamel translucency

Answer 37

incisal porcelain (enamel)