Alloys for PFM Restorations Flashcards Preview

Fixed Prosth, Module I > Alloys for PFM Restorations > Flashcards

Flashcards in Alloys for PFM Restorations Deck (51)
Loading flashcards...
1

____ are used for strength, but this will ultimately be opaqued so you won't see them

connectors

2

Classification of PFM alloys

PFM alloys:
- noble metals - alloys that have more ____
‣ Au: •
____ = the three noble metals associated with dentistry
Au-Pd
Au-Pd-Ag = although silver isn't used as much, because it tends to ____
‣ Pd: •
Pg-Ag,Pd-Cu,orPd-Co

◦ Base metals- alloys with ____
‣ Ni-Cr-Be
‣ Ni-Cr
‣ Co-Cr = ____ metal frameworks
‣ Ti & Ti alloys = ____ work; also used for undercasting of PFM

gold
Au-Pt-Pd
corrode

nickel
partial
implant

3

ADA classification system

High noble
Gold content: ____
Noble metal content: ____

Noble
Gold content: ____
Noble metal content: ____

Predominantly base-metal
Gold content: ____
Noble metal content: ____

>=40
>=60
not required
>= 25
not required < 25

4

Noble metals

Gold (Au) resistance to
____, good malleability, ____ melting point

Palladium (Pd) ____
melting point, ____ than gold, not used in pure form

Platinum (Pt) ____ melting point, does not ____ as
freely with gold, most expensive

corrosion
low
higher
harder
highest
mix

5

Carat & Fineness
• Pure gold ____ carat = 100% gold
• Alloy 50% gold ____ carat
• ____ carat jewelry 75% gold
• Pure gold fineness rating ____ • 18 carat gold ____ fine

more gold = ____ the alloy will be

24
12
18
1000
750
softer

6

Base metals

Nickel chromium cobalt
titanium

Copper & Silver: increase the ____ of gold based alloys
Zinc: decreases ____ and increases ____

hardness
oxidation
hardness

7

Terminology:
- ____ (Precious) - Noble (Semiprecious) - ____
(Non precious) (Non noble)

terms precious , etc refere to ____ - NOT DENTISTRY

high-noble
base
jewelery

8

Grain & Crystal Structure

Similar to how ice forms.
Grains are formed by a ____; visible by ____ microscopy.
Grain boundaries are subject to ____ attack.
Alloys with ____ grains have more uniform properties.
Iridium & Ruthenium are grain ____.
Base metals have ____ grains.
Wrought alloys are drawn into wire & the grain structure has a ____ appearance.

Cast noble alloys have an ____ crystal structure which is affected by how the alloy is ____ and cooled; this is not true with ____.

crystal lattice
light
corrosive
smaller
refiners
larger
fibrous

ordered
heated
base alloys

9

CRITERIA FOR ALLOY SELECTION FOR
P-FM RESTORATIONS
Physical/Chemical properties
- ____
- Noble metal content
--____ resistance
- Hardness
- ?Laboratory recommendation

- copper appears ____; high-nobles will be ____

color
corrosion
gold
yellow

10

Physical/chemical properties

- Modulus of elasticity (____ of the material)
• Important for occlusal forces
- Yield strength
(plastic deformation, force required to ____ distort alloy)
- Elongation (____)
• Noble alloys can be changed in shape
- Thermal Properties
-Melting range: ____
-Thermal Creep
- Density (higher, weighs more, easier to ____)

• We need to have an undercasting that can withstand the temperature that will melt the porcelain
◦ Since we have an alloy, we have a "____"
‣ Solidus - when all the alloy components are fused together as a ____
‣ Liquidus - when all the alloy components ____
◦ Creep- the porcelain oven is lower temp than will melt the ____, but we also don't want it to change shape

stiffness
permanently
ductility
solidus/liquidus
cast
melting range
solid
undercasting

11

COST

• Some labs will charge you for the ____ metal
• Highest-lowest expense: ____>noble>base
• Base metals-labs have a difficult time fitting them becauseof how ____

specific
high-noble
hard

12

Physical Properties
Do not memorize, just look at the trends*
• High-noble melting ranges are ____ than base-metal alloys
• Density= the more gold, the ____ the alloy
• Yield strength and ____ are linked
together: the more gold, the softer the material

lower
denser
hardness

13

Physical/chemical Properties

Biocompatibility
- Cytotoxicity
- Tissue irritation
• Allergies - ____

- Laboratory Workability
-____ accuracy
-Ease of cutting/finishing

- Porcelain Compatibility
- ____
- thermal expansion
- bond strength

• Biocompatibility =anything that is ____ is considered very biocompatible (be weary of silver allergies)
• Beryllium: take caution, because when ground up the inhaled particles can cause lung cancer-so technicians
work in hoods with respirators
• Alloy and porcelain systems are designed to work together

nickel and beryllium
casting
comoposition
noble

14

Oxidation of PFM Alloys

Adherence Controlling Elements ____, Sn, ____

- allows fusing to occur in ____ amounts

small

15

Oxides on PFM Alloys

• Au-Pd-Pt
• ____ oxide
(moderate)

• Pd-Cu
• ____ oxide (high)

• Pd-Ag
• ____ (thin)

medium gray
dark brown to black
light gray

16

orcelain Bonding to PFM Alloys

• Oxides on metal surface bond ____ to oxides in porcelain

chemically

17

Greening of Porcelain

• Porcelain discolorationin crowns a & c (____)
• Nodiscoloration of crown b (____)

Pd-Ag
NiCr

18

Physical/Chemical properties
Other Factors:
- Span length, ____
- Metal/porcelain occlusal
- ____

- sag resistance - you want to withstand the pressures of mastication
-- can't have alloy that is too ____ > flexing of undercasting with fracture
-- flexing can occur if bridge > ____ > pressure gets placed on one of abutments
- make stiffer for ____

sag resistance
cost
soft
loose
bruxers

19

Physical properties

Table, ya!

ya

20

*Au-Pt-Pd AlloyCompositions

____ % Au, ____ % Pt, ____ % Pd, ____ % Ag ____ %basemetals(Fe,Sn,In)•

84-86
4-10
5-7
1-4
2-3

21

Au-Pt-Pd General Features
- Costly
- ____ color
- High density
- Good ____
- Solidus/Liquidus: ____ oC

yellow
handling
1040-1190

22

Au-Pt-Pd General Features
- Low ____, tensile strength
- Low ____, not for long
span
- ____ may be low for occlusal
wear resistance
- High cost

- will work for 3 unit, but not for a ____ bc shitty sag resistance
- for bruxers, pick hardness similar to ____

modulus
sag resistance
hardness
6 unit
enamel

23

Au-Pt-Pd General Features
-Good ____ resistance -Good ____ bond strength -Ideal____ for finishing -____ grain refining element

corrosion
porcelain
hardness
indium

24

Au-Pd-Ag Alloy Compositions
____% Au, ____% Pd, ____% Ag, with ____ elements (Fe, Sn, In)

51-54
26-31
14-16
base

25

Au-Pd-Ag General Features

- Lower ____
- ____ color
- Good mechanical properties
-- MOE, ____
- High ____
- Good for ____ bridges
- Solidus/Liquidus: ____ oC

cost
gray
tensile strength
sag resistance
long span
1200-1300

26

Au-Pd-Ag General Features

-Good porcelain ____ -Good ____ resistance -Ag may cause ____ of
porcelain

porcelain
corrosion
greening

27

Thermal Expansion & Porcelain Bonding
• Thermal expansion of metal must be nearly identical to that of the ____.
• If metal shrinks a lot less than the porcelain during cooling ____occurs.
• If metal shrinks a lot more than the porcelain during cooling ____ occurs.
• Porcelain needs to be slightly in ____ so alloy must contract slightly more than the porcelain during cooling to prevent cracking.

porelain
crazing
shiver or puckering
compression

28

Palladium based alloys Pd-Ag Alloy Compositions

____% Pd, ____% Ag, ____% base element (Sn,In);

53-60
30-37
10

29

Pd-Ag General Features
-____ cost
-Low ____
-High thermal expansion; not suited for ____ porcelain -
High ____
-High ____ -Solidus/Liquidus: ____ oC

low
density
vita
modulus
sag resistance
1230-1300

30

Pd-Ag General Features

- Good ____ bond strength
- Good ____

porcelain
tarnish and corrosion resistance