Alloys for PFM Restorations Flashcards by J L

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

connectors

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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 &amp; Ti alloys = \_\_\_\_ work; also used for undercasting of PFM

gold
Au-Pt-Pd
corrode

nickel
partial
implant

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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

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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

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Carat &amp; 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

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Base metals

Nickel chromium cobalt
titanium

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

hardness
oxidation
hardness

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

terms precious , etc refere to ____ - NOT DENTISTRY

high-noble
base
jewelery

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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

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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

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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

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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

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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

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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

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Oxidation of PFM Alloys

Adherence Controlling Elements ____, Sn, ____

allows fusing to occur in ____ amounts

small

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Oxides on PFM Alloys

• Au-Pd-Pt
• ____ oxide
(moderate)

Pd-Cu
____ oxide (high)
Pd-Ag
____ (thin)

medium gray
dark brown to black
light gray

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orcelain Bonding to PFM Alloys

• Oxides on metal surface bond ____ to oxides in porcelain

chemically

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Greening of Porcelain

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

Pd-Ag

NiCr

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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

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Physical properties

Table, ya!

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*Au-Pt-Pd AlloyCompositions

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

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

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Au-Pt-Pd General Features

Costly
____ color
High density
Good ____
Solidus/Liquidus: ____ oC

yellow
handling
1040-1190

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

Au-Pt-Pd General Features

-Good ____ resistance -Good ____ bond strength -Ideal____ for finishing -____ grain refining element

corrosion
porcelain
hardness
indium

Au-Pd-Ag Alloy Compositions

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

51-54
26-31
14-16
base

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 ```

Au-Pd-Ag General Features -Good porcelain ____ -Good ____ resistance -Ag may cause ____ of porcelain

porcelain corrosion greening

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

Palladium based alloys Pd-Ag Alloy Compositions ____% Pd, ____% Ag, ____% base element (Sn,In);

53-60 30-37 10

``` 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 ```

Pd-Ag General Features - Good ____ bond strength - Good ____

porcelain | tarnish and corrosion resistance

Pd-Ag General Features - Potential for ____ of porcelain - - Use metal surface ____ agents - - ____-carat gold - - modified porcelains

greening coupling 24

Porcelain Greening • Non greening porcelains do not discolor on ____ alloys (a, c) • Greening occurs on ____ (b)

Pd-Ag | conventional porcelain

*Au-Pd Alloy Compositions | ____% Au, ____% Pd, with In, Sn, sometimes ____

45-42 38-45 gallium

Au-Pd General Features - ____ alloy, no discernible oxide - ____ cast - Good ____ - Good porcelain bond strength - Solidus/Liquidus: ____ oC

white easily sag resistance 1270-1304

Au-Pd General Features - Higher ____, modulus, ____, and elongation after heat treatment - Low ____

strength hardness thermal expansion

* Pd-Cu Alloy Compositions ____% Pd, ____% Cu, Other Ga, ____

70-80 10-15 Au

Pd-Cu General Features - Heavy ____ layer, difficult to cover with ____ - High ____, hardness but low MOE - Good ____ characteristics - Poor ____, improved by ____g Cu

``` oxide opaque strength working sag resistance reducing ```

Oxides on PFM Alloys * A. Pd-Cu alloy with ____, ____ oxide * B. Pd-Ag alloy with a ____, ____ oxide

thick dark thin light gray

Pd-Cu General Features - Reports of porous oxide and porcelain attributed to ____ in alloy or reduction of ____ - More difficult to cast than other ____ alloys

C CuO noble

Base Metal Alloys - General Concerns ``` Corrosion resistance • ____ layer (less reactive) Physical Properties • Modulus of ____ • Tensile strength- ____ sections • Hardness • ____ • Finishing ```

chromium oxide passivating elasticity thin metal occlusal coverage

screw-retained implant bridge > base metals are ____ metals - not cemented to the patient's mouth

go-to

Physical properties * Hardness, elastic modulus, and yield strength = all ____ * Specific gravity (density) = ____

increase | decrease

``` Base Metal Alloys - General Concerns • ____ problems • High ____ • High c____ • (2.3% vs 1.4% for gold alloys) • Beryllium • Castability, ____ bond • ____ • Not in the patient's mouth (only for the technicians working with it) • Nickel ____ ```

``` casting melting temp casting shrinkage porcelain toxicity allergy ```

Base Metal Alloys - General Considerations ____ ``` Unreliable ____ (So they are casted as individual units) • Green or black oxides ``` ____ sections

sag resistance soldering thin

Oxides on PFM Alloys * A.Ni-Cr-B ealloy * B.Ni-Cralloy * C. Co-Cr alloy * Note differences of degree of ____

oxidation and color

*Ni-Cr Compositions ____% Ni, ____% Cr, ____% Molybdenum (Mo), ____% Be These are commonly used, so just keep in mind that you want to make sure the patient isn't allergic to ____

65-80 16-24 3-6 0-2

Ni-Cr General Features - If no Be, may be difficult to ____ - Green or black oxides - Variations in ____ composition - -high ____ (Authentic porcelain systems) - -low ____ (Vita or Ceramco porcelain systems) - Solidus/Liquidus: ____oC

``` cast alloy composition expansion expansion 1230-1350 ```

*Co-Cr Alloy Compositions. ____% Co, ____% Cr, with Gallium (Ga), Niobium (Nb) can be used for crown and bridge alloys; but mostly used for ____

60 30 PFM

Titanium Alloy Compositions - pure Ti - Ti-____%, Al-____%, Vanadium (45% of all Ti alloy production) - ____

6 4 Ti-Ag-Cu

Titanium Alloy General Features - Casting temperature ~ ____ oC - ____ reactions - Passivation limits based on ____ content passivation - treated so that their surface is ____ - important for osseointegration of implants

2000 investment Ti non-corrosive

Sintered Alloy Composites • ____ class of alloy • ____ not cast • ____ used • ____ Au, Pd, Pt in wax melted away to form ____, metals don’t ____ • Second firing infuses (____) gold silver alloy into sponge creating thin ____ • Ceramic is applied by ____ alloy - captek uses a refractory die - - die has material that can be put into burn-out oven - - spongy matrix > first firing - - second firing > dome, opaques the metal - this blocks out ____ of the tooth underneath - - ceramic needs to have a good shine-through, so this works well

``` newer sintered refractory die high-noble sponge melt capillary action coping third ``` discoloration

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Alloys for PFM Restorations Flashcards

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