RESTORATION ALLOYS

Important factors and properties of dental alloys? (7)

Cost

Dentisty

Biocompatibilty

corrosion/tarnish

Accurate fit

Ease of casting and finishing

Mechanical properties

Noble metals in dentistry???

Major? **

Grain refiners? ( )

Palladium **

(Ruthenium)

Osmium

Gold **

Rhodium

(Iridium)

Platinum **

< 1 wt% of (3???) is added to some ____ casting alloys

Iridium (Ir), ruthenium (Ru), or rhenium(Re)

noble

Finer Grain Size:

Melting points?

Yield Strength?

Composition ______

______ Resistance

Increased

Increased

Uniformity

Corrosion

T or F: In pure form, base metals have a greater tendency to corrode in the mouth compared to noble metals

T

ADA Alloy Classification:

High Noble Alloys??

Titanium and Titanium Alloys??

Noble Alloys??

Predominantly Base Alloys??

Gold (Au) ≥ 40 wt%Noble metal content ≥ 60 wt%

Titanium ≥ 85 wt%

Noble metal content ≥ 25 wt%

Noble metal content < 25 wt%

ADA Alloy Classification by Physical Properties: Tensile strength and elongation:

Soft (I)

Medium (II)

Hard (III)

Extra Hard (IV)

<140, 18

140-200, 18

201-340, 12

>340, 10

Indications for Types of Alloys:

I

II

III

IV

Inlays

Onlays and inlays

Crowns and short span FPDs

Thin veneer crowns, long span FPDs, RPDs

High gold vs low gold alloys?

Greater than 70% gold

Less than 70% gold 

Name of the ____ component in an alloy is listed first followed by the ____ one or two _____ components

major

next

largest

When are minor elements included in naming?

If important for biocompatibilty concerns. (NiCr, or CoCr)

Rank the Costs: Platinum, Gold, Palladium, Silver?

Gold > Platinum > Palladium > Silver

Rank Density Platinum, Gold, Palladium,??

Platinum > Gold > Palladium

What collor is palladium?

White

Silver may cause _____ of porcelain

What does it look like?

How does it happen?

Greening

Yellow/light brown surface discoloration

Escape of silver vapor during porcelain firing. Silver diffueses into the porcelain with the subsequqnt reduction of ionic silver within the superfical layers of procealin to form colloidal metallic silver

Is silver considered noble in dentistry?

No

Greening tends to increase with what two things?

Increased Ag content

# of firings

T or F: All silver containing products exhibit greening

F

Use for high noble alloys?

Full cast or metal ceramic

AuPtPd: Content?

75-88% Au

Less than 8% Pt

Less than 11% Pd

Which alloy is Easily cast, finished, burnished; Good corrosion properties

AuPtPd

AuPtPd:

very high ______

Poor _______ resistance

Low ______

High ______

Cost

Sag

Hardness

Density

AuPdAg:

• Content?

• Use?

40-53% Au, Pd 25-25%, Ag

Full cast or metal ceramic 

Could be high or low silver

AuPdAg:

Easily ____ and _____

Improved ____, ______ and ____ over AuPtPd

Cast and finish

Sag, rigidity and hardness

AuPdAg: Disadvantage:

• ________ cost

• Silver induced what?

high

porcelain staining potential

AuPd:

• Content?

• Uses?

Au 44-55%, Pd 35-45%, Ga, In, other

Full cast or metal ceramic 

AuPd:

Easily ___

Good _____ properties;

No ___

Improved ____ &lower _____ over AuPtPd

Disadvantage?

Cast

corrosion

corrosion

strength, density

High cost

Advantage of AuCuAgPd

Disadvantage

Use? Why?

Good corrosion properties

High cost

Full cast only - lower melting range

Advantage of AuCuAgPd noble alloy?

Lower Au content than the high-noble version, therefore lower cost. Also, comparatively higher yield strength and hardness

Uses of PdAg or AgPD?

Full cast or metal ceramic

Disadvantages of PdAg or AgPd

Possible Ag-induced porcelaindiscoloring; Some casting issues

Advanates of PdAg or AgPd?

Lower cost and density, lower sag resistance, corrosion properties (PdAg)

Advantages of PdCu, PdGa, PdCo or "High Palladium"?

Lower cost and density; good castability. high stiffness (PdCu)

Disadvantages of PdCu, PdGa, PdCo or "High Palladium"?

Dark oxides (PdCu/Co);Sag (PdCu); Biocompatibility issues withsome compositions-Pd allergy

CoPdCr and NiPdCr: modification of CoCr and NiCr base metal alloys with palladium greater than what % to be noble?

25%

Main 3 types of Base Metals?

NiCr

CoCr

Ti

Uses for base metals (3)

Crowns & Bridges

40% of metal-ceramic in U.S.

Most removable partial denture frameworks

General Characteristics of Base Metal Alloys:

Higher (3)

Lower ____

More difficult to (3)

Higher _____ range

Higher ______ shrinkage

_____ cost

Relatively _____ corrosion rates, but variable

yield strength stiffness, hardness

density

cast, polish, and solder

melting

solidification

Lower

greater

What can lower the melting range in NiCr base metal alloys?

1-2% Be

CoCr have generally slightly higher _____ and ____ compared to NiCr

Strength and hardness

What are the two ususal compostions of Ti-base metal alloys?

1. Commercially pure titatnium

2. Titanium aluminum vanadium alloy 

Why are Ti base metal alloys not commonly used?

special casting and investment requirements needed since c.p. Ti ischemically reactive and has a melting point~1700 o C

Why are base metal alloys protected by passivity?

Ti and Cr are able to form a surface oxide layer that is coherent, continuous, and relatively impermeable to water and oxygen.

• Protects the metal or alloy from corrosion

Printing orientation and laser properties may affect (3) , but generally _____ CoCr has favorable properties and fit

properties, fit, and microstructure

SLM

Virtually every alloy known will corode to some extent ___________, but alloys vary signficantly in this regard.

Corrosion elemental release:

• Class 3?

• Class 2?

• Class 1?

100-1000 ug/cm squared per week

10-100

0-10

Most common metal allergen?

Nickle (15%)

Palladium:

• 2-18% frequency of _________

• Cross reactivity between what?

• Almost all allergic to Pd also allergic to what?

sensitivity

Ni and Pd

Ni 

Threat to personnel who inhale metal dust during polishing or grinding, leading to a chronic inflammatory condition

Beryllium 

What metal is also known as a carcinogen?

Beryllium

Guidelines for Alloy Selection:

Develop an ______ of the alloys

Use ____ ______ products from quality manufacturers

Develop a clinical _____

understanding

clinically proven

philosophy

Guidelines for alloy selection

Avoid selection based upon _____ unless all other factors are equal

Know the _____

Use ____ phase alloys over _____ phase if possible

Use a _____ system of alloys used in the patient

color

composition

single - multiple

tracking

Guidelines for Alloy Selection

Use companies who ______ and _____

Use alloys tested for _____ and _____

Use a dental lab that is _____ about its alloys

research and manufacture

corrosion and elemental release

knowledgeable

Develop a clinical philosophy:

• long term __________- and ________

• Consider __________ situation for alloy selection

performacne and cost

alloy selection 

Additional metal requirements vs full cast metal:

• Produce ________ _______ for chemcial bonding to porcelain. Due ot base metal additives.

• _________ compatibility. Slightly greater ___ than porcelain

• Melting range ______ than fusing range of porcelain.

• No ________ at firing temperatures of porcelain.

surface oxides

Thermal

CTE

Higher

distoration 

In PFM alloys when _____ spans are heated during porcelain firing, _____ occurs due to the _______ of material and ____ temperature imvolved.

long

creep

weight and high

Base metal are more sag resistant thatn what?

High noble/ noble alloys part of reason for use in long spans

Application of opaque porelain creates a _____

Primarily wht type?

Possibly? (3)

bond

direct chemical bond

mechanical retention, compression bonding via CTE mismatches, van der Waal forces

Metal-ceramic restorations:

• No difference in alloys compared to traditional, what was altered?

The ceramic 

Pressed ceramic and layered procelain have equivalent what?

Bond strength

What are the 3 non traditional metal ceramic restorations?

1. Captek

2. Sinterkor

3. Very high gold copings with small amounts of Ag, Pd, or Pt

Porcelain bonding in Captek by mechanical interlocking primaruily supplied by what agent?

CapBond

What is used for full cast gold crowns in clinic?

Type 4 gold casting alloy ney oro G3, JLCB, Eclipse, verity 

What is the survival rate of metal ceramic crowns?

10 years?

20 years?

90%

78%

What was the most common reason for failure of high noble FPDs?

Tooth fracture