Dental 'casting' alloys

Question 1

Dental alloys

Answer 1

Rarely are metals used in their pure form in dentistry with the exception of titanium.
Although we mostly use alloys of titanium too.
Historically cohesive gold was used which was packed into a prepared cavity

Question 2

Dental casting alloys groups

Answer 2

Gold Alloys
Precious metal alloys
Nickel Chromium alloys
Cobalt Chromium alloys
Titanium alloys

Question 3

Casting alloys

Answer 3

RPDs
-Co-Cr
-Ti
-Ti alloy
-gold
Metal restorations
-Co-Cr
-Ti
-Ti alloy
-gold (high, medium, low)
-Ag-Pd
-Pd-Ag
Metal-ceramic restorations (bonding alloys) - becoming progressively used for other things
-Co-Cr
-Ti
-Ti alloy
-Gold (high, medium, low)
-Ag-Pd
-Pd-Ag
Bonding alloys may be used for ‘all metal’ restorations, however the other metal alloys can not be used for bonding to ceramic

Question 4

Desirable properties

Answer 4

Biocompatibility
Corrosion & tarnish resistant
Optimum mechanical properties
Bond to ceramic (for metal ceramic)
Aesthetic
Cheap

Question 5

Removable partial dentures

Answer 5

Most commonly cast Co-Cr
Historically Au
Ti alloy is available
SLM (selective laser melting) production is rapidly developing

Question 6

CoCr properties

Answer 6

Casting temp ~1500 degrees C
-very high - specialist equipment needed
Density 8.9 gm/cm^3
Casting shrinkage 2.3%
Tensile strength 850 MPa
Yield stress ~550 MPa
Elastic modulus 190-230 GPa
Hardness 360-430 VHN
Ductility 2-8%

Question 7

All metal restorations

Answer 7

Type I-IV Au
Other precious metals
Co Cr
Ni Cr
Ti

Question 8

Gold alloys indications

Answer 8

I (soft): inlay
-80-90% Au, 3-12% Aga
-contains 2-5% Cu
II (medium): onlay
-75-78% Au, 12-15% Ag
-7-10% Cu, 0-1 % Pt, 1-4% Pd
III (hard): crowns
-62-78% Au, 8-26% Ag
-8-11% Cu, 0-3% Pt, 2-4% Pd
IV (extra hard): crown, bridge, post and core, RPD
-60-70% Au, 4-20% Ag
-quite expensive
-11-16% Cu, 0-4% Pt, 0-5% Pd
KNOW ABOUT THESE TYPES

Question 9

Mechanical properties of gold alloys

Answer 9

More Copper in Type III and Type IV alloys increases yield strength, decreasing plastic deformation of the alloy

Question 10

Medium and low gold alloys properties

Answer 10

Less gold content

A lot cheaper to use

Question 11

Non-precious metals

Answer 11

Ni-Cr
Co-Cr
Ti
Ti-Al-V

Question 12

Bonding alloys

Answer 12

Melting Temperature has to be relatively high because we are going to sinter ceramic on to surface of that metal (950-1000 degrees C)
TEC (CTE) that matches that of the ceramic on surface
Oxide Layer created by base metals - acts as wetting agent for ceramic
Modulus of Elasticity - must be very stiff

Question 13

For steps of process listen on encore

-beginning may be at end of Ceramic Veneers II

Answer 13

Encore

Question 14

SLM (selective laser melting) production

Answer 14

We can design RPD in CAD package
3D printing
Send design off to production house

Question 15

Bonding alloys types

Answer 15

Au alloys
Ni Cr
Co Cr
Ti alloys