Dental alloys for Complete veneer crowns

Question 1

Chemical properties of Gold

Answer 1

Most noble and corrosion-resistant metal
Not tarnished by air or water
Does not dissolve in HCL, H2SO4, HNO3

Question 2

MEchanical Properties of Gold

Answer 2

Most ductile and malleable metal

Question 3

Problem with Gold for Dental restorations and how to fix

Answer 3

Too weak, must use other alloying elements

Question 4

How to etch gold

Answer 4

aqua regia (1HNO3: 3 HCl)

Question 5

What are nobile metals chemically

Answer 5

do not form stable oxides at room temp

Lowest tendency to lose elctrons

Question 6

What are the noble metals

Answer 6

Gold
Platinum
Palladium
Iridium
Ruthenium
rhodium
osmium

Question 7

What are the noble metals content of dental alloys

Answer 7

Au+Pt+Pd

Question 8

Is silver a noble metal in oral envirnoment

Answer 8

NO (forms black AgS)

Question 9

What defines a Precious metal

Answer 9

By price, NOT electrochem

Question 10

Can common metals become precious

Answer 10

Yes, when very high purity is required

Question 11

What is a Carat

Answer 11

Parts out of 24 with pure gold, tels nothing about other elements

Question 12

what is Fineness

Answer 12

PArts out of 1000 with pure gold

Question 13

When is fineness used

Answer 13

For specification of dental solders

Question 14

What is 1 pound Avoirdupois

Answer 14

16 oz

Question 15

What is 1 pound troy

Answer 15

12 oz

Question 16

when would you use pound troy

Answer 16

Noble metals

Question 17

Ratio of pounds troy to pounds avoirdupois

Answer 17

.823 pounds

Question 18

1 troy oz is how many pennyweights (dwt)

Answer 18

20 penny weights

Question 19

1 pennyweight is how many grams

Answer 19

1.555 grams

Question 20

What kind of gold used to be used in dental casting alloys

Answer 20

Coin gold and 22k gold

types I-IV high gold casting

Question 21

How much gold is in todays casting

Answer 21

lower gold

Question 22

What specification of dental castinga lloys has been withdrawn

Answer 22

Historic ANSI/ADA specification No.5

Question 23

What is the current standard for dental casting alloys

Answer 23

ISO 22674 (types 0-5)

Question 24

The ability of a metal to stretch and seal a margin

Answer 24

Burnishability

Question 25

what are additional alloy selection factors

Answer 25

Cost of the metal per pennyweight Burnishability Solderability Experience of the dental lab

Question 26

when to use type 0 alloys

Answer 26

Very low stress-bearing (small veneered 1 surface inlays) Veneered crowns metallic materials for metal-ceramic crowns produced by electroforming or sintering

Question 27

when to use type 1 alloys

Answer 27

Low stress bearing single tooth restorations ( veneered or unveneered one surface inlays, Veneered crowns

Question 28

When to use type 2 alloys

Answer 28

single tooth fixed restorations (Crowns or inlays without restriction on number of surfaces)

Question 29

When to use type 3 alloys

Answer 29

Multiple-unit fixed restorations (bridges)

Question 30

When to use type 4 alloys

Answer 30

Thin sections subject to very high forces (RPD, clasps, thin veneered crowns, bridges with wide spans or small cross-sections, attachments, implant retained superstructures)

Question 31

When to use type 5 alloys

Answer 31

Appliances requiring combination of high stiffness and strength (thin RPDs, parts with thin cross-sections, clasps)

Question 32

What is the trend as you go from type 0 to type 5 gold casting alloys

Answer 32

More other elements Easier to melt HArder to burnish and adjust

Question 33

Roll of gold in gold casting alloys

Answer 33

Provide ductility | tarnish and corrosion resistance

Question 34

Roll of Copper in gold casting alloys

Answer 34

Principle element for hardening and strength)

Question 35

How much copper has to be added for a reduction in tarnish and corrosion resistance

Answer 35

exceeding 12%

Question 36

Roll of silver in gold cast alloys

Answer 36

Counteracts effect of copper on color and substitutes economically for gold without degrading mech properties

Question 37

Roll of Platinum and palladium in gold casting alloys

Answer 37

Provides tarnish and corrosion resistance | Strength

Question 38

How much platinum and palladium can be added

Answer 38

Not much because itll raise the melting temp

Question 39

Roll of zinc in Gold casting alloys

Answer 39

OXygen scavenger during melting to minimize oxidation of other elements improve castability and fluidity of molten alloy

Question 40

Different strucutres of AuCu3

Answer 40

disorded (fcc strucutre) | Ordered alpha prime(simple cubic strucutre)

Question 41

when does the orded alpha prime strucutre of AuCu3 form

Answer 41

below about 400 degrees celcius

Question 42

When does the Disordered structure form

Answer 42

At high temperatures (usually has a lot of gold)

Question 43

Roll of small amounts of Indium and gallium in gold casting alloys

Answer 43

Provide hardening and strengthening

Question 44

why add small amounts of iridium to gold casting alloys

Answer 44

grain refinement

Question 45

What does grain refinement do

Answer 45

Improves mechanicalproperties, composition uniformity in microstrucutre and corrosion resistance

Question 46

Solid solution hardening is provided by what elements

Answer 46

Copper, platinum, palladium, silver and zinc

Question 47

Order hardneing is provided by

Answer 47

Copper (but a lot needed for the transition to occur)

Question 48

what allows ordering to occure

Answer 48

Slow cooling through appropriate temperature range

Question 49

what leads to a softened contion of gold casting alloys

Answer 49

Quenching leads to unordered transformtion (too fast)

Question 50

what leads to a hardened condition

Answer 50

Bench-cooling Furnace heat treat -ordered transformation