Dental Materials Alloys

Front 1

What is an alloy?

Back 1

Metals and nonmetals mixed together.

Front 2

How are alloys formed into restorations?

Back 2

By casting

Front 3

High-Noble:
What is its gold content?
What is its Noble Metal Content?

Back 3

Gold Content > or = to 40% by wt.

Noble metal content > or = 60%

Front 4

Noble:
What is its gold content?
What is its Noble Metal Content?

Back 4

Gold Content-No requirement

Noble metal content > or = 25%

Front 5

Predominantly base metal:
What is its gold content?
What is its Noble Metal Content?

Back 5

Gold Content-No requirement

Noble metal content < 25%

Front 6

Alloy types:
Soft
Medium
Hard
Extra Hard

Back 6

Soft-Type I-low stress, inlays, less than 140 MPa yield strength
Medium-Type II-moderate stress, inlays & onlays, 140-200 MPa yield strength
Hard-Type III-high stress, crowns, partial dentures, 201-340 MPa yield strength
Extra Hard-Type IV-very high stress, crowns, fixed & removable dentures, greater than 340 MPa yield strength

Front 7

What are noble metals?

Back 7

Those metals that retain metallic luster in dry air.
They resist tarnish and corrosion during heating, casting, soldering or use in the mouth.

Front 8

What are the main noble metals?

Back 8

1. Gold (Au)
2. Platinum (Pt)
3. Palladium (Pd)

Front 9

What is the melting temperature of Gold?

Back 9

1064 degrees C

Front 10

Which noble metal has the highest ductility?

Back 10

Gold

Front 11

What % of gold is 24K?
18K?
12K?
10K?

Back 11

100%
75%
50%
40%

Front 12

Gold-based dental solders are expressed in these terms?

Back 12

Fineness. Multiply the % of gold by 10.
Pure gold (100%) would have a F = 1000

Front 13

Rank in order of melting points, lowest to highest:
Gold, Platinum, Palladium

Back 13

Gold < Palladium < Platinum

Front 14

What are the common base metals in alloys?
What are they needed for?
What is their limitation?

Back 14

Copper (Cu), Zinc (Zn), Silver (Ag), Nickel (Ni), Titanium (Ti)
Base metals are required for strength, flexibility and wear properties

They have a tendency to corrode in the mouth.

Front 15

What are the important characteristics of Copper as a base metal in alloys?

Back 15

Malleable and ductile
Red color
Increases strength and hardness
MP=1083 degrees C

Front 16

What are the important characteristics of Zinc as a base metal in alloys?

Back 16

Acts as a scavenger (deoxidizing agent)
Improves the castability and fluidity of the alloy
MP=419 degrees C

Front 17

What are the important characteristics of Silver as a base metal in alloys?

Back 17

Malleable and ductile
Improves mechanical properties of gold alloys
MP=960 degrees C

Front 18

What are the important characteristics of Nickle as a base metal in alloys?

Back 18

Hard and ductile
Improves mechanical properties of base metal alloys
MP=1453 degrees C

Front 19

High-noble alloys:
How much % noble metals?
How much % gold?

Back 19

At least 60% Au, Pt, or Pd
At least 40% Au

Front 20

Advantages & disadvantages of high-noble alloys?

Back 20

1. Ease of manipulation
2. Low corrosion

Dis-Most expensive

Front 21

Noble alloys:
How much noble metal content?

Back 21

25% noble metal content

Front 22

Varieties of Noble alloys?

Back 22

They could be:
Gold based (40%)
Palladium based (77%) with very little Au
Silver based

Front 23

Noble alloys:
What is possible in terms of yield strength and hardness?

Back 23

Can attain equal or greater yield strength and hardness to high-noble alloys

Front 24

Noble alloys:
Advantages & disadvantages?

Back 24

Ads:
1. Very low corrosion

Dis:
1. Very expensive

Front 25

What is the main use for noble alloys?

Back 25

Fixed partial dentures

Front 26

What metals are primarily used for base metal alloys?

Back 26

Nickel, cobalt or titanium
May contain minor amounts of noble metals

Front 27

Base-metal alloys:
Advantages & disadvantages?

Back 27

Ad:
1. Extremely high yield strengths and hardness
2. Very low cost

Dis:
1. Very difficult to manipulate in lab
2. High corrosion
3. Questionable biocompatibility in mouth (Ni & Co)

Front 28

What are the main uses for base-metal alloys?

Back 28

Crowns
FPD
RPD
Implants
Wrought forms

Front 29

Biocompatibility of an alloy is related to its __________.

Back 29

corrosion

Front 30

What does corrosion do to influence biocompatibility?

Back 30

Releases elements into the mouth.

Front 31

What are some manifestations of poor biocompatibility of alloys?

Back 31

Unpleasant tastes
Irritation
Allergy

Front 32

What metal has the most frequent occurence of allergy?

Back 32

Nickel (8-15% of population)

Front 33

What are wrought alloys?

Back 33

Alloys that are shaped into another form by a mechanical force.

Front 34

Wrought alloys have a _________ grain structure.

Back 34

fibrous

Front 35

What are the main uses for wrought alloys?

Back 35

Orthodontic wires
Endodontic files
RPD clasps

Front 36

Ceramic bonding alloys:
These three elements are added to high-noble and some noble alloys to form the oxide layer.

Back 36

gallium
indium
tin

Front 37

The melting range of ceramic bonding alloys is critical, what is it?

Back 37

850-1350 degrees C

Front 38

What are some problems that you can encounter with ceramic bonding alloys?

Back 38

1. The color of the oxide
2. Greening
3. Debonding of the ceramic

Front 39

What are some uses for solders?

Back 39

1. Join ortho wire to a band
2. Join a clasp wire to RPD
3. Join two units of FPD
4. Add proximal contact
5. Repair and occlusal defect in a casting

Front 40

How hot must it be to solder?

Back 40

Above 425 degrees C

Front 41

What is a flux?

Back 41

A material that cleans the alloy to be soldered and dissolves any surface oxide on the metal.
Necessary for soldering

Front 42

How can you heat in soldering?

Back 42

Blow torch
Traditional oven
Laser