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42 Cards in this Set
- Front
- Back
What is an alloy?
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Metals and nonmetals mixed together.
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How are alloys formed into restorations?
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By casting
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High-Noble:
What is its gold content? What is its Noble Metal Content? |
Gold Content > or = to 40% by wt.
Noble metal content > or = 60% |
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Noble:
What is its gold content? What is its Noble Metal Content? |
Gold Content-No requirement
Noble metal content > or = 25% |
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Predominantly base metal:
What is its gold content? What is its Noble Metal Content? |
Gold Content-No requirement
Noble metal content < 25% |
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Alloy types:
Soft Medium Hard Extra Hard |
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 |
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What are noble metals?
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Those metals that retain metallic luster in dry air.
They resist tarnish and corrosion during heating, casting, soldering or use in the mouth. |
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What are the main noble metals?
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1. Gold (Au)
2. Platinum (Pt) 3. Palladium (Pd) |
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What is the melting temperature of Gold?
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1064 degrees C
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Which noble metal has the highest ductility?
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Gold
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What % of gold is 24K?
18K? 12K? 10K? |
100%
75% 50% 40% |
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Gold-based dental solders are expressed in these terms?
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Fineness. Multiply the % of gold by 10.
Pure gold (100%) would have a F = 1000 |
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Rank in order of melting points, lowest to highest:
Gold, Platinum, Palladium |
Gold < Palladium < Platinum
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What are the common base metals in alloys?
What are they needed for? What is their limitation? |
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. |
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What are the important characteristics of Copper as a base metal in alloys?
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Malleable and ductile
Red color Increases strength and hardness MP=1083 degrees C |
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What are the important characteristics of Zinc as a base metal in alloys?
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Acts as a scavenger (deoxidizing agent)
Improves the castability and fluidity of the alloy MP=419 degrees C |
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What are the important characteristics of Silver as a base metal in alloys?
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Malleable and ductile
Improves mechanical properties of gold alloys MP=960 degrees C |
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What are the important characteristics of Nickle as a base metal in alloys?
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Hard and ductile
Improves mechanical properties of base metal alloys MP=1453 degrees C |
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High-noble alloys:
How much % noble metals? How much % gold? |
At least 60% Au, Pt, or Pd
At least 40% Au |
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Advantages & disadvantages of high-noble alloys?
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1. Ease of manipulation
2. Low corrosion Dis-Most expensive |
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Noble alloys:
How much noble metal content? |
25% noble metal content
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Varieties of Noble alloys?
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They could be:
Gold based (40%) Palladium based (77%) with very little Au Silver based |
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Noble alloys:
What is possible in terms of yield strength and hardness? |
Can attain equal or greater yield strength and hardness to high-noble alloys
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Noble alloys:
Advantages & disadvantages? |
Ads:
1. Very low corrosion Dis: 1. Very expensive |
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What is the main use for noble alloys?
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Fixed partial dentures
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What metals are primarily used for base metal alloys?
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Nickel, cobalt or titanium
May contain minor amounts of noble metals |
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Base-metal alloys:
Advantages & disadvantages? |
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) |
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What are the main uses for base-metal alloys?
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Crowns
FPD RPD Implants Wrought forms |
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Biocompatibility of an alloy is related to its __________.
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corrosion
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What does corrosion do to influence biocompatibility?
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Releases elements into the mouth.
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What are some manifestations of poor biocompatibility of alloys?
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Unpleasant tastes
Irritation Allergy |
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What metal has the most frequent occurence of allergy?
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Nickel (8-15% of population)
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What are wrought alloys?
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Alloys that are shaped into another form by a mechanical force.
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Wrought alloys have a _________ grain structure.
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fibrous
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What are the main uses for wrought alloys?
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Orthodontic wires
Endodontic files RPD clasps |
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Ceramic bonding alloys:
These three elements are added to high-noble and some noble alloys to form the oxide layer. |
gallium
indium tin |
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The melting range of ceramic bonding alloys is critical, what is it?
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850-1350 degrees C
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What are some problems that you can encounter with ceramic bonding alloys?
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1. The color of the oxide
2. Greening 3. Debonding of the ceramic |
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What are some uses for solders?
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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 |
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How hot must it be to solder?
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Above 425 degrees C
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What is a flux?
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A material that cleans the alloy to be soldered and dissolves any surface oxide on the metal.
Necessary for soldering |
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How can you heat in soldering?
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Blow torch
Traditional oven Laser |