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62 Cards in this Set

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  • Back
What gives ceramic bonding alloys the chemical and mechanical retention?
An oxide layer
What is the amount of expansion or contraction called?
Coefficient of thermal expansion
What is the melting range of ceramic bonding alloys?
850-1350 deg C
In ceramic bonding alloys, what elements are added to high-noble & noble alloys to form the oxide layer?
Gallium, indium, or tin
What are solders used for?
a. join an orthodontic wire to a band
b. join a clasp wire to a RPD
c. join two units of a FPD
d. Add proximal contact
e. Repair an occlusal defect in a casting
What is the melting point of solder?
425 deg C
A material that cleans the alloy to be soldered and dissolves any surface oxide on the metal is called what?
Flux
What is the advantage of a laser solder
Very precise and solders in seconds
What is the relationship between the melting point of the solder and that of the metal you are soldering to?
MP (melting pt) of solder has to be lower than the MP of the metal you are soldering
What are some common uses for wrought alloys?
a. orthodontic wires
b. endodontic files
c. RPD clasps
What are wrought alloys?
Alloys that are shaped into another form by mechanical force
What is significant about the grain structure of wrought alloys?
Wrought alloys have a grain structure often described as fibrous
When might you be suspicious of a metal allergy?
Inflammation around the margin- if the crown is placed correctly, etc suspect that it might be an allergy
What is the most common allergy to metal?
Nickel
What is the biocompatibility of alloys related to?
Corrosion
Why is corrosion bad?
Corrosion releases more of its elements into the mouth increasing the risk for unwanted reactions
What symptoms might a patient experience from corrosion of an alloy?
a. unpleasant tastes
b. irritation
c. allergy
What do base-metal alloys primarily contain?
Nickel, cobalt, or titanium
What alloy is considered the most difficult to manipulate in the laboratory?
Base-metal alloys
What are the best features of base-metal alloys?
a. Extremely high yield strength & hardness
b. Very low cost
What are the negative features of base metal alloys?
High corrosion and questionable biocompatibility in the mouth
What are the main uses for base-metal alloys?
Crowns, FPD, RPD, implants, & wrought forms
What % of noble metal content do noble alloys contain?
At least 25% of noble metal content
What are the primary bases that compose noble alloys?
a. gold-based
b. palladium-based
c. silver-based
What alloy has a higher yield strength and hardness, high-noble alloys or noble alloys?
Noble alloys
What are the biggest draw-backs to noble alloys?
They are expensive
What is the corrosion like in noble alloys?
Low
What are the main uses for noble alloys?
FPD and crowns
What % of gold, palladium, or platinum must an alloy be to be considered a high-noble alloy?
60%
What alloy is easy to manipulate in the lab?
High-noble alloys
What is corrosion like for high-noble alloys?
Very low corrosion
What are the grains between crystals referred to as?
Grain boundaries
What are grain refiners?
Small size of the grains give better properties to the alloy
What are the grains between crystal called?
Grain boundaries
What is the benefit of nickel added to an alloy?
Improves mechanical properties of base metal alloys
What are some base metals?
a. Nickel
b. Silver
c. Zinc
d. Copper
e. Titanium
What is the benefit of copper added to an alloy?
It increases strength and hardness
What is the benefit of zinc added to an alloy?
a. Acts as a scavenger (deoxidizing agent)
b. Improves the castability and fluidity of the alloy
What is the benefit of silver added to an alloy?
Improves mechanical properties of gold alloys
What properties are base metals required in alloys for?
a. strength
b. flexibility
c. wear
What is a negative feature of base metals?
Corrosion
What does a higher melting temperature indicate?
Harder to cast
What system is used to describe gold-based dental solders?
Fineness
How is fineness obtained?
F = %gold x 10
What is the melting temperature of platinum?
1755 deg C
What is the melting temperature of palladium?
1555 deg C
Which noble metal has a higher melting temperature, platinum or palladium?
Platinum (1755 deg C)
How are carats calculated?
K = 24 x %gold/100
How may gold content be expressed in terms of?
a. percentages
b. carat
c. fineness
d. color
What is the melting temp of gold?
1063 deg C
What are the noble metals?
Au Pt & Pd
What are the good properties of gold?
Soft, malleable, ductile metal w/high nobility that resists tarnish & corrosion
What is an alloy?
Mixture of different metals
What is a casting?
The melting process of the metal forming the alloy
How are solders heated?
a. blow torch
b. traditional oven
c. laser
_______ & ________ are combined to create an alloy
Metals & nonmetals
What is the yield strength of a soft alloy, restorations subjected to low stress: some inlays?
type I alloy <140
What is the yield strength of a medium alloy, restorations subjected to moderate stress: inlays & onlays
Type II alloy 140-200
What is the yield strength of a hard alloy, restorations subjected to high stress: crowns, thick veneer crowns, long-span FPD, RPD
Type III alloy 201-340
What is the yield strength of a extra hard alloy, restorations subjected to very high stress: thin veneer crowns, long span FPD, RPD
Type IV alloy >340
What are some problems associated with Ceramic Bonding alloys?
The color of the oxide
Greening
Debonding of the ceramic
What is greening in ceramic bonding alloys?
Vaporization of metal alloys that will discolor the ceramic matrix, making it look greenish, due to high amounts of silver and copper.