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