Gold (Bling Bling) Flashcards
(24 cards)
Most noble, corrosion resistant, ductile, and malleable metal.
Gold
Gold is too weak for dental restoration unless _____ are used
Other alloying elements
Gold can be etched by ____
Aqua Regia
Expresses the relative amount of gold in an alloy.
How much is pure gold?
Carat (k)
24k
Percentage of gold content multiplied by a factor of 10 (75 percent is 750). Used for specification of dental solders
Fineness
The current standard for dental casting alloys is ____
ISO 22674
ISO Standard 22764 Mechanical Property requirements:
0.2% offset yield strength minimum
Minimum percentage elongation after fracture
Additional alloy selection factors:
- Cost of metal per pennyweight
- Burnishability
- Solderability
- Experience of dental lab
ISO Type ___ Alloy: Very low stress-bearing restorations (small veneered one-surface inlays, veneered crowns; also metallic materials for metal-ceramic crowns produced by electroforming/sintering)
Type 0
ISO Type ___ Alloy: Single-tooth fixed restorations (crowns/inlays without restriction on number of surfaces)
Type 2
ISO Type ___ Alloy: Appliances requiring combination of high stiffness and strength (thin RPDs, parts with thin cross-sections, clasps)
Type 5
ISO Type ___ Alloy- low stress bearing single tooth restorations (veneered or unveneered one-surface inlays, veneered crowns)
Type 1
ISO Type ___ Alloy- Multiple-unit fixed restoration (bridges)
Type 3
ISO Type ___ Alloy: Thin sections subjected to very high forces (RPDs, clasps, thin veneered crowns, etc.)
Type 4
ISO Types ___ and ___ alloys are usually used in dental schools
2 and 3
Principal element for hardening and strengthening
Copper
Counteracts effect of copper on color and substitutes economically for gold w/out degrading mechanical properties
Silver
Provide tarnish and corrosion resistance as well as strengthening (used sparingly because of raised alloy melting temps)
Platinum and Palladium
Provides ductility, tarnish, and corrosion resistance to alloy
Gold
Oxygen scavenger during melting to minimize oxidation of other elements; considered to improve castability or fluidity of molten alloy
Zinc
Small amounts of indium and gallium may be prevalent in alloy to provide ____ and ____. Very small amounts of iridium are generally incoporated to provide desired _____.
Hardening
Strengthening
Grain Refinement (small grain size- improves mechanical properties, uniformity in microstructure, corrosion resistance)
Characteristic trends on going from ISO Type 1 to 5 casting alloys:
- More yield strength/hardness
- Less ductility
- Less gold
- Less ease of adjustment/burnishability (for casting)
- Lower melting temp
Slow cooling of alloy results in ____ material.
Quenching of alloy results in ____ material.
Harder
Softer
(Needs time for ordering transformation)
The special _____ containing gold alloy age-hardens rapidly at room temperature.
Gallium
