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robbypowell's version from 2016-12-09 22:31

casting alloys

Question Answer
definition: element that forms positive ions in solutions (they lose electrons in solutions)metal
T/F: very few pure metals are used in dentistryTrue
T/F: pure metals are used in dentistry more frequently than alloysFalse ( very few pure metals are used in dentistry)
The number of electrons that pure metals give up in solution vary from ____ to ____ electrons pure metal atom1-4 electrons
Why are metal atoms highly responsive to electric and magnetic forces?because electrons, in the negatively charged electron cloud of metal atoms, are free to move
Which has greater density and liquidus High noble or NobleHigh Noble ("Noble's density and liquidus are generally lower than high-noble alloys")
High gold and Platinum content would lead to ______ (greater/less) densitygreater density
As Platinum and Palladium (Pt & Pd) content increases in High noble alloys... this affects liquidus of alloy how?Increases
As Gold (Au) content of alloy increases, this affects elongation factor how?Increases (allows burnishing)
any alloy that has at least ___ wt% Pt or Pd is usually white, not gold, even if the alloy composed mainly of gold10%
Adding what metal to an alloy makes it not good for use with porcelain due to discoloration?Copper (Cu) (e.g. High Noble AuCuAgPd & Noble AuCuAgPd that vary on composition proportions)
What has greater Liquidus: Base Metal, Noble Metal, & High Noble MetalBase Metal
Okay so... what is Liquidus... tell me, bruh!it is the Temp at which a metal is completely melted... so Melting Temp, basically
_____ is the most allergenic metal, and so often cannot be used because of patient allergyNickel
_____ is the second-most allergenic metalCobalt
In Gold-Platinum alloys, _______ acts as an oxygen scavenger, improves the castability, and is used as a "dispersed phase hardener"Zinc (Zn)
What is the purpose of Zinc (Zn) in Gold-Platinum alloys (Au-Pt)acts as an oxygen scavenger, improves the castability, and is used as a "dispersed phase hardener"
______ (metal) is used in alloys to Lower the Liquidus, and therefore improve castability... but can cause systemic health complications including coughing, shortness of breath, and weight lossBeryllium
What is the purpose of adding Beryllium to an alloy?lower liquidus (and therefore improve castability)
The presence of what metal in an alloy can affect the lungs and skin?Beryllium
Patient just had metal base maxillary denture inserted and very soon after has symptoms of coughing, shortness of breath, and weight loss that begin abruptly... what is the condition and what metal in the base would you expect to be responsible?Acute Berylliosis; Beryllium
How does chronic berylliosis manifest?abnormal formation of inflammatory granulomas and widespread scarring and thickening of deep lung tissues
T/F: all alloys corrode and release elements to their environmentTrue
T/F: only alloys with specific metals such as copper or silver corrode and release elements to their environmentFalse ("ALL alloys corrode and release elements to their environment")(they do vary in there corrosion rate, though... inclusion of some metals make them corrode much more)
T/F: Because metal alloys need an oxide layer to bond to porcelain, the thicker oxide layers make for more success of porcelain fused to metal restorationsFalse (this layer is brittle, so a thinner layer is ideal)
T/F: Metal alloys bond to porcelain through an oxide layer; a thinner oxide layer makes for a more successful restoration of PFMTrue (oxide layer is brittle, and needs to be thin)
Porcelain must have Coefficient of thermal expansion that is _______ (higher/lower) than the metal and it must be within _____ of the metal's COTE (coefficient of thermal expansion)Lower; 0.5
In PFM bonding, after the materials are heated and are bonded together, metal will shrink little bit _____ (more/less) than the porcelain; this places the ceramic in a state of ______more; compression
_______ is the condition of creep during the heating process of metals and has potential to ruin the restorationSag
lower nobility ---> _______ (more/less) corrosion; multiple phases ---> ________ (more/less) corrosionMore; more
t/f: Release of materials (degree of corrodability) is related to composition and is not a linear relationshipTrue (lower nobility --> more corrosion; more phases--> more corrosion)
t/f: Release of materials (degree of corrodability) is related to composition and is a linear relationshipFalse, (1st part true... 2nd part false... is NOT a linear relationship)
t/f: color of a metal alloy does not predict composition, mechanical properties, corrosion rates, biocompatibility, cost, or porcelain bonding strengthTRUE
t/f: color of a metal alloy can be a good predictor of composition, mechanical properties, corrosion rates, biocompatibility, cost, and porcelain bonding strengthFALSE (not good predictor of any, why we need to be specific when ordering an alloy)
memorize

which "identalloy type" of metal fits this attribute (can be more than 1 type)

Question Answer
Hardness: softType 1
Strength: lowType 1
Uses: inlays, low stress bearing areasType 1
Type of metal that is easily burnishedType 1
Yield Strength <140Type 1
Elongation factor 18Type 1 & 2
hardness: mediumType 2
Stength: mediumType 2
Uses: 3/4 crowns, pontics, inlays,onlays (mod stress)Type 2
Yield Strength: 140-200Type 2
Hardness: hard (not "extra hard")Type 3
Strength: high (not extra high)Type 3
Uses: short span FPD, full crowns, Ons and InsType 3
heat treatableType 3 & 4
Yield Strength: 201-340Type 3
Elongation Factor: 12Type 3
Hardness: extra hardType 4
Strength: extra highType 4
Uses: RPD, high stressType 4
Yield Strength: >341Type 4
Elongation Factor: 10Type 4
memorize

High Noble, Noble or Base Metal

Question Answer
Composition: 60% noble metal, 40% goldHigh Noble
Composition: >25% noble metalNoble
Composition: <25% nobleBase Metal
Uses: cast or porcelain applicationsHigh Noble
Uses: full cast, porcelain, FPDNoble
Uses: RPD, bridges, thin connectorsBase Metal
Melting Range: Low to ModerateHigh Noble
Melting Range: ModerateNoble
Melting Range: HighBase Metal
Density: highHigh Noble
Density: moderateNoble
Density: lowBase Metal
Yield Strength: moderateHigh Noble
Yield Strength: moderate to highNoble
Yield Strength: highBase Metal
Elongation: excellentHigh Noble
Elongation: moderateNoble
Elongation: lowBase Metal
Hardness: moderateHigh Noble
Hardness: moderate to highNoble
Hardness: highBase Metal
Corrosion: lowHigh Noble
Corrosion: low to moderateNoble
Corrosion: multiple phasesBase Metal
AuPtZn, AuPdAg, and AuCuAgPd. AuPtZn (usually 78 wt% Au with about 10 wt% Pt)High Noble
AuPtZn (78 wt% Au with about 10 wt% Pt)High Noble (higher corrosion rate than most high nobles, zinc precipitates out and leaves metallic taste in some patients mouths)
AuPdAg (40 wt% Au and 40 wt% Pd)High Noble (casts well but it is more flexible and shouldn’t be used for partial dentures)
AuCuAgPd (55-75 wt% Au)High Noble (commonly used for full cast applications but should not be used for porcelain because of discoloration)
AuCuAgPd (Au 40 wt%)Noble (not good for porcelain due to discoloration, stronger than the nigh-noble counterpart)
PdCuGa (PD 77 wt%)Noble (casting this alloy is VERY technique sensitive; hardness of 425 kg/mm2 and can wear enamel)
AgPd or Pd Ag (25-50 wt%)Noble (used for full cast or porcelain application; high corrosion rates and are difficult to use)
CoCrBase Metal
Nickel-chromiumBase Metal (used for full cast, porcelain, partial dentures; careful of nickel allergy)
NiCrBeBase Metal (higher corrosion rate than NiCr and the beryllium preferentially corrodes out of the alloy)
memorize

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