Unless otherwise noted, the content of this course material is licensed under a Creative Commons Attribution 3.0 License. Copyright 2008, Dr. Stephen Bayne. The following information is intended to inform and educate and is not a tool for self-diagnosis or a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. You should speak to your physician or make an appointment to be seen if you have questions or concerns about this information or your medical condition. You assume all responsibility for use and potential liability associated with any use of the material. Material contains copyrighted content, used in accordance with U.S. law. Copyright holders of content included in this material should contact [email protected] with any questions, corrections, or clarifications regarding the use of content. The Regents of the University of Michigan do not license the use of third party content posted to this site unless such a license is specifically granted in connection with particular content objects. Users of content are responsible for their compliance with applicable law. See http://www.dent.umich.edu/license/ for more information. Mention of specific products in this recording solely represents the opinion of the speaker and does not represent an endorsement by the University of Michigan. Viewer discretion advised: Material may contain medical images that may be disturbing to some viewers.
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Unless otherwise noted, the content of this course material is licensed under a Creative Commons Attribution 3.0 License.
Copyright 2008, Dr. Stephen Bayne.
The following information is intended to inform and educate and is not a tool for self-diagnosis or a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. You should speak to your physician or make an appointment to be seen if you have questions or concerns about this information or your medical condition. You assume all responsibility for use and potential liability associated with any use of the material. Material contains copyrighted content, used in accordance with U.S. law. Copyright holders of content included in this material should contact [email protected] with any questions, corrections, or clarifications regarding the use of content. The Regents of the University of Michigan do not license the use of third party content posted to this site unless such a license is specifically granted in connection with particular content objects. Users of content are responsible for their compliance with applicable law. See http://www.dent.umich.edu/license/ for more information.
Mention of specific products in this recording solely represents the opinion of the speaker and does not represent an endorsement by the University of Michigan.
Viewer discretion advised: Material may contain medical images that may be disturbing to some viewers.
3.3. Mechanical Properties:Mechanical Properties:a.a. High E (stiffness)High E (stiffness)b.b. Moderately high YS and H (resistance to plastic Moderately high YS and H (resistance to plastic
deformation)deformation)c.c. Hardenable by heat treatment (retention of polish)Hardenable by heat treatment (retention of polish)
4.4. Biological Properties:Biological Properties:a.a. Biocompatible: no toxic soluble phasesBiocompatible: no toxic soluble phasesb.b. Non-reactive in the oral environmentNon-reactive in the oral environment
GENERAL REQUIREMENTSGENERAL REQUIREMENTS(continued)(continued)
Images source: Steve Bayne, University of Michigan, 2008
CLASSIFICATION OF ALLOYSCLASSIFICATION OF ALLOYS1.1. Full Gold Crown and Bridge Alloys (based on precious metals)Full Gold Crown and Bridge Alloys (based on precious metals)
a.a. ADA Classification System (see phase diagrams)ADA Classification System (see phase diagrams)(1)(1) Type IType I 83% Au+ 83% Au+ (Non-heat hardenable)(Non-heat hardenable) -- inlay-- inlay(2)(2) Type IIType II 78% Au+ 78% Au+ (Non-heat hardenable)(Non-heat hardenable) -- inlay, onlay, …-- inlay, onlay, …(3)(3) Type IIIType III 78% Au+ 78% Au+ (Heat hardenable)(Heat hardenable) -- onlay, crown-- onlay, crown(4)(4) Type IVType IV 75% Au+ 75% Au+ (Heat hardenable)(Heat hardenable) -- crown, bridge-- crown, bridge
Corrosion resistanceCorrosion resistanceHardnessHardnessCounteract orange color of copperCounteract orange color of copperIncrease MP and hardnessIncrease MP and hardnessIncrease MPIncrease MPPrevent oxidation during melting (OPrevent oxidation during melting (O22 getter) getter)
TERMINOLOGYTERMINOLOGY
1.1. Precious MetalPrecious Metal = containing metals of high economic value such as = containing metals of high economic value such as gold, platinum, palladium, silver, (rhodium), (iridium), (rhuthenium), gold, platinum, palladium, silver, (rhodium), (iridium), (rhuthenium), and (osmium).and (osmium).
2.2. Noble MetalNoble Metal = a precious metal that is resistant to tarnish. This = a precious metal that is resistant to tarnish. This excludes “silver” by definition.excludes “silver” by definition.
3.3. Low Gold AlloysLow Gold Alloys = Alloys containing <75% gold (less than 50 a/o gold) = Alloys containing <75% gold (less than 50 a/o gold) which means that gold atoms represent less than every other atom.which means that gold atoms represent less than every other atom.
4.4. Gold-substitute AlloysGold-substitute Alloys = precious metal alloys not containing gold. = precious metal alloys not containing gold.
5.5. Base-Metal AlloysBase-Metal Alloys = alloys not containing precious metals to impart = alloys not containing precious metals to impart their corrosion resistance.their corrosion resistance.
Low Gold AlloysLow Gold Alloys High Gold AlloysHigh Gold Alloys
RandomRandomSolidSolid
SolutionSolution
OrderedOrderedSolidSolid
SolutionSolutionGraph source: Steve Bayne, University of Michigan, 2008
AGAG CUCU
AUAU
+
5
10
15
20
25
30
35
40
50
45
AU-AG-CUAU-AG-CUTenaryTenary
Phase DiagramPhase DiagramType IType IType IIType IIType IIIType III
Type IVIType IVI
T
Graph source: Steve Bayne, University of Michigan, 2008
COMMERCIAL EXAMPLESCOMMERCIAL EXAMPLES
Graph source: Steve Bayne, University of Michigan, 2008
PROCESSING CYCLESPROCESSING CYCLES
inve
stm
ent
all
oy
TIME
Alloy LCTE = 16-18 ppm/C
CASTCASTGOLDGOLDALLOYSALLOYS
Tm 890C
Trt
Graph source: Steve Bayne, University of Michigan, 2008
A.A. DistortionDistortion::
1.1. Margins:Margins: Probability highest in thinner portions of pattern. Probability highest in thinner portions of pattern.a.a. Wax Deformation:Wax Deformation: improper removal or handling of pattern. improper removal or handling of pattern.b.b. Premature Quenching:Premature Quenching: wait until button loses red color. wait until button loses red color.c.c. Investment Expansion/Contraction:Investment Expansion/Contraction:
1.1. Fine Surface Roughness:Fine Surface Roughness: Inherent particle size of investment Inherent particle size of investmenta.a. High W/P ratio increases surface roughness.High W/P ratio increases surface roughness.b.b. Low W/P ratio decreases investment adaptation or flow.Low W/P ratio decreases investment adaptation or flow.c.c. Prolonged burnout encourages investment decomposition.Prolonged burnout encourages investment decomposition.d.d. Overheating alloy encourages investment decomposition.Overheating alloy encourages investment decomposition.e.e. Overheating alloy encourages reaction with investment.Overheating alloy encourages reaction with investment.
2.2. Surface Defects:Surface Defects:a.a. Nodules: air bubbles trapped on the pattern during investing.Nodules: air bubbles trapped on the pattern during investing.
(Use surfactant; paint pattern; vacuum invest; vibrate)(Use surfactant; paint pattern; vacuum invest; vibrate)b.b. Ridges or Veins: poor wetting causing water films on pattern. Ridges or Veins: poor wetting causing water films on pattern.
Image source: Steve Bayne, University of Michigan, 2008
C.C. Incomplete CastingsIncomplete Castings::
1.1. Internal Porosity:Internal Porosity: due to improper solidification. due to improper solidification.a.a. Improper Spruing: Diameter too small or too long.Improper Spruing: Diameter too small or too long.b.b. Low Temperature: Investment or metal too cold.Low Temperature: Investment or metal too cold.c.c. Included Gases: Contaminated gold or oxidized old gold.Included Gases: Contaminated gold or oxidized old gold.d.d. Occluded Gases: Improper burnout of pattern.Occluded Gases: Improper burnout of pattern.
2.2. Incomplete External Shape:Incomplete External Shape:a.a. Insufficient casting pressure.Insufficient casting pressure.b.b. Excessive back pressure from investment.Excessive back pressure from investment.c.c. Suck back into sprue.Suck back into sprue.