amalgam structure and properties ppt
TRANSCRIPT
8/4/2019 AMALGAM Structure and Properties PPT
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DENTALAMALGAM
Stephen C. Bayne Department of Operative DentistrySchool of DentistryUniversity of North CarolinaChapel Hill, NC 27599-7450
2006, Bayne and Thompson
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DENTAL AMALGAM
Where is it?
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BEFORE REACTIONBEFORE REACTION AFTER REACTIONAFTER REACTION
AlloyAlloy
MercuryMercuryReactionReactionProductsProducts
AlloyAlloy
AMALGAM TERMINOLOGY
AMALGAM = an alloy containing Hg as the major ingredient.
DENTAL AMALGAM = an alloy of Hg with Ag-Sn.DENTAL AMALGAM ALLOY = a Ag-Sn alloy (to be mixed with Hg).
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ALLOY PRODUCTION
Melting / Casting / Comminution IRREGULAR Particles
Melting / Spray Atomization SPHERICAL PARTICLES
“Cast ingots --> filed into powder” Irregular particles = lathe cut = filings
Hot alloy sprayed into cold airParticles spherodize and solidify
Polycrystalline particlesHomogenized by HT to remove coringAnnealing HT to relieve cold work in filings
Spheres are acid-washedGenerally spheres are HT
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Hg / Alloy RATIOS
50:50
42:58
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ALLOY MANIPULATION
Manual Trituration Procedures: Alloy + Hg mortar + pestle manual mixing
Mechanical Trituration Procedures: Powdered alloy + Hg capsule + pestle amalgamatorPelleted alloy + Hg capsule + pestle amalgamator
Powdered alloy + Hg pre-capsulated amalgamator
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CLASSIFICATION
• Copper content = low copper, high copper• Particle size (and shape) = irregular, spherical• Number of particle types = 1 or 2• Zinc content = Zn-containing, Zn-free
Application of system of nomenclature
Alloy Copper Particle Number of Zinc Name: Content: Shape: Particles: Content:
New True Dentalloy Low Irregular 1 Particle No
Velvalloy Low Irregular 1 Particle No“Dispersalloy” High Both 2 Particles Yes“Tytin” High Spherical 1 Particle No
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Rx and MICROSTRUCTURE
IrregularAlloy
SphericalAlloy
Ag Primary reactantSn Creates solubility, fluidityCu Reacts with SnZn Alloy processing aidHg Reactant with Ag (and Sn)
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SETTING REACTIONS
Low-Copper Dental Amalgam:
2-Particle High-Copper Dental Amalgam:
1-Particle High-Copper Dental Amalgam:
S-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 Ag3Sn/Cu+ Hg Ag3Sn/Cu + Ag2Hg3 + CuSn + Cu3Sn g + Hg g + g 1 + e + h
I-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 g + Hg g (Ag3Sn) + g 1 + (g 2)
S-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2 Alloy + Hg Alloy (Ag-Cu) + g 1 + e + h
I/S-Alloy + Hg Residual Alloy + Matrix-1 + Matrix-2Ag-Sn + Hg Ag-Sn + Ag-Hg + Sn-HgAg3Sn + Hg Ag3Sn + Ag2Hg3 + Sn7-8Hgg + Hg g + g 1 + g 2
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Rx and MICROSTRUCTURE
+ Hg + +
g g1 g2
BEFORE REACTIONBEFORE REACTION AFTER REACTIONAFTER REACTION
AlloyAlloy
MercuryMercuryReactionReactionProductsProducts
AlloyAlloy
Penetrating Corrosion
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+ Hg + +
g g1+ spheres e + h
Rx and MICROSTRUCTURE
69 Ag
18 Sn12 Cu
1 ZnDISPERSALLOY
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PHASE DIAGRAMS
Ag Hg
Ag3Sn + Hg >>>Ag2Hg3 = g1
(26Ag-74Hg)
g1g + b
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Overview of Manipulation
Selection / Proportioning / Amalgamation / Manipulation / Polishing
Placement andCondensation
Carving Burnishing Polishing
Onset of
MIXING
Onset of
WORKING
Onset of
SETTING
End of
SETTING
24 hours
TIME
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Amalgamators
SPEED TIME
ENERGY = Speed x Time
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Unset amalgam
A
Setting amalgam
B
Ag-Hg crystalreaction products
Residual alloy
Excess Hg-rich matrixeliminated by condensation.
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DIMENSIONAL CHANGES
Dimensional changes on setting: CONTRACTION during alloy dissolutionEXPANSION during impingement of reaction product crystals(EXPANSION if side reactions due to H2O contamination)
EXP (+)
CONT (--)
TIME
Dimensional changes on depend on reaction variables:
Particle size, Hg/alloy ratio, trituration time, condensation, ...
ADA =± 20 mm
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AMALGAM PROPERTIES
2. Clinical Performancea. Longevity = 20-25 yrs ideally, 8-12 yrs practicallyb. Modes of failure = caries, marginal fracture, bulk
UNITEDSTATES
WORLD
ADA FDI
ISOANSI
B. Properties:
1. Physical
2. Mechanical3. Chemical4. Biological
A. Introduction:
1. Specifications for Amalgam Propertiesa. ADA / ANSI and ISOb. Determination of “safety and efficacy”
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Physical Properties
1. Thermal conductivity =2. Electrical conductivity =3. Coefficient of thermal expansion =4. Radiopacity =
5. Color =
[>2 mm Aluminum]
[Lustrous, shiny, white]
25 ppm/ºC[High]
[High]
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Mechanical Properties
Compressive Strength (psi) Tensile Strength (psi)15-min 1-hr 24-hr 15-min 1-hr 24-hr
LOW COPPER: Velvalloy 5,400 17,400 56,200 625 1,900 9,000Spheralloy 5,800 18,500 56,900 450 1,550 8,800
HIGH COPPER: Optalloy II 9,100 23,800 55,900 1,000 2,350 7,250Dispersalloy 6,200 22,400 59,900 575 1,750 6,990Indiloy 4,600 26,300 64,500 450 2,400 6,500Sybraloy 23,800 50,000 72,700 2,190 4,700 6,600Tytin 10,200 40,800 79,100 990 4,000 9,300
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Mechanical Properties
TYTIN (Kerr Dental Mfg) = “tie up the tin” High-Copper, Spherical, 1 Particle, Zn-free42% Hg mixed with alloyFast-settingHigh early strength
PolishedSurface
Fracture
Surface
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Chemical Properties
Clean Surface,High O2 Potential
(CATHODIC)
Plaque Buildup,Low O2 Potential
(ANODIC)
(a)
(b)
(a) (b)
PlaqueBuildup
Clean Surface,High O2 Potential
(CATHODIC)
Plaque Buildup,Low O2 Potential
(ANODIC)
(a)
(b)
(a) (b)
PlaqueBuildup
ELECTROCHEMICAL CORROSION:
• Galvanic corrosion• Local galvanic corrosion (structure selective)• Crevice corrosion (concentration cell)• Stress corrosion
Sn-O-ClSn-O
CHEMICALCORROSION: AgS
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Biological Properties
Mercury Toxicity: OSHA maximum TLV = 50 mg/m3 (vapor) per 40 hr work week.Transient intraoral release (<35 mg/m3).
Mercury Hypersensitivity:
Low level allergic reaction.Estimated to be < 1 / 100,000,000
Amalgam Tatoo: Can occur during amalgam removal if no rubber dam.Embedded amalgam particles corrode and locally discolor gum.
No known adverse reactions.
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Clinical Performance
Reasons for Failure: Low-copper amalgam – marginal fracture and secondary caries.High-copper amalgam – marginal fracture and bulk fracture.
Jorgensen theory of mercuroscopic expansion (and marginal fracture)
Internal corrosion
PenetratingCorrosion
Corrosion at margins
SuperficialCorrosion
Sn-O-Cl and Sn-O
CorrosionProducts
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Clinical Evaluation
Mahler scale:
???
Hi-Cu, no Zn
Hi-Cu, +Zn
Low-Cu, +Zn
Low-Cu, no Zn
Hi-Cu Low-Cu