AMALGAM

aahughes
Mind Map by aahughes, updated more than 1 year ago
aahughes
Created by aahughes almost 6 years ago
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Dental materials Mind Map on AMALGAM, created by aahughes on 03/25/2014.
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AMALGAM
1 Product of amalgamation
2 Alloy and mercury react to form silver hard grey mass
3 2 compositions: conventional + high copper
4 CONVENTIONAL
4.1 65%Ag = Silver
4.2 29%Sn = Tin
4.3 6%Cu = copper
4.4 2%Zn = Zinc
4.5 3%Hg = Mercury
5 Today-traditional conventional superseded by high copper
6 HIGH COPPER
6.1 40%Ag = Silver
6.2 32%Sn = Tin
6.3 30%Cu = copper
6.4 2%Zn = zinc
6.5 3% Hg = Mercury
7 Variations in alloy morphology:
8 LATHE CUT + SPHERICAL
9 Cu has strengthening affect
9.1 Zn acts as a SCAVENGER in alloy production
9.2 MIxing termed TRITURATION
9.3 Hg diffuses into alloy = >30mins small shrinkage
9.4 >30-60mins = expansion due to crystallisation
9.5 Overall effect is a net EXPANSION/CONTRACTION
9.6 Weak in thin sections
10 PLACEMENT TO FUNCTION
10.1 15-20mins and 24 hrs final strength
11 PROPERTIES - CREEP
11.1 Plastic deformation under load
11.2 Clinically flows manifestations of protrusions at rest margins
11.3 # off producing DITCHING
11.4 GAMMA 2 largely responsible
11.5 Corrosion of allot exacerbates release of Hg in marginal crevice
12 PROPERTIES - CORROSION
12.1 Electromechanical interactions of different alloy phases with SALIVA as ELECTOLYTE
12.2 GAMMA 2 phase Anode
12.3 GAMMA 2 breaks down to Sn(tin) + Hg(mercury)
12.4 Not all bad as corrosion products provide marginal seal
12.5 In high copper phase undergoing most corrosion is Cu +sn
13 PROPERTIES - THERMAL
13.1 High thermal diffusity
13.2 Thermal expansion of dentine
14 BIOLOGICAL PROPERTIES
14.1 Hg compounds known to be toxic to CNS
14.2 No conclusive evidence but percieved elevated risk:
14.3 Hg dose HIGH DURING PLACEMENT+CARVING
14.4 Hg CONCENTRATES+CROSSES PLACENTA
15 MANIPULATIVE VARIABLES
15.1 Alloy:Hg ratio
15.2 Drier mix achieved by mechanical mix
15.3 packing+condensing removes excess Hg
16 MANUFACTURER VARIABLES
16.1 Particle size of alloy: small achieves higher1x24hr strenght
16.2 If extremely small- too rapid set+cannot remove Hg layer
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