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AMALGAM

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Dental materials Mind Map on AMALGAM, created by aahughes on 25/03/2014.
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Mind Map by aahughes, updated more than 1 year ago
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Created by aahughes about 10 years ago
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Resource summary

AMALGAM
  1. Product of amalgamation
    1. Alloy and mercury react to form silver hard grey mass
      1. 2 compositions: conventional + high copper
        1. CONVENTIONAL
          1. 65%Ag = Silver
            1. 29%Sn = Tin
              1. 6%Cu = copper
                1. 2%Zn = Zinc
                  1. 3%Hg = Mercury
                  2. Today-traditional conventional superseded by high copper
                    1. HIGH COPPER
                      1. 40%Ag = Silver
                        1. 32%Sn = Tin
                          1. 30%Cu = copper
                            1. 2%Zn = zinc
                              1. 3% Hg = Mercury
                              2. Variations in alloy morphology:
                                1. LATHE CUT + SPHERICAL
                                  1. Cu has strengthening affect
                                    1. Zn acts as a SCAVENGER in alloy production
                                      1. MIxing termed TRITURATION
                                        1. Hg diffuses into alloy = >30mins small shrinkage
                                          1. >30-60mins = expansion due to crystallisation
                                            1. Overall effect is a net EXPANSION/CONTRACTION
                                              1. Weak in thin sections
                                              2. PLACEMENT TO FUNCTION
                                                1. 15-20mins and 24 hrs final strength
                                                2. PROPERTIES - CREEP
                                                  1. Plastic deformation under load
                                                    1. Clinically flows manifestations of protrusions at rest margins
                                                      1. # off producing DITCHING
                                                        1. GAMMA 2 largely responsible
                                                          1. Corrosion of allot exacerbates release of Hg in marginal crevice
                                                          2. PROPERTIES - CORROSION
                                                            1. Electromechanical interactions of different alloy phases with SALIVA as ELECTOLYTE
                                                              1. GAMMA 2 phase Anode
                                                                1. GAMMA 2 breaks down to Sn(tin) + Hg(mercury)
                                                                  1. Not all bad as corrosion products provide marginal seal
                                                                    1. In high copper phase undergoing most corrosion is Cu +sn
                                                                    2. PROPERTIES - THERMAL
                                                                      1. High thermal diffusity
                                                                        1. Thermal expansion of dentine
                                                                        2. BIOLOGICAL PROPERTIES
                                                                          1. Hg compounds known to be toxic to CNS
                                                                            1. No conclusive evidence but percieved elevated risk:
                                                                              1. Hg dose HIGH DURING PLACEMENT+CARVING
                                                                                1. Hg CONCENTRATES+CROSSES PLACENTA
                                                                                2. MANIPULATIVE VARIABLES
                                                                                  1. Alloy:Hg ratio
                                                                                    1. Drier mix achieved by mechanical mix
                                                                                      1. packing+condensing removes excess Hg
                                                                                      2. MANUFACTURER VARIABLES
                                                                                        1. Particle size of alloy: small achieves higher1x24hr strenght
                                                                                          1. If extremely small- too rapid set+cannot remove Hg layer
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