amalgam

an alloy of mercury and silver + tin added copper and zinc too

mercury is a liquid at room temperature making it very workable a con is that it is hard to dispose of due to its toxic nature in large amounts

number of metals (bi, tri, quarternary) uni or admixed (shapes) • fine or coarse • spheroidal or lathe cut zinc content copper content

lathe cut is where rough shapes are cut directly from the amalgam spheroidal is where amalgam is passed into an inert gas which forms it into a spherical ball

silver adds strength to the amalgam mixture it also helps to prevent contraction shrinkage helps with setting

when combined with silver, it helps with setting via corrosion and creep corrosion also a con - also contributes to shrinkage also is weak

helps prevent a large amount of gamma2 phase being present. helps to counter the corrosiveness of tin

a mix of three different phases of the amalgam left after mixing. Y/Gamma phase = mercury + silver-tin - silver tin reacts with liquid mercury to form amalgam. This holds gamma1 and 2 together Y1/Gamma 1 phase = mercury + silver alone - extremely strong Y2 = mercury + tin alone • very weak • however contributes to setting reaction and corrosion to seal margins

deoxidiser, scavenger for oxygen to strengthen the amalgam delays expansion

corrosion can help to seal restoration margins high abrasion resistance - good for posterior teeth ok compressive strength good handling properties and relatively fast mixing and setting time

poor biocompatibility - toxic mercury hard to dispose of no chemical bond to tooth surfaces creep and viscoelasticity poor aesthetics high thermal conductivity and diffusivity (may need a liner)