A marginal gap exists between the amalgam restoration and the cavity w
alls. At this interface, there is a constant percolation of fluid cont
aining ions, molecules and bacteria. With time, corrosion products of
the amalgam components seal the gap at the amalgam/tooth interface. Th
e corrosion processes for conventional and high copper amalgam and fac
tors affecting the corrosion deposits are reviewed. Better amalgam ada
ptation to the cavity walls improves the chances of sealing the restor
ation by corrosion products. The effectiveness of cavity varnish in pr
eventing microleakage until corrosive deposits are formed is discussed
.