Dental Amalgam Flashcards
if a patient is wanting amalgams changed for aesthetic reasons what would you advise the patient?
amalgam fillings are safe
mercury vapour produced on removal
when is amalgam the best choice of filling material?
not good moisture control
large occlusal load
not good supragingival enamel margins
large complex restoration
what happened in 1833
crawcour brothers brought amalgam to the usa, powdered pennies and mercury - expanded on setting
1895?
GVBlack - modern day
67% silver, 27% tin, 5% copper, 1%zinc
what is creep?
when amalgam flows out of restoration and becomes proud
occlusal loading causes fractures
why was copper added?
improves strength of the set material
reduces creep and corrosion
what is the tin mercury phase?
the gamma 2 phase
weakest phase - causes creep
what does copper eliminate?
eliminates the tin mercury phase
no expansion
what does zinc act as in amalgam?
a scavenger
takes up O2 from oxidisation and is easily removed
what happened in the 1960’s?
conventional low copper alloy was lathe cut
= admixture - 1st gen of high copper alloy = spherical AgCu
1970’s
first single composition spherical
1980’s
sim to 1970’s
90’s?
first mercury free alloy - gallium
problems with mercury free alloy?
increased corrosion and excessive post setting expansion
what kind of amalgams are available today?
low copper alloys, admixed high copper alloy, single composition high copper alloy