L8: Dental amalgam Flashcards
what is amalgamation / trituration :
mixing alloy powder with mercury
composition of amalgam :
50% mercury , 50% alloy powder
50% alloy powder consists of 67% silver , 27%tin , 5% copper and 1% zinc
role of silver , tin , copper , and zinc in amalgan :
silver:
increase strength and expansion
tin:
decrease strength and expansion ,
increase setting time
copper:
increase strength ,
decrease tarnish , corrosion , creep , marginal leakage
zinc:
prevent marginal breakdown
causes delayed expansion if contaminated with water
what activates the reaction to form amalgam :
mercury
conventional low copper amalgam has a copper concentration of ___
less than 6%
high copper amalgam has copper concentration of___
11-30%
how will the amalgam turn out if it was over-titurated?
hot mix that sticks to capsule
- has decreased working time / setting time and increased setting contraction
under-triturated amalgam will appear :
grainy and crumbly mix
amalgam with proper trituration will appear :
smooth , shiny , spherical
condensation is :
packing of amalgam into the cavity
-greatest possible density is achieved
-helps reduce excess mercury and porosity within set amalgam
-
which process helps reduce excess amalgam and porosity within set amalgam ?
condensation
which cut of alloy require more force to be condensed and a smaller condenser to be used?
lathe cut
- spherical alloys require less force and a larger condenser may be used
which process removes excess mercury and improves margin adaptation ?
bunishing
which process produces initial smoothness of restoration ?
carving and finishing
polishing :
increases smoothness
-improves luster
-decrease plaque retention
-improves marginal integrity
