EFDA PART 2 FINAL EXAM (Harcum College)

EFDA PART 2 FINAL EXAM ( Harcum Colleg e) Why would someone get an amalgam restoration? ✔✔-when cost is an issue - when moisture is problematic Mercury + Alloy = ✔✔Amalgam Silver ✔✔Combines easily with Mercury Copper ✔✔Strength, decreases expansion Tin ✔✔Aids in combining Mercury with alloy Zinc ✔✔Prevents oxidation Creep ✔✔Slow flow of material, has force Maliable ✔✔(Softness) able to be condensed Ductile ✔✔(Moveable) able to move around What are the characteristics of amalgam ✔✔- strength (- size and shape of alloy particles -ratio of mercury + alloy - manipulation) -setting time Conventional alloy particles ✔✔Regular, fine, micro cut Spherical alloy particles ✔✔Lower mercury to alloy ratio/ more expensive Dispersion alloy particles ✔✔Mix of the different particle types, control the structure of the hardened amalgam/commonly used The higher % of mercury ✔✔Amalgam is easier to mix and slower to set The lower % of mercury ✔✔Weakens the amalgam and makes polishing more difficult What happens if amalgam is contaminated with moisture? ✔✔It will stick to the prep and cause expanded retraction. Try to reduce Overmixed ✔✔Very soupy, hard to remove from capsule, too much mercury, decrease triturator Normal mixed ✔✔Comes out of capsule in one dull mass easily removed from capsule, looks velvety (grayish) Undermixed ✔✔Crumbly, not wet enough with mercury, increase triturator setting What causes amalgam to fail ✔✔-breakdown of the margins; just sits in the tooth does not bond/seal - mercury mixed with tin (gamma 2 phase) will weaken amalgam -CREEP: slow flow of a material overtime under stress (like a force mastication) -manipulation : if not mixed properly What are the physical properties of amalgam? ✔✔- dimensional change - strength - galvanism - creep -corrosion and tarnish Galvanism ✔✔when two dissimilar metals touch with saliva battery causing an electric shock Corrosion ✔✔Deterioration of an eroded metal Tarnish ✔✔Discoloration