Amalgam Flashcards
What is the general setting reaction for amalgams?
Alloy + Hg = Dental amalgam
What is the typical mercury/alloy ratio?
0.5
What are the major elements in the alloy for dental amalgam?
Ag (primary)
Sn (Secondary)
Cu (2-30%)
Zen (0-1%)
How can one obtain a mercury exposure?
Skin contact, inhalation of vapor, airborne droplets
T/F: Some patients may exhibit an allergic skin reaction to dental amalgams.
True
What are operator precaution when working with amalgam?
Wear face mask and use water spray and high vac suction when working with amalgams.
periodically have mercury levels checked by urinalysis
How should scrap dental amalgam be stored?
In a cool space in capped, unbreakable jar holding water with finely divided sulfur.
T/F: Spherical particles are wetted with less mercury than lathe-cut particles.
TRUE
T/F: Spherical particles resist forces of condensation more than lathe-cut particles.
FALSE
Lathe-cut resist condensation better
T/F: Low-copper products have greater clinical longevity in restorations.
FALSE.
High-copper is better
What is the major benefit of heat treating the alloy for dental amalgam?
Provides manufacturer control of setting time.
What is the general setting reaction for dental amalgam?
Gamma (starting alloy particles) + Hg (liquid) -> reaction phases (matrix) + unreacted alloy particles (core)
What would be the bricks in the set amalgam? Mortar?
“Bricks” = alloy particles
“Mortar” = reaction phases
What is the major reaction phase in both low and high copper amalgams?
Gamma1
What forms instead of gamma2 in high-copper amalgams?
n’
Which amalgam has the most contraction over 24 hours?
LCL (Low copper, lathe-cut)
Which amalgam has a slight expansion during 24 hours of being set?
HCB (high-copper blend)
What causes expansion in the amalgam?
Formation and growth of reaction phases
What causes contraction of amalgam?
Final absorption of mercury by remaining alloy particles
What is the strongest alloy phase?
Starting alloy particles (gamma)
What is the weakest phase?
gamma2 in low-copper amalgams
Most prone to corrosion
Why might corrosion occurs?
Corrosion can occur do to lower oxygen levels caused by plaque or lower pH of saliva. Crevices, margins, and scratches in amalgam are most prone to corrosion.
T/F: Amalgam is a brittle material.
True
T/F: Amalgam has a high tensile strength.
False.
Has a high compressive strength.
