CSA Amalgam Flashcards
What is amalgam?
an alloy of mercury
What is mercury ?
liquid at room temperature and only freezes at -39
o form alloys at room temp.
• A toxin that build up and doesn’t break down in food chain
Is dental amalgam inert?
yes
What is the WHO max exposure levels for mercury ?
o 300mg per week
o And/or 25 mg/m3
What does capsule contain ?
o Metal alloy
o Liquid mercury Normally very pure
What does amalgam alloy contain?
o 69% Ag
o 19% Sn
o 11% Cu
o 1% Zn
What does Ag3Sn ratio place alloy in ?
gamma phase
What does mercury do to surface of alloy once mixed?
dissolves it forming new compounds not soluble and precipitate out liquid mercury forming gamma 1/2 phases
What is gamma 1 phase referred to?
the matrix, holds whole structure together
What is gamma 2 phase known for ?
being susceptible to corrosion, can lead to margin failure
What does amalgamator do?
“amalgam alloy” and mercury in capsule separated by membrane > ruptured when button ,
How do we get rid of gamma 2 phase (Sn7Hg)
• Additions of Cu3Sn mops up gamma 2 somore gamma 1 phase and some fine rod like crystals of Cu6Sn5
How is Cu3Sn added to ?
straight into alloy so alloy is 2 intermetallic compounds (Ag3Sn + Cu3Sn) OR added in fine powder
what is retention like with amalgam?
Retention is mechanical, cavities require an undercut
What can happen to silver over time?
tarnish into grey
