Amalgam Flashcards
What are the components of amalgam
Mercury silver copper tin
Palladium
Zinc
Adavantages of amalgam
Easy to insert
Maintains a atomic form well
Adequate resistance to fracture
Prevents marginal leakage with time
Good mechanical and chemical properties
Low cost
Good longevity
Disadavantages fo amalgam
colour does not match natural tooth
technique sensitive- can lead to marginal breakdown
subject to corrosion and galvanic action
brittle and can fracture if incorectly placed
How can amalgam be classified
shape, composition of particles, copper content
What are the parameters for low and high copper
low copper - less than 6%
high copper - 13-30 %
What are the particle shapes for amalgam
spherical, lathe-cut, admixed
What are the functiona of components of amalgam?
Silver- enables setting expansion, increase in strength and resistance corrosion
Tin - controls the reaction between silver and mercury. without reaction would be too fast and seeting expansion unacceptable
copper - increases compressive strength
zinc - scavenger prevents oxidation of other metals
Describe the appearance of under triturated and over triturated amalgam
under - dull, non-uniform, rough ,brittle dry
over - shiny, hot, hard to remove from capsule, wet, soft
normal- shiny, separtes in onemass from capsule
What is amalgam polished with?
fine pumice or tin oxide
24 hrs after restoration
When does amalgam reach its final strength
approx. 7 days
What si the difference between working and setting time
Working time- time to complete condensing and carving
Setting- time from trituration to max strength.
What cancause porosity of amalgam
too large increments
inadequate condensation pressure
What is creep and how does it affect amalgam restorations
deformity of solid material with wear and stress.
amalgam eventually leaves the margin, can fracture off, leaves gaps at the margin.
What can cause delyaed expasnsion of amalagam?
under trituration
contamination of material during restoration with water or saliva leading to the production of hydrogen gas
What is the diagnosis for a pateit complaning of pain 1 day after an amalgam restoration?
Hyperocclusion
