Dental Materials - Amalgam Flashcards
What are the advantages of using Amalgam?
Strong
User friendly
What are the disadvantages of using Amalgam?
Corrosion Leakage (both can cause dark staining of the tooth) Unaesthetic Worry of mercury use
What are the 2 compositions of amalgam available?
Classic
Copper enriched
What are the advantages of a copper enriched amalgam?
Increases strength - especially early on.
Less creep occurs
Higher corrosion resistance
Increased durability of margins.
Describe the amalgam setting reaction.
Y: silver and tin
Good corrosion resistance
Greatest tensile strength
Y1: Silver and mercury
Good corrosion resistance
Y2: Tin and mercury
Weak tensile strength and poor corrosion resistance
Comment on amalgams expansion contraction stresses.
Little clinical sign/effect as it is < 0.2
Describe the compressive strength of amalgam.
Poor strength early on
Improves over time however is still not ideal.
What factors decrease the strength of amalgam?
Undermixing
Slow rate of packing into the prepared cavity
Corrosion - weakens the margins
In what teeth would amalgam restorations have high resistance?
Posterior teeth
Comment on amalgams thermal expansion.
Poor - contracts to 3x gretaer than the tooth.
Potential to create voids
What must be placed in the prepared cavity before placing an amalgam filing and why?
A lining
Amalgam has high thermal conductivity.
In terms of cavity design; what is crucial for an amalgam restoration?
Since amalgam doesn’t bond to tooth tissue RETENTIVE FEATURES must be present in the cavity to ensure the amalgam restoration remains in place.
i.e undercuts and isthmus
What causes amalgam creep?
Repeated low level stresses that are below the elastic limit over a long period of time.
What is the consequence of amalgam creep?
Amalgam protrudes over the occlusal surface where it is more vulnerable to marginal fracture.
