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Restorative (Dental Amalgam and Mercury (Longevity factors (Skill of…
Restorative
Dental Amalgam and Mercury
Longevity factors
Skill of clinician
Amount of tooth structure remaining
Physical properties
Patient cooperation
Quality of finished restoration
Occlusion
Diet and oral hygiene
G.V. Black Amalgam
67% silver
27% tin
5% copper
1% zinc
Low copper, more tin = more corrosion, marginal breakdown (micro-leakage)
High Copper Amalgam
1960
Reduced the weakest phase (tin-mercury)
Strength is increased
Corrosion and marginal breakdown decreased
Copper content 10-30%
Advantages of Amalgam
Durable
Easy to place
Good long term performance
Easy to manipulate
Minimal placement time
Economical
High compressive strength
Disadvantages of Amalgam
Bigger prep
Non insulating
Long term corrosion
Galvanic shock
Local allergic potential
Weakens tooth
Color
Parts of Alloy
Silver
Malleable and ductile
Increases strength
Softer than copper
Resistent to corrosion
High thermal conductivity
Mixes with mercury to harden amalgam
Copper
Increases strength
High thermal conductivity
Decreases corrosion
Decrease tarnish
Decreases ductility
Decreases creep
Tin
Properties are opposite of silver
Decreases setting expansion
Decreases strength
Slow to set
Zinc
Most chemically active
Soft, brittle, low strength
Palladium
Increases strength
Decreases corrosion
Decreases tarnish
Types of Alloy
Lathe cut
Irregular shaped particles
Silver, tin, low copper
Spherical
Round shaped particles of different sizes
Silver, copper, high or low copper
Admix
Lathe cut silver-tin particles + silver-copper spherical particles
Stronger than lathe cut
30-55% spherical high copper particles
Less technique sensitive
Amalgam Reaction
Low copper