Amalgam Flashcards
Dental amalgam is a combination of what 2 things?
liquid elemental mercury & metal alloy
Eames’ ratio
half mercury and half metal alloy
Alloy contains (4):
silver
copper
tin
zinc
alloy that is a provider of strength
silver and copper
alloy that is the primary provider of corrosion products
tin
alloy that is a deoxidizer
zinc
Trituration of amalgam results in 3 phase compositions:
Υ phase = unreacted silver-tin
Υ1 phase = silver-mercury matrix
Υ2 phase = tin-mercury matrix
Trituration of amalgam results in 3 phase compositions.
Which is the strongest and least corrosion resistant?
Y phase
Trituration of amalgam results in 3 phase compositions.
Which phase is the next strongest and corrosion resistant?
Υ1 phase
Which is phase is the weakest and susceptible to corrosion and creep?
Y2 phase
properly triturated vs over-triturated vs under-triturated amalgam
Properly triturated = shiny, smooth, easily loaded, reaches peak strength after 24h
Over-triturated = warm, soft, sets quickly
Under-triturated = dry, crumbly, sets quickly
In the past, copper composition was low inside of dental amalgam. However with time, more copper was incorporated to provide (3):
more strength
lower corrosion ability
longer marginal longevity
low copper vs high copper amalgam
Low copper- contains 12% Cu, yields in the production of Y, Y1, and Y2 phases
High copper- contains over 12% Cu, yields only Y and Y1 phases, with minimum corrosion products and creep
2 alloy particle types
spherical and admixed
alloy particles that are small spheres, contain more plastic, have a quicker set time, condenses better, and are more durable
spherical
alloy particles that contain both spherical and irregular particles, need higher condensation forces, yields better proximal contacts with adjacent teeth
admixed
Indications & contraindications for amalgam:
Indications
- bigger preps that require heavier functional loading
- areas that are harder to isolate from saliva
- teeth which serve as abutments
- non-esthetic regions
- preps that extend to root surfaces
Contraindications:
- esthetics zones
- metal allergy
commonly used instrument used for occlusal carving of amalgam
Hollenback carver
Cleoid-discoid
commonly used instrument for removing excess amalgam on proximal surfaces and carving of the gingival embrasures
amalgam knife
commonly used instrument for occlusal embrasure carving
explorer tip
Potential reasons why a marginal ridge fracture might occur:
- overbuilt marginal ridge
- axiopulpal line angle not being rounded
- excessive carving leaving less than 2mm of thickness
- incorrect removal of matrix band
Class V amalgam restoration preps must demonstrate:
- occlusal divergence due to the enamel rod orientation
- retention features such as gingival or circumferential grooves can be used
greatest health risk from mercury toxicity
inhalation (80% of elemental mercury is absorbed through the lungs)
how to handle amalgam spills
cover with sulfur powder and cleaned with a special vacuum
