amalgam Flashcards
what are the 3 phases of amalgam
gamma
gamma1
gamma 2
which phase is most noble to corrosion
gamma 1, silver mercury
which phase is the strongest
gamma silver-tin
what are the pros of having smaller particles
more rapid hardening, greater early strength, more easily adapted to walls, less pitted, more easy burnishing and polishing, increase in surface area so more mecury needed
which has a smaller surface area, lathe cut or spherical cut
spherical cut, so better properties and less mercury needed
which resists condensation better, lathe cut or spherical cut
lathe cut
what are some factors that decrease expansion
- decrease mercury
- higher condensation pressure
- increase in tituration time –> increases consumption of mercury
- smaller particle size
What causes delayed expansion
- moisture contamination, leading to zinc corroding and H2 being produced. H2 causes an expanding pressure within, decreasing strength and increasing creep due to corrosion and pitting
what can you do to somewhat curb the problem of delayed expansion
use zinc free alloys for places with poor moisture control, however it is more brittle and increases internal porosity
what is the flow of amalgam affected by
magnitude of stress and temperature
what can affect the strength of amalgam
- trituration time
- increasing mercury but <55%, can lead to more rapid hardening
- decreasing porosity
- higher condensation pressure( more alloy, less matrix)
what decreases creep
- decrease in mercury
- higher condensation pressure
what can cause an increase in corrosion
increasing mercury
what are the 2 types of corrosion, which is more damaging
dry corrosion vs wet corrosion, wet corrosion more damaging
how to reduce corrosion
- use fine particle alloy
- proper trituration and condensation
- proper surface finishing decreases surface irregularities
- avoid placing dissimilar restorations in contact
- use non G2 alloy
