amalgam

Question 1

what are the 3 phases of amalgam

Answer 1

gamma

gamma1

gamma 2

Question 2

which phase is most noble to corrosion

Answer 2

gamma 1, silver mercury

Question 3

which phase is the strongest

Answer 3

gamma silver-tin

Question 4

what are the pros of having smaller particles

Answer 4

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

Question 5

which has a smaller surface area, lathe cut or spherical cut

Answer 5

spherical cut, so better properties and less mercury needed

Question 6

which resists condensation better, lathe cut or spherical cut

Answer 6

lathe cut

Question 7

what are some factors that decrease expansion

Answer 7

• decrease mercury
• higher condensation pressure
• increase in tituration time –> increases consumption of mercury
• smaller particle size

Question 8

What causes delayed expansion

Answer 8

• 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

Question 9

what can you do to somewhat curb the problem of delayed expansion

Answer 9

use zinc free alloys for places with poor moisture control, however it is more brittle and increases internal porosity

Question 10

what is the flow of amalgam affected by

Answer 10

magnitude of stress and temperature

Question 11

what can affect the strength of amalgam

Answer 11

1. trituration time
2. increasing mercury but <55%, can lead to more rapid hardening
3. decreasing porosity
4. higher condensation pressure( more alloy, less matrix)

Question 12

what decreases creep

Answer 12

1. decrease in mercury
2. higher condensation pressure

Question 13

what can cause an increase in corrosion

Answer 13

increasing mercury

Question 14

what are the 2 types of corrosion, which is more damaging

Answer 14

dry corrosion vs wet corrosion, wet corrosion more damaging

Question 15

how to reduce corrosion

Answer 15

1. use fine particle alloy
2. proper trituration and condensation
3. proper surface finishing decreases surface irregularities
4. avoid placing dissimilar restorations in contact
5. use non G2 alloy

Question 16

what happens to strength and creep in excess of mecury

Answer 16

strength decreases, creep increases

Question 17

what has lesser expansion, tin rich or silver rich alloy

Answer 17

tin rich

Question 18

what alloy is more susceptible to corrosion

Answer 18

tin