Amalgam Lecture

Question 1

mercury issues for patient

Answer 1

toxic (b/c ^ vapor P) - can go thru skin lungs or GI tract
allergies
poor esthetics

Question 2

mercury issues for operator

Answer 2

weakening of tooth from removal of structure
doesn’t bind to teeth
brittle
need barriers

Question 3

disposal/ cautions w/ amalgam

Answer 3

check air and urine 
no baseboard heating
single use capsules
no touch technique
put in unbreakable jar w/ h2o and sulfur

Question 4

Hg/alloy ratio

Answer 4

42-45%

Question 5

Role of Cu in amalgam

Answer 5

^ longevity and decreases creep.

Question 6

amalgams considered high copper with _____%

Answer 6

12+

Question 7

role of Zn in amalgam, and prob w/ it

Answer 7

Zn helps be lathe cut and ^ corrosion resistance but if exposed to moisture causes delayed expansion

Question 8

what’s gamma?

Answer 8

alloy, starting material for amalgam

Question 9

phases of amalgam?

Answer 9

y= stongest
y1 = major rxn phase
y2 = weakest and corrosion prone
n' = margin sealing phase

Question 10

formula for amalgam rxn

Answer 10

y + Hg –> y1 + y2 (n’ in high Cu)+ unreacted particles

Question 11

what happens after amalgam is set?

Answer 11

there’s no more free Hg and it contracts

Question 12

mechanical properties of amalgam

Answer 12

brittle w/ poor edge strength

stronger in compression than tension

Question 13

what causes creep?

Answer 13

grain boundary sliding of y1, it’s blocked by n’ ‘s margin sealing in high Cu amalgam

Question 14

advantages to amalgam

Answer 14

cheep, easy, margin sealing and long lasting

Question 15

3 phases of alloy

Answer 15

y (Ag3Sn) B (Ag-Sn) E (Cu3Sn)

Question 16

shapes of alloy particles

Answer 16

spherical or lathe cut (lathe helps w/ condensation)

Question 17

types of amalgam corrosion

Answer 17

galvanic (gold), crevice (margins), electrochemical, @ scratches /2’ anatomy b/c low pH and [O2] of saliv, under plaque, and on occlusal surfaces when rxn happens w/ S ions

Question 18

what enhances and how do you minimize amalgam corrosion

Answer 18

enhanced by Sn, Cu, and O2

use Zn, and polish to avoid

Question 19

Effects of amalgam corrosion

Answer 19

microleakge.

Question 20

components of alloy

Answer 20

Ag and Sn