Dental Amalgams

Question 1

Amalgams have served as a dental restoration for over

Answer 1

165 years

Question 2

Amalgam alloy COMPOSITION***

Answer 2

wt% in the Hg

**– Silver (Ag) 40-60 wt%
**– Tin (Sn) 27-30 wt%
**– Cooper (Cu) 6- 30 wt%
**– Zinc (Zn). 0.01-2 wt%
– Palladium (Pd) less than 1%
– Indium (In) 10–15 %

Question 3

Admixed alloy particles

Answer 3

Mixture of lathe cut

and spherical particles

Question 4

How are Spherical particles made?

Answer 4

By atomizing liquid alloy

Question 5

when is the gamma phase is produced?

Answer 5

When an alloy containing approx. 27% tin is slowly cooled below a temperature of 480oC, an inter metallic compound (Ag3Sn)

Question 6

Which phase is is the weakest and the most susceptible to corrosion.

Answer 6

g2 phase

Question 7

Causes the g2 phase to be eliminated within a few hours after its formation.

Answer 7

e phase

Question 8

What are the immediate dimensional changes that can take place in dental amalgam?

Answer 8

Contraction during the first 20min. Expansion after that Stable at 6-8 hrs.

Question 9

What can cause excessive expansion in amalgam alloys?

Answer 9

Zinc (Zn) containing alloy gets contaminated with water = excessive expansion.

Question 10

Corrosion is higher in what type of amalgam alloy?

Answer 10

In High copper alloys = 100-500 µm

Question 11

What are the properties of high coper amalgam?

Answer 11

Lower tensile strength, higher compressive strength, and lower creep.

Question 12

What is Creep?

Answer 12

Permanent deformation under static

loads. Low (0.05 - 6.3%)

Question 13

Name the amalgam...
Lower Hg content 42% 
No Zn content 
100% ↑ copper spheres 
Smoother carving u Excellent margin adaptation
Eliminate  g2 phase

Ag 58%, Cu 14% Sn 28%

Answer 13

Megalloy EZ by Dentsply-Caulk

Question 14

↑ Zinc` 
excessive expansion with water
Condense time: 3:30
Set setting 4:30 
Lathe-cut particles 
Eliminate  g2 phase

Answer 14

Dispersalloy by Dentsply-Caulk

Question 15

Megalloy condensing and set time

Answer 15

Condense time: 2:30

Set time: 3:00

Question 16

Dispersalloy condensing and set time

Answer 16

Condense time: 3:30

Set time: 4:30

Question 17

Benefits of High-copper alloy

Answer 17

1. Higher strength
2. Less corrosion
3. Better longevity at the margins

Question 18

Dull and crumbly indicates?

Answer 18

Undermixed

Question 19

shiny and separates in a single mass

from the capsule indicates…

Answer 19

Normal mix

Question 20

Soupy and tends to stick to the walls of the capsule

Answer 20

Overmixed

Question 21

To enhance the surface to make the restoration

less prone to tarnish and corrosion what would you use?

Answer 21

Use a green carborundum or white alumina
stone. Then reevaluate margins.

Next a light touch with a finishing bur ***

Followed by a coarse rubber abrasive point at low
speed.