Amalgam

Question 1

what is amalgam an alloy of?

Answer 1

silver, mercury and tin

Question 2

how do we mix amalgam?

Answer 2

amalgamator - reduce exposure and encapsulated

Question 3

how is amalgam set?

Answer 3

gamma rays

Question 4

the reaction between mercury and silver tin?

Answer 4

silver mercury amalgam and tin mercury amalgam

Question 5

what is bad about tin mercury amalgam

Answer 5

may leach contents and discolour

Question 6

how do we get rid of tin mercury

Answer 6

higher copper amalgam

Question 7

what’s the reaction between copper mercury amalgam, tin mercury and silver tin? What gamma does it produce?

Answer 7

copper mercury + tin mercury + silver tin
= copper tin + silver mercury

• silver mercury produces gamma 2
• unwanted
• reduced by adding copper
• responsible for corrosion and creep

Question 8

PRO of amalgam (8)

Answer 8

long lasting
cheap
easy to use

wear resistance
compressive
chemical set

radioopaque
good contact points

Question 9

CONS of amalgam (7)

Answer 9

aesthetic
doesn’t adhere to tooth
needs base underneath
needs polishing

poor tensile strength
thermal conductor
lichenoid-type reactions

Question 10

What Compounds can be Created When Amalgamated, and what Gamma do they Produce?

Answer 10

silver tin = gamma 1
silver mercury = gamma 2
mercury tin = gamma 3

Question 11

What are the 2 Forms of Amalgam Powder?

Answer 11

Spherical Form
- spray molten metal into fine mist, hardening as It softens
= softer and more flowable

Lathe Cut
- ingot of alloy and grind into powder
= less flowable, good for building large tooth structure

Question 12

Why is 50% Mercury the Optimum?

Answer 12

• less is dry and crumbly
• but with more mercury = weaker restoration so pack the material to remove excess

Question 13

Why can Zinc be Added?

Answer 13

• no benefit
• prevents silver from oxidising
• not needed if powder is manufactured in a vacuum
• can cause material to expand whilst setting as it absorbs moisture

Question 14

Where is Amalgam Used? (6)

Answer 14

• larger cavities in posterior teeth
• teeth with heavy occlusal forces
• high caries rate patient
• posterior restorations extending subgingivally
• build up broken teeth prior to crown
• when aesthetics aren’t important

Question 15

Which Features can Help a Tooth Retain Amalgam?

Answer 15

• dovetail design
• pits and grooves into the dentine
• undercut more than 70º
• no unsupported enamel
• wet RMGIC on the base of the cavity to chemically bond to amalgam

Question 16

How is Mercury Harmful to the Environment?

Answer 16

converted by bacterial into methyl mercury
= highly poisonous